chlorophyll Content

This study reports hydrographic and biological observations from three cruises where cyclonic and anticyclonic eddies were observed downstream of Gran Canaria island. Based on field data and remote sensing images (AVHRR and CZCS), two mechanisms associated with islandgenerated eddies, largely responsible for the formation and distribution of chlorophyll around the Canary Islands, are proposed. First, nutrient pumping and vertical uplifting of the deep chlorophyll maximum by cyclonic eddies might represent important sources of primary production in the oligotrophic waters of the Canary region. Second, eddies are responsible for the horizontal transport and distribution of chlorophyll originating near the islands or off the African coast. Water with high chlorophyll content, resulting from island stirring or local upwelling at the flanks of the islands, is incorporated into cyclonic eddies in their development and subsequently transported downstream. On the other hand, anticyclonic eddies can also entrain water rich in chlorophyll when interacting with the offshore boundary of the African coastal upwelling. This chlorophyll will be advected southward as the eddy drifts. The recurrence of cyclonic and anticyclonic eddies, together with the presence of upwelling filaments throughout the year, must have important biological consequences in the formation and transport of organic matter in the Canary region. 0 1997

Tobacco (Nicotiana tabacum L.) is a tolerant species that accumulates cadmium. We studied the effect of Cd (0, 10, 25, 50, 100 lM) on growth parameters, chlorophyll and proline contents, enzymatic antioxidative response and lipid peroxidation of tobacco plants grown in hydroponic culture for 11 days to clarify the strategy of plant response against oxidative stress caused by this heavy metal. Cadmium accumulated more in roots than in shoots. Plant growth was not significantly affected by the cadmium concentrations used. Young leaves were more affected, showing visible chlorosis and a significant decrease in chlorophyll content at high Cd concentrations. Dry weight of both leaves and roots increased indicating a lower capacity for roots to absorb water. An increase in malondialdehyde levels was observed, indicating that lipid peroxidation occurred as a result of ROS formation. The activity of guaiacol peroxidase in leaves increased, indicating that it was very important in the scavenging of H 2 O 2 , while superoxide dismutase activity only increased in old leaves. Ascorbate peroxidase showed constant activity levels in tobacco leaves, suggesting that the ascorbate-glutathione pathway was less important as a defense mechanism.

Screen house experiments were conducted under no choice conditions, to determine the tolerance, a mechanism of resistance, in cotton under a population pressure of 150 and 300 pairs of whiteflies Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae). Twelve cotton genotypes, viz., four resistant (NHH 44, Supriya, LD694 and PA 183), four susceptible (F 846, IS-376/4/ 1/20/72, LK 861 and RS 2013) and four with moderate reaction (T x Maroon 2-78, MRC 6304Bt, RS 2098 and CNH 911) to B. tabaci were assessed in terms of decrease in plant height, number of nodes and chlorophyll content (a, b and total) from control. The study revealed that all three characters are important to identify tolerance. A strong tolerance mechanism is operating in NHH 44. The genotypes LD 694 and PA 183 were rated as moderately tolerant, however, IS 376/4/1/20/72, Tx Maroon 2-78, MRC 6304Bt, F 846 and CNH 911 exhibited no tolerance mechanism and were categorized as the most susceptible genotypes.

Growth and water uptake both decreases when tomato plants are irrigated with saline water. To determine the relative contribution of physiological traits to these decreases plant fresh and dry weight, leaf area, leaf water (c w) and osmotic (c P) potentials, gas exchange parameters, stomatal density, leaf chlorophyll and Na content were investigated in the tomato (Lycopersicon esculentum) cultivars, Daniela and Moneymaker. Plants were grown in greenhouse, in sand culture, and irrigated with a complete nutrient solution supplied with 0 (control), 35 and 70 mM NaCl over a period of 2 months. Salinity reduced plant dry weight, height and number of leaves even at 35 mM NaCl. Leaf c w and c P decreased with salinity but leaf turgor pressures were significantly higher in salinised than in control plants which suggests that bulk tissue turgor did not limit growth under the saline conditions tested. Increasing salinity in the irrigation solution led to both morphological changes [(reduction of plant leaf area and stomatal density) and physiological changes [reduction of stomatal conductance, transpiration, and net CO 2 assimilation (A CO 2)] Plant water uptake, measured as the difference between volume of nutrient solution supplied and drainage collected, was closely related to transpiration, stomatal conductance, and stomatal density. Chlorophyll content per unit of leaf area increased with salinity. Reduction of net A CO 2 with salinity was explained in higher degree by stomatal conductance and stomatal density than by Na accumulation in the leaves. Although plant water uptake was similar for the two cultivars, Daniela transported, per unit of water uptake, more Na to the leaves than did Moneymaker. However, Daniela reduced leaf area less than did Moneymaker. Water use efficiency, calculated either as the ratio between total plant dry matter and total plant water uptake, or as the ratio between net A CO 2 and transpiration, did not change under our saline growth conditions. The contribution of the observed salt-responses to reduction in shoot water loss, plant water uptake and salt loading, while keeping water use efficiency, is discussed in relation to salt tolerance. Because some of these salt-responses take a long time to develop, growing seedlings in seedbeds with saline media could be of interest to better tolerate further salty conditions in the field or greenhouse.

Ecophysiological strategies were examined for some species colonizing the different habitat types of north Egypt, namely, saline flat covered by sand sheets, a transitional area between the saline flat and rocky ridge, rocky ridge covered by gravely sand deposits and a non-saline depression. These habitats are characterized by marked soil variations which affect species tolerance. Water content, relative water content, pH, dry matter percentage, chlorophyll content, proline and carbohydrates varied in the species characteristic of each habitat type. Such information has made it possible to identify the most suitable habitat for each species within the range of habitats where they occur.

In this study, the genetic diversity of 50 individuals of rocket, Eruca vesicaria, from five accessions, four of them wild type collected from different parts of Spain and one commercial, were evaluated using morphological, agronomical and inter simple sequence repeat DNA (ISSR) data. Molecular analysis was carried out using the ISSR technique with 20 primers. Out of these 20 primers, nine were polymorphic, producing a total of 395 DNA bands, 247 of which were polymorphic among the accessions. A dendrogram drawn on the basis of a similarity matrix using the UPGMA algorithm revealed that the 50 samples of rocket plants could be classified into three major clusters at a Nei's genetic distance of 0.36. The experiment shows that molecular markers such as ISSR are a good instrument for distinguishing and selecting rocket accessions to group different wild populations. In general, a high variation was observed for most of the 16 morphological and 6 agronomical traits showing significant differences. Some morphological traits such as leaf length, petiole length and lamina width explained 69.1% of the whole variation observed in the populations, and some agronomical traits such as leaf area, nitrate and chlorophyll contents accounted for 65.7%, but the clusters generated by means of agronomical and morphological variables were less evident than when ISSR markers used. Some accessions showed good qualities, such as small leaves, high chlorophyll content, late-flowering or low nitrate content. All these parameters, together with the high degree of genetic homogeneity found, could make the local accessions good candidates for a future breeding programme. ß

Nitrogen (N) is the largest agricultural input in many Australian cropping systems and applying the right amount of N in the right place at the right physiological stage is a significant challenge for wheat growers. Optimizing N uptake could reduce input costs and minimize potential off-site movement. Since N uptake is dependent on soil and plant water status, ideally, N should be applied only to areas within paddocks with sufficient plant available water. To quantify N and water stress, spectral and thermal crop stress detection methods were explored using hyperspectral, multispectral and thermal remote sensing data collected at a research field site in Victoria, Australia. Wheat was grown over two seasons with two levels of water inputs (rainfall/irrigation) and either four levels (in 2004; 0, 17, 39 and 163 kg/ha) or two levels (in 2005; 0 and 39 kg/ha N) of nitrogen. The Canopy Chlorophyll Content Index (CCCI) and modified Spectral Ratio planar index (mSRpi), two indices designed to measure canopy-level N, were calculated from canopy-level hyperspectral data in 2005. They accounted for 76% and 74% of the variability of crop N status, respectively, just prior to stem elongation (Zadoks 24). The Normalised Difference Red Edge (NDRE) index and CCCI, calculated from airborne multispectral imagery, accounted for 41% and 37% of variability in crop N status, respectively. Greater scatter in the airborne data was attributable to the difference in scale of the ground and aerial measurements (i.e., small area plant samples against whole-plot means from imagery). Nevertheless, the analysis demonstrated that canopy-level theory can be transferred to airborne data, which could ultimately be of more use to growers. Thermal imagery showed that mean plot temperatures of rainfed treatments were 2.7 8C warmer than irrigated treatments (P < 0.001) at full cover. For partially vegetated fields, the two-Dimensional Crop Water Stress Index (2D CWSI) was calculated using the Vegetation Index-Temperature (VIT) trapezoid method to reduce the contribution of soil background to image temperature. Results showed rainfed plots were consistently more stressed than irrigated plots. Future work is needed to improve the ability of the CCCI and VIT methods to detect N and water stress and apply both indices simultaneously at the paddock scale to test whether N can be targeted based on water status. Use of these technologies has significant potential for maximising the spatial and temporal efficiency of N applications for wheat growers.

Two cherry tomato plant cultivars (Lycopersicon esculentum Miller, cultivars ‘Koko’ and ‘Pepe’) were supplied with high (395 ppm), medium (266 ppm) and low (199 ppm) concentrations of nitrogen to determine the influence of nitrogen fertilization on development, cultivar preference and honeydew production by greenhouse whiteflies, Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae). The nitrogen, protein, and chlorophyll contents of tomato leaves were higher in the

This paper reports experimental measurements of the radiation characteristics of green algae used for carbon dioxide fixation via photosynthesis. The generated biomass can be used to produce not only biofuels but also feed for animal and food supplements for human consumptions. Particular attention was paid to three widely used species namely Botryococcus braunii, Chlorella sp., and Chlorococcum littorale. Their extinction and absorption coefficients were obtained from normal-normal and normal-hemispherical transmittance measurements over the spectral range from 400 to 800 nm. Moreover, a polar nephelometer was used to measure the scattering phase function of the microorganisms at 632.8 nm. It was observed that for all strains, scattering dominates over absorption. The magnitudes of the extinction and scattering crosssection are functions of the size, shape, and chlorophyll content of each strain in a nontrivial manner. Absorption peaks at 435, 475, and 676 nm corresponding to chlorophyll a and chlorophyll b. The results can be used for scaling and optimization of CO 2 fixation in ponds or photobioreactors as well as in the development of controlled ecological life support systems.

Research was conducted to determine the effect of salinity on Rhizobium and growth of dry bean. A commercial cultivar (Akman 98) of dry bean (Phaseolus vulgaris L.) was inoculated with Rhizobium tropici strain CIAT899 and native Rhizobium in solution culture with different salt concentrations (control, 5, 10, 20 and 40 mmol À1) added before inoculation. The results indicated that population of R. tropici strain CIAT899 and natural Rhizobium were decreased with salinity levels. However, the population count train CIAT899 was inversely proportional to salt concentration with high growth (8.0e9.0 Â 10 5 cfu ml À1) at lower concentrations of control e 5 mmol À1 and low growth (4.0e6.0 Â 10 5 cfu ml À1) at higher salt concentrations of 20 mmol À1. The plant root and shoot dry weight, chlorophyll content, plant height, root length, total nitrogen, symbiotic efficient and efficient rate were affected by salt stress in tested plant and both inoculations. Total nitrogen content decreased significantly at the highest level of salinity. It is important to decrease the soil salinity and to improve the yield of dry bean (P. vulgaris L.) as well as the Rhizobium sp. associated with it.

Transgenic technology provides currently the best hope for improvement in plants where traditional breeding is not feasible. Strawberry is one such plant where polyploidy complicates breeding efforts. Introduction of genes directly into strawberry has been successfully achieved. The study presented here is the first report where transgenic plants of strawberry tolerant to salt stress were produced. Leaf discs of in vitro grown plantlets of strawberry (cv. Chandler) were used as explants and Agrobacterium tumefaciens strain GV2260 harbouring osmotin gene under the control of CaMV 35S promoter in a binary vector system (pBinAR) was used in co-cultivation experiments. Transgene integration and copy number were assessed by PCR and Southern hybridization confirming single copy as well as multiple copies of transgene integration in 10 different lines of transgenic strawberry. Expression of osmotin gene was confirmed in transgenic lines T L3 , T L5 , T L9 using northern hybridization, while biochemical analyses of these transgenic plants revealed enhanced levels of proline, total soluble protein and chlorophyll content as compared to the wild plants. Leaf disc senescence assay showed that these transgenic lines were tolerant to salt stress. The growth pattern of transgenic plants overexpressing osmotin did not show any abnormality, except their growth rate being slower than other plants. #

Selenicereus megalanthus and Hylocereus polyrhizus, hemiepiphytic cacti of shady habitats, have recently been introduced as fruit crops to the Negev Desert of Israel. Since they become bleached and die when they are grown in full sunlight, the shading responses of these cacti were studied. Both species showed typical CAM CO fixation, namely CO was fixed during the night, 2 2 followed by acid accumulation. Nocturnal acid accumulation and the concentration of photosyn-Ž. thetic pigments chlorophyll and carotenoids were determined in short term experiments in the summer under full sunlight or in net houses with 30, 60 or 90% shade. The effect of shading on morphological traits, growth and fruiting was determined in long term experiments, in net-houses only, since plants usually degenerate under full sunlight. S. megalanthus was found to be more sensitive to high light flux density and better adapted to deep shade than H. polyrhizus, as judged from the more marked decrease in both nocturnal acid accumulation and in the concentrations of chlorophyll and carotenoids under full sunlight in the former species. In addition, under 90% shade the stem biomass of S. megalanthus was reduced less than that of H. polyrhizus. In response to the shade, stem ribs became shallow, root dry weight decreased and shoot water content increased in both species. The most favorable conditions for growth and fruit production were found to be 30% shade for H. polyrhizus while for S. megalanthus 60% shade seemed to be preferable, since it facilitated higher acid accumulation, carotenoid and chlorophyll content, and better stem appearance. H. polyrhizus was distinguished by its higher fruit yield, estimated at 16 ton ha y1 vs. 3.8 ton ha y1 for S. megalanthus in the second year after planting when both species were growing under optimal conditions. The differences between the species in terms of light adaptation may be partially related to the wax layer coating the stem and sunken stomata of H.

— A pot experiment was conducted to study the effects of potting media on sprouting and seedling growth of grape cuttings. Three grape varieties viz. Red globe, Thomson seedless and Crimson seedless were planted in four different growth media: CS-Canal silt, CSFYM-Canal silt (75%) + FYM (25%), CSB-Canal silt (25%) + Bagasse (75%) and CSBCP-Canal silt (25%) + Bagasse (50%) + Coco peat (25%). The experiment was conducted in Completely Randomized Design (CRD) along with three replications. The results revealed that almost all observed parameters were significantly influenced by the potting media. However, grape varieties and their interaction with the potting media exhibited non-significant effect for sprouting percentage and most of the seedling related attributes of growth. Minimum days to sprouting (6.78),highest sprouting percentage (84.44), maximum rooting percentage (84.44) and maximum chlorophyll content of leaves (56.23) were observed from the cuttings planted in CSBCP. However, maximum number of sprouts (5.55), number of leaves (13.77), fresh weight of leaves (2.27g), fresh weight of the roots (2.16 g), were observed from CSB. No grape seedling mortality was also observed CSB and CSBCP growth media. On the basis of varietal comparison, Thompson seedless exhibited the best results for number of leaves per cutting (11.50), fresh weight of the roots (1.64 g) and number of roots per cutting (29.17 g) as compared to rest of the grape varieties. The research establishes the potential for locals to use available materials in potting media preparation for healthier and stronger grape seedlings for subsequent improved grape plantation.

Lead (Pb) has limited solubility in the soil environment owing to complexation with various soil components. Although total soil Pb concentrations may be high at a given site, the fraction of soluble Pb that plants can extract is very small, which is the major limiting factor for Pb phytoremediation. The symbiotic effect of arbuscular mycorrhizal (AM) fungus, Glomus mosseae was examined on growth and phytoextraction of lead (Pb) by vetiver grass [Chrysopogon zizanioides (L.)]. A hydroponic study, Phase I (0, 1, 2, and 4 mM Pb) was conducted followed by an incubation pot study, Phase II (0, 400, 800, and 1200 mg kg −1 Pb) where vetiver plants were colonized with G. mosseae. The results obtained indicate that plants colonized by the AM fungi not only exhibit better growth (increase in plant biomass), but also significantly increase Pb uptake in root and higher translocation to the shoot at all given treatments. Moreover, plants colonized with AM fungi had higher chlorophyll content and reduced levels of low molecular weight thiols, indicating the ability to better tolerate metal-induced stress. Results from this study indicate that vetiver plants in association with AM fungi can be used for improved phytoextraction of Pb from contaminated soil.

The objective of the present work was to study biochemical alterations in corn plants infected by the maize bushy stunt phytoplasma. A resistant and a susceptible corn hybrid were used and changes in protein, phenolic compounds, chlorophyll and reducing sugars in infected plants were evaluated. The experiments were carried out inside greenhouse, and the corn plants were inoculated by using infective Dalbulus maidis leafhoppers 10 days after seeding. When symptoms started to appear, leaf samples were harvested at different times for the biochemical analyses. The results showed an increase in all biochemical parameters evaluated for both hybrids, with exception for the chlorophyll content that decreased. In a general way, the values observed for the level of the different compounds were higher in the susceptible hybrid when compared to the resistant one. The increases in protein, reducing sugar and phenolic compound contents in inoculated plants point out changes in host metabolism due to the phytoplasma, and the reduction in chlorophyll content shows that the phytoplasma can interfere in photosynthesis and perhaps speedy senescence in the leaf tissue. q

Methyl parathion (MeP) is a very hazardous pesticide freely used in agriculture in Mexico. This pesticide and others, arriving through different processes, exert significant effects on water quality with serious consequences for environmental and human health. This study evaluates the removal efficiency of common cattail Typha latifolia L. on MeP in water and artificial sediments. The effects of the pesticide on this macrophyte after 10 days of exposure were determined using a concentration range of 0-200 mg l À1 , 198.1 ± 1.79 g average biomass, pH 7.0, 18-22°C temperature and natural daylight/darkness periods, using chlorophyll production as a biomarker. Removal kinetics were conducted under similar conditions on days 0, 3, 7, 9, 11 and 14 of exposure, using 6 mg l À1 in each system. Pesticide concentration, chlorophyll content and glutathione S-transferase (GST) activity were quantified. Results show a high removal efficiency of cattails on MeP in water and sediments relative to controls. An increase in GST activity and a decline in chlorophyll content in the test systems were not significantly different relative to controls. Cattails may thus be a good candidate for development of a phytoremediation system for MeP-contaminated water and artificial sediments.

The evolution of leaf area, root volume, chlorophyll content and peroxidase activity for some Romanian sunflower hybrids, under optimal and drought conditions was established. Five Romanian sunflower hybrids was grown in the greenhouse under two watering regimes for each genotype: control variant -in which plants were maintained at 70% from TSWC (total soil water capacity)] and stress treatment in which sunflower seedlings were irrigated no more than 40% from TSWC. The results showed that hydric stress induced the decrease of leaf area, shoot size, root volume, chlorophyll content and a significant increase of peroxidase activity. Some differences between the tested sunflower hybrids were registered. Also, a significant effect of hydric stress on fatty acid composition of seeds of sunflower plants was registered. In the normal sunflower hybrids, like the hybrids of this study, in addition to the reduction of oleic acid concentration, a simultaneous increase in the content of linoleic acid under drought conditions was registered.

Chlorophylls are the most abundant plant pigments in nature. Recent studies have shown that chlorophyll derivatives can exhibit healthpromoting activities, apart from their use as food and pharmaceutical colorants. Nevertheless, information regarding their absorption is almost inexistent. In the present model study with dogs the apparent absorption was calculated, based on chlorophyll content in food, minus the excreted chlorophyll, and the eventual appearance of any chlorophyll derivative in the bloodstream was investigated. Spinach was added to a commercial dog food and animals in the experimental group were held on this diet for 10 days. Chlorophylls a and b were transformed into their respective pheophytins during the G.I. passage. Beyond pheophytinization no other important degradation occurred. The apparent absorption of the chlorophyll derivatives ranged from 2.5 to 4.0%, with an average of 3.4%. In a second experiment, where dogs consumed a diet containing 10% dried spinach, no chlorophyll derivatives could be found in the peripheral blood until 150 min after consumption, which seems to evidence either their low absorption or their quick metabolization. Consequently, a low systemic exposure to chlorophylls or their derivatives is expected.

The effect of spent engine oil on the height, leaf number, leaf area, stem girth, chlorophyll, and moisture contents of Corchorus olitorius grown on 0, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 2.0%, and 3.0% (v/w oil/soil) oil-contaminated soil was investigated. The engine oil at all concentrations delayed the germination of C. olitorius by 2 days (compared to control) and there was a general significant reduction in all the growth parameters in plants grown on contaminated soil compared to control plants. The highest leaf area of 26.8 cm2 was found in the control plant and least was found in the 0.6% soil (0.11 cm2) after 3 weeks while no values were recorded on the 0.8–3.0% engine-oil-contaminated soil after 5 weeks of experiment. The highest chlorophyll content was also found in the control plant (11.5 mg/l). This showed that spent engine oil has an adverse effect on the growth of C. olitorius plant.

In wheat (Triticum aestivum L.) plants, deficiency of an essential element may drastically affect growth, appearance, and most importantly yield. Wheat, the focus of this study, is one of the crops studied in the CELSS program. Information about nutrient deficiencies in crops grown in controlled environment is essential to optimize food productivity. The main objective of this study was to determine whether deficiency of Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca) and Magnesium (M) alters spectral reflectance properties of wheat leaves. Plants were grown in the greenhouse and growth chamber, in a modified HoaglandÕs nutrient solution. Spectral reflectance of fully expanded wheat leaves from 280 to 1100 nm, nutrient concentrations (N, P, K, and Ca) and chlorophyll (Chl) were determined when deficiency symptoms were first evident (%6-7 weeks). Chlorophyll content and fresh and dry weight, were used to assess the severity of the nutrient stress. All nutrient deficiencies affected chlorophyll content and generally increased reflectance in the visible (VIS) 400-700 nm and infrared (IR) 700-1100 nm ranges. Magnesium and nitrogen deficiencies had the most pronounced effect on chlorophyll concentration height, and reflectance. All macronutrient deficiencies tested reduced chlorophyll concentration, increase reflectance in the visible range and caused a shift in the position of the red edge (the point of maximum slope on the reflectance spectrum of vegetation between red and near-infrared wavelengths) toward shorter or longer wavelengths; depending upon the element.

Leaf chlorophyll content in coniferous forest canopies, a measure of stand condition, is the target of studies and models linking leaf reflectance and transmittance and canopy hyperspectral reflectance imagery. The viability of estimation of needle chlorophyll content from airborne hyperspectral optical data through inversion of linked leaf level and canopy level radiative transfer models is discussed in this paper. This study is focused on five sites of Jack Pine (Pinus banksiana Lamb.) in the Algoma Region (Canada), where field, laboratory and airborne data were collected in 1998 and 1999 campaigns. Airborne hyperspectral CASI data of 72 bands in the visible and near-infrared region and 2 m spatial resolution were collected from 20 Â 20 m study sites of Jack Pine in 2 consecutive years. It was found that needle chlorophyll content could be estimated at the leaf level (r 2 = 0.4) by inversion of the PROSPECT leaf model from needle reflectance and transmittance spectra collected with a special needle carrier apparatus coupled to the Li-Cor 1800 integrating sphere. The Jack Pine forest stands used for this study with LAI > 2, and the high spatial resolution hyperspectral reflectance collected, allowed the use of the SPRINT canopy reflectance model coupled to PROSPECT for needle chlorophyll content estimation by model inversion. The optical index R750/ R710 was used as the merit function in the numerical inversion to minimize the effect of shadows and LAI variation in the mean canopy reflectance from the 20 Â 20 m plots. Estimates of needle pigment content from airborne hyperspectral reflectance using this linked leafcanopy model inversion methodology showed an r 2 = 0.4 and RMSE = 8.1 Ag/cm 2 when targeting sunlit crown pixels in Jack Pine sites with pigment content ranging between 26.8 and 56.8 Ag/cm 2 (1570 -3320 Ag/g).

Tetrastigma hemsleyanum Diels et Gilg was grown under full sunlight and moderate and high levels of shade for one month to evaluate its photosynthetic and chlorophyll fluorescence response to different light conditions. The results showed that T. hemsleyanum attained greatest leaf size and P n when cultivated with 67% shade. Leaves of seedlings grown with 90% shade were the smallest. Leaf color of plants grown under full sunlight and 50% shade was yellowish-green. The P n value increased rapidly as PPFD increased to 200 mol m −2 s −1 and then increased slowly to a maximum, followed by a slow decrease as PPFD was increased to 1000 mol m −2 s −1 . P n was highest for the 67% shade treatment and the LSP for this shade treatment was 600 mol m −2 s −1 . Full sunlight and 50% shade treatments resulted in significant reduction of ETR and qP and increased NPQ. Chl a, Chl b and total chlorophyll content increased and Chl a/b values decreased with increased shading. Results showed that light intensity greater than that of 50% shade depressed photosynthetic activity and T. hemsleyanum growth. Irradiance less than that of 75% shade limited carbon assimilation and led to decreased plant growth. Approximately 67% shade is suggested to be the optimum light irradiance condition for T. hemsleyanum cultivation.

The effect of three shade levels on morphology, growth and productivity of 'Grand Nain' (AAA) bananas during their first and second production cycles was studied in the Jordan Valley, Israel. In vitro propagated plants that were planted in the field in April 1990 were shaded with black Saran screens of different densities, installed above the canopy level. The resultant photosynthetic photon flux density (PPFD) was reduced to 80%, 60% or 30% of the unshaded control. Although only the heaviest shade affected plant vegetative growth in the first cycle, bunch weight was reduced by 7% and 32% under medium and heavy shade, respectively. A highly significant effect on vegetative growth and production was observed during the second cycle. Flowering date was delayed by 6 days, 9 days and 15 days, and bunch weight was reduced by 8%, 21% and 55% under light, medium and heavy shade, respectively. Yield was reduced by all levels of shade, owing to the combined effect of reduced bunch weight and a lower stand. Shading reduced the rate of leaf emergence, leaf and foliage area, plant height and pseudostem circumference. The leaves had thinner laminae, with a reduced number of stomata and higher chlorophyll content. Our observations indicate a significant effect of long-term shade on bananas, and the utilization of high levels of PPFD by the banana plant. * Corresponding author. 0304-4238/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDIO304-4238(95)00763-6

Central broccoli heads (cv. de Cicco) were harvested and treated with UV-C light (4, 7, 10, or 14 kJ m −2). All treatments delayed yellowing and chlorophyll degradation at 20 • C but the irradiation dose of 10 kJ m −2 allowed retaining the highest chlorophyll content yet had lower amounts of pheophytins than every treatment other than 7 kJ m −2. This dose was selected to analyze the effect of UV-C on postharvest broccoli senescence at 20 • C. The UV-C treatment delayed yellowing, chlorophyll a and b degradation, and also the increase in pheophytins during storage. The activity of chlorophyll peroxidase and chlorophyllase was lower in UV-C treated broccoli. Instead, Mg-dechelatase activity increased immediately after the treatment, but after 4 and 6 d this activity was lower in UV-C treated florets than in controls. Treated broccoli also displayed lower respiration rate, total phenols and flavonoids, along with higher antioxidant capacity. The results suggest that UV-C treatments could be a useful non-chemical method to delay chlorophyll degradation, reduce tissue damage and disruption, and maintain antioxidant capacity in broccoli.

The objective of this study was to examine the role of root carbohydrate levels and metabolism in the waterlogging tolerance of contrasting pigeon pea genotypes. An experiment was conducted with 4 pigeon pea (Cajanus cajan) genotypes, 2 tolerant (ICPL 84023 and ICP 301) and 2 susceptible (ICP 7035 and Pusa 207) to waterlogging stress. Waterlogging treatment was given by placing pots with 25 days old plants in plastic troughs filled with water. Waterlogging resulted in decrease in leaf area, dry matter, relative water content and chlorophyll content in leaves, and membrane stability index in root and leaf tissues. The decline was greater in ICP 7035 and Pusa 207, which also suffered almost 100% mortality during recovery of 6 days waterlogged plants, than ICPL 84023 and ICP 301. Tolerant genotypes ICPL 84023 and ICP 301 showed higher total, reducing and non-reducing sugars content than ICP 7035 and Pusa 207. Waterlogging resulted in decline in total and non-reducing sugars in all the genotypes and reducing sugars in ICP 7035 and Pusa 207, while the content of reducing sugars increased in ICPL 84023 and ICP 301. The pattern of variation in reducing sugar content in the 4 genotypes was parallel to sucrose synthase activity. ICPL 84023 and ICP 301 also showed fewer declines in total and non-reducing sugars and greater increase in reducing sugar and sucrose synthase (SuSy) activity than ICP 7035 and Pusa 207. Waterlogging resulted in increase in alcohol dehydrogenase (ADH) activity, and increase was higher in ICPL 84023 and ICP 301 than ICP 7035 and Pusa 207. Gene expression studies done by RT-PCR under 24 h waterlogging showed enhanced expression of ADH and SuSy in the roots of ICPL 84023, while in ICP 7035 there was no change in expression level in control or treated plants. The susceptible genotype ICP 7035 showed mutation in the CAAT box region of the ADH promoter, which could be the possible reason of lower ADH gene expression, activity and sensitivity to waterlogging. The results suggest that waterlogging tolerance of pigeon pea genotypes ICPL 84023 and ICP 301 depends on the availability of sufficient sugar reserve in the roots, activity of sucrose synthase to provide reducing sugars for glycolytic activity and ADH for the recycling of NADH for the continuation of glycolysis, the major source of energy under hypoxia. This was reflected in better RWC and Chl content in leaves, and membrane stability of leaf and root tissue in ICPL 84023 and ICP 301.

Chlorophyll is a pigment used as colorant in the food, pharmaceutical and cosmetic industries. It can be obtained in considerable quantities from Spirulina platensis biomass. In this work, the cultivation of the microalga was done using urea as the nitrogen source by a fed-batch process. The addition of urea was done in four di erent modes: intermittent addition every 24 or 48 h, continuous addition by exponentially increasing the added mass, and continuous addition by using a constant mass ow rate. The experiments were carried out at three di erent temperatures: 27 • C; 30 • C and 33 • C and at a constant light intensity of 3:5 klx. The results showed a positive in uence of urea in the growth of Spirulina but no e ect on the ÿnal chlorophyll content of the cultures. Best results were obtained by continuous urea addition in exponentially increasing amount, at 30 • C. ?

Different nitrogen (N) treatments of four common green-leafy vegetable varieties with different leaf color: lettuce (Lactuca sativa L. var. crispa L.) with yellow green leaves, pakchoi (Brassica chinensis L.) var. aijiaohuang in Chinese (AJH) with middle green leaves, spinach (Spinacia oleracea L.) with green leaves and pakchoi (B. chinensis L.) var. shanghaiqing in Chinese (SHQ) with dark green leaves, were carried out to achieve a wide range of chlorophyll content. The relationship of vegetable leaf hyperspectral response to its chlorophyll content was examined in this study. Almost all reported successful leaf chlorophyll indices in the literature were evaluated for their ability to predict the chlorophyll content in vegetable leaves. Some new indices based on the first derivative curve were also developed, and compared with the chlorophyll indices published. The results showed that most of the indices showed a strong relation with leaf chlorophyll content. In general, modified indices with the blue or near red edge wavelength performed better than their simple counterpart without modification, ratio indices performed a little better than normalized indices when chlorophyll expressed on area basis and reversed when chlorophyll expressed on fresh weight basis. A normalized derivative difference ratio (BND: (D 722 − D 700 )/(D 722 + D 700 ) calibrated by Maire et al. [Maire, G., Francois, C., Dufrene, E., 2004. Towards universal broad leaf chlorophyll indices using PROSPECT simulated database and hyperspectral reflectance measurements. Remote Sensing of Environment 89 (1), 1-28]) gave the best results among all published indices in this study (RMSE = 22.1 mg m −2 ), then the mSR-like indices with the RMSE between 22.6 and 23.0 mg m −2 .

This paper outlines the first part of a series of research studies to investigate the potential and approaches for using optical remote sensing to assess vegetation water content. It first analyzes why most methods used as approximations of vegetation water content (such as vegetation stress indices, estimation of degree of curing and chlorophyll content) are not suitable for retrieving water

While temperature management is a usual accepted practice and is the simplest and easiest way of delaying vegetable deterioration, maintenance of the recommended relative humidity (RH) during postharvest storage is not always carried out. The objectives of this work were to simulate two RH conditions: optimal (95-98%) and low (70-72%) during the storage of lettuce heads at recommended temperatures (0-2 • C), and to address how deviation of RH from optimal conditions affects lettuce quality indices. The effects of storage on quality parameters were assayed as follows: weight loss and water content as physical indices, chlorophyll content as a greenness index, native microflora (mesophilic bacteria, psychrotrophic bacteria, lactic acid bacteria, total coliforms, yeast and molds) as microbiological quality indices, ascorbic acid retention as a nutritional quality index, and overall quality as a sensory acceptability index. Additionally, these indices (with the exception of weight loss) were analyzed in three lettuce sections: external (composed by outer and older leaves), middle (composed by mid leaves) and internal (composed by inner and younger leaves). Shelf-life of lettuce was significantly affected by RH. The exposure of lettuce heads to low RH drastically reduced shelf-life by 75%. Plants exposed to low RH had considerable weight loss from the first day to the end of storage. For both RHs, the middle and internal sections did not show chlorophyll changes during storage while the external section showed pigment degradation characterized by first order kinetics. Ascorbic acid underwent first order degradation for all situations (sections and RH conditions), but with different degradation rates. The microbial population counts were slightly affected by RH. The overall quality of lettuce stored at low RH decreased rapidly. The shelf-life of material stored at this relative humidity condition was 5 days, when the overall quality scores of middle and external sections were below the acceptability limit and only the internal section had a score above the limit. In addition, overall quality of lettuce stored at optimal RH decreased slowly. At day 5 of storage the three lettuce sections had high scores and the product was satisfactory. Only at day 20 did the external section show a score just on the acceptability limit.

Drought is a major abiotic stress that severely affects food production worldwide. Agronomic and physiological traits associated with drought tolerance are suitable indicators for selection of drought tolerance genotypes to reduce the impact of water deficit on crop yield in breeding program. The objective of this study was to identify indicators related to drought tolerance through analysis of photosynthetic traits in barley (Hordeurn vulgare L.). These traits included chlorophyll content, initial fluorescence (F,), maximum primary yield of photochemistry of photosystem 11 (F, / F,) and maximum quantum yield of photosystem I1 (Fv/Fm). Four genotypes (Tadmor, Arta, Morocco9-75 and WI2291) variable in drought tolerance were used to investigate the correlation between these traits and drought tolerance. The results reflected that all of these traits were affected negatively in the four genotypes at different levels of post-anthesis drought stress, but the decrease in drought tolerant genotypes was much less than that of drought sensitive genotypes. The results further revealed that the components of the photosynthetic apparatus could be damaged significantly in drought sensitive genotypes, while drought tolerant genotypes were relatively less affected. On the other hand, the values of chlorophyll content, F,, F,/F, and F,/F, in drought tolerance genotypes were significantly higher than those in drought sensitive genotypes under drought stress. It was concluded that chlorophyll content, F,, F,/F, and F,/F, could be considered as reliable indicators in screening barley germplasm for drought tolerance.

Okra, Abelmoschus esculentus (L.) Moench, is attacked by the adult chrysomelid flea beetles, Podagrica spp. Information on physiological disruptions that occur due to flea beetle infestation affecting okra yield loss is incomplete. Screenhouse and field experiments were established to examine the effects of insect populations on leaf abscission, chlorophyll concentration, and biomass partitioning. Okra plants were grown in wire mesh screen cages and artificially infested with flea beetles, P. uniforma Jac., at population densities of 0, 5, 10, 20, 30, and 40 pairs per plant at 3 weeks after sowing (1 pair = 1 male and 1 female). In both experiments, okra plants had increased leaf abscission up to 100% at the 40-pair level in response to P. uniforma-induced injury. There were no significant differences in chlorophyll concentrations of plants at 0-, 5-, and 10-pair levels of infestation, suggesting the use of a compensatory mechanism by plants; at the 20-pair level a significant reduction occurred. Number of leaves per plant, shoots, roots, and dry fruit and total dry matter yield were reduced with infestation above the 20-pair level. More biomass was partitioned into roots at the 5-and 10-pair levels, but insect damage at populations beyond these levels completely suppressed the plant's ability to partition biomass. Dry fruit yields were reduced more than 50% when beetle populations increased beyond 20 pairs in both experiments. There was a correlation between insect density and number of leaves per plant and shoot, root, dry

Two critical limitations for using current satellite sensors in real-time crop management are the lack of imagery with optimum spatial and spectral resolutions and an unfavorable revisit time for most crop stress-detection applications. Alternatives based on manned airborne platforms are lacking due to their high operational costs. A fundamental requirement for providing useful remote sensing products in agriculture is the capacity to combine high spatial resolution and quick turnaround times. Remote sensing sensors placed on unmanned aerial vehicles (UAVs) could fill this gap, providing low-cost approaches to meet the critical requirements of spatial, spectral, and temporal resolutions. This paper demonstrates the ability to generate quantitative remote sensing products by means of a helicopter-based UAV equipped with inexpensive thermal and narrowband multispectral imaging sensors. During summer of 2007, the platform was flown over agricultural fields, obtaining thermal imagery in the 7.5-13-μm region (40-cm resolution) and narrowband multispectral imagery in the 400-800-nm spectral region (20-cm resolution). Surface reflectance and temperature imagery were obtained, after atmospheric corrections with MODTRAN. Biophysical parameters were estimated using vegetation indices, namely, normalized difference vegetation index, transformed chlorophyll absorption in reflectance index/optimized soil-adjusted vegetation index, and photochemical reflectance index (PRI), coupled with SAILH and FLIGHT models. As a result, the image products of leaf area index, chlorophyll content (C ab ), and water stress detection from PRI index and canopy temperature were produced and successfully validated. This paper demonstrates that results obtained with a low-cost UAV system for agricultural applications yielded comparable estimations, if not better, than those obtained by traditional manned airborne sensors. at 18:50 from IEEE Xplore. Restrictions apply. Jose A. J. Berni (S'07) received the degree in agricultural engineering from the Faculty of Agricultural Engineering and Forestry, University of Córdoba, Córdoba, Spain. He is currently working toward the Ph.D. degree in remote sensing and plant water management at the Institute for Sustainable Agriculture, Spanish Council for Scientific Research, Córdoba.

A pot experiment was carried out to study the effect of lead and chromium on growth, chlorophyll contents and yield components in two mash bean [Vigna mungo (L.) Hepper] cultivars i.e. Fs-1 and Mash-97. Fourteen-day old plants were exposed to 20 or 40 mg L -1 lead or chromium whereas control plants were treated with distilled water only. Application of both lead and chromium caused a significant reduction in all growth parameters as compared with that of control. The extent of decrease in growth due to chromium compared with lead. Although high concentration of both metals in the rooting media drastically reduced all photosynthetic pigments, chromium application caused more reducing effect as compared to chromium. In addition, all yield attributes of both cultivars of mash bean reduced due to both metals in rooting medium. The sensitivity of mash bean to chromium was greater as compared to lead. In conclusion, mash bean cultivar FS-1 proved to be tolerant as it showed less reduction in growth, photosynthetic pigments and yield as compared to Mash-97.

Quantifying photosynthetic activity at the regional scale can provide important information to resource managers, planners and global ecosystem modelling efforts. With increasing availability of both hyperspectral and narrow band multispectral remote sensing data, new users are faced with a plethora of options when choosing an optical index to relate to their chosen leaf or canopy parameter. The literature base regarding optical indices (particularly chlorophyll indices) is wide ranging and extensive, however it is without much consensus regarding robust indices. The wider spectral community could benefit from studies that apply a variety of published indices to differing sets of species data. The consistency and robustness of 73 published chlorophyll spectral indices have been assessed, using leaf level hyperspectral data collected from three crop species and a variety of savanna tree species. Linear regression between total leaf chlorophyll content and bootstrapping were used to determine the predictive capabilities of the various indices. The indices were then ranked based on the prediction error (the average root mean square error (RMSE)) derived from the bootstrapping process involving 1000 iterative resampling with replacement. The results show two red-edge derivative based indices (Red-edge position via linear extrapolation index and the modified red-edge inflection point index) as the most consistent and robust, and that the majority of the top performing indices (in spite of species variability) were simple ratio or normalised difference indices that are based on off-chlorophyll absorption centre wavebands (690 -730 nm).

The aim of this study was to access the bioassociative effect of two rhizospheric Pseudomonas spp. with effective root nodulating symbiotic nitrogen fixer Rhizobium leguminosarum-PR1 on plant growth and nutrients uptake of lentil (Lens culinaris L.) plant under greenhouse conditions. Lentil seeds of variety VL Masoor 507 were inoculated with two cold tolerant Pseudomonas sp. strains (NARs1, PGERs17) and R. leguminosarum-PR1, individually or in combination, and were grown in pots using nonsterile sandy loam Entisol. Inoculation with Pseudomonas sp. strain PGERs17 exhibits more vigorous vegetative growth with increase in nodulation (55.0%), leghaemoglobin content (27.7%), physiologically available iron (24.1%), total iron (90.7%) chlorophyll content (43.9%), P uptake (37.1%) and N uptake (27.1%) over R. leguminosarum-PR1 alone at 60 days after sowing (DAS). Coinoculation of Pseudomonas sp. strain NARs1 with R. leguminosarum-PR1 recorded maximum increase in the nodulation 27.5, leghaemoglobin content-45.9, total iron-115.7, total chlorophyll content-21.3, N uptake-52.1 and P uptake-88.9% over R. leguminosarum-PR1 alone at 60 DAS, which suggest that a strong selective synergistic relationship existed between cold tolerant Pseudomonas sp. strain NARs1 and R. leguminosarum-PR1. The variations in efficacy of different treatment combinations indicate the specificity of the inoculation response. These results provide a basis for the selection of an appropriate combination of specific Pseudomonas sp. and R. leguminosarum which could further be utilized for verifying the symbiotic effectiveness and competitive ability of microsymbionts under field condition of hill agro ecosystem.

A neural network is developed to operationally estimate biophysical variables over land surfaces from the observations of the ENVISAT-MERIS instrument: the leaf area index (LAI), the fraction of absorbed photosynthetically active radiation ( fAPAR), the fraction of vegetation cover (fCover), and the canopy chlorophyll content (LAI×C ab ). The neural network requires as input the geometry of observation and the top of canopy reflectances, corrected from the atmospheric effects, in eleven spectral bands. It is trained on a reflectance database made of radiative transfer model simulations. The principles underlying the generation of the database and the design of the network are first presented. The estimated variables are then compared to other existing products, LAI-and fAPAR-MODIS and MGVI-MERIS, and validated against ground measurements performed in the framework of the VALERI project. Results show remarkable consistency of the temporal dynamics between the several products with however some differences in the range of variation. When compared to actual VALERI ground measurements, the proposed algorithm shows the best performances for LAI (RMSE = 0.47) and fAPAR (RMSE = 0.09).

Large-scale experimental exclusion of lugworms (Arenicola marina) from 400 m 2 intertidal fine sand revealed significant effects of their bioturbation and bioirrigation on sediment characteristics, benthic infauna composition, and the dominant mineralization and benthic-pelagic exchange processes in the sediment. Absence of lugworms resulted in sediment clogging with organic-rich fine particles, an eightfold decrease in sediment permeability, low oxygen penetration depths, and accumulation of reduced mineralization products in the pore water. The sand flat inhabited by lugworms had low fine-particle and chlorophyll contents and low sulfide and nutrient concentrations in the pore water. The effects were not limited to the vicinity of lugworm burrows but extended throughout the entire sediment down to ,20-cm depth. Sediments with the lugworm shared the characteristic of low-organic, advection-driven permeable sand rather than of muddy, diffusion-dominated sediments in the absence of lugworms. Areal oxygen uptake rates depended strongly on hydrodynamic conditions: under calm conditions, sedimentary oxygen uptake was slightly higher at the exclusion site. Experimental flushing using controlled hydrodynamic conditions showed that oxygen uptake at the lugworm site would be higher during more dynamic conditions (e.g., storms) due to significantly deeper oxygen penetration permitted by higher sediment permeability. Our results indicate an interactive effect of bioturbating organisms and hydrodynamics on water-sediment exchange processes and highlight the importance of benthic infauna for sedimentary processes even in physically dominated systems.

The effects of NaCl stress on the activity of antioxidant enzyme such as superoxide dismutase (SOD: EC 1.15.1.1), peroxidase (POD: EC 1.11.1.7), glutathione reductase (GR: EC 1.6.4.2), rate of lipid peroxidation, gas-exchange, chlorophyll content and chlorophyll fluorescence were investigated in two cotton cultivars, Guazuncho and Pora (hybrids between Gossypium hirsutum×G. arboretum×G. raimondii) grown in nutrient solution. Plants were treated with three salt concentrations (50, 100 and 200 mol m−3 NaCl) for 21 days. The SOD activity in Pora increases with the increase in the intensity of NaCl stress, but salt treatment had no significant effect on this enzyme activity in Guazuncho. The POD and GR activities showed similar trends under salt stress, in both cotton cultivars. In Pora, there was an average increase in GR activity of about 53%, but there was no further increase at higher NaCl concentrations. In Guazuncho, no change in GR activity was observed. Net photosynthesis and stomatal conductance decreased in response to salt stress, but Pora showed a smaller reduction in photosynthesis than Guazuncho. The results indicated that stomatal aperture limited leaf photosynthetic capacity in the NaCl-treated plants of both cultivars. However, significant reduction in the leaf chlorophyll contents due to NaCl stress was observed only on Guazuncho. In both cotton cultivars, the photochemical efficiency of PSII was not affected by salt stress. These results suggest that salt-tolerant cotton varieties may have a better protection against reactive oxygen species (ROS) by increasing the activity of antioxidant enzymes under salt stress.

A growing number of studies have focused on evaluating spectral indices in terms of their sensitivity to vegetation biophysical parameters, as well as to external factors affecting canopy reflectance. In this context, leaf and canopy radiative transfer models are valuable for modeling and understanding the behavior of such indices. In the present work, PROSPECT and SAILH models have been used to simulate a wide range of crop canopy reflectances in an attempt to study the sensitivity of a set of vegetation indices to green leaf area index (LAI), and to modify some of them in order to enhance their responsivity to LAI variations. The aim of the paper was to present a method for minimizing the effect of leaf chlorophyll content on the prediction of green LAI, and to develop new algorithms that adequately predict the LAI of crop canopies. Analyses based on both simulated and real hyperspectral data were carried out to compare performances of existing vegetation indices Normalized Difference Vegetation Index [NDVI], Renormalized Difference Vegetation Index [RDVI], Modified Simple Ratio [MSR], Soil-Adjusted Vegetation Index [SAVI], Soil and Atmospherically Resistant Vegetation Index [SARVI], MSAVI, Triangular Vegetation Index [TVI], and Modified Chlorophyll Absorption Ratio Index [MCARI]