Photosynthetic Pigment

The time dependence of photobleaching of photosynthetic pigments under high light illumination of isolated spinach thylakoid membranes at 22 and 4 8C was investigated. At 22 8C, the bleaching at 678, 472 and 436 nm was prominent but lowering the temperature up to 4 8C during illumination prevented the pigments from bleaching almost completely. The accelerating effect on pigment photobleaching by the presence of 3-(3,4 dichlorophenyl)-1,1dimethyl-urea)-(DCMU), a well-known inhibitor of the electron transport and known to prevent photosystem I (PSI) and photosystem II (PSII) against photoinhibitory damage, was also suppressed at low temperature. At 22 8C in the presence and absence of DCMU, the decrease of the absorption at 678 and 472 nm was accompanied by a shift to the shorter wavelengths. To check the involvement of reactive oxygen species in the process, pigment photobleaching was followed in anaerobiosis. The effects of the three different environmental factors-light, temperature and DCMU-on the dynamics of photobleaching are discussed in terms of different susceptibility of the main pigment-protein complexes to photoinhibition. ᮊ

PROSPECT, a widely-used leaf directional-hemispherical reflectance and transmittance model, currently treats the behaviour of chlorophylls a, b, carotenoids, and anthocyanins uniformly, leading to errors. A finer discrimination among these pigments in lightabsorbing plant tissues should improve the model. In this paper, a new calibration and validation phase of PROSPECT is performed using two comprehensive databases containing hundreds of leaves collected in temperate latitudes in Angers, France, and in a tropical environment in Hawaii, USA. Leaf biochemical (chlorophylls a, b, carotenoids, water, and dry matter) and optical properties (directional-hemispherical reflectance and transmittance measured from 400 nm to 2500 nm) were measured and used in the model development steps. The first step consists in providing distinct in vivo specific absorption coefficients for the leaf pigments using the Angers database. The model is then inverted to predict the biochemical content of intact ...

Elevated ultraviolet irradiance (UVR, 280-400 nm) damages DNA and induces reorganisation within biological communities at the Earth's surface. Southern high latitude aquatic ecosystems may be particularly susceptible because of low stratospheric ozone levels and extremely low contents of photoprotective dissolved organic matter (DOM). Surveys of shallow lakes and ponds in eastern Antarctica show that cyanobacteria survive elevated UVR exposure by increasing extra-cellular concentrations of photoprotective compounds, which are preserved in sediments together with photosynthetic pigments. Thus, reconstruction of long-term changes in biological UVR receipt, to provide a context for evaluating the long-term significance of recent changes in ozone column depth, is feasible in Antarctic settings. The sediment in Lake Reid (698 23V S, 768 53V E), Antarctica, spans the late-Pleistocene and contains UVR-absorbing pigments from benthic cyanobacteria. Here we show that mean exposure of these benthic cyanobacteria to UVR during the last glacial was more than three times higher than during the Holocene, likely due to short periods of photosynthetic activity coinciding with relatively high UVR fluxes, or due to increased UVR transmission to the Earth's surface resulting from changes in external factors such as stratospheric ozone levels, cloud cover and surface albedo. D

The photosynthetic performance and pigment content of Gracilaria chilensis Bird, McLachlan, and Oliveira were measured under natural solar radiation in the Quempillen river estuary (southern Chile) in order to assess the short-term acclimation of this species to the current levels of ultraviolet (UV) radiation during midsummer. The effect of the tidal fluctuation was evaluated in algae exposed for 3 days to two light climates in cages suspended at two depths (0.5 and 1.5 m from the bottom). Responses to high solar radiation at noon were also assessed to gain insights into rapid photochemical kinetics and the degree of photoinhibition. Results indicated that G. chilensis is a shade-adapted species with a high content of photosynthetic pigments (Chl a and phycobilins), high quantum efficiency (a), and low light saturating point (E k ) between 60 and 170 Amol m À2 s À1 reflecting the high turbidity and marked light attenuation (K d ) of both UV and photosynthetically active radiation (PAR): 1% of the UVB radiation (280-320 nm) reaches 1.8 m depth only during high tide, whereas during ebb tide, UVB can only be detected at 30 cm depth. In the case of PAR, 1% penetration depth was close to 2.7 m during low tide. Under these conditions decreases in rates of photosynthesis at noon did not exceed 23%, even in the presence of UVB. When algae were exposed to full solar radiation at noon for 3 h and then incubated under shaded conditions for recovery, evidence for photoinhibition was observed: in algae exposed to PAR+UVA+UVB, photosynthesis decreased by 16%, while recovery was close to 88% of the control. In treatments deprived of UVB, recovery was close to 100%. These results suggest that G. chilensis is not commonly exposed to high irradiances in the field and that UVB is potentially detrimental for photosynthesis when algae are maintained close to the surface, at least during summer. This was corroborated by the low content of UV-absorbing compounds (mycosporine-like amino acids, or MAAs; between 0.89 and 1.75 mg g DW).

Vetiver grass (Vetiveria zizanioides) has been widely confirmed to have very strong tolerance to flooding and even complete submergence and, therefore, is a considerably excellent species for stabilization and revegetation of "wet" barren slopes and for wastewater treatment. However, it is poorly documented why vetiver is so tolerant to submergence. To understand the mechanisms of vetiver's tolerance to submergence, an

The south-American cordgrass, Spartina densiflora, has become the dominant plant species on recent tidal marsh restorations in the Doñ ana National Park (SW Spain). We examined the effect of different doses of glyphosate (720-7200 g a.i. ha À1 ) and imazamox (20-68 g a.i. ha À1 ) on growth and photosynthetic apparatus of S. densiflora. Imazamox had no effect on neither on growth nor photosynthetic apparatus of S. densiflora. On the contrary, glyphosate inhibited photochemical efficiency of photosynthesis from day one. Net photosynthetic rate, stomatal conductance and photosynthetic pigments and the number of new tillers were reduced. Glyphosate at high doses (ca. 7200 g a.i. ha À1 ) could be an appropriate method of control, since it has a negative effect over the photosynthetic apparatus and growth of S. densiflora. Furthermore, glyphosate and its main metabolite, AMPA, were not extracted from the soil, since they were retained by the very high iron and aluminum oxide content of this soil.

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.

The response to molybdenum (Mo) was studied in the metal-tolerant hydrophyte Trapa natans L. Previously, it was shown that the plant accumulates Mn in the floating lamina by means of phenolic compounds and responded with acclimation responses of the chloroplast. Since the involvement of phenolics has been proposed also in Mo resistance, we tested the response of T. natans to increasing doses (5, 50, 150, 600 µM) of Mo using the photosynthetic apparatus as an indicator of cellular stress. Only 5 μM Mo did not cause evident modifications with respect to controls. Conversely, 50 to 600 μM Mo induced progressively marked alterations of the lamina morphology. The chloroplast ultrastructure showed disorganisation of the thylakoid system, and correspondingly, the photosynthetic pigment pattern was altered with a fall-down in photosynthesis. Microspectrofluorimetry indicated alterations of photosystem II, with differences among the three cell layers (first and second palisade and spongy tissues). While the highest dose caused plant death, 50 and 150 μM Mo-treated plants underwent partial recovery, and the plant survived up to the end of the vegetative season. However, reproduction was unsuccessful. Mo treatment did not induce increase in total phenolics, but only in anthocyanin. In contrast to Mn, detoxification of Mo by chelation inside vacuoles, possibly by anthocyanins, is suggested to be an insufficient mechanism to reduce Mo toxicity, which probably includes an impairment of nitrogen metabolism. However, the metal was accumulated in the lamina. On the whole, T. natans showed limited capabilities to survive Mo excess as compared with Mn.

Experiments were conducted on tomato to study the potential of brown alga Sargassum johnstonii as a biofertilizer. Seaweed extract was applied as a foliar spray, soil drench, and soil drench + foliar spray to assess its effect on plant growth, yield, and concentration of lycopene and vitamin C. The main objective of the study was to enhance the biochemical constituents with neutraceutical and antioxidant values in tomato fruit. Different concentrations (0.1%, 0.4%, 0.8%, 2%, 6%, 8%, and 10%; v/v) of seaweed extract were used and growth was observed over a period of 7 months. A total of 14 sprays/drenches were applied at 15-day intervals during the entire vegetative and reproductive phase. A statistically significant increase in vegetative growth (plant height, shoot length, root length, and number of branches), reproductive parameters (flower number, fruit number, and fresh weight), and biochemical constituents (photosynthetic pigments, proteins, total soluble sugars, reducing sugars, starch, phenols, lycopene, and vitamin C) was recorded following all three methods of treatment at higher concentrations of seaweed extract. The study also reports auxin- and cytokinin-like activity, and the presence of macro- (Ca, Mg, Na, and K) and micronutrients (Fe, Cu, Zn, and Mn), in seaweed extract of S. johnstonii, which makes it a potential biofertilizer.

Plant growth and productivity is adversely affected by nature's wrath in the form of various biotic and abiotic stress factors. Water deficit is one of the major abiotic stresses, which adversely affects crop growth and yield. These changes are mainly related to altered metabolic functions, one of those is either loss of or reduced synthesis of photosynthetic pigments. This results in declined light harvesting and generation of reducing powers, which are a source of energy for dark reactions of photosynthesis. These changes in the amounts of photosynthetic pigments are closely associated to plant biomass yield. This review describes some aspects of drought induced changes in morphological, physiological and pigments composition in higher plants.

Salt-induced changes in growth, photosynthetic pigments, various gas exchange characteristics, relative membrane permeability (RMP), relative water content (RWC) and ion accumulation were examined in a greenhouse experiment on eight sunflower (Helianthus annuus L.) cultivars. Sunflower cultivars, namely Hysun-33, Hysun-38, M-3260, S-278, Alstar-Rm, Nstt-160, Mehran-II and Brocar were subjected to non-stress (0 mM NaCl) or salt stress (150 mM NaCl) in sand culture. On the basis of percent reduction in shoot biomass, cvs. Hysun-38 and Nstt-160 were found to be salt tolerant, cvs. Hysun-33, M-3260, S-278 and Mehran-II moderately tolerant and Alstar-Rm and Brocar salt sensitive. Salt stress markedly reduced growth, different gas exchange characteristics such as photosynthetic rate (A), water-use efficiency (WUE) calculated as A/E, transpiration rate (E), internal CO 2 concentration (C i ) and stomatal conductance (g s ) in all cultivars. The effect of 150 mM NaCl stress was non-significant on chlorophyll a and b contents, chlorophyll a/b ratio, RWC, RMP and leaf and root Cl -, K ? and P contents; however, salt stress markedly enhanced C i /C a ratio, free proline content and leaf and root Na ? concentrations in all sunflower cultivars. Of all cultivars, cv. Hysun-38 was higher in gas exchange characteristics, RWC and proline contents as compared with the other cultivars. Overall, none of the earlier-mentioned physiological attributes except leaf K ? /Na ? ratio was found to be effective in discriminating the eight sunflower cultivars as the response of each cultivar to salt stress appraised using various physiological attributes was cultivar-specific.

The red algae (Rhodophyta) form a distinct photosynthetic eukaryotic lineage that consists of around 6,000 species including unicellular to large multicellular taxa (http://www.algaebase.org/). The red algae are unique among eukaryotes in lacking both flagella and centrioles during their entire life cycle (Gabrielson et al., 1990; Graham and Wilcox, 2000). Pit connections, pit plugs, and a triphasic life cycle that are mostly found in the Florideophyceae are also distinguishing characters of the red algae. The photosynthetic organelle (plastid) of red algae is bounded by two membranes and contains chlorophyll-a, phycocyanin, and phycoerythrin as photosynthetic pigments. These pigment complexes, organized in phycobilisomes, are located on the surface of unstacked thylakoid membranes to capture light energy. As a storage product, the red algae produce granulated floridean starch in the cytoplasm that is different from green algal starch. In addition to these unique features, the monop...

Bleaching of corals by loss of symbiotic dinoflagellate algae and/or photosynthetic pigments is commonly triggered by elevated temperatures coupled with high irradiance, and is a first-order threat to coral reef communities. In this study, a high-resolution high-performance liquid chromatography method integrated with mass spectrometry was applied to obtain the first definitive identification of chlorophyll and carotenoid pigments of three clades of symbiotic dinoflagellate algae ( Symbiodinium ) in corals, and their response to experimentally elevated temperature and irradiance. The carotenoids peridinin, dinoxanthin, diadinoxanthin (Dn), diatoxanthin (Dt) and b -carotene were detected, together with chlorophylls a and c 2 , and phaeophytin a , in all three algal clades in unstressed corals. On exposure to elevated temperature and irradiance, three coral species ( Montastrea franksi and Favia fragum with clade B algae, and Montastrea cavernosa with clade C) bleached by loss of 50-80% of their algal cells, with no significant impact to chlorophyll a or c 2 , or peridinin in retained algal cells. One species ( Agaricia sp. with clade C) showed no significant reduction in algal cells at elevated temperature and irradiance, but lost substantial amounts of chlorophyll a and carotenoid pigments, presumably through photo-oxidative processes. Two coral species ( Porites astreoides and Porites porites both bearing clade A algae) did not bleach. The impact of elevated temperature and irradiance on the levels of the photoprotective xanthophylls (Dn + Dt) and b -carotene varied among the corals, both in pool size and xanthophyll cycling, and was not correlated to coral bleaching resistance.

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.

The photophysical and photochemical reactions, after light absorption by a photosynthetic pigmentprotein complex, are among the fastest events in biology, taking place on timescales ranging from tens of femtoseconds to a few nanoseconds. The advent of ultrafast laser systems that produce pulses with femtosecond duration opened up a new area of research and enabled investigation of these photophysical and photochemical reactions in real time. Here, we provide a basic description of the ultrafast transient absorption technique, the laser and wavelengthconversion equipment, the transient absorption setup, and the collection of transient absorption data. Recent applications of ultrafast transient absorption spectroscopy on systems with increasing degree of complexity, from biomimetic light-harvesting systems to natural light-harvesting antennas, are presented. In particular, we will discuss, in this educational review, how a molecular understanding of the light-harvesting and photoprotective functions of carotenoids in photosynthesis is accomplished through the application of ultrafast transient absorption spectroscopy.

The pigment compositions of 37 species (65 strains) of cultured haptophytes were analysed using improved HPLC methods. We distinguished 8 pigment types based on the distribution of 9 chlorophyll c (chl c) pigments and 5 fucoxanthin derivatives. All types contained chl c 2 and Mg-2, 4-divinyl phaeoporphyrin a 5 monomethyl ester (MgDVP), fucoxanthin, diadinoxanthin and β,βcarotene. Pigment types were based on the following additional pigments: Type 1: chl c 1 ; Type 2: chl c 1 and chl c 2 -Pavlova gyrans-type; Type 3: chl c 1 and chl c 2 -monogalactosyl diacylglyceride ester (chl c 2 -MGDG [18:4/14:0]); Type 4: chl c 1 , chl c 3 and non-polar chl c 1 -like; Type 5: chl c 1 , chl c 3 , chl c 2 -MGDG [18:4/14:0] and 4-keto-fucoxanthin; Type 6: chl c 3 , monovinyl chl c 3 (MV-chl c 3 ), chl c 2 -MGDG [18:4/14:0], 19'-hexanoyloxyfucoxanthin and its 4-keto derivative, and traces of 19'-butanoyloxyfucoxanthin; Type 7: similar to Type 6, minus MV-chl c 3 but with chl c 2 -MGDG [14:0/14:0] added; Type 8

Life on Earth depends on photosynthesis. Photosynthetic systems evolved early in Earth history and have been stable for 2.5 billion years, providing prima facie evidence for the significance of pigments in plant functions. Photosynthetic pigments fill multiple roles from increasing the range of energy captured for photosynthesis to protective functions. Given the importance of pigments to leaf functioning, greater effort is needed to determine whether individual pigments can be identified and quantified in vivo using high fidelity spectroscopy. We review recent advances in detecting plant pigments at the leaf level and discuss successes and reasons why challenges remain for robust remote observation and quantification. New methods to identify and quantify individual pigments in the presence of overlapping absorption features would provide a major advance in understanding their biological functions, quantifying net carbon exchange, and identifying plant stresses.

Two cyanobacterial species (Nostoc entophytum and Oscillatoria angustissima) were tested as biofertilizers, substituting the normally used chemical fertilizer, for pea plant. Inoculation of soil with a suspension of each species or a combination of the two species significantly increased the germination percentage and stimulated the other measured growth parameters and photosynthetic pigment fractions of pea. However, the soil inoculation with one cyanobacterial species and the addition of the recommended dose or half the recommended dose of chemical fertilizer were usually more effective and also increased carbohydrate and protein contents of produced pea seeds. However, biofertilization combined with half the recommended dose of the chemical fertilizer was usually more effective than the addition of the full rate of the chemical fertilizer, and this may allow saving 50% of the used chemical fertilizer. The protein profile of the produced seeds showed appearance and disappearance of some protein bands in response to fertilization treatments compared to the control. Blue green algae analyses show that N. entophytum fixed more N, produced more exopolysaccharide, and contained more auxin and cytokinin than O. angustissima, the latter contained more gibberellins. These data may explain their different influences on growth and yield of pea.

To determine the nutrient needs required to produce high quality transplants, artichoke (Cynara scolymus L.) Fj '137' hybrid seedlings were fertilized seven times by nutrient solutions containing N, P, and K far 14 days until at least one treatment out of all the replications had reached minimal transplanting stage (i.e.: 15 cm high with four true leaves). As N rate increased fram lO to 250 mg liter-l, shoot fresh weight and specific leaf area increased. Plant height, leaf number, leaf area and dry shoot weight were higher at 130 than at lO mg N liter-l, with no further increases above 130 mg liter-l; while raot dry weight and root:shoot dry weight ratio were higher at lO than 130 or 250 mg N liter 1.The highest P rate had a positive effect on seedling height, leaf area and shoot fresh weight, while it reduced raot dry weight and raot: shoot dry weight ratio. Increasing the K rate fram lO to 250 mg liter-l caused a significant increase in leaf area, shoot fresh and dry weight and root dry weight. Therefare, to grow high-quality artichoke transplants, nutrient solutions should contain at least 130N-100P-250K (ppm) if a vermiculite-perlite-peat medium low in N, P and K is used.

A total of 210 Salmonella isolates, representing 64 different serovars, were isolated from imported seafood samples, and 55/210 isolates were found to be resistant to at least one antibiotic. Class 1 integrons from three multidrug-resistant Salmonella enterica strains (Salmonella enterica serovars Newport [strain 62], Typhimurium var. Copenhagen [strain 629], and Lansing [strain 803], originating from Hong Kong, the Philippines, and Taiwan, respectively) were characterized. Southern hybridization of plasmids isolated from these strains, using a class 1 integron probe, showed that trimethoprim-sulfamethoxazole and streptomycin resistance genes were located on a megaplasmid in strain 629. Our study indicates that imported seafood could be a reservoir for Salmonella isolates resistant to multiple antibiotics.

Investigations were carried out to envisage the effect of the cypress canker infection on some features of the thylakoids from field grown cypress (Cupressus sempervirens) needles. Changes in photosynthetic pigments, soluble proteins, soluble starch, starch, ribulose-1,5-bisphosphate carboxylase, nitrate reductase, photosynthetic activities and thylakoid membrane proteins were investigated. The level of total chlorophyll and carotenoids were markedly reduced in cypress canker-infected needles. Similar results were also observed for soluble proteins, nitrate reductase and ribulose-1,5-bisphosphate carboxylase activity. In contrast, the content of soluble starch and sugar were increased in infected needles. In isolated thylakoids, cypress canker infection caused marked inhibition of whole chain and photosystem II activity while the inhibition of photosystem I activity was only marginal. The artificial exogenous electron donors, diphenyl carbazide and hydroxylamine significantly restored the loss of photosystem II activity in infected needles. The same results were obtained when Fv/Fm was evaluated by chlorophyll fluorescence measurements. The marked loss of photosystem II activity in infected needles could be due to the loss of 47, 43, and 15 kDa polypeptides. It is concluded that cypress canker infection inactivates the donor side of photosystem II. This conclusion was confirmed by immunological studies showing that the content of the 33 kDa protein of the water-splitting complex was diminished significantly in infected needles. q

Our objective was to evaluate the physiological response of Fischerella ambigua FS18 to the combined influence of pH (5, 7 and 9) and light intensity (3 and 300 μmol photon m−2 s−1). Growth rates were similar at pH 9 and pH 7. There was no growth at pH 5. Increasing light intensity did not have any considerable influence on growth rates. Chlorophyll concentration was higher at pH 7 at all light intensities. Chlorophyll concentration decreased with increasing light intensity from 3 to 300 μmol photon m−2 s−1. Synthesis of the phycobiliproteins (PBP), phycocyanin (PC) and allophycocyanin (APC) had the highest rate in pH 7. Increasing irradiance decreased the concentrations of all PBPs. The light-saturated photosynthetic rate was clearly higher at high light intensity. With respect to nitrogenase activity, the highest rate was at pH 9 and 300 μmol photon m−2 s−1. Irradiance did not affect significantly this activity at pH 7. This cyanobacterium seems to be alkalophilic with maximum nitrogenase activity and photosynthesis at pH 9. It can also adapt its photosynthetic apparatus to the variable factors that are found in rice fields.

The in-vitro acclimatization of Phalaenopsis plantlets under photoautotrophic conditions, with 0 (control), 3.43, 6.86 and 13.72 mM uniconazole (UCZ) treatments for 30 days was investigated before the plantlets were transferred to ex-vitro environments for 14 days. The physiological and growth characters of in-vitro acclimatized, and ex-vitro adapted plantlets were measured. Chlorophyll a (Chl a ), chlorophyll b (Chl b ), total chlorophyll (TC) and total carotenoid (C x+c ) content in plantlets treated with 6.86 mM UCZ were maintained at higher levels than those in plantlets of the control, by 1.82, 1.85, 1.83 and 1.93 times, respectively, leading to enrichment of the pigments in ex-vitro conditions. The maximum quantum yield of PSII (F v /F m ), photon yield of PSII (F PSII ), photochemical quenching (qP) and non-photochemical quenching (NPQ) in UCZ treated plantlets and in ex-vitro adaptation were not significantly different. Proline was accumulated in the control plantlets in both in-vitro acclimatization and ex-vitro conditions, while proline in those plantlets with UCZ treatments was maintained at a low level, which was defined by unstressed conditions. Net photosynthetic rate (P n ) in 6.86 mM UNZ treated plantlets peaked at a higher level than that of the control plantlets, both in-vitro and ex-vitro, by 3.27 and 2.93 times, respectively. In addition, proline content and P n were inversely related in both in-vitro acclimatization and ex-vitro adaptation. The P n in UCZ acclimatized plantlets was negatively correlated with plant dryweight. In-vitro photoautotrophic Phalaenopsis plantlets were successfully acclimatized using a 6.86 mM UCZ treatment which caused them to adapt quickly to ex-vitro environments.

Effects of illumination spectrum on the morphogenesis of chrysanthemum plantlets (Chrysanthemum morifolium Ramat. 'Ellen') grown in vitro were studied using an illumination system consisting of four groups of light-emitting diodes (LEDs) in the following spectral regions: blue (450nm), red (640nm), red (660nm), and far-red (735nm). Taking into account all differences in shoot height, root length, and fresh and dry weight (FW and DW, respectively), observed while changing the total photon flux density (PFD), the optimal total PFD for growth of chrysanthemum plantlets in vitro was estimated. For 16 h photoperiod and typical fractions of the spectral components (14%, 50%, 28%, and 8%, respectively), the optimal total PFD was found to be 40 µmol m -2 s -1 . Our study shows that the blue component in the illumination spectrum inhibits the plantlet extension and formation of roots and simultaneously increases the DW to FW ratio and content of photosynthetic pigments. We demonstrate photomorphogenetic effects in the blue region and its interaction with the fractional PFD of the far-red spectral component. Under constant fractional PFD of the blue component, the root number, length of roots and stems, and fresh weight of the plantlets have a correlated nonmonotonous dependence on the fractional PFD of the far-red component.

The present study investigated the chemical composition and allelopathic potential of volatile oil from Eucalyptus tereticornis on growth and establishment of Amaranthus viridis, a wasteland weed. The volatile oil was rich in monoterpenoids and a total of 34 components were identified by gas chromatography/gas chromatographyÁmass spectroscopy analyses, constituting 98.52%. a-Pinene (32.5%) and 1,8-cineole (22.4%) were the two major constituents. The volatile oil and two major components were evaluated for their allelopathic potential against A. viridis. A significant reduction in early seedling growth and seedling vigor of A. viridis was observed in response to volatile oil or its major monoterpenes. Further, the contents of photosynthetic pigments, i.e. chlorophylls a and b, and carotenoids, and cellular respiration in oil-/monoterpene-treated seedlings were significantly reduced thereby indicating adverse effects of the oil on photosynthetic machinery and energy metabolism. Based on the study, it can be concluded volatile oil of E. tereticornis possess allelopathic potential and could be explored as bioherbicide for future weed management programs.

Ocimum tenuiflorum L. exposed to various concentrations of chromium (0.0, 10.0, 20.0, 50.0, 100.0 M) accumulated high amount of chromium in various plant parts in a concentration and duration dependent manner. Chromium induced lipid peroxidation coupled with potassium leakage. Toxic effects of chromium on O. tenuiflorum were reflected by the reductions in photosynthetic pigments, protein, cysteine, ascorbic acid and non-protein thiol contents. In addition, chromium toxicity resulted in the reduction of nitrate reductase activity through impaired substrate utilization. However, chromium treated O. tenuiflorum leaves showed increased proline content. Hyperactivity of the superoxide dismutase (SOD), guaiacol peroxidase (GPX) and catalase indicated that antioxidant enzymes played an important role in protecting the plant from chromium toxicity. However, APX took a little part in detoxification of H 2 O 2 due to its sensitivity to chromium. Therefore, reduced ascorbate peroxidase activity in chromium treated O. tenuiflorum plants was recorded. This reflects the sensitivity of the enzyme to the chromium. Further, chromium treated plants yielded more eugenol (a major component of Ocimum essential oil) in comparison to the control (14.46, 24.61, 16.80, 3.83% more eugenol from 10, 20, 50 and 100 M chromium exposed plants, respectively). The study concludes that plant could grow under chromium stress and protect themselves from phytotoxicity of Cr by altering various metabolic processes. Further, the use of leaves collected from chromium polluted habitat in medicinal preparation is not safe for human health due to high chromium contents.

Aquatic plants are known to accumulate and bioconcentrate heavy metals. In this study, several physiological responses of aquatic vascular plant Lemna trisulca L. to elevated concentrations of cadmium (up to 10 mM) and copper (up to 50 mM) were investigated. It was found that Lemna fronds were able to accumulate both cadmium and copper, but Cu-treated material showed pronounced toxic symptoms at concentrations 1000-fold lower in comparison to Cd. Lemna trisulca could tolerate elevated levels of Cd, i.e. up to 10 mM, without significant changes in photosynthetic pigments concentration. On the contrary, Cu in concentrations 25 and 50 mM promoted significant pigment degradation. The main processes affected by Cd in Lemna fronds were total gas exchange and net photosynthesis. On the contrary, the inhibition of total gas exchange and net photosynthesis caused by Cu (2-50 mM) correlated with Chl a and carotenoid concentrations decrease as well as with the decay of fluorescence from PS II. Also, an increasing impact of respiration in total oxygen exchange was observed after treatment of Lemna with increasing Cd concentrations (up to 5 mM) and with Cu in concentration range between 2 and 50 mM. In Cd-treated fronds, a dose-dependent accumulation of two polypeptides with apparent molecular weights 18 and 10 kDa, respectively as well as the appearance of two smaller polypeptides (apparent molecular weights 8 and 7 kDa) was observed in SDS-PAGE. The nature of these polypeptides remains to be determined. On the contrary, in Cu-treated fronds neither accumulation of existing proteins nor appearance of any extra protein was observed.

To investigate the ability of pioneer and late-successional species to adapt to a strong light environment in a reforestation area, we examined the activities of antioxidant enzymes in relation to photosystem II, chlorophyll a fluorescence and photosynthetic pigment concentration for eight tropical tree species grown under 100% (sun) and 10% (shade) sunlight irradiation. The pioneer (early-succession) species (PS) were Cecropia

The lipophilic pigment content and composition and in vivooptical density (OD) spectra for batch cultures of the Florida (USA) red-tide dinoflagellate Gyn~nodinium breve Davis were analyzed after exposure to irradiance treatments representative of an irradiance gradient that cells might experience in a coastal water column. Decreases in total chlorophyll (chl) content (attributable to decreasesin chls a, c,/c2 and c3) and total carotenoid content (attributable to decreases in total fucoxanthin and 19'-acylofucoxanthins, and gyroxanthin-diester) coincided with exposure to increased irradiance. The relative abundances of chl pigments remained constant whereas decreases in the relative abundances of total fucoxanthin and 19'-acylofucoxanthins, and p-v-carotene and an increase in the relative abundance of diadinoxanthin coincided with exposure to increased irradiance. Because gyroxanthin-diester has been observed only in a lim~ted number of toxic dinoflagellates (of which G. breve is the only warm-water taxon), was consistently quant~f~able throughout various irradiance-lnduced physiological states, and had a distinctive elution pos~tlon and absorption maxima in the chromatographic eluent, this carotenoid may serve as a 'biomarker' for G. breve within Florida coastal waters. An analysis of variance, performed on fourthderivative plots derived from normalized OD spectra, identified portions of the OD spectra which differed among irradiance treatments. Designated wavelengths coincided with wave crests in the fourth-derivative plots representative of absorption maxima for total chl c (460 to 468, 585 to 590 nm) and total fucoxanthin and 19'-acylofucoxanthins, and diadinoxanthin (490 to 496 nm). Stepwise discriminant analysis identified a set of 6 wavelengths (403,541,546,509,673 and 663 nm) which optimally classified OD spectra for populations among irradiance treatments. l k s lack of correspondence between wavelengths identified by the 2 statistical techniques was not unexpected; fourth-derivative analysis identified portions of the OD spectra where differences in the sharpness of curvature (as produced by absorption maxima of component pigments) occurred among treatments whereas discriminant analysis identified portions of the spectra which could be used to classify populations among treatments and did not necessarily have to correspond to absorption maxima. Such detectable differences in the bio-optical 'signatures' of G. breve indicate that previous light history, as manifested in the pigment component, could be incorporated into future pigment-based monitoring applications to allow for the detection and/or physiological characterization of problematic taxa prior to bloom status.

High ammonia (i.e. the total of NH 3 and NH þ 4 ) concentration or nitrogen deficiency in water can exert stress on growth and health of many aquatic plants. To investigate the physiological impacts of high ammonia-N (NH 4 Cl) concentration and nitrogen deficiency on plant physiology, apical shoots of submerged macrophyte Egeria densa were first treated with five levels of nitrogen: 0, 1, 10, 30, 60 mg L À1 ammonia-N (NH 4 Cl) for 5 d. After having explored the stress range of ammonia-N, its effect on E. densa was further examined at three levels of ammonium (0, 1, 30 mg L À1 ammonia-N) and at six exposure times (0, 1, 2, 3, 5 and 7 d). In testing the concentration-dependent stress, the increase of ammonia-N reduced the amounts of total chlorophyll (chl a and b), soluble proteins and soluble carbohydrates, but increased the activity levels of malondialdehyde (MDA), superoxide dismutase (SOD), catalase and peroxidase in E. densa. In the N-free medium, total chlorophyll, soluble proteins, soluble carbohydrates and the activities of SOD and peroxidase in E. densa decreased significantly compared with the control (1 mg L À1 ammonia-N). When comparing the ammonia-N impacts over time, the plants showed a declining trend in total chlorophyll, soluble proteins and soluble carbohydrates, but an rising trend in MDA, SOD, peroxidase and catalase in 30 mg L À1 ammonia-N over 7 d. Compared with the control, the N-free medium significantly decreased the amounts of total chlorophyll, soluble proteins, soluble carbohydrates, SOD and peroxidase in E. densa over time. Our study indicates that high ammonium (ammonia-N P 10 mg L À1 ) affects the growth of E. densa through inducing oxidative stress and inhibiting photosynthesis, and nitrogen deficiency can also induce an abiotic stress condition for the E. densa growth by reducing photosynthetic pigments, soluble proteins, soluble carbohydrates, and the activity of antioxidant enzymes.

In order to assess as to whether treated textile effluent could be safely used to irrigate some winter vegetables, growth room experiments were conducted. Varying levels of treated and untreated textile effluents were applied to germinating seeds of some winter vegetables and their effect was evaluated on germination and early growth stage using seed germination, growth, and biochemical attributes. From the results, it was obvious that textile effluent reduced seed germination and early growth of all vegetables. However, this effect was more pronounced at the highest concentration of textile effluent. Furthermore, treated textile effluent did not show any inhibitory effect on seed germination of all vegetables. Photosynthetic pigments such as chlorophyll a and b, and protein contents were higher in the leaves of all vegetable plants irrigated with treated textile effluent than those of supplied with untreated textile effluents. It has been observed that heavy metals were lower in concentration in treated textile effluent as compared with untreated textile effluent.

Defining ‘plants’ inclusively as ‘photosynthetic eukaryotes’, four basic body plans are identifiable among plant lineages (unicellular, siphonous, colonial and multicellular). All of these body plans occur in most plant lineages, but only the multicellular body plan was carried onto land by the embryophytes. Extensive morphological and anatomical homoplasy is evident among species with different body plans. This is ascribed to the facts that the acquisition of nutrients and radiant energy is affected by plant body size, shape and geometry, and that, with the exception of the unicellular body plan, each of the other body plans involves an ‘open and indeterminate’ ontogeny capable of modifying body size, shape and geometry regardless of how organized growth is achieved. In terms of unicellular species, the available data indicate that size-dependent variations in surface area, metabolic constituents (e.g. photosynthetic pigments), and reproductive rates limit maximum body size in nutr...

Antarctic macroalgae survive extended periods of darkness followed by rapid and extreme increases in irradiance when sea-ice breaks out in summer. Algae from dark, ice-covered locations had low values of saturating irradiance (E k : 4-19 mmol photons m À2 s À1 ), low relative rates of electron transport (rETR max : 2.0-3.6 mmol electrons m À2 s À1 ) and high values of effective quantum yield (ÁF/F 0 m : 0.52-0.70). Algae from brighter open-water locations had high E k (13-67), high rETR max (3.1-22.9) and lower ÁF/F 0 m (0.28-0.50). Overall values of ÁF/F 0 m and maximum quantum yield (F v /F m ) were generally higher for ice-covered algae. Photosynthetic pigment, C : N and 13 C varied little with irradiance. Diel photosynthetic changes were measured in situ using a custom-built, multi-channel fluorometer. Under sea-ice, ÁF/F 0 m of Iridaea mawsonii increased significantly from 0.54 at midday ($4 mmol photons m À2 s À1 ) to 0.64 at midnight, despite the relatively low midday irradiance. ÁF/F 0 m of ice-free macroalgae also varied significantly over 24 h and between-sample variation exceeded that of under-ice algae. In vivo comparisons of ETR and oxygen evolution of I. mawsonii, Desmarestia menziesii and Himantothallus grandifolius suggested that over 50% of excitation energy was diverted from linear photosynthetic electron flow at E k ; quenching analysis indicated at least partial diversion to non-photochemical quenching (NPQ). During the increasing irradiance of a rapid light curve, values of photochemical quenching (qP) and NPQ of ice-covered algae changed more rapidly than those of open-water algae. Only ice-free H. grandifolius maintained high qP values when exposed to high actinic irradiances (a capacity apparently induced on sea-ice break out), while both ice-free and ice-covered I. mawsonii maintained high NPQ at low actinic irradiances (apparently a constitutive capacity). These attributes help explain the local distribution of macroalgae in the Antarctic, and show strong linkages with the rapid changes in irradiance during sea-ice break-out events.

The impact of two intensities (2.5 W m -2 and 5 W m -2 ) of ultraviolet-B (UV-B) radiation on growth, photosynthetic pigments, photosynthetic activity and membrane leakage has been studied in Chlorococcum sp. isolated from El-Kased fresh water canal, Tanta, Egypt. Exposure of Chlorococcum sp. for 60 and 35 min of 2.5 and 5 W m -2 , respectively, inhibited growth by 50%. Chlorophyll a and chlorophyll b were decreased in Chlorococcum sp. by exposure to UV-B, but the effect was more pronounced on chlorophyll b. On the other hand, carotenoids were stimulated at small doses (time of exposure and intensity) of UV-B whether at 2.5 or 5 W m -2 . However, oxygen amount, total soluble carbohydrates, and total soluble proteins were inhibited by UV-B treatment at all exposure times but the effect of 5 W m -2 was more than that of 2.5 W m -2 and O 2 was completely abolished after 90 and 120 min at 2.5 and 5 W m -2 , respectively. With regard to extracellular polysaccharides, there was a significant increase at small doses of UV-B but reduction observed at high doses. Exposing cells to 2.5 and 5 W m -2 UV-B caused 22.7 and 39.6% increase, respectively, in electrolyte leakage than in control.

Mechanisms of photoprotection and antioxidant protection, including changes in chlorophylls, xanthophyll cycle components and levels of low-molecular-weight chloroplastic antioxidants (lutein, ␤-carotene and ␣-tocopherol) were studied together with levels of malondialdehyde, a product of lipid peroxidation, in the response of rosemary (Rosmarinus officinalis L.) plants to salt stress. Plants were exposed to increasing NaCl concentrations (50, 100 and 150 mM) for 6 weeks, and two concentrations of the following chloride salts: KCl, CaCl 2 , MgCl 2 and FeCl 3 , were used together with 100 mM NaCl to explore the extent to which these salts can alter the mechanisms of photoprotection, antioxidant protection and malondialdehyde accumulation in leaves. Increasing concentrations of NaCl decreased leaf water contents and photosynthetic pigment levels, while the contents of ␣-tocopherol and malondialdehyde increased, but with completely different kinetics. ␣-Tocopherol levels increased in a dose-dependent manner as stress progressed, while malondialdehyde levels increased at the highest dose (150 mM NaCl) but only during early phases of stress. Furthermore, although the addition of chloride salts to NaCl-treated plants apparently improved leaf physiological status, in terms of water and chlorophyll contents, plants showed an increased photoprotective demand and increased oxidative stress, particularly in FeCl 3 -treated plants. It is concluded that (i) rosemary plants can withstand moderate doses of NaCl in the medium (at least 150 mM NaCl for 6 weeks), (ii) oxidative stress may be a mechanism for protecting plants from moderate doses of salt stress rather than causing damage to plants, and (iii) the addition of chloride salts to NaCl-treated plants may dramatically increase the photoprotective demand and oxidative stress of leaves, while plant growth is not negatively affected.

The fluorescence spectrum of an allenic carotenoid, all-trans-fucoxanthin isolated from a brown alga, has been reported for the first time. This carotenoid is known to function efficiently as a primary photosynthetic antenna pigment in marine algae. The emission bands were located around 630, 685 and 750 nm in CS2 at 20°C, absorption bands being located at 448, 476 and 505 nm. The energy difference between the 0-0 bands of absorption and emission spectra was about 3900 cm(-1) and location of the emission maximum was less sensitive to the polarizability of solvents than that of the absorption maximum. These clearly indicate that the emission originates from the optically forbidden singlet state (2Ag). This is in contrast to other carotenoids whose emission is assigned to 1Bu state, probably due to the symmetric structure of the conjugated double bond responsible for the absorption in the visible region. A rapid internal conversion from 1Bu to 2Ag state might be facilitated by distort...