Journal of the American Society for Horticultural Science, Sep 1, 2000
Water relations and fruit development were studied for up to 100 days after anthesis for potted p... more Water relations and fruit development were studied for up to 100 days after anthesis for potted plants of Opuntia ficus-indica (L.) Mill. (a prickly pear) that were either well-watered or water-stressed, each plant consisting of a medium-sized cladode bearing two or three fruit. Even though cladodes of water-stressed plants lost up to 50% of their thickness, their fruit continued to gain water and to develop; at ripening such fruit had only 16% less water than fruit of watered plants. Maturation indicated by the decrease in fractional peel content and increases in pulp weight and in pulp soluble sugar content was hastened by water stress, leading to ripening ≈88 days after anthesis for water-stressed plants, which was 10 days earlier than for watered plants. Fruit had a lower stomatal frequency than the cladodes but both exhibited Crassulacean acid metabolism behavior. Transpiration occurred mainly at night, and the daily amount of water transpired per unit fruit surface area decreased with time, especially for fruit of water-stressed plants. This decrease was related to fruit expansion (leading to decreased stomatal frequency) for watered plants and to both fruit expansion and water stress for water-stressed plants. At 75 days after anthesis, daily diameter changes of fruit were correlated with transpiration, contraction occurring at night and expansion during the daytime, and changes were greater for watered plants for which daily transpiration was higher. fruit weight . However, because water stored in the inner cladode tissues can be used during drought and because fruit have a considerable peel mass at the beginning of the last stage , it is hypothesized that fruit may mature successfully to a similar size and quality even when water stress is imposed during the last stage of development. Thus, the water relations of cladodes and fruit were investigated for potted plants of O ficus-indica that were well-watered or water-stressed during the last stage of fruit development. PLANT MATERIAL. Terminal cladodes with newly initiated flower buds were harvested at the beginning of March 1999 from a prickly pear cactus (Opuntia ficus-indica) (accession number 1279 from Texas A & M Univ., Kingsville) growing at the Agricultural Research Station, University of California, Riverside. The cladodes were 37 ± 3 cm long, 21 ± 2 cm wide, and 2.0 ± 0.1 cm thick. After the cut surface of the cladodes had dried for 3 weeks, the cladodes were planted in 1.5-L pots containing a loamy soil (Arlington loam, ApB) from the Agricultural Research Station and maintained in a greenhouse. Average daily maximum/minimum air temperatures in the greenhouse were 25/14 °C for March to June and 28/16 °C for July and early August 1999; maximum/minimum relative humidities averaged 75%/40%. The plants were irrigated twice weekly with half-strength Hoagland solution until drainage occurred from the pots. Root initiation began immediately after planting. Flowers opened from mid-April to mid-May and were hand pollinated with their own pollen on the day of opening, leading to the setting of two or three fruit per plant. Two groups of 15 plants each that flowered at the beginning of May were selected from 20 to 25 June (≈50 d after anthesis); water was applied every other day to one group and was withheld from the other group. The seedcoats became dark, indicating seed maturation, by mid-June. MEASUREMENTS. Fruit length, diameter at midfruit, and thickness at midcladode were measured every 6 to 9 d with calipers for six
Growth, gas exchange rates, and carbohydrate content were studied for developing fruits of the cu... more Growth, gas exchange rates, and carbohydrate content were studied for developing fruits of the cultivated cactus Opuntia ®cus-indica (L.) Miller, including effects of drought and exogenous gibberellic acid (GA 3 ). Fruit development required 110 d from the time of bud differentiation to ripening at 80 d after anthesis, when the fruit mass averaged 67 g. Stomatal conductance and net CO 2 uptake rates for fruits were higher during the night; they were maximal at 7 d before anthesis and decreased as development progressed. Fruits undergoing drought, imposed by detaching terminal stems bearing fruits, were 50% smaller than the control at 80 d after anthesis and did not ripen. Fruits injected with 2 ml of 500 ppm GA 3 were 30% smaller than the control at 80 d after anthesis; they contained a large proportion of aborted seeds that produced a weak sink signal for dry mass accumulation. Gas exchange was higher at 21 d after anthesis for fruits treated with GA 3 . Total soluble sugars represented 40% of the fruit's dry mass until 45 d after anthesis, when the sugar content rapidly increased, reaching 90% at 73 d after anthesis. Such an increase was not observed for fruits treated with GA 3 , and the sugar content for fruits undergoing drought remained low throughout development. Starch content increased for developing fruits of O. ®cus-indica until 14 d after anthesis and, except for the fruits undergoing drought, decreased thereafter. Fruit development for O. ®cusindica is apparently regulated by water availability as well as hormonal signals originating both within and outside the fruit.
Journal of the American Society for Horticultural Science, Nov 1, 1995
Flower and fruit production by the columnar cactus, Stenocereus queretaroensis (Weber) Buxbaum, o... more Flower and fruit production by the columnar cactus, Stenocereus queretaroensis (Weber) Buxbaum, occurred during the dry season in the late winter and spring, and the relatively small annual stem extension occurred primarily during the fall. Thus, reproductive growth does not directly compete with vegetative growth for resources such as reducing sugars, which increased during the wet summer season, a period when total sugars were decreasing. Stem extension, reproductive demography, fruit quality, seed size, and seed quality were not influenced by irrigation. Final fruit size and seed germination, however, were enhanced by applying water. The times from flower bud differentiation to flower opening and from anthesis to fruit ripening were relatively short and unaffected by irrigation. Pitayos (Stenocereus spp.) are columnar cacti native to subtropical regions of Mexico that produce attractively colored edible fruit . Pitayo cultivation using relatively low inputs of anthropogenic energy has increased the economic viability of small and medium farms in Mexico, because the fruit ripen before local markets are supplied with other summer fruit (Pimienta- . Although pitayos have been cultivated in Mexico for over 100 years, efforts to improve this fruit crop are rather recent and have been made primarily by selecting outstanding phenotypes, with emphasis on fruit quality rather than biomass productivity . As is the case for many undomesticated fruit, the reproductive development of Stenocereus is asynchronous and the rate of net CO 2 uptake is relatively low . Reproductive and vegetative growth occur during the dry season, presumably drawing on resources from the previous wet summer season . To help understand the relation between growth and carbohydrate resources, reproductive and vegetative growth of S. queretaroensis were periodically determined and related to the monthly variations in the content of total and reducing sugars. Also, the water supply was manipulated by irrigating certain plants to compare genetic vs. environmental influences on growth. In particular, whether stem extension, reproductive effort, and accumulation of soluble sugars were water limited was examined.
The effects of shade on the physiology of opuntias have received little attention, notwithstandin... more The effects of shade on the physiology of opuntias have received little attention, notwithstanding that shade regularly occurs in both wild stands and cultivated populations. This research evaluates the effects of shade on the physiology of cladodes of Opuntia ficus-indica, with and without daughter cladodes, as they are exposed to progressive drought. The stress caused by shade, drought and daughter cladodes reduced photosynthesis by mother cladodes and was associ- ated with decreases in relative water content, parenchyma thickness and chlo- rophyll content. Shade exacerbated the physiological drought of mother cladodes imposed by daughter cladodes and by reduced soil water content.
Abstract Pitayos ( Stenocereus spp.) are columnar cacti native to subtropical regions of Mexico t... more Abstract Pitayos ( Stenocereus spp.) are columnar cacti native to subtropical regions of Mexico that produce edible fruits. Vegetative and reproductive growth for S. qureretaroensis occurs in the dry season but not simultaneously. Most daily net CO 2 uptake by S. queretaroensis occurs at night, with the highest values during the late autumn and early winter dry season. Its fine roots are colonized by arbuscular mycorrhizal fungi that enhance stem and fruit growth, apparently due to better P nutrition. The seeds are small, and germinate in response to light. The fruits of S. queretaroensis are valuable resources to wild animals, and can help sequester atmospheric carbon during the dry season.
Of the thirty-three perennial species recorded along line transects at a site in the northwestern... more Of the thirty-three perennial species recorded along line transects at a site in the northwestern Sonoran Desert, nine species were succulents from different families (Cactaceae, Crassulaceae, and Agavaceae) and a further eight were from the Asteraceae. The CAM succulent Agave deserti, the C 3 drought-deciduous Encelia farinosa, and the C 4 bunchgrass Pleuraphis rigida were codominant, with 33%, 13%, and 15%, respectively, of the total cover. Agave deserti, which is clonal and had a clumped distribution, was the most abundant species on all slopes except south-facing ones, where the randomly distributed E. farinosa was dominant. Enceliafarinosa was infrequent on west-and north-facing slopes, were the randomly distributed P. rigida reached its maximum cover. Although intra-and interspecific competition was evident for all three species, their frequency was dependent predominantly on microclimate.
Fourteen accessions of Opuntia ficus-indica, O. fusicaulis, O. hypriacantha, O. megacantha, O. ra... more Fourteen accessions of Opuntia ficus-indica, O. fusicaulis, O. hypriacantha, O. megacantha, O. rastrera, O. stricta, and O. streptacantha, whose low-temperature damage in the field in south Texas had previously been determined, were examined for low-temperature tolerance in the laboratory. Those platyopuntia accessions exhibiting the least low-temperature damage in the field had the greatest low-temperature tolerance in the laboratory, assayed using uptake of a vital stain (neutral red) by the chlorenchyma cells. All 14 accessions exhibited low-temperature acclimation as the day/night air temperatures for growth were reduced from 3soC12SoC to 2soCIlSoC to ISoC/soC, the greatest low-temperature tolerance being associated with the greatest acclimation ability. To screen for possibledifferences in COl uptake ability among the six accessionsexhibiting the greatest low-temperature tolerance, the nocturnal increases in tissue acidity and osmotic pressure were determined in the laboratory for these Crassulacean acid metabolism plants. Both measures of COl uptake were maximalat the intermediate growth temperature, 2soC/ISoC. Moreover, the two variables were highly correlated (,2 = 0'87, P < 0'001), indicating that either laboratory test could be used to predict COl uptake. The three accessions (of O. rastrera and O. streptacantha) with the greatest metabolic activity at 1SoC/SoC all showed nocturnal acid accumulation at day/night air temperatures of SOC/-SoC. Such metabolic activity at sub-zero temperatures was substantiated for an accession of O. streptacantha, which exhibited a net CO;z uptake at night at chlorenchyma temperatures of -3°C. Breeding for low-temperature tolerance is necessary to extend the regions where platyopuntias can be cultivated, an endeavor that can be aided by the relatively simple laboratory tests for low-temperature tolerance and metabolic activity described here.
International Journal of Plant Sciences, Nov 1, 1996
To help understand what conditions lead to the development of new organs on shoots of Opuntia fic... more To help understand what conditions lead to the development of new organs on shoots of Opuntia ficus-indica, a widely cultivated prickly pear cactus, detached cladodes were kept in a glasshouse and were shaded, exposed to full sunlight, or exposed to full sunlight and injected with various osmotica and hormones. Daughter cladodes emerged more slowly on cladodes detached in January (mean time of 12.6 wk) than in May (4.2 wk). In the field, new organ development was more rapid and more fruits were produced compared with cladodes detached in January and kept in a glasshouse. Shading by 94% essentially eliminated the development of daughter cladodes for cladodes harvested in both seasons over the 18-wk observation period. Daughter cladodes had a lower percentage dry mass and a higher water potential than the detached cladodes on which they developed, suggesting that water entered them primarily via the phloem. Compared with detached cladodes injected weekly with 1% of the cladode fresh mass of water for 6 wk, injection of 1.5 M sucrose accelerated daughter cladode development by 1.4 wk, 750 mM KCl by 3.0 wk, and 750 mM KNO3 by 4.8 wk. Injection of 20 μM gibberellic acid ( GA3 and ${\rm GA}_{4}$) virtually eliminated the development of daughter cladodes. Injection of 800 μM indole-3-acetic acid accelerated cladode development by 3.1 wk and 800 μM kinetin by 4.0 wk, both resulting in a greater biomass for the new organs. Thus production of daughter cladodes by detached cladodes of O. ficus-indica was enhanced by a higher tissue osmotic pressure, indole-acetic acid, and kinetin and was inhibited by shading and gibberellic acid.
Journal of the American Society for Horticultural Science, Sep 1, 2000
Water relations and fruit development were studied for up to 100 days after anthesis for potted p... more Water relations and fruit development were studied for up to 100 days after anthesis for potted plants of Opuntia ficus-indica (L.) Mill. (a prickly pear) that were either well-watered or water-stressed, each plant consisting of a medium-sized cladode bearing two or three fruit. Even though cladodes of water-stressed plants lost up to 50% of their thickness, their fruit continued to gain water and to develop; at ripening such fruit had only 16% less water than fruit of watered plants. Maturation indicated by the decrease in fractional peel content and increases in pulp weight and in pulp soluble sugar content was hastened by water stress, leading to ripening ≈88 days after anthesis for water-stressed plants, which was 10 days earlier than for watered plants. Fruit had a lower stomatal frequency than the cladodes but both exhibited Crassulacean acid metabolism behavior. Transpiration occurred mainly at night, and the daily amount of water transpired per unit fruit surface area decreased with time, especially for fruit of water-stressed plants. This decrease was related to fruit expansion (leading to decreased stomatal frequency) for watered plants and to both fruit expansion and water stress for water-stressed plants. At 75 days after anthesis, daily diameter changes of fruit were correlated with transpiration, contraction occurring at night and expansion during the daytime, and changes were greater for watered plants for which daily transpiration was higher. fruit weight . However, because water stored in the inner cladode tissues can be used during drought and because fruit have a considerable peel mass at the beginning of the last stage , it is hypothesized that fruit may mature successfully to a similar size and quality even when water stress is imposed during the last stage of development. Thus, the water relations of cladodes and fruit were investigated for potted plants of O ficus-indica that were well-watered or water-stressed during the last stage of fruit development. PLANT MATERIAL. Terminal cladodes with newly initiated flower buds were harvested at the beginning of March 1999 from a prickly pear cactus (Opuntia ficus-indica) (accession number 1279 from Texas A & M Univ., Kingsville) growing at the Agricultural Research Station, University of California, Riverside. The cladodes were 37 ± 3 cm long, 21 ± 2 cm wide, and 2.0 ± 0.1 cm thick. After the cut surface of the cladodes had dried for 3 weeks, the cladodes were planted in 1.5-L pots containing a loamy soil (Arlington loam, ApB) from the Agricultural Research Station and maintained in a greenhouse. Average daily maximum/minimum air temperatures in the greenhouse were 25/14 °C for March to June and 28/16 °C for July and early August 1999; maximum/minimum relative humidities averaged 75%/40%. The plants were irrigated twice weekly with half-strength Hoagland solution until drainage occurred from the pots. Root initiation began immediately after planting. Flowers opened from mid-April to mid-May and were hand pollinated with their own pollen on the day of opening, leading to the setting of two or three fruit per plant. Two groups of 15 plants each that flowered at the beginning of May were selected from 20 to 25 June (≈50 d after anthesis); water was applied every other day to one group and was withheld from the other group. The seedcoats became dark, indicating seed maturation, by mid-June. MEASUREMENTS. Fruit length, diameter at midfruit, and thickness at midcladode were measured every 6 to 9 d with calipers for six
Growth, gas exchange rates, and carbohydrate content were studied for developing fruits of the cu... more Growth, gas exchange rates, and carbohydrate content were studied for developing fruits of the cultivated cactus Opuntia ®cus-indica (L.) Miller, including effects of drought and exogenous gibberellic acid (GA 3 ). Fruit development required 110 d from the time of bud differentiation to ripening at 80 d after anthesis, when the fruit mass averaged 67 g. Stomatal conductance and net CO 2 uptake rates for fruits were higher during the night; they were maximal at 7 d before anthesis and decreased as development progressed. Fruits undergoing drought, imposed by detaching terminal stems bearing fruits, were 50% smaller than the control at 80 d after anthesis and did not ripen. Fruits injected with 2 ml of 500 ppm GA 3 were 30% smaller than the control at 80 d after anthesis; they contained a large proportion of aborted seeds that produced a weak sink signal for dry mass accumulation. Gas exchange was higher at 21 d after anthesis for fruits treated with GA 3 . Total soluble sugars represented 40% of the fruit's dry mass until 45 d after anthesis, when the sugar content rapidly increased, reaching 90% at 73 d after anthesis. Such an increase was not observed for fruits treated with GA 3 , and the sugar content for fruits undergoing drought remained low throughout development. Starch content increased for developing fruits of O. ®cus-indica until 14 d after anthesis and, except for the fruits undergoing drought, decreased thereafter. Fruit development for O. ®cusindica is apparently regulated by water availability as well as hormonal signals originating both within and outside the fruit.
Journal of the American Society for Horticultural Science, Nov 1, 1995
Flower and fruit production by the columnar cactus, Stenocereus queretaroensis (Weber) Buxbaum, o... more Flower and fruit production by the columnar cactus, Stenocereus queretaroensis (Weber) Buxbaum, occurred during the dry season in the late winter and spring, and the relatively small annual stem extension occurred primarily during the fall. Thus, reproductive growth does not directly compete with vegetative growth for resources such as reducing sugars, which increased during the wet summer season, a period when total sugars were decreasing. Stem extension, reproductive demography, fruit quality, seed size, and seed quality were not influenced by irrigation. Final fruit size and seed germination, however, were enhanced by applying water. The times from flower bud differentiation to flower opening and from anthesis to fruit ripening were relatively short and unaffected by irrigation. Pitayos (Stenocereus spp.) are columnar cacti native to subtropical regions of Mexico that produce attractively colored edible fruit . Pitayo cultivation using relatively low inputs of anthropogenic energy has increased the economic viability of small and medium farms in Mexico, because the fruit ripen before local markets are supplied with other summer fruit (Pimienta- . Although pitayos have been cultivated in Mexico for over 100 years, efforts to improve this fruit crop are rather recent and have been made primarily by selecting outstanding phenotypes, with emphasis on fruit quality rather than biomass productivity . As is the case for many undomesticated fruit, the reproductive development of Stenocereus is asynchronous and the rate of net CO 2 uptake is relatively low . Reproductive and vegetative growth occur during the dry season, presumably drawing on resources from the previous wet summer season . To help understand the relation between growth and carbohydrate resources, reproductive and vegetative growth of S. queretaroensis were periodically determined and related to the monthly variations in the content of total and reducing sugars. Also, the water supply was manipulated by irrigating certain plants to compare genetic vs. environmental influences on growth. In particular, whether stem extension, reproductive effort, and accumulation of soluble sugars were water limited was examined.
The effects of shade on the physiology of opuntias have received little attention, notwithstandin... more The effects of shade on the physiology of opuntias have received little attention, notwithstanding that shade regularly occurs in both wild stands and cultivated populations. This research evaluates the effects of shade on the physiology of cladodes of Opuntia ficus-indica, with and without daughter cladodes, as they are exposed to progressive drought. The stress caused by shade, drought and daughter cladodes reduced photosynthesis by mother cladodes and was associ- ated with decreases in relative water content, parenchyma thickness and chlo- rophyll content. Shade exacerbated the physiological drought of mother cladodes imposed by daughter cladodes and by reduced soil water content.
Abstract Pitayos ( Stenocereus spp.) are columnar cacti native to subtropical regions of Mexico t... more Abstract Pitayos ( Stenocereus spp.) are columnar cacti native to subtropical regions of Mexico that produce edible fruits. Vegetative and reproductive growth for S. qureretaroensis occurs in the dry season but not simultaneously. Most daily net CO 2 uptake by S. queretaroensis occurs at night, with the highest values during the late autumn and early winter dry season. Its fine roots are colonized by arbuscular mycorrhizal fungi that enhance stem and fruit growth, apparently due to better P nutrition. The seeds are small, and germinate in response to light. The fruits of S. queretaroensis are valuable resources to wild animals, and can help sequester atmospheric carbon during the dry season.
Of the thirty-three perennial species recorded along line transects at a site in the northwestern... more Of the thirty-three perennial species recorded along line transects at a site in the northwestern Sonoran Desert, nine species were succulents from different families (Cactaceae, Crassulaceae, and Agavaceae) and a further eight were from the Asteraceae. The CAM succulent Agave deserti, the C 3 drought-deciduous Encelia farinosa, and the C 4 bunchgrass Pleuraphis rigida were codominant, with 33%, 13%, and 15%, respectively, of the total cover. Agave deserti, which is clonal and had a clumped distribution, was the most abundant species on all slopes except south-facing ones, where the randomly distributed E. farinosa was dominant. Enceliafarinosa was infrequent on west-and north-facing slopes, were the randomly distributed P. rigida reached its maximum cover. Although intra-and interspecific competition was evident for all three species, their frequency was dependent predominantly on microclimate.
Fourteen accessions of Opuntia ficus-indica, O. fusicaulis, O. hypriacantha, O. megacantha, O. ra... more Fourteen accessions of Opuntia ficus-indica, O. fusicaulis, O. hypriacantha, O. megacantha, O. rastrera, O. stricta, and O. streptacantha, whose low-temperature damage in the field in south Texas had previously been determined, were examined for low-temperature tolerance in the laboratory. Those platyopuntia accessions exhibiting the least low-temperature damage in the field had the greatest low-temperature tolerance in the laboratory, assayed using uptake of a vital stain (neutral red) by the chlorenchyma cells. All 14 accessions exhibited low-temperature acclimation as the day/night air temperatures for growth were reduced from 3soC12SoC to 2soCIlSoC to ISoC/soC, the greatest low-temperature tolerance being associated with the greatest acclimation ability. To screen for possibledifferences in COl uptake ability among the six accessionsexhibiting the greatest low-temperature tolerance, the nocturnal increases in tissue acidity and osmotic pressure were determined in the laboratory for these Crassulacean acid metabolism plants. Both measures of COl uptake were maximalat the intermediate growth temperature, 2soC/ISoC. Moreover, the two variables were highly correlated (,2 = 0'87, P < 0'001), indicating that either laboratory test could be used to predict COl uptake. The three accessions (of O. rastrera and O. streptacantha) with the greatest metabolic activity at 1SoC/SoC all showed nocturnal acid accumulation at day/night air temperatures of SOC/-SoC. Such metabolic activity at sub-zero temperatures was substantiated for an accession of O. streptacantha, which exhibited a net CO;z uptake at night at chlorenchyma temperatures of -3°C. Breeding for low-temperature tolerance is necessary to extend the regions where platyopuntias can be cultivated, an endeavor that can be aided by the relatively simple laboratory tests for low-temperature tolerance and metabolic activity described here.
International Journal of Plant Sciences, Nov 1, 1996
To help understand what conditions lead to the development of new organs on shoots of Opuntia fic... more To help understand what conditions lead to the development of new organs on shoots of Opuntia ficus-indica, a widely cultivated prickly pear cactus, detached cladodes were kept in a glasshouse and were shaded, exposed to full sunlight, or exposed to full sunlight and injected with various osmotica and hormones. Daughter cladodes emerged more slowly on cladodes detached in January (mean time of 12.6 wk) than in May (4.2 wk). In the field, new organ development was more rapid and more fruits were produced compared with cladodes detached in January and kept in a glasshouse. Shading by 94% essentially eliminated the development of daughter cladodes for cladodes harvested in both seasons over the 18-wk observation period. Daughter cladodes had a lower percentage dry mass and a higher water potential than the detached cladodes on which they developed, suggesting that water entered them primarily via the phloem. Compared with detached cladodes injected weekly with 1% of the cladode fresh mass of water for 6 wk, injection of 1.5 M sucrose accelerated daughter cladode development by 1.4 wk, 750 mM KCl by 3.0 wk, and 750 mM KNO3 by 4.8 wk. Injection of 20 μM gibberellic acid ( GA3 and ${\rm GA}_{4}$) virtually eliminated the development of daughter cladodes. Injection of 800 μM indole-3-acetic acid accelerated cladode development by 3.1 wk and 800 μM kinetin by 4.0 wk, both resulting in a greater biomass for the new organs. Thus production of daughter cladodes by detached cladodes of O. ficus-indica was enhanced by a higher tissue osmotic pressure, indole-acetic acid, and kinetin and was inhibited by shading and gibberellic acid.
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