首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 62 毫秒
1.
The climate of the native tropical forest habitats of Hylocereus undatus, a hemiepiphytic cactus cultivated in 20 countries for its fruit, can help explain the response of its net CO2 uptake to environmental factors. Under wet conditions, about 85% of the total daily net CO2 uptake occurs at night via Crassulacean acid metabolism, leading to a high water‐use efficiency. Total daily net CO2 uptake is reduced 57% by only 10 days of drought, possibly involving stomatal closure induced by abscisic acid produced in the roots, which typically occupy a small substrate volume. Total daily net CO2 uptake for H. undatus is maximal at day/night air temperatures of 30/20°C, optimal temperatures that are higher than those for desert cacti but representative of ambient temperatures in the tropics; its total daily net CO2 uptake becomes zero at day/night air temperatures of 42/32°C. Stem damage occurs at 45°C for H. undatus, whose photosynthetic cells show little acclimation to high temperatures compared with other cacti and are also sensitive to low temperatures, ‐1.5°C killing half of these cells. Consistent with its shaded habitat, total daily net CO2 uptake is appreciable at a total daily PPF of only 2 mol m2 day' and is maximal at 20 mol m?2 day?1, above which photoinhibition reduces net CO2 uptake. Net CO2 uptake ability, which is highly correlated with stem nitrogen and chlorophyll contents, changes only gradually (halftimes of 2–3 months) as the concentration of applied N is changed. Doubling the atmospheric CO2 concentration raises the total daily net CO2 uptake of H. undatus by 34% under optimal conditions and by even larger percentages under adverse environmental conditions.  相似文献   

2.
Hylocereus undatus (Haworth) Britton and Rose growing in controlled environment chambers at 370 and 740 μmol CO2 mol?1 air showed a Crassulacean acid metabolism (CAM) pattern of CO2 uptake, with 34% more total daily CO2 uptake under the doubled CO2 concentration and most of the increase occurring in the late afternoon. For both CO2 concentrations, 90% of the maximal daily CO2 uptake occurred at a total daily photosynthetic photon flux density (PPFD) of only 10 mol m?2 day?1 and the best day/night air temperatures were 25/15°C. Enhancement of the daily net CO2 uptake by doubling the CO2 concentration was greater under the highest PPFD (30 mol m?2 day?1) and extreme day/night air temperatures (15/5 and 45/35°C). After 24 days of drought, daily CO2 uptake under 370 μmol CO2 mol?1 was 25% of that under 740 μmol CO2 mol?1. The ratio of variable to maximal chlorophyll fluorescence (Fy/Fm) decreased as the PPFD was raised above 5 mol m?2 day?1, at extreme day/night temperatures and during drought, suggesting that stress occurred under these conditions. Fv/Fm was higher under the doubled CO2 concentration, indicating that the current CO2 concentration was apparently limiting for photosynthesis. Thus net CO2 uptake by the shade-tolerant H. undatus, the photosynthetic efficiency of which was greatest at low PPFDs. showed a positive response to doubling the CO2 concentration, especially under stressful environmental conditions.  相似文献   

3.
Physiological responses of Opuntia ficus-indica to growth temperature   总被引:2,自引:0,他引:2  
The influences of various day/night air temperatures on net CO2 uptake and nocturnal acid accumulation were determined for Opuntia ficus-indica, complementing previous studies on the water relations and responses to photosynthetically active radiation (PAR) for this widely cultivated cactus. As for other Crassulacean acid metabolism (CAM) plants, net nocturnal CO2 uptake had a relatively low optimal temperature, ranging from 11°C for plants grown at day/night air temperatures of 10°C/0°C to 23°C at 45°C/35°C. Stomatal opening, which occurred essentially only at night and was measured by changes in water vapor conductance, progressively decreased as the measurement temperature was raised. The CO2 residual conductance, which describes chlorenchyma properties, had a temperature optimum a few degrees higher than the optimum for net CO2 uptake at all growth temperatures. Nocturnal CO2 uptake and acid accumulation summed over the whole night were maximal for growth temperatures near 25°C/15°C, CO2 uptake decreasing more rapidly than acid accumulation as the growth temperature was raised. At day/night air temperatures that led to substantial nocturnal acid accumulation (25°C/15°C.). 90% saturation of acid accumulation required a higher total daily PAR than at non-optimal growth temperatures (10°C/0°C and 35°C/25°C). Also, the optimal temperature of net CO2 uptake shifted downward when the plants were under drought conditions at all three growth temperatures tested, possibly reflecting an increased fractional importance of respiration at the higher temperatures during drought. Thus, water status, ambient PAR, and growth temperatures must all be considered when predicting the temperature response of gas exchange for O. ficus-indica and presumably for other CAM plants.  相似文献   

4.
When the day/night air temperatures were raised from 10°C/10°C to 30°C/30°C, the optimal tempearture for nocturnal CO2 uptake by six species of cacti and three species of agave shifted from an average of 12°C to an average of 20°C. The maximum rate of CO2 uptake was higher for Agave americana at the higher ambient temperature, lower for A. deserti , and much lower for A. utahensis , consistent with the relative mean temperatures of their native habitats. For the cactus Coryphantha vivipara , which had the greatest temperature shift observed (13°C), the halftime was 8 days for the upward shift and 4 days for the downward shift. The halftimes for the comparable shifts averaged 1.6 days for three other species of cacti and less than 1 day for two agave species. The shifts in the optimal temperature for nocturnal CO2 uptake were in response to changes in nighttime temperature, at least for C. vivipara , and reflected temperature responses of both the stomates and the chlorenchyma.  相似文献   

5.
Net CO2 uptake rates (P N) were measured for the vine cacti Hylocereus undatus and Selenicereus megalanthus under relatively extreme climatic conditions in Israel. Withholding water decreased rates and the daily amount of CO2 uptake by about 10 % per day. Compared with more moderate climates within environmental chambers, the higher temperatures and lower relative humidity in the field led to a more rapid response to drought. The upper envelopes of scatter diagrams for P N versus temperature for these Crassulacean acid metabolism species, which indicate the maximal rates at a particular temperature, were determined for both night time CO2 uptake in Phase I (mediated by phosphoenolpyruvate carboxylase, PEPC) and early morning uptake in Phase II (mediated by ribulose-1,5-bisphosphate carboxylase/oxygenase, RuBPCO). As stem temperature increased above 13 °C, the maximal P N increased exponentially, reaching maxima near 27 °C of 12 and 8 μmol m−2 s−1 for Phases I and II, respectively, for H. undatus and 6 and 4 μmol m−2 s−1, respectively, for S. megalanthus. Based on the Arrhenius equation, the apparent activation energies of PEPC and RuBPCO were 103 and 86 kJ mol−1, respectively, for H. undatus and 77 and 49 kJ mol−1, respectively, for S. megalanthus, within the range determined for a diverse group of species using different methodologies. Above 28 °C, P N decreased an average of 58 % per °C in Phase I and 30 % per °C in Phase II for the two species; such steep declines with temperature indicate that irrigation then may lead to only small enhancements in net CO2 uptake ability.  相似文献   

6.
Branches of 22-year-old loblolly pine (Pinus taeda, L.) trees growing in a plantation were exposed to ambient CO2, ambient + 165 μmol mol?1 CO2 or ambient + 330 μmol mol?1 CO2 concentrations in combination with ambient or ambient + 2°C air temperatures for 3 years. Field measurements in the third year indicated that net carbon assimilation was enhanced in the elevated CO2 treatments in all seasons. On the basis of A/Ci, curves, there was no indication of photosynthetic down-regulation. Branch growth and leaf area also increased significantly in the elevated CO2 treatments. The imposed 2°C increase in air temperature only had slight effects on net assimilation and growth. Compared with the ambient CO2 treatment, rates of net assimilation were ~1·6 times greater in the ambient + 165 μmol mol?1 CO2 treatment and 2·2 times greater in the ambient + 330 μmol mol?1 CO2 treatment. These ratios did not change appreciably in measurements made in all four seasons even though mean ambient air temperatures during the measurement periods ranged from 12·6 to 28·2°C. This indicated that the effect of elevated CO2 concentrations on net assimilation under field conditions was primarily additive. The results also indicated that the effect of elevated CO2 (+ 165 or + 330 μmol mol?1) was much greater than the effect of a 2°C increase in air temperature on net assimilation and growth in this species.  相似文献   

7.
Abstract. The productivity of the prickly-pear cactus Opuntia ficus-indica, which is cultivated worldwide for its fruits and stem segments, was predicted based on the responses of its net CO2 uptake to soil water status, air temperature and photosynthetic photon flux density (PPFD). Each of these environmental factors was represented by an index with a maximum value of unity when that factor was not limiting net CO2 uptake over a 24-h period. The water index, the temperature index, and the PPFD index were determined for 87 sites in the contiguous United States using data from 189 weather stations and for 148 sites worldwide using data from 1464 weather stations. The product of these three indices, the environmental productivity index (EPI), was used to predict the productivity of O. ficus-indica under current climatic conditions and under those accompanying a possible increase in the atmospheric CO2 level to 650μumol mol?1. Sites with temperatures always above -10°C and hence suitable for prickly-pear cultivation numbered 37 in the United States and 110 worldwide; such sites increased by 43 and 5%, respectively, for the global warming accompanying the elevated CO2. Productivity of O. ficus-indica was at least 15 tonnes dry weight hectare?1 year?1, comparable to that of many agronomic crops, for 20 sites with temperatures always above -10°C in the contiguous United States and for 12 such sites worldwide under current climatic conditions; such sites increased by 85 and 117%, respectively, under the elevated CO2 condition, mainly because of direct effects of the atmospheric CO2 level on net CO2 uptake. In summary, simulations based on EPI indicate that O. ficus-indica may presently be advantageously cultivated over a substantial fraction of the earth's surface, such regions increasing markedly with a future doubling in atmospheric CO2 levels.  相似文献   

8.
The mechanisms controlling the photosynthetic performance of C4 plants at low temperature were investigated using ecotypes of Bouteloua gracilis Lag. from high (3000 m) and low (1500 m) elevation sites in the Rocky Mountains of Colorado. Plants were grown in controlled‐environment cabinets at a photon flux density of 700 μ mol m?2 s?1 and day/night temperatures of 26/16 °C or 14/7 °C. The thermal response of the net CO2 assimilation rate (A) was evaluated using leaf gas‐exchange analysis and activity assays of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco), phosphoenolpyruvate carboxylase (PEPCase) and pyruvate,orthophosphate dikinase (PPDK). In both ecotypes, a reduction in measurement temperature caused the CO2‐saturated rate of photosynthesis to decline to a greater degree than the initial slope of A versus the intercellular CO2 response, thereby reducing the photosynthetic CO2 saturation point. As a consequence, A in normal air was CO2‐saturated at sub‐optimal temperatures. Ecotypic variation was low when grown at 26/16 °C, with the major difference between the ecotypes being that the low‐elevation plants had higher A; however, the ecotypes responded differently when grown at cool temperature. At temperatures below the thermal optimum, A in high‐elevation plants grown at 14/7 °C was enhanced relative to plants grown at 26/16 °C, while A in low‐elevation plants grown at 14/7 °C was reduced compared to 26/16 °C‐grown plants. Photoinhibition at low growth temperature was minor in both ecotypes as indicated by small reductions in dark‐adapted Fv/Fm. In both ecotypes, the activity of Rubisco was equivalent to A below 17 °C but well in excess of A above 25 °C. Activities of PEPCase and PPDK responded to temperature in a similar proportion relative to Rubisco, and showed no evidence for dissociation that would cause them to become principal limitations at low temperature. Because of the similar temperature response of Rubisco and A, we propose that Rubisco is a major limitation on C4 photosynthesis in B. gracilis below 17 °C. Based on these results and for theoretical reasons associated with how C4 plants use Rubisco, we further suggest that Rubisco capacity may be a widespread limitation upon C4 photosynthesis at low temperature.  相似文献   

9.
Abstract The effect of freezing night temperatures on net photosynthesis, stomatal conductance, and internal CO2 concentration was investigated in unhardened seedlings of Engelmann spruce. Exposure to – 2.5°C in the dark for 10 h caused a slight and reversible reduction in gas-exchange parameters on the following days. Substantial and irreversible inhibition of photosynthesis occurred after exposure to -4°C or –5°C. Despite a parallel decline in stomatal conductance and net photosynthesis, exposure to a hard freeze caused a decrease in the stomatal limitation to gas exchange. Hard-freeze conditions (less than – 4°C) also caused a decrease in carboxylation efficiency and apparent quantum yield, indicating a freeze-induced failure of the dark reactions and electron transport. There was no significant difference in the photosynthetic response to freezing temperatures in different elevational populations of spruce, although acclimatory adjustments were observed. Gas exchange in seedlings grown under cool conditions (14°C day/9°C night) was less affected and recovered more rapidly after exposure to a hard freeze than in seedlings grown under warm conditions (24°C day/19°C night).  相似文献   

10.
Plants of the crassulacean acid metabolism (CAM) species Plectranthus marrubioides (Lamiaceae) were subjected to short- and long-term changes in air humidity in controlled-environment experiments. Stomata of well-watered individuals of this all-cell leaf-succulent taxon responded directly, quickly and reversibly to variations of the water vapour gradient between leaf and air (Δw). Mean night-time leaf conductance to water vapour decreased curvilinearly with increasing Δw but linearly with lowered relative air humidity. Stomatal response was generally independent of the prevailing temperature and was not linked to CO2 uptake rates. Therefore, net night-time carbon gain, nocturnal malic acid accumulation and, thus, relative carbon recycling were not influenced by changes in air humidity in the temperature range tested. Mean nocturnal molar water use efficiency, however, decreased with decreasing air humidity because of the increased transpirational water loss. If watering was repeatedly withheld for several days during the experiments, employing a temperature regime of 35/30°C day and night, stomatal conductance became low enough to inhibit CO2 uptake, but only at the highest Δw. The results suggest that drought stress was necessary to increase responsiveness of plants to the point where CAM was also inhibited by decreases in air humidity.  相似文献   

11.
CO2 exchange rates per unit dry weight, measured in the field on attached fruits of the late-maturing Cal Red peach cultivar, at 1200 μmol photons m?2S?1 and in dark, and photosynthetic rates, calculated by the difference between the rates of CO2 evolution in light and dark, declined over the growing season. Calculated photosynthetic rates per fruit increased over the season with increasing fruit dry matter, but declined in maturing fruits apparently coinciding with the loss of chlorophyll. Slight net fruit photosynthetic rates ranging from 0. 087 ± 0. 06 to 0. 003 ± 0. 05 nmol CO2 (g dry weight)?1 S?1 were measured in midseason under optimal temperature (15 and 20°C) and light (1200 μmol photons m?2 S?1) conditions. Calculated fruit photosynthetic rates per unit dry weight increased with increasing temperatures and photon flux densities during fruit development. Dark respiration rates per unit dry weight doubled within a temperature interval of 10°C; the mean seasonal O10 value was 2. 03 between 20 and 30°C. The highest photosynthetic rates were measured at 35°C throughout the growing season. Since dark respiration rates increased at high temperatures to a greater extent than CO2 exchange rates in light, fruit photosynthesis was apparently stimulated by high internal CO2 concentrations via CO2 refixation. At 15°C, fruit photosynthetic rates tended to be saturated at about 600 μmol photons m?2 S?1. Young peach fruits responded to increasing ambient CO2 concentrations with decreasing net CO2 exchange rates in light, but more mature fruits did not respond to increases in ambient CO2. Fruit CO2 exchange rates in the dark remained fairly constant, apparently uninfluenced by ambient CO2 concentrations during the entire growing season. Calculated fruit photosynthetic rates clearly revealed the difference in CO2 response of young and mature peach fruits. Photosynthetic rates of younger peach fruits apparently approached saturation at 370 μl CO21?2. In CO2 free air, fruit photosynthesis was dependent on CO2 refixation since CO2 uptake by the fruits from the external atmosphere was not possible. The difference in photosynthetic rates between fruits in CO2-free air and 370 μl CO2 1?1 indicated that young peach fruits were apparently able to take up CO2 from the external atmosphere. CO2 uptake by peach fruits contributed between 28 and 16% to the fruit photosynthetic rate early in the season, whereas photosynthesis in maturing fruits was supplied entirely by CO2 refixation.  相似文献   

12.
Plants of alfalfa (Medicago sativa) and orchard grass (Dactylus glomerata) were grown in controlled environment chambers at two CO2 concentrations (350 and 700 μmol mol-1) and 4 constant day/night growth temperatures of 15, 20, 25 and 30°C for 50–90 days to determine changes in growth and whole plant CO2 efflux (dark respiration). To facilitate comparisons with other studies, respiration data were expressed on the basis of leaf area, dry weight and protein. Growth at elevated CO2 increased total plant biomass at all temperatures relative to ambient CO2, but the relative enhancement declined (P≤0.05) as temperature increased. Whole plant respiration (Rd) at elevated CO2 declined at 15 and 20°C in D. glomerata on an area, weight or protein basis and in M. sativa on a weight or protein basis when compared to ambient CO2. Separation of Rd into respiration required for growth (Rg) and maintenance (Rm) showed a significant effect of elevated CO2 on both components. Rm was reduced in both species but only at lower temperatures (15°C in M. sativa and 15 and 20°C in D. glomerata). The effect on Rm could not be accounted for by protein content in either species. Rg was also reduced with elevated CO2; however no particular effect of temperature was observed, i. e. Rg was reduced at 20, 25 and 30°C in M. sativa and at 15 and 25°C in D. glomerata. For the two perennial species used in the present study, the data suggest that both Rg and Rm can be reduced by anticipated increases in atmospheric CO2; however, CO2 inhibition of total plant respiration may decline as a function of increasing temperature  相似文献   

13.
For most of the past 250 000 years, atmospheric CO2 has been 30–50% lower than the current level of 360 μmol CO2 mol–1 air. Although the effects of CO2 on plant performance are well recognized, the effects of low CO2 in combination with abiotic stress remain poorly understood. In this study, a growth chamber experiment using a two-by-two factorial design of CO2 (380 μmol mol–1, 200 μmol mol–1) and temperature (25/20 °C day/night, 36/29 °C) was conducted to evaluate the interactive effects of CO2 and temperature variation on growth, tissue chemistry and leaf gas exchange of Phaseolus vulgaris. Relative to plants grown at 380 μmol mol–1 and 25/20 °C, whole plant biomass was 36% less at 380 μmol mol–1× 36/29 °C, and 37% less at 200 μmol mol–1× 25/20 °C. Most significantly, growth at 200 μmol mol–1× 36/29 °C resulted in 77% less biomass relative to plants grown at 380 μmol mol–1× 25/20 °C. The net CO2 assimilation rate of leaves grown in 200 μmol mol–1× 25/20 °C was 40% lower than in leaves from 380 μmol mol–1× 25/20 °C, but similar to leaves in 200 μmol mol–1× 36/29 °C. The leaves produced in low CO2 and high temperature respired at a rate that was double that of leaves from the 380μmol mol–1× 25/20 °C treatment. Despite this, there was little evidence that leaves at low CO2 and high temperature were carbohydrate deficient, because soluble sugars, starch and total non-structural carbohydrates of leaves from the 200μmol mol–1× 36/29 °C treatment were not significantly different in leaves from the 380μmol mol–1× 25/20 °C treatment. Similarly, there was no significant difference in percentage root carbon, leaf chlorophyll and leaf/root nitrogen between the low CO2× high temperature treatment and ambient CO2 controls. Decreased plant growth was correlated with neither leaf gas exchange nor tissue chemistry. Rather, leaf and root growth were the most affected responses, declining in equivalent proportions as total biomass production. Because of this close association, the mechanisms controlling leaf and root growth appear to have the greatest control over the response to heat stress and CO2 reduction in P. vulgaris.  相似文献   

14.
Abstract The regulation of crassulacean acid metabolism (CAM) under controlled environmental conditions has been investigated for two tropical epiphytes, relating plant water and carbon balance to growth form and habitat preference under natural conditions. Aechmea fendleri is restricted to wet, upper montane regions of Trinidad, while A. nudicaulis has a wider distribution extending into more arid regions of the island. Morphological characteristics of these plants are related to habitat preference in terms of leaf succulence (0.44 and 0.94 kg m?2 for the two species respectively) and a distinct layer of water storage parenchyma in A. nudicaulis In contrast, the thinner leaves of A. fendleri contain little water-storage parenchyma and less chlorenchyma per unit area, but the plants have a more open leaf rosette. The two species differ in expression of CAM, since the proportion of respiratory CO2 recycled as part of CAM had been found to be much lower in A. fendleri This study compared the efficiency of water use and role of respiratory CO2 recycling under two PAR regimes (300 and 120 μnol m?2 s?1) and three night temperatures (12, 18 and 25 °C). Dark CO2 uptake rates for both species were comparable to plants in the field (maximum of 2.3 ± 0.2 μmol m?2s?1± SD, n= 3). Total net CO2 uptake at night increased on leaf area basis with temperature for both species under higher PAR, although under the low PAR regime CO2 uptake was maximal at 18 °C. Water-use efficiency (WUE) increased at 18 °C and 25 °C during dark CO2 uptake (Phase I) and also during late afternoon photosynthesis (Phase IV) in both species. For A. fendleri, dawn to dusk changes in titrable acidity (ΔH +) were similar under high and low PAR, although ΔH+ was correlated to night temperature and PAR in A. nudicaulis. The proportion of ΔH+ derived from respiratory CO2 also varied with experimental conditions. Thus percentage recycling was lower in A. fendleri under high PAR (0–10%), but was only reduced at 18 °C under low PAR. Recycling by A. nudicaulis ranged from 32–42% under high PAR, but was also reduced to 6% under low PAR at 18 °C; at 12 °C and 25 °C, recycling was 37% and 52% respectively. Previous studies have suggested a relationship between the proportion of recycling and degree of water stress. This study indicated that CAM as a CO2 concentrating mechanism regulates both water-use efficiency and plant carbon balance in these epiphytes, in response to PAR and night temperature. However, the precise relationship between respiratory processes and the balance between external and internal sources of CO2 is as yet unresolved.  相似文献   

15.
Abstract Soil surface temperatures in deserts can reach 70 °C, far exceeding the high-temperature tolerance of most vascular plants of about 55 °C. In this study a computer model indicated that the maximum temperatures of small spherical cacti would approach soil surface temperatures, in agreement with measurements on seedlings of Ferocactus acanthodes. Shortwave radiation was the most important environmental variable affecting maximum cactus temperatures: a 70% reduction in shortwave radiation by shading lowered both predicted and measured stem surface temperatures by 17 °C for plants 2 cm in diameter. High-temperature tolerance, measured as the temperature that halved the fraction of cells taking up a vital stain after a 1 h high-temperature treatment, could reach 60 °C for the detached stems of Opuntia bigelovii, which appears crucial for its vegetative reproduction, and 70 °C for O. ficus-indica, apparently the greatest high-temperature tolerance so far reported for higher vascular plants. Two-fold increases in shortwave absorptance from Epithelantha bokei to Mammillaria lasiacantha to Ariocarpus fissuratus led to a 5 °C predicted increase in maximum temperature. However, compensatory differences in high-temperature tolerances occurred for these dwarf cacti, helping to explain their occurrence in the same open habitat in the Chihuahuan Desert. All six species showed acclimation of their high-temperature tolerance as ambient temperatures were increased, including acclimation by the roots of the dwarf cacti, where the greater sensitivity to high temperatures of roots would exclude them from the upper 2 cm of the soil. Using the model, the observed high-temperature acclimation, and the temperatures needed to reduce stain uptake to zero, the three dwarf cacti were predicted to be able to survive soil surface temperatures of up to 74 °C.  相似文献   

16.
Mycorrhizas are ubiquitous symbioses that may have an important role in the movement of C from air to soil. Studies on the effects of climate change factors on mycorrhizas have been concentrated on the effects of atmospheric [CO2] whereas temperature effects have been neglected. Based on previous results showing no effect of varying atmospheric [CO2] on the development and P uptake of the arbuscular mycorrhizal fungi (AMF) colonizing plants growing in controlled conditions, we hypothesized that soil temperature would have a higher impact on AMF development and nutrient uptake than the effects of [CO2] on the host plant. Pea plants were grown in association with either a single isolate of Glomus caledonium or AMF from field soil in factorial combination with the corresponding current (10 °C) or elevated (15 °C) soil temperatures at current (350 p.p.m) or elevated (700 p.p.m) atmospheric [CO2]. 33P uptake by extraradical AMF hyphae was measured independently from root P uptake in a root exclusion compartment. Intraradical colonization developed well at both soil temperatures and almost duplicated from 10 to 15 °C. Extraradical mycelium developed only at 15 °C in the root exclusion compartment and hyphal P uptake could therefore be studied at 15 °C only. Hyphal P uptake differed markedly between inoculum types, but was not altered by growing the host plants at two atmospheric [CO2] levels. No significant [CO2] × soil temperature interactions were observed. The results suggested that, in the system tested, AMF development and function is likely more influenced by the temperature component of climate change than by its [CO2] component. We suggest that much more attention should be paid to temperature effects in future studies.  相似文献   

17.
Nowadays, a quest for efficient greenhouse heating strategies, and their related effects on the plant’s performance, exists. In this study, the effects of a combination of warm days and cool nights in autumn and spring on the photosynthetic activity and efficiency of Phalaenopsis were evaluated; the latter, being poorly characterised in plants with crassulacean acid metabolism (CAM) and, to our knowledge, not reported before in Phalaenopsis. 24-h CO2 flux measurements and chlorophyll (Chl) fluorescence analyses were performed in both seasons on Phalaenopsis ‘Hercules’ exposed to relatively constant temperature regimes, 25.5/24.0°C (autumn) and 30/27°C (spring) respectively, and distinctive warm day/cool night temperature regimes, 27/20°C (autumn) and 36/24°C (spring), respectively. Cumulated leaf net CO2 uptake of the distinctive warm day/cool night temperature regimes declined with 10–16% as compared to the more constant temperature regimes, while the efficiency of carbon fixation revealed no substantial differences in both seasons. Nevertheless, a distinctive warm day/cool night temperature regime seemed to induce photorespiration. Although photorespiration is expected not to occur in CAM, the suppression of the leaf net CO2 exchange during Phase II and Phase IV as well as the slightly lower efficiency of carbon fixation for the distinctive warm day/cool night temperature regimes confirms the involvement of photorespiration in CAM. A seasonal effect was reflected in the leaf net CO2 exchange rate with considerably higher rates in spring. In addition, sufficiently high levels of photosynthetically active radiation (PAR) in spring led to an efficiency of carbon fixation of 1.06–1.27% which is about twice as high than in autumn. As a result, only in the case where a net energy reduction between the temperature regimes compensates for the reduction in net CO2 uptake, warm day/cool night temperature regimes may be recommended as a practical sustainable alternative.  相似文献   

18.
Abstract Associations between photosynthetic responses to CO2 at rate-saturating light and photosynthetic enzyme activities were compared for leaves of maize grown under constant air temperatures of 19, 25 and 31°C. Key photosynthetic enzymes analysed were ribulose bisphosphatc (RuBP) carboxylase, phosphoenolpyruvate (PEP) carboxylase, NADP-malic enzyme and pyruvate, Pi dikinasc. Rates of CO2-saturated photosynthesis were similar in leaves developed at 19°C and 25°C but were decreased significantly by growth at 31°C. In contrast, carboxylation efficiency differed significantly between all three temperature regimes. Carboxylation efficiency was greatest in leaves developed at 19°C and decreased with increasing temperature during growth. The changes of carboxylation efficiency were highly correlated with changes in the activity of pyruvate, Pi dikinase (r= 0.95), but not with other photosynthetic enzyme activities. The activities of these latter enzymes, including that of RuBP carboxylase, were relatively insensitive to temperature during growth. The sensitivity of quantum yield to O2 concentration was lower in leaves grown at 19°C than in leaves grown at 31°C. These observations support the novel hypothesis that variation in the capacity for CO2 delivery to the bundle sheath by the C4 cycle, relative to the capacity for net assimilation by the C2 cycle, can be a principal determinant of C4 photosynthetic responses to CO2.  相似文献   

19.
Park S. Nobel 《Oecologia》1977,27(2):117-133
Summary The structural characteristics, water relations, and photosynthesis of Ferocactus acanthodes (Lemaire) Britton and Rose, a barrel cactus exhibiting Crassulacean acid metabolism (CAM), were examined in its native habitat in the western Colorado desert. Water storage in its succulent stem permitted nighttime stomatal opening ot continue for about 40 days after the soil water potential became less than that of the stem, a period whe the plant would be unable to extract water from the soil. After 7 months of drought and consequent unreplenished water loss from a plant, diurnal stomatal activity was not observed and the stem osmotic pressure was 6.4 bars, more than double the value measured during wet periods with nighttime stomatal opening. F. acanthodes had a shallow root system (mean depth of 8 cm) which responded within 24 h to rainfall.When the nocturnal stem surface temperature was raised from 8.0° C to 35.0° C, the stomatal resistance increased 4-fold, indicating that cool nighttime temperatures are advantageous for gas exchange by F. acanthodes. Moreover, the optimal temperature for CO2 uptake in the dark was only 12.6° C. CO2 uptake at night became maximal for 3.0 mEinsteins cm-2 of photosynthetically active radiation incident during the preceding day, and the minimum number of incident quanta absorbed per CO2 fixed was 68. The transpiration ratio (mass of water transpired/mass of CO2 fixed) had the relatively low value of 70 for an entire year, consistent with values obtained for other CAM plants. The total amount of water annually diverted to the floral structures was about 6% of the stem wet weight. The annual growth increment estimated from the net CO2 assimilation corresponded to about 10% of the stem mass for barrel cacti 34 cm tall, in agreement with measured dimension changes, and indicated that such plants were about 26 years old.  相似文献   

20.
Abstract When tomato plants of the high-altitude species Lycopersicon hirsutum and of the cultivated Lycopersicon esculentum were grown at 24/18°C (day/night), the effects of temperature, photon flux density, and intercellular CO2 concentration up to about 600 μl l?1 on net CO2 uptake were similar in the two species. Acclimation of these plants at 12/6°C (day/night) resulted, after 4 d or longer, in a similar downward shift of about 5°C in the optimum temperature for CO2 uptake. However, in comparison with the cultivated species, the high-altitude plants achieved a higher rate of CO2 uptake at saturating concentrations of intercellular CO2, maintained a higher level of saturating-light CO2 uptake rate at 10°C after exposure to chilling stress (10°C and photon flux density of 400 μmol m?2s?1 d and 5°C night) for 7–18 d, and displayed a better capacity for rapid recovery after prolonged stress. The greater capacity for CO2 uptake observed in the high-altitude species during and after exposure to chilling stress was also reflected in its higher growth rate under those conditions compared with plants of L. esculentum. These advantages of the high-altitude species may partly explain its ability to survive and complete its life cycle under the environmental conditions prevailing in its natural habitat.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号