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1.
Besides the paucity of information on the effects of drought stress on photosynthesis and yield in sweet potato [ Ipomoea batatas (L.) Lam.], available reports are also contradictory. The aim of this study was to shed light on the effects of long-term restricted water supply on shoot development, photosynthesis and storage root yield in field-grown sweet potato. Experiments were conducted under a rainout shelter where effects of restricted water supply were assessed in two varieties (Resisto and A15). Large decreases in stomatal conductance occurred in both varieties after 5 weeks of treatment. However, continued measurements revealed a large varietal difference in persistence of this response and effects on CO2 assimilation. Although restricted water supply decreased leaf relative water content similarly in both varieties, the negative effects on stomatal conductance disappeared with time in A15 (indicating high drought acclimation capacity) but not in Resisto, thus leading to inhibition of CO2 assimilation in Resisto. Chlorophyll a fluorescence measurements, and the relationship between stomatal conductance, intercellular CO2 concentration and CO2 assimilation rate, indicated that drought stress inhibited photosynthesis primarily through stomatal closure. Although yield loss was considerably larger in Resisto, it was also reduced by up to 60% in A15, even though photosynthesis, expressed on a leaf area basis, was not inhibited in this variety. In A15 yield loss appears to be closely associated with decreased aboveground biomass accumulation, whereas in Resisto, combined effects on biomass accumulation and photosynthesis per unit leaf area are indicated, suggesting that research aimed at improving drought tolerance in sweet potato should consider both these factors. 相似文献
2.
Parameters related to leaf photosynthesis were evaluated in three genotypes of common bean ( Phaseolus vulgaris L.) with contrasting tolerance to Mn toxicity. Two short-term studies in solution culture were used to assess the effect of excess Mn on CO2 assimilation in mature and immature leaves. Mn toxicity decreased total chlorophyll content only in immature leaves, with a consequent reduction of leaf CO2 assimilation. Mature leaves that showed brown speckles characteristic of Mn toxicity, did not suffer any detriment in their capacity to assimilate CO2 , at least in a 4-day experiment. Stomatal conductance and transpiration were not affected by the presence of high levels of Mn in leaf tissue. Lower stomatal conductance and transpiration rates were observed only in leaves with advanced chlorosis. Differences among genotypes were detected as increased chlorosis in the more sensitive genotype ZPV-292, followed by A-283 and less chlorosis in the tolerant genotype CALIMA. Since CO2 assimilation expressed per unit of chlorophyll was not different between high-Mn plants and control plants, we conclude that the negative effect of Mn toxicity on CO2 assimilation can be explained by a reduction in leaf chlorophyll content. 相似文献
3.
Z. Tuba H. K. Lichtenthaler Zs. Csintalan Z. Nagy K. Szente 《Physiologia plantarum》1996,96(3):383-388
During a slow desiccation in photosynthetically fully active leaves of the poikilochlorophyllous desiccation-tolerant (PDT) monocotyledon Xerophyta scabrida (Pax) Th. Dur. et Schinz (Velloziaceae), thylakoid activity, CO2 assimilation and respiration decline and chlorophylls and carotenoids are successively broken down. The initially slow rate of leaf water loss is related to the large reduction in leaf area which is reflected in the decrease of specific leaf area. Chlorophylls are broken down faster than carotenoids. The ratio of the variable chlorophyll fluorescence, an indicator of photosynthetic activity (Rfd690-values), shows that the functionality of thylakoids and chlorophylls is successively lost during desiccation. The decline in net CO2 assimilation in desiccating leaves is largely caused by stomatal closure. The complete cessation of CO2 assimilation, however, is due to the breakdown of chlorophylls and thylakoids. Respiration continued during desiccation and remained active far below -3.2 MPa leaf water potential. The differences during desiccation of the photosynthetic apparatus between poikilochlorophyllous and homoiochlorophyllous desiccation-tolerant plants are discussed. 相似文献
4.
The role of temperature in determining the stimulation of CO2 assimilation at elevated carbon dioxide concentration in soybean seedlings 总被引:1,自引:0,他引:1
Soybean ( Glycine max cv. Clark) was grown at both ambient (ca 350 μmol mol−1 ) and elevated (ca 700 μmol mol−1 ) CO2 concentration at 5 growth temperatures (constant day/night temperatures of 20, 25, 30, 35 and 40°C) for 17–22 days after sowing to determine the interaction between temperature and CO2 concentration on photosynthesis (measured as A, the rate of CO2 assimilation per unit leaf area) at both the single leaf and whole plant level. Single leaves of soybean demonstrated increasingly greater stimulation of A at elevated CO2 as temperature increased from 25 to 35°C (i.e. optimal growth rates). At 40°C, primary leaves failed to develop and plants eventually died. In contrast, for both whole plant A and total biomass production, increasing temperature resulted in less stimulation by elevated CO2 concentration. For whole plants, increased CO2 stimulated leaf area more as growth temperature increased. Differences between the response of A to elevated CO2 for single leaves and whole plants may be related to increased self-shading experienced by whole plants at elevated CO2 as temperature increased. Results from the present study suggest that self-shading could limit the response of CO2 assimilation rate and the growth response of soybean plants if temperature and CO2 increase concurrently, and illustrate that light may be an important consideration in predicting the relative stimulation of photosynthesis by elevated CO2 at the whole plant level. 相似文献
5.
Effects of manganese toxicity on photosynthesis of white birch (Betula platyphylla var. japonica) seedlings 总被引:5,自引:0,他引:5
The effects of manganese (Mn) toxicity on photosynthesis in white birch ( Betula platyphylla var. japonica ) leaves were examined by the measurement of gas exchange and chlorophyll fluorescence in hydroponically cultured plants. The net photosynthetic rate at saturating light and ambient CO2 (Ca ) of 35 Pa decreased with increasing leaf Mn concentrations. The carboxylation efficiency, derived from the difference in CO2 assimilation rate at intercellular CO2 pressures attained at Ca of 13 Pa and O Pa, decreased with greater leaf Mn accumulation. Net photosynthetic rate at saturating light and saturating CO2 (5%) also declined with leaf Mn accumulation while the maximum quantum yield of O2 evolution at saturating CO2 was not affected. The maximum efficiency of PSII photochemistry (Fv /Fm ) was little affected by Mn accumulation in white birch leaves over a wide range of leaf Mn concentrations (2–17 mg g−1 dry weight). When measured in the steady state of photosynthesis under ambient air at 430 μmol quanta m−2 s−1 , the levels of photochemical quenching (qP) and the excitation capture efficiency of open PSII (F'v /F'm ) declined with Mn accumulation in leaves. The present results suggest that excess Mn in leaves affects the activities of the CO2 reduction cycle rather than the potential efficiency of photochemistry, leading to increases in QA reduction state and thermal energy dissipation, and a decrease in quantum yield of PSII in the steady state. 相似文献
6.
The effects of CO2 enrichment on growth of Xanthomonas campestris pv. pelargonii and the impact of infection on the photosynthesis and export of attached, intact, 'source' leaves of geranium ( Pelargonium x domesticum, 'Scarlet Orbit Improved' ) are reported. Two experiments were performed, one with plants without flower buds, and another with plants which were flowering. Measurements were made on healthy and diseased leaves at the CO2 levels (35 Pa or 90 Pa) at which the plants were grown. There were no losses of chlorophyll, or any signs of visible chlorosis or necrosis due to infection. Lower numbers of bacteria were found in leaves at high CO2 , suggesting growth at elevated CO2 created a less favourable condition in the leaf for bacterial growth. Although high CO2 lowered the bacterial number in infected leaves, reductions in photosynthesis and export were greater than at ambient CO2 . The capacity of infected source leaves to export photoassimilates at rates observed in the controls was reduced in both light and darkness. In summary, the severity of infection on source leaf function by the bacteria was increased, rather than reduced by CO2 enrichment, underscoring the need for further assessment of plant diseases and bacterial virulence in plants growing under varying CO2 levels. 相似文献
7.
8.
Highbush blueberry plants ( Vaccinium corymbosum L. cv. Bluecrop) growing in containers were flooded in the laboratory for various durations to determine the effect of flooding on carbon assimilation, photosynthetic response to varying CO2 and O2 concentrations and apparent quantum yield as measured in an open flow gas analysis system. Hydraulic conductivity of the root was also measured using a pressure chamber. Root conductivity was lower and the effect of increasing CO2 levels on carbon assimilation less for flooded than unflooded plants after short-(i-2 days), intermediate-(10–14 days) and long-term (35–40 days) flooding. A reduction in O2 levels surrounding the leaves from 21 to 2% for unflooded plants increased carbon assimilation by 33% and carboxylation efficiency from 0.012 to 0.021 mol CO2 fixed (mol CO2 )−1 . Carboxylation efficiency of flooded plants, however, was unaffected by a decrease in percentage O2 , averaging 0.005 mol CO2 fixed (mol CO2 )−1 . Apparent quantum yield decreased from 2.2 × 10−1 mol of CO2 fixed (mol light)−1 for unflooded plants to 2.0 × 10−3 and 9.0 × 10−4 for intermediate- and long-term flooding durations, respectively. Shortterm flooding reduced carbon assimilation via a decrease in stomatal conductance, while longer flooding durations also decreased the carboxylation efficiency of the leaf. 相似文献
9.
Gas exchange parameters, water relations and carbohydrate partitioning in leaves of field-grown Prunus domestica following fruit removal 总被引:1,自引:0,他引:1
The effect of fruit removal on gas exchange, water relations, chlorophyll and non-structural carbohydrate content of leaves from mature, field-grown plum trees ( Prunus domestica L. cv. Stanley) was determined over 2 consecutive growing seasons. Removal of fruits during stage II of fruit development decreased CO2 assimilation rate within 24 h from 12.6 to 8.5 μmol m-2 s-1 in 1986, and from 12.1 to 10.2 μmol m-2 s-1 in 1987. Depression of net photosynthesis persisted for at least 5 days and was greatest in the early afternoon. Recovery of the CO2 assimilation rate to pretreatment levels coincided in defruited trees with vegetative growth that was more than 5-fold that of fruiting trees in the first 6 weeks after fruit removal in 1986. Estimated photorespiration was similar in both fruiting and defruited trees. The stomatal contribution to the decrease of CO2 assimilation rate, calculated from assimilation/intercellular CO2 curves, ranged from 31 to 46%. Defruiting did not affect leaf water potential, but decreased leaf osmotic potential. Leaf levels of chlorophyll, fructose, glucose, sorbitol and sucrose were not affected by defruiting, whereas starch content increased up to 51% in leaves of defruited trees within 24 h after fruit removal. However, because of the small starch pool present in plum leaves (<1.9% dry weight) it is unlikely that starch accumulation was responsible for the observed decline in CO2 assimilation rate after fruit removal. The decrease of CO2 assimilation rate is discussed in relation to the hypothesis of assimilate demand regulating photosynthesis through a feedback mechanism. 相似文献
10.
We evaluated diurnal and seasonal patterns of carbon isotope composition of leaf dark-respired CO2 ( δ 13 Cl ) in the C3 perennial shrub velvet mesquite ( Prosopis velutina ) across flood plain and upland savanna ecosystems in the south-western USA. δ 13 Cl of darkened leaves increased to maximum values late during daytime periods and declined gradually over night-time periods to minimum values at pre-dawn. The magnitude of the diurnal shift in δ 13 Cl was strongly influenced by seasonal and habitat-related differences in soil water availability and leaf surface vapour pressure deficit. δ 13 Cl and the cumulative flux-weighted δ 13 C value of photosynthates were positively correlated, suggesting that progressive 13 C enrichment of the CO2 evolved by darkened leaves during the daytime mainly resulted from short-term changes in photosynthetic 13 C discrimination and associated shifts in the δ 13 C signature of primary respiratory substrates. The 13 C enrichment of dark-respired CO2 relative to photosynthates across habitats and seasons was 4 to 6‰ at the end of the daytime period (1800 h), but progressively declined to 0‰ by pre-dawn (0300 h). The origin of night-time and daytime variations in δ 13 Cl is discussed in terms of the carbon source(s) feeding respiration and the drought-induced changes in carbon metabolism. 相似文献
11.
J. W. Moon D. A. Bailey Jr. E. Fallahi R. G. Jensen G. Zhu 《Physiologia plantarum》1990,80(4):612-618
The relationships between increasing nitrogen fertilization and growth, maximum CO2 assimilation and the initial slope of the CO2 response curve were studied in 2 ecotypes of wild strawberry, Fragaria chiloensis (L.) Duchn. Nitrogen accumulation of CA11, an ecotype from a low-nutrient dune site, was greater at all nitrogen concentrations than that of RCP37, an ecotype from a higher-nutrient strand site. Maximum CO2 assimilation, total Rubisco activity, dry weight, and initiation of leaves and crowns were higher in CAI1 than RCP37 as nitrogen treatment was increased from 0 to 200 mg l-1 , whereas these parameters were lower in CAl1 when fertilized at 300 mg T1 , but not in RCP37. The mean leaf area of CA11 was greater than RCP37 when grown with no supplemental nitrogen, but mean leaf area of the 2 lines was similar under nitrogen fertilization. Maximum CO2 assimilation and carboxylation efficiency increased with increasing leaf nitrogen in both clones. At equivalent concentrations of leaf nitrogen, RCP37 had higher CO2 assimilation and carboxylation efficiency than CA11 and the difference between the 2 clones increased as ieaf nitrogen increased. Thus, RCP37 had a higher photosynthetic nitrogen use efficiency than CA11. However, at a given applied nitrogen level, CA11 allocated more nitrogen to a unit of leaf area so that photosynthetic rates were higher than RCP37, except at the highest application of 300 mg l-1 . The high nitrogen accumulation capacity and resource allocation to fruiting structures (crowns) in CA11 leads us to suggest that this clone may possess genes that could increase fruit yield in cultivated strawberry. 相似文献
12.
Abstract. A portable apparatus has been constructed to measure simultaneously the quantum yield of CO2 assimilation, light absorption, chlorophyll fluorescence emission and water vapour exchange of attached intact leaves in the field. The core of the instrument is a light-integrating spherical leaf chamber which includes ports for a light source, photosynthetically active radiation sensor, fluorescence probes and gas inlet and outlet manifolds. Measurement of the quantum flux inside the empty chamber and with a leaf present allows determination of leaf absorptance. An open gas exchange system is employed using an infra-red analyser to measure leaf CO2 exchange. Using a DC white light source the quantum yield of CO2 assimilation based on absorbed light (φabs ) may be determined rapidly in either ambient air or artificial gas mixtures. Inclusion of capacitance humidity probes into the gas inlet and outlet ports allows simultaneous determination of water vapour exchange and subsequent estimation of stomatal conductance to CO2 and intercellular CO2 concentration. Measurement of fluorescence emission by the sample leaf exposed to white light is achieved by a modulated fluorescence detection system. In addition to determination of the minimal, maximal and variable fluorescence levels, a further analysis allows the photochemical and non-photochemical components of fluorescence quenching, to be estimated. The theory and design of this apparatus is described in detail. The use of the apparatus in the field is demonstrated through a study of the photosynthetic performance of a maize and bean crop during the growing season and by analysis of the photosynthetic performance of crops subjected to nitrogen-stress and a herbicide treatment. 相似文献
13.
The progressive development of the photosynthetic apparatus occurring along the length of the Zea mays leaf offers a convenient system with which to examine the limitations to photosynthetic CO2 assimilation during biogenesis of a C4 leaf. Changes in light-induced O2 evolution and CO2 assimilation, chlorophyll content, activity of PEP-carboxylase, NADP-malic enzyme and the 'R5P system' (consisting of d -ribose-5-phosphate-keto isomerase, ATP- d -ribulose-5 phosphate 1-phosphotransferase and d -ribulose-1,5-bisphosphate carboxylase) and fluorescence emission characteristics were examined along the length of the second leaf of 7-day-old plants grown under a diurnal light regime. The results suggest that the major limitation to CO2 assimilation in the leaf sheath lies within the chlorenchyma and is either energy supply for carboxylation or the capacity of key photosynthetic enzymes. In the leaf blade stomatal resistance to CO2 diffusion constitutes a major fraction of the total leaf resistance to CO2 assimilation implicating the stoma as the major limiting factor to photosynthetic CO2 assimilation. 相似文献
14.
For cacti with persistent, relatively large leaves, most shoot CO2 uptake under well-watered conditions occurs by the leaves using the C3 pathway. For three species in the primitive subfamily Pereskioideae, droughts of 7 or 14 days decreased leaf daytime net CO2 uptake by an average of 49 and 88%, respectively; these species always had a net CO2 release at night by the leaves and both at night and during the day by the stems. For three leafy species in subfamily Opuntioideae, 7 and 14 days of drought reduced leaf daytime net CO2 uptake by 90 and 100%, respectively. Although drought reduced the total CO2 uptake over 24 h, the average percentage occurring at night by the leaves of these species increased from 5% under wet conditions to 71% after 7 days of drought to 99% after 14 days of drought. For two of the three species of Opuntioideae, 7 days of drought caused the small net CO2 uptake by the sterns to shift from the daytime to the nighttime, while for the third species drought caused a reduction of its stem nocturnal net CO2 uptake. Thus, shifts from predominantly daytime to predominantly nighttime net CO2 uptake can be induced by drought for the leaves and the stems of leafy cacti in subfamily Opuntioideae, indicating a high degree of biochemical versatility. 相似文献
15.
Canopy development of a model herbaceous community exposed to elevated atmospheric CO2 and soil nutrients 总被引:1,自引:0,他引:1
To test the prediction that elevated CO2 increases the maximum leaf area index (LAI) through a stimulation of photosynthesis, we exposed model herbaceous communities to two levels of CO2 crossed with two levels of soil fertility. Elevated CO2 stimulated the initial rate of canopy development and increased cumulative LAI integrated over the growth period, but it had no effect on the maximum LAI. In contrast to CO2 , increased soil nutrient availability caused a substantial increase in maximum LAI. Elevated CO2 caused a slight increase in leaf area and nitrogen allocated to upper canopy layers and may have stimulated leaf turnover deep in the canopy. Gas exchange measurements of intact communities made near the time of maximum LAI indicated that soil nutrient availability, but not CO2 enrichment, caused a substantial stimulation of net ecosystem carbon exchange. These data do not support our prediction of a higher maximum LAI by elevated CO2 because the initial stimulation of LAI diminished by the end of the growth period. However, early in development, leaf area and carbon assimilation of communities may have been greatly enhanced. These results suggest that the rate of canopy development in annual communities may be accelerated with future increases in atmospheric CO2 but that maximum LAI is set by soil fertility. 相似文献
16.
Chlorophyll fluorescence measured using the Fraunhofer line-depth principle and relationship to photosynthetic rate in the field 总被引:1,自引:1,他引:0
Abstract. A field study was conducted to determine the relationship of solar-excited chlorophyll a fluorescence to net CO2 assimilation rate in attached leaves. The Fraunhofer line-depth principle was used to measure fluorescence at 656.3 nm wavelength while leaves remained exposed to full sunlight and normal atmospheric pressures of CO2 and O2 . Fluorescence induction kinetics were observed when leaves were exposed to sunlight after 10 min in darkness. Subsequently, fluorescence varied inversely with assimilation rate. In the C4 Zea mays , fluorescence decreased from 2.5 to 0.8 mW m-2 nm-1 as CO2 assimilation rate increased from 1 to 8 μmol m-2 s-1 (r2 = 0.520). In the C3 Liquidambar styraciflua and Pinus taeda , fluorescence decreased from 6 to 2 mW m-2 nm-1 as assimilation rate increased from 2 to 5 or 0 to 2 μmol m-2 s-1 (r2 = 0.44 and 0.45. respectively). The Fraunhofer line-depth principle enables the simultaneous measurement of solar-excited fluorescence and CO2 assimilation rate in individual leaves, but also at larger scales. Thus, it may contribute significantly to field studies of the relationship of fluorescence to photosynthesis. 相似文献
17.
Elevated CO2 enhances stomatal responses to osmotic stress and abscisic acid in Arabidopsis thaliana 总被引:1,自引:0,他引:1
A , carbon assimilation rate
ABA, abscisic acid
Ci , intercellular space CO
g , leaf conductance
WUE, water use efficiency
Carbon dioxide and abscisic acid (ABA) are two major signals triggering stomatal closure. Their putative interaction in stomatal regulation was investigated in well-watered air-grown or double CO
18.
Effect of root zone carbon dioxide enrichment on ethylene inhibition of carbon assimilation in potato plants 总被引:2,自引:0,他引:2
Potato plants ( Solanum tuberosum L. var. Russet Burbank) treated with 1 μl ethylene 1−1 of air showed an inhibition of CO2 assimilation by 18%. The inhibition occurred after 3 h of exposure to ethylene and was not mediated through closure of the stomata. The enrichment of the root zone with CO2 almost completely abolished the ethylene inhibition of CO2 assimilation which was apparently due to an increase in the intercellular concentration of CO2 in leaves following enrichment. The effect of application of CO2 to the root zone on ethylene inhibition of CO2 assimilation seemed to last for a few days. Potato plants treated with aminoethoxyvinlglycine (AVG) showed an increase in fresh and dry weight as compared to non-treated plants. Our results indicate that both CO2 and AVG alter the effect of ethylene and promote growth in plants by inhibiting ethylene action and biosynthesis, respectively. 相似文献
19.
The response of Phaseolus vulgaris L. cv. Contender grown under controlled environment at either ambient or elevated (360 and 700 μmol mol-1 , respectively) CO2 concentrations ([CO2 ]), was monitored from 10 days after germination (DAG) until the onset of senescence. Elevated CO2 had a pronounced effect on total plant height (TPH), leaf area (LA), leaf dry weight (LD), total plant biomass (TB) accumulation and specific leaf area (SLA). All of these were significantly increased under elevated carbon dioxide with the exception of SLA which was significantly reduced. Other than high initial growth rates in CO2 -enriched plants, relative growth rates remained relatively unchanged throughout the growth period. While the trends in growth parameters were clearly different between [CO2 ], some physiological processes were largely transient, in particular, net assimilation rate (NAR) and foliar nutrient concentrations of N, Mg and Cu. CO2 enrichment significantly increased NAR, but from 20 DAG, a steady decline to almost similar levels to those measured in plants grown under ambient CO2 occurred. A similar trend was observed for leaf N content where the loss of leaf nitrogen in CO2 -enriched plants after 20 DAG, was significantly greater than that observed for ambient-CO2 plants. Under enhanced CO2 , the foliar concentrations of K and Mn were increased significantly whilst P, Ca, Fe and Zn were reduced significantly. Changes in Mg and Cu concentrations were insignificant. In addition. high CO2 grown plants exhibited a pronounced leaf discoloration or chlorosis, coupled with a significant reduction in leaf longevity. 相似文献
20.
Fruit effects on photosynthesis in Prunus persica 总被引:1,自引:0,他引:1
T. M. DeJong 《Physiologia plantarum》1986,66(1):149-153
Seasonal measurements of net CO2 assimilation, leaf conductance and mesophyll conductance were made in the field on mature, fruiting and defruited Prunus persica L. Batsch trees. During early stages of fruit growth there were no significant differences in leaf gas exchange characteristics between fruiting and defruited trees. During the early part of the last stage of fruit growth, CO2 assimilation rates were 11–15% higher in fruiting trees than defruited trees. These increased assimilation rates corresponded with approximately 30% increases in leaf conductance and only minor changes in mesophyll conductances or leaf CO2 assimilation capacity as indicated by leaf nitrogen content. It is concluded that under the field conditions of this study the fruit effect on photosynthesis is primarily related to stomatal behavior. 相似文献