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SEBASTIÀ MARTORELL ANTONIO DIAZ‐ESPEJO HIPÓLITO MEDRANO MARILYN C. BALL BRENDAN CHOAT 《Plant, cell & environment》2014,37(3):617-626
In woody plants, photosynthetic capacity is closely linked to rates at which the plant hydraulic system can supply water to the leaf surface. Drought‐induced embolism can cause sharp declines in xylem hydraulic conductivity that coincide with stomatal closure and reduced photosynthesis. Recovery of photosynthetic capacity after drought is dependent on restored xylem function, although few data exist to elucidate this coordination. We examined the dynamics of leaf gas exchange and xylem function in Eucalyptus pauciflora seedlings exposed to a cycle of severe water stress and recovery after re‐watering. Stomatal closure and leaf turgor loss occurred at water potentials that delayed the extensive spread of embolism through the stem xylem. Stem hydraulic conductance recovered to control levels within 6 h after re‐watering despite a severe drought treatment, suggesting an active mechanism embolism repair. However, stomatal conductance did not recover after 10 d of re‐watering, effecting tighter control of transpiration post drought. The dynamics of recovery suggest that a combination of hydraulic and non‐hydraulic factors influenced stomatal behaviour post drought. 相似文献
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Long term water stress inactivates Rubisco in subterranean clover 总被引:11,自引:0,他引:11
In long-term field experiments, during consecutive years, microswards of subterranean clover were irrigated to minimise water deficits or subjected to progressively increasing drought over 30 days. Both leaf water potential and relative water content steadily decreased during the experiments. Plants affected by drought grew more slowly and photosynthesis was decreased. Photosynthetic rate (A) and Rubisco were analysed in relation to midday water potentials and relative water contents. The difference in A between draughted and irrigated plants increased progressively, in part as a result of decreased stomatal conductance and CO2 concentration within leaf (Ci). However, A-Ci curves suggest that the photosynthetic capacity in plants experiencing long-term stress was reduced by 50% when compared with irrigated plants. Drought decreased both the initial and the total Rubisco activity per unit area in a similar way but did not reduce the amount of Rubisco protein per unit leaf area. Thus, the specific activity of Rubisco, rather than its activation state, decreased suggesting that under water stress the active sites were blocked by inhibitors. 相似文献
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Forage shrub production in the Mediterranean region is frequently limited by soil water availability. To study plant responses to water deficit under such conditions is important for improving crop management and for selecting better yielding forage shrub species. Pre-dawn leaf water potential (Ψpd), plant leaf area (PLA), leaf area per stem (LAs), leaf appearance rate (LAR1;), leaf senescence rate (LSR), individual leaf area (LA) and maximal leaf elongation rate (LER) were studied throughout the year for Medicago arborea (MA) and Medicago citrina (MC) under irrigated (control) and low rainfall field conditions, at the experimental field site of the University of the Balearic Islands in Spain. With irrigation, the highest LA and LER were observed in autumn and spring and the lowest in winter and summer. LAR; was similar for both species in autumn and winter. Throughout the spring, LAR1 was higher for MC compared to MA. PLA was similar for both species during the autumn, winter and spring seasons; however, during the summer PLA of MA was significantly reduced by 53%. This decline was attributed to higher leaf senescence during seed maturity. As a consequence, MC maintained higher leaf area (∼ 5 m2 plant−1) than MA (3 m2 plant−1). Under natural field conditions, soil water deficit increased from February to late August. The main effect of water stress was a marked reduction in LAR1, LA and LER reflected in lower LAs and PLA. Leaf area was severely reduced for both species during the summer, but much more intensively in MA, which developed full leaf senescence. Thus, MC maintained higher PLA than MA (0.5 m2 compared to 0.0 m2). Throughout the year, but especially in the driest months, MC was superior to MA in leaf growth parameters and PLA. 相似文献
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Rubisco specificity factor tends to be larger in plant species from drier habitats and in species with persistent leaves 总被引:10,自引:2,他引:10
JERONI GALMÉS JAUME FLEXAS ALFRED J. KEYS JOSEP CIFRE ROWAN A. C. MITCHELL PIPPA J. MADGWICK RICHARD P. HASLAM HIPÓLITO MEDRANO & MARTIN A. J. PARRY 《Plant, cell & environment》2005,28(5):571-579
The specificity factor of Rubisco is a measure of the relative capacities of the enzyme to catalyse carboxylation and oxygenation of ribulose 1,5-bisphosphate and hence to control the relative rates of photosynthetic carbon assimilation and photorespiration. Specificity factors of purified Rubisco from 24 species of C3 plants found in diverse habitats with a wide range of environmental growth limitations by both water availability and temperature in the Balearic Islands were measured at 25 °C. The results suggest that specificity factors are more dependent on environmental pressure than on phylogenetic factors. Irrespective of phylogenetic relationships, higher specificity factors were found in species characteristically growing in dryer environments and in species that are hemideciduous or evergreen. Effects of temperature on specificity factor of the purified enzyme from 14 species were consistent with the concept that higher specificity factors were associated with an increase in the activation energy for oxygenation compared to carboxylation of the 2,3-enediolate of RuBP to the respective transition state intermediates. The results are discussed in terms of selection pressures leading to the differences in specificity factors and the value of the observations for identifying useful genetic manipulation to change Rubisco polypeptide subunits. 相似文献
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Water stress induces different levels of photosynthesis and electron transport rate regulation in grapevines 总被引:13,自引:1,他引:12
A, net CO2 assimilation rateE, leaf transpirationETR, electron transport rateFs, fluorescence yield at steady stateFm and Fm', maximal fluorescence levels when all PSII reaction centres are closed in dark- and light-acclimated leaves, respectivelyFo and Fo', initial fluorescence levels when all PSII reaction centres are closed in dark- and light-acclimated leaves, respectivelyFv/Fm, efficiency of excitation capture by open PSII in dark-adapted leavesΔF/Fm', actual photochemical efficiency of PSIIg, stomatal conductanceNPQ, non-photochemical quenching of chlorophyll fluorescencePPFD, photosynthetic photon flux densityΨPD and ΨMD, leaf water potential at pre-dawn and midday, respectivelyRl, estimated photorespiration rateI1 and I2, Irrigation treatmentsR, Recovery treatmentD1 and D2, drought treatmentsHD1 and HD2, hard drought treatmentsDiurnal time courses of chlorophyll fluorescence and gas-exchange rates were measured in young potted grapevines (Vitis vinifera L. cv. Tempranillo) subjected to different conditions of water supply under Mediterranean summer conditions. The irrigated plants exhibited typical diurnal patterns for all measured parameters, showing a correspondence between electron transport rate, net CO2 assimilation and stomatal conductance. Mild decreases in soil-water availability led to different degrees of down-regulation of photosynthesis and increased nonphotochemical quenching of chlorophyll fluorescence. A good correspondence between electron transport rate and CO2 assimilation was still maintained, suggesting a coregulation of both photosynthetic processes. In contrast, a severe water deficit induced a drastic down-regulation of photosynthesis and breakage of the above-mentioned link. Both midday net CO2 assimilation and electron transport rate significantly correlated with pre-dawn water potential (ΨPD) (r2 = 0·65 and r2 = 0·92, P < 0·001, respectively). However, when field data were analysed, the relationship between electron transport rate and ΨPD was not maintained, although net CO2 assimilation was similarly correlated with ΨPD. Interestingly, the steady-state chlorophyll fluorescence yield was a good indicator of plant water stress. 相似文献