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1.
冬小麦光合特征及叶绿素含量对保水剂和氮肥的响应 总被引:9,自引:0,他引:9
以不施保水剂和氮(N)肥为对照,测定了保水剂(60 kg·hm-2)与不同N肥水平(0、225、450 kg·hm-2)及其配施条件下大田小麦的光合特征、叶绿素含量和水分利用效率等指标,研究了冬小麦拔节期和灌浆期光合生理特征、叶绿素含量及水分利用对保水剂和N肥的响应.结果表明:灌浆期各处理的光合速率、气孔导度、胞间CO2浓度、叶片水分利用效率及叶绿素含量均大于拔节期.在拔节期,单施N肥条件下,随施N量的增加,单叶水分利用效率提高,光合速率、气孔导度、胞间CO2浓度及蒸腾速率均先增后减;225 kg·hm-2 N肥处理的叶绿素含量最高.施用保水剂后,随施N量的增加,胞间CO2浓度降低,而光合速率等均提高;单施保水剂及其与N肥配施提高了叶绿素含量,而过多N肥效果不显著在灌浆期,单施N肥显著提高了小麦的光合速率及水分利用效率,降低了气孔导度、胞间CO2浓度及蒸腾速率;叶绿素含量随N肥用量的增加而增加.施用保水剂后,随N肥用量的增加,光合速率和叶片水分利用效率均先增后减,而胞间CO2浓度和蒸腾速率先减后增,但均低于对照,气孔导度随施N量的增加而提高.单施保水剂的叶绿素含量显著提高,但其与N肥配施叶绿素含量有所降低.保水剂与N肥配合施用显著提高了小麦的千粒重、产量及水分生产效率.其中,保水剂与225 kg·hm-2N肥配施处理的产量及水分生产效率均最高. 相似文献
2.
KATHERINE C. MARTIN DAN BRUHN CATHERINE E. LOVELOCK ILKA C. FELLER JOHN R. EVANS MARILYN C. BALL 《Plant, cell & environment》2010,33(3):344-357
Effects of salinity and nutrients on carbon gain in relation to water use were studied in the grey mangrove, Avicennia marina, growing along a natural salinity gradient in south‐eastern Australia. Tall trees characterized areas of seawater salinities (fringe zone) and stunted trees dominated landward hypersaline areas (scrub zone). Trees were fertilized with nitrogen (+N) or phosphorus (+P) or unfertilized. There was no significant effect of +P on shoot growth, whereas +N enhanced canopy development, particularly in scrub trees. Scrub trees maintained greater CO2 assimilation per unit water transpired (water‐use efficiency, WUE) and had lower nitrogen‐use efficiency (NUE; CO2 assimilation rate per unit leaf nitrogen) than fringe trees. The CO2 assimilation rates of +N trees were similar to those in other treatments, but were achieved at lower transpiration rates, stomatal conductance and intercellular CO2 concentrations. Maintaining comparable assimilation rates at lower stomatal conductance requires greater ribulose 1·5‐bisphosphate carboxylase/oxygenase activity, consistent with greater N content per unit leaf area in +N trees. Hence, +N enhanced WUE at the expense of NUE. Instantaneous WUE estimates were supported by less negative foliar δ13C values for +N trees and scrub control trees. Thus, nutrient enrichment may alter the structure and function of mangrove forests along salinity gradients. 相似文献
3.
SHULI NIU XUERONG XING ZHE ZHANG JIANYANG XIA XUHUI ZHOU BING SONG LINGHAO LI SHIQIANG WAN 《Global Change Biology》2011,17(2):1073-1082
Water‐use efficiency (WUE) has been recognized as an important characteristic of ecosystem productivity, which links carbon (C) and water cycling. However, little is known about how WUE responds to climate change at different scales. Here, we investigated WUE at leaf, canopy, and ecosystem levels under increased precipitation and warming from 2005 to 2008 in a temperate steppe in Northern China. We measured gross ecosystem productivity (GEP), net ecosystem CO2 exchange (NEE), evapotranspiration (ET), evaporation (E), canopy transpiration (Tc), as well as leaf photosynthesis (Pmax) and transpiration (Tl) of a dominant species to calculate canopy WUE (WUEc=GEP/T), ecosystem WUE (WUEgep=GEP/ET or WUEnee=NEE/ET) and leaf WUE (WUEl=Pmax/Tl). The results showed that increased precipitation stimulated WUEc, WUEgep and WUEnee by 17.1%, 10.2% and 12.6%, respectively, but decreased WUEl by 27.4%. Climate warming reduced canopy and ecosystem WUE over the 4 years but did not affect leaf level WUE. Across the 4 years and the measured plots, canopy and ecosystem WUE linearly increased, but leaf level WUE of the dominant species linearly decreased with increasing precipitation. The differential responses of canopy/ecosystem WUE and leaf WUE to climate change suggest that caution should be taken when upscaling WUE from leaf to larger scales. Our findings will also facilitate mechanistic understanding of the C–water relationships across different organism levels and in projecting the effects of climate warming and shifting precipitation regimes on productivity in arid and semiarid ecosystems. 相似文献
4.
Regulation of Transpiration to Improve Crop Water Use 总被引:1,自引:0,他引:1
Decreasing fresh water supplies and increasing agricultural drought threaten sustainable worldwide crop production. Consequently, there is a global priority to develop crops with higher water use efficiency (WUE): biomass production or yield per unit of water used. Water use efficiency varies substantially among species and genotypes within a species, and a major effort is now underway to identify the genetic determinants of WUE. Today, it is known that genotypes in primary gene pools exhibit allelic variation for WUE through mechanisms that regulate transpiration, which is the conductance of water through stomata, the cuticle, and the boundary layer. Because of the differential diffusion properties of water and carbon dioxide (CO2) through these pathways, it is feasible that WUE could be improved by decreasing transpiration without a concomitant reduction in CO2 uptake. Since CO2 uptake and transpirational water loss occur predominantly through stomatal pores, it is not surprising that genes involved in stomatal development and stomatal opening/closing impact WUE. Furthermore, loss- and gain-of-function genetic screens have identified genes that regulate transpiration and WUE by yet undetermined mechanisms. This review will discuss the genetic determinants that regulate transpiration and WUE in the context of the modern agricultural goal of improving WUE while sustaining biomass and yield. 相似文献
5.
We measured rates of leaf senescence and leaf level gas exchange during autumnal senescence for seedlings of five temperate forest tree species under current and elevated atmospheric CO2 concentrations and low- and high-nutrient regimes. Relative indices of whole canopy carbon gain, water loss and water use efficiency through the senescent period were calculated based on a simple integrative model combining gas exchange per unit leaf area and standing canopy area per unit time. Seedlings grown under elevated [CO2] generally had smaller canopies than their current [CO2]-grown counterparts throughout most of the senescent period. This was a result of smaller pre-senescent canopies or accelerated rates of leaf drop. Leaf-level photosynthetic rates were higher under elevated [CO2] for grey birch canopies and for low-nutrient red maple and high-nutrient ash canopies, but declined rapidly to values below those of their current [CO2] counterparts by midway through the senescent period. CO2 enrichment reduced photosynthetic rates for the remaining species throughout some or all of the senescent period. As a result of smaller canopy sizes and reduced photosynthetic rates, elevated [CO2]-grown seedlings had lower indices of whole canopy end-of-season carbon gain with few exceptions. Leaf level transpiration rates were highly variable during autumnal senescence and neither [CO2] nor nutrient regime had consistent effects on water loss per unit leaf area or integrated whole canopy water loss throughout the senescent period. Indices of whole canopy, end-of-season estimates of water use efficiency, however, were consistently lower under CO2 enrichment, with few exceptions. These results suggest that whole canopy end-of-season gas exchange may be altered significantly in an elevated [CO2] world, resulting in reduced carbon gain and water use efficiency for many temperate forest tree seedlings. Seedling growth and survivorship, and ultimately temperate forest regeneration, could be reduced in CO2-enriched forests of the future. 相似文献
6.
Jianjun Chen Richard J. Henny Dennis B. McConnell Russell D. Caldwell 《Plant Growth Regulation》2003,40(1):1-6
Changes in net photosynthetic rate (PN), stomatal conductance (gs), intercellular CO2 concentrations (Ci), transpiration rate (E) and water use efficiency (WUE) were measured in Plantago major L. plants grown under sufficient soil water supply or under soil water stress conditions. The plants had high PN in a wide range of soil water potential and temperature regimes. Soil water had little effect on PN under ambient CO2 concentrations, which was explained by a high carboxylation rate, but increased the dark respiration rate. Carboxylation activity at low Ci depended on RuBP regeneration, whereas at high Ci it depended on the phosphate regeneration rate. The gs and E values were low in plants under stress as compared to the controls that resulted in an increase of WUE. The results obtained show that Plantago major plants have different ways of adaptation to soil water deficit conditions. 相似文献
7.
Warren K. Coleman 《Environmental and Experimental Botany》2008,62(3):221-230
Since drought is a major factor limiting global potato production, identification of Solanum germplasm with drought resistance features is essential. The current study compared responses of Solanum tuberosum L. ‘Kennebec’ to those of the wild tuber bearing species, Solanum gandarillasii Cardenas, with respect to drought and heat stress. The cultivar Kennebec exhibited more leaf water loss as well as increased osmotic adjustment compared to S. gandarillasii during the imposition of progressively severe drought. In Kennebec, this stress led to severe leaf wilting and eventual canopy loss. However, S. gandarillasii was less sensitive to prolonged drought in terms of reduced loss of above ground biomass. The conservative “water saving” responses of S. gandarillasii included drought sensitive stomata resulting in low transpiration rates. Coupled with this apparent loss of an effective cooling mechanism, S. gandarillasii demonstrated superior thermal tolerance. Decreased intrinsic water use efficiency (WUE) at the leaf level was evident in Kennebec compared to S. gandarillasii when exposed to increasing levels of soil moisture stress and regardless of radiation level. This difference in WUE could be attributed to differences in transpiration rate and not to photosynthetic rate. S. gandarillasii may be appropriate for growth areas exhibiting drought conditions where reduced desiccation and thermal damage to leaf tissues are assets. Kennebec, however, was a ‘water spender’ that would be more appropriately grown under temperate growing conditions with an adequate water supply. 相似文献
8.
In the global change scenario, increased CO2 may favour water use efficiency (WUE) by plants. By contrast, in arid and semiarid areas, salinity may reduce water uptake from soils. However, an elevated WUE does not ensure a reduced water uptake and upon salinity this fact may constitute an advantage for plant tolerance. In this work, we aimed to determine the combined effects of enhanced [CO2] and salinity on the plant water status, in relation to the regulation of PIP aquaporins, in the root and leaf tissues of broccoli plants (Brassica oleracea L. var Italica), under these two environmental factors. Thus, different salinity concentrations (0, 60 and 90 mM NaCl) were applied under ambient (380 ppm) and elevated (800 ppm) [CO2]. Under non-salinised conditions, stomatal conductance (Gs) and transpiration rate (E) decreased with rising [CO2] whereas water potential (Ψω) was maintained stable, which caused a reduction in the root hydraulic conductance (L0). In addition, PIP1 and PIP2 abundance in the roots was decreased compared to ambient [CO2]. Under salinity, the greater stomatal closure observed at elevated [CO2] – compared to that at ambient [CO2] – caused a greater reduction in Gs and E and allowed plants to maintain their water balance. In addition, a lower decrease in L0 under salt stress was observed at elevated [CO2], when comparing with the decrease at ambient [CO2]. Modifications in PIP1 and PIP2 abundance or their functionality in the roots is discussed. In fact, an improved water status of the broccoli plants treated with 90 mM NaCl and elevated [CO2], evidenced by a higher Ψω, was observed together with higher photosynthetic rate and water use efficiency. These factors conferred on the salinised broccoli plants greater leaf area and biomass at elevated [CO2], in comparison with ambient [CO2]. We can conclude that, under elevated [CO2] and salt stress, the water flow is influenced by the tight control of the aquaporins in the roots and leaves of broccoli plants and that increased PIP1 and PIP2 abundance in these organs provides a mechanism of tolerance that maintains the plant water status. 相似文献
9.
Short- and long-term responses to seasonal drought in ponderosa pines growing at different plantation densities in Patagonia, South America 总被引:1,自引:0,他引:1
Javier Gyenge María Elena Fernández Santiago Varela 《Trees - Structure and Function》2012,26(6):1905-1917
Trees drought responses could be developed in the short- or in the long-term, aiming at sustaining carbon fixation and water use efficiency (WUE). The objective of this study was to examine short- and long-term adjustments occurring in different size Pinus ponderosa Dougl. ex P. & C. Laws trees in response to seasonal drought when they are growing under different competition level. The following variables were studied: branch and stem hydraulic conductivity, canopy and stomatal conductance (gc, gs), transpiration (E), photosynthesis (A max), wood δ13C (as a proxy of intrinsic WUE), leaf to sapwood area ratio (A L:A s) and growth in the biggest (B) and the smallest (S) trees of high (H) and low (L) density stands. A L:A s was positively correlated with tree size and negatively correlated with competition level, increasing leaf hydraulic conductance in H trees. Accordingly, higher gc and E per unit A L were found in H than in L trees when soil water availability was high, but decreased abruptly during dry periods. BL trees maintained stable gc and E values even during the summer drought. The functional adjustments observed in H trees allow them to maintain their hydraulic integrity (no apparent k s losses), but their stem and leaf growth were severely affected by drought events. iWUE was similar between all tree groups in a wet season, whereas it significantly decreased in SH trees in a dry season suggesting that when radiation and water are co-limiting gas exchange, functional adjustments not only affect absolute growth, but also WUE. 相似文献
10.
Importance of Aerodynamic Resistance to Water Use Efficiency in Three Conifers under Field Conditions 总被引:4,自引:1,他引:3
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Smith WK 《Plant physiology》1980,65(1):132-135
The quantitative importance of aerodynamic resistance to H2O vapor and CO2 exchange was determined for shoots from saplings of three conifers (Abies lasiocarpa [Hook] Nutt., Pinus contorta Dougl., Juniperus communis L.) under natural conditions in the field. A combination of relatively low stomatal resistances (<300 seconds per centimeter) and low wind speeds (<30 centimeters per second) led to substantial contributions of the aerodynamic resistance (Rwva) to water use efficiency (WUE = photosynthesis/transpiration) for all three species. For A. lasiocarpa, transpiration was calculated to be 44% less and photosynthesis 17% less due to the presence of Rwva, which led to a predicted increase in WUE of 57% compared to the calculated WUE when Rwva was assumed negligible. Similar increases in WUE were computed for P. contorta (48%) with somewhat smaller values for J. communis (34%). These results are discussed in terms of the estimated importance of Rwva on water and photosynthetic relations of plants that have relatively low stomatal resistances and grow in microhabitats with low winds. 相似文献
11.
Summary Kudzu occurs in a variety of habitats in the southeastern United States. It is most common in exposed, forest edge sites and road cuts where it forms an extensive ground canopy as well as a canopy overtopping nearby trees, but it can also be found in completely open fields and deeply shaded sites within a forest. Microclimate, stomatal conductance, leaf water potential and photosynthetic responses to light, temperature and humidity were measured in two contrasting microhabitats on Pueraria lobata, kudzu. Midsummer leaf temperatures and leaf-to-air water vapor deficits for plants growing in an exposed site were significantly greater than for those in a shaded site, exceeding 35° C and 50 mmol mol-1, respectively. Maximum stomatal conductance exceeded 400 mmol m-2 s-1 in exposed leaves during peak vegetative growth. Stomatal conductance in shaded leaves was approximately half the value measured in exposed leaves on any particular dya. Maximum photosynthetic carbon uptake was also higher in leaves growing in exposed sites compared to leaves in shaded sites, exceeding 18.7 and 14.0 mol m-2 s-1, respectively. Photosynthesis, stomatal conductance and intercellular CO2 concentration decreased dramatically in response to increasing water vapor deficit for leaves from both sites. However, transpiration showed an initial increase at intermediate water vapor deficits, leveling off or even decreasing at higher values. Leaf water potential demonstrated marked diurnal variation, but remained constant over a wide range of transpirational water fluxes. This latter feature, combined with microenvironmental modification through rapid leaf orientation and pronounced stomatal responses to water vapor deficits may represent important adaptive responses in the exploitation of a diverse array of habitats by kudzu. 相似文献
12.
CO2 exchange, transpiration and leaf water potential of Welwitschia mirabilis were measured in three contrasting habitats of the Namib desert. From these measurements stomatal conductance, internal CO2concentration and WUE were calculated. In two of the three habitats photosynthetic CO2 uptake decreased and transpiration increased with increasing leaf age while in the third habitat CO2 uptake increased and transpiration decreased with leaf age. Except for the stomata of young leaf sections in this habitat, stomata closed with increasing δw leading to a pronounced midday depression of CO2 uptake. The high stomatal limitation of photosynthetic CO2 uptake of glasshouse-grown plants was verified in the natural habitat. Photosynthetic CO2 uptake saturated between 800 and 1300 μmol photons m?2 s?1depending on leaf age and habitat. CO2 uptake had a broad temperature optimum declining significantly beyond 32 °C. Predawn leaf water potential reflected water availability and atmospheric conditions in the three habitats and ranged from ? 2.5 to ? 6.2 MPa. There was a pronounced diurnal course of leaf water potential in all habitats. During the day a gradient in water potential developed along the leaf axis with the lowest potential at the leaf's tip. With respect to whole plant balances of CO2 exchange and transpiration, there were marked differences between Welwitschias in the three habitats. Despite a negative CO2 balance over a period of five months, leaves in the driest habitat grew constantly at the expense of carbon reserves in the plant. Only at the wettest site did carbon gain exceed carbon demand for growth. The WUE of whole plants was insignificant in all habitats. The results were as contrasting as the habitats and plants and did not allow generalisations about adaptational features of Welwitschia mirabilis. 相似文献
13.
14.
Although the processes governing photosynthesis are well understood, scaling from shoot to canopy in coniferous forests is complex. Development of different sap-flow techniques has made it possible to measure transpiration of whole trees and thereby also of whole canopies. There is a strong link between photosynthesis and transpiration, for which reason it would be interesting to test whether measurements of canopy transpiration could also be used to estimate canopy photosynthesis. As a first step towards this, water-use efficiency (WUE) was studied at branch and canopy scales on the basis of branch gas-exchange measurements, with half-hourly and daily temporal resolution. Half-hourly and daily WUE at both branch and canopy scales showed a strong dependency on vapour-pressure deficit ('e). Branch photosynthesis modelled from branch transpiration and 'e mimicked well measured branch photosynthesis. Also, modelled photosynthesis, scaled to canopy and compared to net forest CO2 exchange measured by the eddy-covariance technique, occasionally showed good agreement. In spite of these seemingly promising results, there was a difference in the response to 'e between branches and between years, which needs to be better understood. 相似文献
15.
The response of adaxial and abaxial stomatal conductance in Rumex obtusifolius to growth at elevated atmospheric concentrations of CO2 (250 μmol mol?1 above ambient) was investigated over two growing seasons. The conductance of both the adaxial and abaxial leaf surfaces was found to be reduced by elevated concentrations of CO2. Elevated CO2 caused a much greater reduction in conductance for the adaxial surface than for the abaxial surface. The absence of effects upon stomatal density indicated that the reductions were probably the result of changes in stomatal aperture. Partitioning of gas exchange between the leaf surfaces revealed that increased concentrations of CO2 caused increased rates of photosynthesis only via the abaxial surface. Additionally, leaf thickness was found to increase during growth at elevated concentrations of CO2. The tendency for these amphistomatous leaves to develop a distribution of conductance approaching that of hypostomatous leaves clearly reduced their maximum photosynthetic potential. This conclusion was supported by measurements of stomatal limitation, which showed greater values for the adaxial surfaces, and greater values at elevated CO2. This reduction in photosynthesis may in part be caused by higher diffusive limitations imposed because of increased leaf thickness. In an uncoupled canopy, asymmetrical stomatal responses of the kind identified here may appreciably reduce transpiration. Species which show symmetrical responses are less likely to show reduced transpirational rates, and a redistribution of water loss between species may occur. The implications of asymmetrical stomatal responses for photosynthesis and canopy transpiration are discussed. 相似文献
16.
对南亚热带常绿阔叶林中着生在林冠层不同部位的4种藤本植物(白背瓜馥木(Fissistigma glaucescens)、瓜子金(Dischidia chinensis)、蔓九节(Psychotria serpens)和山蒌(Piper hancei))的光合生理生态特性进行比较, 探讨着生在林冠不同部位的藤本植物的光合生理特性随光照、温度、湿度等变化的规律。结果表明, 鼎湖山南亚热带常绿阔叶林微生境由上至下发生了较大变化, 相对于林内, 冠层顶部具有高温、高光强、低湿度的特征。受这些变化的环境因子的影响, 着生在林冠不同部位的藤本植物之间的光合生理特征存在着较大差异: 着生于林冠层中上部的瓜子金和蔓九节的最大净光合速率分别为(2.9 ± 0.6)和(6.3 ± 1.3) μmol CO2·m-2·s-1, 光饱和点为(168.5 ± 83.4)和(231.4 ± 147.8) μmol·m-2·s-1, 显著小于位于冠层下部的白背瓜馥木和山蒌的最大净光合速率值(8.9 ± 2.9)和(8.6 ± 2.3) μmol CO2·m-2·s-1以及光饱和点值(491.6 ± 230.8)和(402.3 ± 112.8) μmol·m-2·s-1。瓜子金和蔓九节的光补偿点值为(16.1 ± 5.9)和(10.1 ± 5.7) μmol·m-2·s-1, 水分利用效率值为(11.5 ± 3.9)和(8.7 ± 1.6) μmol CO2·mmol-1 H2O, 显著大于林内的白背瓜馥木和山蒌的光补偿点值(5.6 ± 1.9)和(5.4 ± 1.7) μmol·m-2·s-1以及水分利用效率值(6.7 ± 1.8)和(6.8 ± 1.3) μmol CO2·mmol-1 H2O。这些光合生理指标的变化显示出植物对不同的温度、光照、湿度的适应, 是植物适应环境条件的重要表现。 相似文献
17.
Qiaoyan Li Liming Lai Jihua Zhou Hui Du Tianyu Guan Xiaolong Zhang Lianhe Jiang Yuanrun Zheng Yi Yu Yong Gao Ping An Hideyuki Shimizu 《Ecological Research》2018,33(5):863-871
In view of the increase in global warming and carbon dioxide (CO2) concentrations, it is essential to investigate the influences of climate change on plant growth and water use in arid and semi-arid grassland species. Experiments were conducted to understand the ecophysiological response of four indigenous species to elevated CO2 in the semi-arid sandy grassland of central Inner Mongolia. Seedlings of the four species were grown for 8 weeks at four different consistently elevated CO2 concentrations in the environment-controlled growth chambers. All four elevated CO2 concentrations (400, 800, 1200, 1600 ppm) were found to result in decreased stomatal conductance (26–86%), decreased transpiration rate (21–80%), increased shoot water potential (1–42%) and increased water use efficiency (WUE) (10–412%) for two Artemisia species and Caragana korshinskii. Under our experimental conditions, the two Artemisia species and C. korshinskii would benefit more than Hedysarum laeve from exposure to elevated CO2 in terms of higher shoot water potential and WUE combined with lower stomatal conductance and transpiration rate. The results indicate that in a warmer, CO2-enriched future atmospheric environment, WUE in semi-arid grasslands may be higher than previously expected. Our findings will provide information for screening appropriate species for restoration of the degraded sandy grasslands in semi-arid areas under future climate change scenarios. 相似文献
18.
Transpiration-induced changes in the photosynthetic capacity of leaves 总被引:18,自引:0,他引:18
Thomas D. Sharkey 《Planta》1984,160(2):143-150
High transpiration rates were found to affect the photosynthetic capacity of Xanthium strumarium L. leaves in a manner analagous to that of low soil water potential. The effect was also looked for and found in Gossypium hirsutum L., Agathis robusta (C. Moore ex Muell.) Bailey, Eucalyptus microcarpa Maiden, Larrea divaricata Cav., the wilty flacca tomato mutant (Lycopersicon esculentum (L.) Mill.) and Scrophularia desertorum (Munz) Shaw. Two methods were used to distinguish between effects on stomatal conductance, which can lower assimilation by reducing CO2 availability, and effects on the photosynthetic capacity of the mesophyll. First, the response of assimilation to intercellular CO2 pressure (C
i) was compared under conditions of high and low transpiration. Second, in addition to estimating C
i using the usual Ohm's law analogy, C
i was measured directly using the closed-loop technique of T.D. Sharkey, K. Imai, G.D. Farquhar and I.R. Cowan (1982, Plant Physiol, 60, 657–659). Transpiration stress responses of Xanthium strumarium were compared with soil drought effects. Both stresses reduced photosynthesis at high C
i but not at low C
i; transpiration stress increased the quantum requirement of photosynthesis. Transpiration stress could be induced in small sections of leaves. Total transpiration from the plant did not influence the photosynthetic capacity of a leaf kept under constant conditions, indicating that water deficits develop over small areas within the leaf. The effect of high transpiration on photosynthesis was reversed approximately half-way by returning the plants to low-transpiration conditions. This reversal occurred as fast as measurements could be made (5 min), but little further recovery was observed in subsequent hours.Abbreviations and symbols
A
photosynthetic CO2 assimilation rate
-
C
a
ambient CO2 partial pressure
-
C
i
partial pressure of CO2 inside the leaf
- VPD
leaf-to-air water-vapor pressure difference
This research was begun while the author was a Postdoctoral Research Fellow at the Australian National University, Canberra 相似文献
19.
Stomatal conductance in mature deciduous forest trees exposed to elevated CO<Subscript>2</Subscript>
Sonja Gisela Keel Steeve Pepin Sebastian Leuzinger Christian Körner 《Trees - Structure and Function》2007,21(2):261-159
Stomatal conductance (g
s) of mature trees exposed to elevated CO2 concentrations was examined in a diverse deciduous forest stand in NW Switzerland. Measurements of g
s were carried out on upper canopy foliage before noon, over four growing seasons, including an exceptionally dry summer (2003).
Across all species reductions in stomatal conductance were smaller than 25% most likely around 10%, with much variation among
species and trees. Given the large heterogeneity in light conditions within a tree crown, this signal was not statistically
significant, but the responses within species were surprisingly consistent throughout the study period. Except during a severe
drought, stomatal conductance was always lower in trees of Carpinus betulus exposed to elevated CO2 compared to Carpinus trees in ambient air, but the difference was only statistically significant on 2 out of 15 days. In contrast, stomatal responses
in Fagus sylvatica and Quercus petraea varied around zero with no consistent trend in relation to CO2 treatment. During the 2003 drought in the third treatment year, the CO2 effect became reversed in Carpinus, resulting in higher g
s
in trees exposed to elevated CO2 compared to control trees, most likely due to better water supply because of the previous soil water savings. This was supported
by less negative predawn leaf water potential in CO2 enriched Carpinus trees, indicating an improved water status. These findings illustrate (1) smaller than expected CO2-effects on stomata of mature deciduous forest trees, and (2) the possibility of soil moisture feedback on canopy water relations
under elevated CO2.
An erratum to this article can be found at 相似文献
20.
A widespread perception is that, with increasing wind speed, transpiration from plant leaves increases. However, evidence suggests that increasing wind speed enhances carbon dioxide (CO2) uptake while reducing transpiration because of more efficient convective cooling (under high solar radiation loads). We provide theoretical and experimental evidence that leaf water use efficiency (WUE, carbon uptake per water transpired) commonly increases with increasing wind speed, thus improving plants' ability to conserve water during photosynthesis. Our leaf‐scale analysis suggests that the observed global decrease in near‐surface wind speeds could have reduced WUE at a magnitude similar to the increase in WUE attributed to global rise in atmospheric CO2 concentrations. However, there is indication that the effect of long‐term trends in wind speed on leaf gas exchange may be compensated for by the concurrent reduction in mean leaf sizes. These unintuitive feedbacks between wind, leaf size and water use efficiency call for re‐evaluation of the role of wind in plant water relations and potential re‐interpretation of temporal and geographic trends in leaf sizes. 相似文献