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1.
Daily patterns of stomatal conductance (gs), xylem pressure potential (P) and canopy microclimatic variables were recorded on 11 sample days as part of a one-year study of the water use of Eucalyptus grandis Hill ex Maiden in the eastern Transvaal, South Africa. Measured gs was found to be largely controlled by quantum flux density (Q) and ambient vapour pressure deficit (D). Canopy conductance (gc) was determined for hourly intervals using gs measurements and leaf areas in four different canopy levels. A simple model was constructed to allow the prediction of gc and transpiration from Q, D and season of year. The model was used to estimate transpiration rates from 10 trees in a later study of similarly-aged E. grandis trees, in which sap flow in each tree was measured using the heat pulse velocity (HPV) technique. Five of the trees were monitored on a summer day and five on a winter day. Correspondence between HPV sap flow and modelled transpiration was good for the summertime comparisons, but measured winter-time sap flow rates were underestimated by the model, especially under conditions of high sap flow. The discrepancy is believed to result from having insufficient data from the conductance study to describe the response of gs to relatively high D in winter. Marked variation in transpiration per unit leaf area indicates that a relatively large number of trees must be sampled for the HPV technique to be used to obtain a mean rate for an entire stand in winter. 相似文献
2.
Stomatal conductance and transpiration were measured concurrently in an irrigated Eucalyptus globulus Labill. plantation. Canopy stomatal conductance, canopy boundary layer conductance and the dimensionless decoupling coefficient (Ω) were calculated (a) summing the conductance of three canopy layers (gc) and (b) weighting the contribution of foliage according to the amount of radiation received (gc′). Canopy transpiration was then calculated from gc and gc′ for Ω = 1 (Eeq), Ω = 0 (Eimp) and by weighting Eeq and Eimp using Ω (EΩ). Eeq, Eimp and EΩ were compared to transpiration estimated from measurements of heat pulse velocity. The mean value of Ω was 0·63. Transpiration calculated using gc and assuming perfect coupling (12·5 ± 0·9 mmol m?2 s?1) significantly overestimated measured values (8·7 ± 0·8 mmol m?2 s?1). Good estimates of canopy transpiration were obtained either (a) calculating EΩ separately for the individual canopy layers or (b) treating the canopy as a single layer and using gc′ in a calculation of Eimp (Ω = 0). The latter approach only required measurement of stomatal conductance at a single canopy position but would be unsuitable for use in combined models of canopy transpiration and assimilation. It should however, be suitable for estimating transpiration in forests regardless of the degree of coupling. 相似文献
3.
Apparent responses of stomata to transpiration and humidity in a hybrid poplar canopy 总被引:11,自引:1,他引:10
It has been proposed that the stomatal response to humidity relies on sensing of the transpiration rate itself rather than relative humidity or the saturation deficit per se. We used independent measurements of stomatal conductance (gs), transpiration (E), and leaf-to-air vapour pressure difference (V) in a hybrid poplar canopy to evaluate relationships between gs and E and between gs and V. Relationships between E, V and total vapour phase conductance or crown conductance (gc) were also assessed. Conductance measurements were made on exposed and partially shaded branches over a wide range of incident solar radiation. In exposed branches, gs appeared to decline linearly with increasing E and increasing V at both high and low irradiance. However, in a partially shaded branch, a bimodal relationship between gs and E was observed in which gs continued to decrease after E had reached a maximum value and begun to decrease. The relationship between gs and V for this branch was linear. Plots of gc against E always yielded bimodal or somewhat variable relationships, whereas plots of gc against V were invariably linear. It was not possible to derive a unique relationship between conductance and E or V because prevailing radiation partially determined the operating range for conductance. Normalization of data by radiation served to linearize responses observed within the same day or type of day, but even after normalization, data collected on partly cloudy days could not be used to predict stomatal behaviour on clear days and vice versa. An additional unidentified factor was thus also involved in determining operating ranges of conductance on days with different overall radiation regimes. We suggest that the simplest mechanism to account for the observed humidity responses is stomatal sensing of the epidermal or cuticular transpiration rate rather than the bulk leaf or stomatal transpiration rate. 相似文献
4.
Stomatal acclimation to vapour pressure deficit doubles transpiration of small tree seedlings with warming 总被引:1,自引:0,他引:1
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Renée M. Marchin Alice A. Broadhead Laura E. Bostic Robert R. Dunn William A. Hoffmann 《Plant, cell & environment》2016,39(10):2221-2234
Future climate change is expected to increase temperature (T) and atmospheric vapour pressure deficit (VPD) in many regions, but the effect of persistent warming on plant stomatal behaviour is highly uncertain. We investigated the effect of experimental warming of 1.9–5.1 °C and increased VPD of 0.5–1.3 kPa on transpiration and stomatal conductance (gs) of tree seedlings in the temperate forest understory (Duke Forest, North Carolina, USA). We observed peaked responses of transpiration to VPD in all seedlings, and the optimum VPD for transpiration (Dopt) shifted proportionally with increasing chamber VPD. Warming increased mean water use of Carya by 140% and Quercus by 150%, but had no significant effect on water use of Acer. Increased water use of ring‐porous species was attributed to (1) higher air T and (2) stomatal acclimation to VPD resulting in higher gs and more sensitive stomata, and thereby less efficient water use. Stomatal acclimation maintained homeostasis of leaf T and carbon gain despite increased VPD, revealing that short‐term stomatal responses to VPD may not be representative of long‐term exposure. Acclimation responses differ from expectations of decreasing gs with increasing VPD and may necessitate revision of current models based on this assumption. 相似文献
5.
Environmental and physiological regulation of transpiration in tropical forest gap species: the influence of boundary layer and hydraulic properties 总被引:19,自引:0,他引:19
F. C. Meinzer G. Goldstein P. Jackson N. M. Holbrook M. V. Gutiérrez J. Cavelier 《Oecologia》1995,101(4):514-522
Environmental and physiological regulation of transpiration were examined in several gap-colonizing shrub and tree species during two consecutive dry seasons in a moist, lowland tropical forest on Barro Colorado Island, Panama. Whole plant transpiration, stomatal and total vapor phase (stomatal + boundary layer) conductance, plant water potential and environmental variables were measured concurrently. This allowed control of transpiration (E) to be partitioned quantitatively between stomatal (g
s) and boundary layer (g
b) conductance and permitted the impact of invividual environmental and physiological variables on stomatal behavior and E to be assessed. Wind speed in treefall gap sites was often below the 0.25 m s–1 stalling speed of the anemometer used and was rarely above 0.5 m s–1, resulting in uniformly low g
b (c. 200–300 mmol m–2 s–1) among all species studied regardless of leaf size. Stomatal conductance was typically equal to or somewhat greater than g
b. This strongly decoupled E from control by stomata, so that in Miconia argentea a 10% change in g
s when g
s was near its mean value was predicted to yield only a 2.5% change in E. Porometric estimates of E, obtained as the product of g
s and the leaf-bulk air vapor pressure difference (VPD) without taking g
b into account, were up to 300% higher than actual E determined from sap flow measurements. Porometry was thus inadequate as a means of assessing the physiological consequences of stomatal behavior in different gap colonizing species. Stomatal responses to humidity strongly limited the increase in E with increasing evaporative demand. Stomata of all species studied appeared to respond to increasing evaporative demand in the same manner when the leaf surface was selected as the reference point for determination of external vapor pressure and when simultaneous variation of light and leaf-air VPD was taken into account. This result suggests that contrasting stomatal responses to similar leaf-bulk air VPD may be governed as much by the external boundary layer as by intrinsic physiological differences among species. Both E and g
s initially increased sharply with increasing leaf area-specific total hydraulic conductance of the soil/root/leaf pathway (G
t), becoming asymptotic at higher values of G
t. For both E and g
s a unique relationship appeared to describe the response of all species to variations in G
t. The relatively weak correlation observed between g
s and midday leaf water potential suggested that stomatal adjustment to variations in water availability coordinated E with water transport efficiency rather than bulk leaf water status. 相似文献
6.
Combining quantitative trait loci analysis with physiological models to predict genotype‐specific transpiration rates
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GRETCHEN A. REUNING WILLIAM L. BAUERLE JACK L. MULLEN JOHN K. MCKAY 《Plant, cell & environment》2015,38(4):710-717
Transpiration is controlled by evaporative demand and stomatal conductance (gs), and there can be substantial genetic variation in gs. A key parameter in empirical models of transpiration is minimum stomatal conductance (g0), a trait that can be measured and has a large effect on gs and transpiration. In Arabidopsis thaliana, g0 exhibits both environmental and genetic variation, and quantitative trait loci (QTL) have been mapped. We used this information to create a genetically parameterized empirical model to predict transpiration of genotypes. For the parental lines, this worked well. However, in a recombinant inbred population, the predictions proved less accurate. When based only upon their genotype at a single g0 QTL, genotypes were less distinct than our model predicted. Follow‐up experiments indicated that both genotype by environment interaction and a polygenic inheritance complicate the application of genetic effects into physiological models. The use of ecophysiological or ‘crop’ models for predicting transpiration of novel genetic lines will benefit from incorporating further knowledge of the genetic control and degree of independence of core traits/parameters underlying gs variation. 相似文献
7.
Stomatal behaviour in a beech canopy: an analysis of Bowen ratio measurements compared with porometer data 总被引:3,自引:0,他引:3
M. HERBST 《Plant, cell & environment》1995,18(9):1010-1018
On the basis of measurements or stand transpiration and microclimate, the bulk stomatal or bulk leaf conductance (gL) of a beech forest in northern Germany was calculated for periods in which leaves were fully expanded and the canopy was dry. This conductance depends strongly on light and humidity conditions above the forest. During periods with photosynthetic photon flux densities Q > 1200 μmol m?2s?1, gL was reduced from 1500mmol m?2s?1 at a vapour pressure deficit D= 0.5kPa to 500 mmol m?2s?1 at D= 2kPa. Light saturation of gL was not reached until Q= 1200 μmol m?2s?1 at low D, or until even higher Q at higher D. The dependence of gL, on Q and D was described mathematically by a non-linear equation that requires two empirical parameters. Values for gL as simulated by this equation provided a satisfactory agreement with independent porometer data collected on single leaves and scaled up to the canopy. A comparison of stomatal and aerodynamic conductances showed a strong coupling between the forest canopy and the atmosphere, indicating that transpiration of the beech forest is controlled mainly by the stomata. 相似文献
8.
Seasonal variability of the parameters of the Ball–Berry model of stomatal conductance in maize (Zea mays L.) and sunflower (Helianthus annuus L.) under well‐watered and water‐stressed conditions
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The Ball–Berry (BB) model of stomatal conductance (gs) is frequently coupled with a model of assimilation to estimate water and carbon exchanges in plant canopies. The empirical slope (m) and ‘residual’ gs (g0) parameters of the BB model influence transpiration estimates, but the time‐intensive nature of measurement limits species‐specific data on seasonal and stress responses. We measured m and g0 seasonally and under different water availability for maize and sunflower. The statistical method used to estimate parameters impacted values nominally when inter‐plant variability was low, but had substantial impact with larger inter‐plant variability. Values for maize (m = 4.53 ± 0.65; g0 = 0.017 ± 0.016 mol m?2 s?1) were 40% higher than other published values. In maize, we found no seasonal changes in m or g0, supporting the use of constant seasonal values, but water stress reduced both parameters. In sunflower, inter‐plant variability of m and g0 was large (m = 8.84 ± 3.77; g0 = 0.354 ± 0.226 mol m?2 s?1), presenting a challenge to clear interpretation of seasonal and water stress responses – m values were stable seasonally, even as g0 values trended downward, and m values trended downward with water stress while g0 values declined substantially. 相似文献
9.
Control of transpiration from the upper canopy of a tropical forest: the role of stomatal, boundary layer and hydraulic architecture components 总被引:6,自引:4,他引:6
F. C. MEINZER J. L. ANDRADE G. GOLDSTEIN N. M. HOLBROOK J. CAVELIER P. JACKSON 《Plant, cell & environment》1997,20(10):1242-1252
Concurrent, independent measurements of stomatal conductance (gs), transpiration (E) and microenvironmental variables were used to characterize control of crown transpiration in four tree species growing in a moist, lowland tropical forest. Access to the upper forest canopy was provided by a construction crane equipped with a gondola. Estimates of boundary layer conductance (gb) obtained with two independent methods permitted control of E to be partitioned quantitatively between gs and gb using a dimensionless decoupling coefficient (Ω) ranging from zero to 1. A combination of high gs (c. 300–600 mmol m?2 s?1) and low wind speed, and therefore relatively low gb (c. 100–800 mmol m?2 s?1), strongly decoupled E from control by stomata in all four species (Ω= 0.7–0.9). Photosynthetic water-use efficiency was predicted to increase rather than decrease with increasing gs because gb was relatively low and internal conductance to CO2 transfer was relatively high. Responses of gs to humidity were apparent only when the leaf surface, and not the bulk air, was used as the reference point for determination of external vapour pressure. However, independent measurements of crown conductance (gc), a total vapour phase conductance that included stomatal and boundary layer components, revealed a clear decline in gc with increasing leaf-to-bulk air vapour pressure difference (Va because the external reference points for determination of gc and Va were compatible. The relationships between gc and Vc and between gs and Vs appeared to be distinct for each species. However, when gs and gc were normalized by the branch-specific ratio of leaf area to sapwood area (LA/SA), a morphological index of potential transpirational demand relative to water transport capacity, a common relationship between conductance and evaporative demand for all four species emerged. Taken together, these results implied that, at a given combination of LA/SA and evaporative demand scaled to the appropriate reference point, the vapour phase conductance and therefore transpiration rates on a leaf area basis were identical in all four contrasting species studied. 相似文献
10.
油松是黄土高原重要的造林树种,模拟其冠层气孔导度和蒸腾对区域水量平衡计算和人工林可持续经营具有重要意义。基于2015—2018年TDP(Thermal dissipation probes)方法所测得液流数据,分析了黄土高原地区油松冠层平均气孔导度(gc)与冠层蒸腾(Tr)的变化特征与影响因素,并采用Penman-Monteith公式和Jarvis型气孔导度模型模拟了其gc和Tr的变化过程,结果表明:(1)该地区油松gc和Tr日内变化均呈现单峰型,日均蒸腾耗水量为(1.25±0.57) mm/d,生长季(4—10月)总蒸腾耗水量均值为195.47 mm。(2)gc的日内变化受太阳辐射(Rad)驱动(偏相关系数为0.65),当Rad高于300 W/m2时,驱动作用减弱;gc的日内变化受水汽压亏缺(VPD)控制(偏相关系数为-0.41),随VPD的增加而降低;gc的日际变化受土壤水分限制(偏相关系数为0.46),当根区相对有效含水率(RE... 相似文献
11.
Survey and synthesis of intra- and interspecific variation in stomatal sensitivity to vapour pressure deficit 总被引:20,自引:8,他引:12
R. Oren J. S. Sperry G. G. Katul D. E. Pataki B. E. Ewers N. Phillips & K. V. R. Schäfer 《Plant, cell & environment》1999,22(12):1515-1526
Responses of stomatal conductance (gs) to increasing vapour pressure deficit (D) generally follow an exponential decrease described equally well by several empirical functions. However, the magnitude of the decrease – the stomatal sensitivity – varies considerably both within and between species. Here we analysed data from a variety of sources employing both porometric and sap flux estimates of gs to evaluate the hypothesis that stomatal sensitivity is proportional to the magnitude of gs at low D ( ≤ 1 kPa). To test this relationship we used the function gs = gsref–m· lnD where m is the stomatal sensitivity and gsref = gs at D = 1 kPa. Regardless of species or methodology, m was highly correlated with gsref (average r2 = 0·75) with a slope of approximately 0·6. We demonstrate that this empirical slope is consistent with the theoretical slope derived from a simple hydraulic model that assumes stomatal regulation of leaf water potential. The theoretical slope is robust to deviations from underlying assumptions and variation in model parameters. The relationships within and among species are close to theoretical predictions, regardless of whether the analysis is based on porometric measurements of gs in relation to leaf-surface D (Ds), or on sap flux-based stomatal conductance of whole trees (GSi), or stand-level stomatal conductance (GS) in relation to D. Thus, individuals, species, and stands with high stomatal conductance at low D show a greater sensitivity to D, as required by the role of stomata in regulating leaf water potential. 相似文献
12.
Stomatal and environmental control of transpiration in a lowland tropical forest tree 总被引:11,自引:8,他引:3
F. C. MEINZER G. GOLDSTEIN N. M. HOLBROOK P. JACKSON J. CAVELIER 《Plant, cell & environment》1993,16(4):429-436
Stomatal control of crown transpiration was studied in Anacardium excelsum, a large-leaved, emergent canopy species common in the moist forests of Central and northern South America. A construction crane equipped with a gondola was used to gain access to the uppermost level in the crown of a 35-m-tall individual. Stomatal conductance at the single leaf scale, and transpiration and total vapour phase conductance (stomatal and boundary layer) at the branch scale were measured simultaneously using the independent techniques of porometry and stem heat balance, respectively. This permitted the sensitivity of transpiration to a marginal change in stomatal conductance to be evaluated using a dimensionless coupling coefficient (1-ω) ranging from zero to 1, with 1 representing maximal stomatal control of transpiration. Average stomatal conductance varied from 0.09 mol m?2 s?1 during the dry season to 0.3 mol m?2 s?1 during the wet season. Since boundary layer conductance was relatively low (0.4 mol m?2 s?1), 1-ω ranged from 0.46 during the dry season to only 0.25 during the wet season. A pronounced stomatal response to humidity was observed, which strongly limited transpiration as evaporative demand increased. The stomatal response to humidity was apparent only when the leaf surface was used as the reference point for measurement of external vapour pressure. Average transpiration was predicted to be nearly the same during the dry and wet seasons despite a 1 kPa difference in the prevailing leaf-to-air vapour pressure difference. The patterns of stomatal behaviour and transpiration observed were consistent with recent proposals that stomatal responses to humidity are based on sensing the transpiration rate itself. 相似文献
13.
J.-H. Li W. A. Dugas† G. J. Hymus D. P. Johnson C. R. Hinkle‡ B. G. Drake B. A. Hungate§ 《Global Change Biology》2003,9(1):96-105
Elevated atmospheric carbon dioxide (Ca) usually reduces stomatal conductance, but the effects on plant transpiration in the field are not well understood. Using constant‐power sap flow gauges, we measured transpiration from Quercus myrtifolia Willd., the dominant species of the Florida scrub‐oak ecosystem, which had been exposed in situ to elevated Ca (350 µmol mol ? 1 above ambient) in open‐top chambers since May 1996. Elevated Ca reduced average transpiration per unit leaf area by 37%, 48% and 49% in March, May and October 2000, respectively. Temporarily reversing the Ca treatments showed that at least part of the reduction in transpiration was an immediate, reversible response to elevated Ca. However, there was also an apparent indirect effect of Ca on transpiration: when transpiration in all plants was measured under common Ca, transpiration in elevated Ca‐grown plants was lower than that in plants grown in normal ambient Ca. Results from measurements of stomatal conductance (gs), leaf area index (LAI), canopy light interception and correlation between light and gs indicated that the direct, reversible Ca effect on transpiration was due to changes in gs caused by Ca, and the indirect effect was caused mainly by greater self‐shading resulting from enhanced LAI, not from stomatal acclimation. By reducing light penetration through the canopy, the enhanced self‐shading at elevated Ca decreased stomatal conductance and transpiration of leaves at the middle and bottom of canopy. This self‐shading mechanism is likely to be important in ecosystems where LAI increases in response to elevated Ca. 相似文献
14.
Estimating the sensitivity of stomatal conductance to photosynthesis: a review 总被引:2,自引:0,他引:2
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Grace L. Miner William L. Bauerle Dennis D. Baldocchi 《Plant, cell & environment》2017,40(7):1214-1238
A common approach for estimating fluxes of CO2 and water in canopy models is to couple a model of photosynthesis (An) to a semi‐empirical model of stomatal conductance (gs) such as the widely validated and utilized Ball–Berry (BB) model. This coupling provides an effective way of predicting transpiration at multiple scales. However, the designated value of the slope parameter (m) in the BB model impacts transpiration estimates. There is a lack of consensus regarding how m varies among species or plant functional types (PFTs) or in response to growth conditions. Literature values are highly variable, with inter‐species and intra‐species variations of >100%, and comparisons are made more difficult because of differences in collection techniques. This paper reviews the various methods used to estimate m and highlights how variations in measurement techniques or the data utilized can influence the resultant m. Additionally, this review summarizes the reported responses of m to [CO2] and water stress, collates literature values by PFT and compiles nearly three decades of values into a useful compendium. 相似文献
15.
Persistent negative temperature response of mesophyll conductance in red raspberry (Rubus idaeus L.) leaves under both high and low vapour pressure deficits: a role for abscisic acid?
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Changpeng Qiu Gilbert Ethier Steeve Pepin Pascal Dubé Yves Desjardins André Gosselin 《Plant, cell & environment》2017,40(9):1940-1959
The temperature dependence of mesophyll conductance (gm) was measured in well‐watered red raspberry (Rubus idaeus L.) plants acclimated to leaf‐to‐air vapour pressure deficit (VPDL) daytime differentials of contrasting amplitude, keeping a fixed diurnal leaf temperature (Tleaf) rise from 20 to 35 °C. Contrary to the great majority of gm temperature responses published to date, we found a pronounced reduction of gm with increasing Tleaf irrespective of leaf chamber O2 level and diurnal VPDL regime. Leaf hydraulic conductance was greatly enhanced during the warmer afternoon periods under both low (0.75 to 1.5 kPa) and high (0.75 to 3.5 kPa) diurnal VPDL regimes, unlike stomatal conductance (gs), which decreased in the afternoon. Consequently, the leaf water status remained largely isohydric throughout the day, and therefore cannot be evoked to explain the diurnal decrease of gm. However, the concerted diurnal reductions of gm and gs were well correlated with increases in leaf abscisic acid (ABA) content, thus suggesting that ABA can induce a significant depression of gm under favourable leaf water status. Our results challenge the view that the temperature dependence of gm can be explained solely from dynamic leaf anatomical adjustments and/or from the known thermodynamic properties of aqueous solutions and lipid membranes.? 相似文献
16.
Jimei Han Zhangying Lei Yujie Zhang Xiaoping Yi Wangfeng Zhang Yali Zhang 《Physiologia plantarum》2019,166(3):873-887
Mesophyll conductance (gm) is one of the major determinants of photosynthetic rate, for which it has an impact on crop yield. However, the regulatory mechanisms behind the decline in gm of cotton (Gossypium. spp) by drought are unclear. An upland cotton (Gossypium hirsutum) genotype and a pima cotton (Gossypium barbadense) genotype were used to determine the gas exchange parameters, leaf anatomical structure as well as aquaporin and carbonic anhydrase gene expression under well‐watered and drought treatment conditions. In this study, the decrease of net photosynthetic rate (AN) under drought conditions was related to a decline in gm and in stomatal conductance (gs). gm and gs coordinate with each other to ensure optimum state of CO2 diffusion and achieve the balance of water and CO2 demand in the process of photosynthesis. Meanwhile, mesophyll limitations to photosynthesis are equally important to the stomatal limitations. Considering gm, its decline in cotton leaves under drought was mostly regulated by the chloroplast surface area exposed to leaf intercellular air spaces per leaf area (Sc/S) and might also be regulated by the expression of leaf CARBONIC ANHYDRASE (CA1). Meanwhile, cotton leaves can minimize the decrease in gm under drought by maintaining cell wall thickness (Tcw). Our results indicated that modification of chloroplasts might be a target trait in future attempts to improve cotton drought tolerance. 相似文献
17.
Water relations and hydraulic control of stomatal behaviour in bell pepper plant in partial soil drying 总被引:4,自引:0,他引:4
Two experiments, a split-root experiment and a root pressurizing experiment, were performed to test whether hydraulic signalling of soil drying plays a dominant role in controlling stomatal closure in herbaceous bell pepper plants. In the split-root experiment, when both root parts were dried, synchronous decreases in stomatal conductance (gs), leaf water potential (LWP) and stem sap flow (SFstem) were observed. The value of gs was found to be closely related to soil water potential (SWP) in both compartments. Tight relationships were observed between gs and stem sap flow under all conditions of water stress, indicating a complete stomatal adjustment of transpiration. When the half-root system has been dried to the extent that its water uptake dropped to almost zero, declines in gs of less than 20% were observed without obvious changes in LWP. The reduced plant hydraulic conductance resulting from decreased sap flow and unchanged LWP may be a hydraulic signal controlling stomatal closure; the results of root pressurizing supported this hypothesis. Both LWP and gs in water-stressed plants recovered completely within 25 min of the application of root pressurizing, and decreased significantly within 40 min after pressure release, indicating the hydraulic control of stomatal closure. Our results are in contrast to those of other studies on other herbaceous species, which suggested that chemical messengers from the roots bring about stomatal closure when plants are in water stress. 相似文献
18.
Sang-Ho Lee Rajesh Kumar Tewari Eun-Joo Hahn Kee-Yoeup Paek 《Plant Cell, Tissue and Organ Culture》2007,90(2):141-151
The aim of the study was to establish whether the quantity and the quality of light affect growth and development of Withania somnifera plantlets. We have studied growth and histo-physiological parameters [stomatal characteristics, chloroplastic pigments concentrations,
photosynthesis, and transpiration (E)] of W. somnifera plantlets regenerated under various light intensities, or monochromatic light or under a mixture of two colors of light in
tissue culture conditions. Plantlets grown under a photon flux density (PFD) of 30 μmol m-2 s-1 showed greater growth and development than those raised under other PFDs. Chlorophylls and carotenoids, numbers of stomata,
rate of photosynthesis (PN) and transpiration (E), stomatal conductance (gs), and water use efficiency (WUE) increased with increasing the PFD up to 60 μmol m-2 s-1. Light quality also affected plantlets growth and physiology. Highest growth was observed under fluorescent and in a mixture
of blue and red light. Very few stomata were developed in any of the monochromatic light but under fluorescent or under a
mixture of two colors stomatal numbers increased. Similarly, gs, E, PN, and WUE were also higher under fluorescent light and under a mixture of red and blue light. Regressional analysis showed
a linear relationship between PN (r
2 = 70) and gs and between E (r
2 = 0.95) and gs. In conclusion, both the quality and the quantity of light affect growth of plantlets, development of stomata and physiological
responses differently depending on the intensity and the wavelength of light. 相似文献
19.
Leaf stomatal density (SD), net photosynthetic rates (P
N), and stomatal conductance (g
s) of Hordeum vulgare and Pisum sativum cultivars in Himalaya increased with altitude. Higher P
N and leaf temperature under low CO2 partial pressure at high altitudes could evoke a higher g
s and SD to allow sufficient influx of CO2 as well as more efficient leaf cooling through transpiration. 相似文献
20.
We assessed the daily time‐courses of CO2 assimilation rate (A), leaf transpiration rate (E), stomatal conductance for water vapour (gs), leaf water potential ( Ψ w) and tree transpiration in a wet and a dry season for three late‐stage canopy rainforest tree species in French Guiana differing in leaf carbon isotope composition ( δ 13C). The lower sunlit leaf δ 13C values found in Virola surinamensis ( ? 29·9‰) and in Diplotropis purpurea ( ? 30·9‰), two light‐demanding species, as compared to Eperua falcata ( ? 28·6‰), a shade‐semi‐tolerant species, were clearly associated with higher maximum gs values of sunlit leaves in the two former species. These two species were also characterized by a high sensitivity of gs, sap flow density (Ju) and canopy conductance (gc) to seasonal soil drought, allowing maintenance of high midday Ψ w values in the dry season. The data for Diplotropis provided an original picture of increasing midday Ψ w with increasing soil drought. In Virola, stomata were extremely sensitive to seasonal soil drought, leading to a dramatic decrease in leaf and tree transpiration in the dry season, whereas midday Ψ w remained close to ? 0·3 MPa. The mechanisms underlying such an extremely high sensitivity of stomata to soil drought remain unknown. In Eperua, gs of sunlit leaves was non‐responsive to seasonal drought, whereas Ju and gc were lower in the dry season. This suggests a higher stomatal sensitivity to seasonal drought in shaded leaves than in sunlit ones in this species. 相似文献