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1.
The role of the mesophyll in stomatal responses to light and CO2 总被引:1,自引:0,他引:1
Stomatal responses to light and CO2 were investigated using isolated epidermes of Tradescantia pallida , Vicia faba and Pisum sativum . Stomata in leaves of T. pallida and P. sativum responded to light and CO2 , but those from V. faba did not. Stomata in isolated epidermes of all three species could be opened on KCl solutions, but they showed no response to light or CO2 . However, when isolated epidermes of T. pallida and P. sativum were placed on an exposed mesophyll from a leaf of the same species or a different species, they regained responsiveness to light and CO2 . Stomatal responses in these epidermes were similar to those in leaves in that they responded rapidly and reversibly to changes in light and CO2 . Epidermes from V. faba did not respond to light or CO2 when placed on mesophyll from any of the three species. Experiments with single optic fibres suggest that stomata were being regulated via signals from the mesophyll produced in response to light and CO2 rather than being sensitized to light and CO2 by the mesophyll. The data suggest that most of the stomatal response to CO2 and light occurs in response to a signal generated by the mesophyll. 相似文献
2.
The responses of guard and mesophyll cell photosynthesis to CO2, O2, light,and water stress in a range of species are similar 总被引:6,自引:0,他引:6
High resolution chlorophyll a fluorescence imaging was used to compare the photosynthetic efficiency of PSII electron transport (estimated by Fq'/Fm') in guard cell chloroplasts and the underlying mesophyll in intact leaves of six different species: Commelina communis, Vicia faba, Amaranthus caudatus, Polypodium vulgare, Nicotiana tabacum, and Tradescantia albifora. While photosynthetic efficiency varied between the species, the efficiencies of guard cells and mesophyll cells were always closely matched. As measurement light intensity was increased, guard cells from the lower leaf surfaces of C. communis and V. faba showed larger reductions in photosynthetic efficiency than those from the upper surfaces. In these two species, guard cell photosynthetic efficiency responded similarly to that of the mesophyll when either light intensity or CO2 concentration during either measurement or growth was changed. In all six species, reducing the O2 concentration from 21% to 2% reduced guard cell photosynthetic efficiency, even for the C4 species A. caudatus, although the mesophyll of the C4 species did not show any O2 modulation of photosynthetic efficiency. This suggests that Rubisco activity is significant in the guard cells of these six species. When C. communis plants were water-stressed, the guard cell photosynthetic efficiency declined in parallel with that of the mesophyll. It was concluded that the photosynthetic efficiency in guard cells is determined by the same factors that determine it in the mesophyll. 相似文献
3.
SHU‐WEI WANG YING LI XIAO‐LU ZHANG HAI‐QIANG YANG XUE‐FEI HAN ZHAO‐HUI LIU ZHONG‐LIN SHANG TOMOYA ASANO YASUSHI YOSHIOKA CHUN‐GUANG ZHANG YU‐LING CHEN 《Plant, cell & environment》2014,37(9):2201-2210
Controversies regarding the function of guard cell chloroplasts and the contribution of mesophyll in stomatal movements have persisted for several decades. Here, by comparing the stomatal opening of guard cells with (crl‐ch) or without chloroplasts (crl‐no ch) in one epidermis of crl (crumpled leaf) mutant in Arabidopsis, we showed that stomatal apertures of crl‐no ch were approximately 65–70% those of crl‐ch and approximately 50–60% those of wild type. The weakened stomatal opening in crl‐no ch could be partially restored by imposing lower extracellular pH. Correspondingly, the external pH changes and K+ accumulations following fusicoccin (FC) treatment were greatly reduced in the guard cells of crl‐no ch compared with crl‐ch and wild type. Determination of the relative ATP levels in individual cells showed that crl‐no ch guard cells contained considerably lower levels of ATP than did crl‐ch and wild type after 2 h of white light illumination. In addition, guard cell ATP levels were lower in the epidermis than in leaves, which is consistent with the observed weaker stomatal opening response to white light in the epidermis than in leaves. These results provide evidence that both guard cell chloroplasts and mesophyll contribute to the ATP source for H+ extrusion by guard cells. 相似文献
4.
光合作用对光和CO2响应模型是研究植物生理和植物生态学的重要工具, 可为植物光合特性对主要环境因子的响应提供科学依据。该文综述了当前光合作用对光和CO2响应模型的研究进展和存在的问题, 并在此基础上探讨了这些模型的可能发展趋势。光合作用涉及光能的吸收、能量转换、电子传递、ATP合成、CO2固定等一系列复杂的物理和化学反应过程。光合作用由原初反应、同化力形成和碳同化3个基本过程构成, 任一个过程均可对光合作用速率产生直接的影响。光合作用对光响应模型只涉及光能的转换, 而光合作用的生化模型包含了同化力形成和碳同化这两个基本过程。把光合作用的原初反应, 即把参与光能吸收、传递和转换的捕光色素分子的物理参数(如捕光色素分子数、捕光色素分子光能吸收截面、捕光色素分子处于激发态的平均寿命等)结合到生化模型中, 可能是今后光合作用对光响应机理模型的发展方向。 相似文献
5.
Coupled response of stomatal and mesophyll conductance to light enhances photosynthesis of shade leaves under sunflecks
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Courtney E. Campany Mark G. Tjoelker Susanne von Caemmerer Remko A. Duursma 《Plant, cell & environment》2016,39(12):2762-2773
Light gradients within tree canopies play a major role in the distribution of plant resources that define the photosynthetic capacity of sun and shade leaves. However, the biochemical and diffusional constraints on gas exchange in sun and shade leaves in response to light remain poorly quantified, but critical for predicting canopy carbon and water exchange. To investigate the CO2 diffusion pathway of sun and shade leaves, leaf gas exchange was coupled with concurrent measurements of carbon isotope discrimination to measure net leaf photosynthesis (An), stomatal conductance (gs) and mesophyll conductance (gm) in Eucalyptus tereticornis trees grown in climate controlled whole‐tree chambers. Compared to sun leaves, shade leaves had lower An, gm, leaf nitrogen and photosynthetic capacity (Amax) but gs was similar. When light intensity was temporarily increased for shade leaves to match that of sun leaves, both gs and gm increased, and An increased to values greater than sun leaves. We show that dynamic physiological responses of shade leaves to altered light environments have implications for up‐scaling leaf level measurements and predicting whole canopy carbon gain. Despite exhibiting reduced photosynthetic capacity, the rapid up‐regulation of gm with increased light enables shade leaves to respond quickly to sunflecks. 相似文献
6.
Modulation of photosynthesis and respiration in guard and mesophyll cell protoplasts by oxygen concentration 总被引:3,自引:0,他引:3
B. T. MAWSON 《Plant, cell & environment》1993,16(2):207-214
Stomatal movement is an energetic oxygen-requiring process. In the present study, the effect of oxygen concentration on mitochondrial respiratory activity and red-light-dependent photosynthetic oxygen evolution by Vicia faba and Brassica napus guard cell protoplasts was examined. Comparative measurements were made with mesophyll cell protoplasts isolated from the same species. At air saturated levels of dissolved oxygen in the protoplast suspension media, respiration rates by mesophyll protoplasts ranged from 6 to 10μmoles O2 mg?1 chl h?1, while guard cell protoplasts respired at rates of 200–300 μmoles O2 mg chl?1 h?1, depending on the species. Lowering the oxygen concentration below 50–60 mmol m?3 resulted in a decrease in guard cell respiration rates, while rates by mesophyll cell protoplasts were reduced only at much lower concentrations of dissolved oxygen. Rates of photosynthesis in mesophyll cell protoplasts isolated from both species showed only a minor reduction in activity at low oxygen concentrations. In contrast, photosynthesis by guard cell protoplasts isolated from V. faba and B. napus decreased concomitantly with respiration. Oligomycin, an inhibitor of oxidative phos-phorylation, reduced photosynthesis in mesophyll cell protoplasts by 27–46% and in guard cell protoplasts by 51–58%. The reduction in both guard cell photosynthesis and respiration following exposure to low oxygen concentrations suggest close metabolic coupling between the two activities, possibly mediated by the availability of substrate for respiration associated with photosynthetic electron transport activity and subsequent export of redox equivalents. 相似文献
7.
Disentangling the contributions of osmotic and ionic effects of salinity on stomatal,mesophyll, biochemical and light limitations to photosynthesis
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There are conflicting opinions on the relative importance of photosynthetic limitations under salinity. Quantitative limitation analysis of photosynthesis provides insight into the contributions of different photosynthetic limitations, but it has only been applied under saturating light conditions. Using experimental data and modelling approaches, we examined the influence of light intensity on photosynthetic limitations and quantified the osmotic and ionic effects of salinity on stomatal (LS), mesophyll (LM), biochemical (LB) and light (LL) limitations in cucumber (Cucumis sativus L.) under different light intensities. Non‐linear dependencies of LS, LM and LL to light intensity were found. Osmotic effects on LS and LM increased with the salt concentration in the nutrient solution (Ss) and the magnitude of LM depended on light intensity. LS increased with the Na+ concentration in the leaf water (Sl) and its magnitude depended on Ss. Biochemical capacity declined linearly with Sl but, surprisingly, the relationship between LB and Sl was influenced by Ss. Our results suggest that (1) improvement of stomatal regulation under ionic stress would be the most effective way to alleviate salinity stress in cucumber and (2) osmotic stress may alleviate the ionic effects on LB but aggravate the ionic effects on LS. 相似文献
8.
Dynamic light conditions require continuous adjustments of stomatal aperture. The kinetics of stomatal conductance (gs) is hypothesized to be key to plant productivity and water use efficiency (WUE). Using step-changes in light intensity, we studied the diversity of light-induced gs kinetics in relation to stomatal anatomy in five banana genotypes (Musa spp.) and modeled the impact of both diffusional and biochemical limitations on photosynthesis (A). The dominant A limiting factor was the diffusional limitation associated with gs kinetics. All genotypes exhibited a strong limitation of A by gs, indicating a priority for water saving. Moreover, significant genotypic differences in gs kinetics and gs limitations of A were observed. For two contrasting genotypes, the impact of differential gs kinetics was further investigated under realistic diurnally fluctuating light conditions and at the whole-plant level. Genotype-specific stomatal kinetics observed at the leaf level was corroborated at whole-plant level by transpiration dynamics, validating that genotype-specific responses are still maintained despite differences in gs control at different locations in the leaf and across leaves. However, under diurnally fluctuating light conditions the impact of gs speediness on A and intrinsic (iWUE) depended on time of day. During the afternoon there was a setback in kinetics: absolute gs and gs responses to light were damped, strongly limiting A and impacting diurnal iWUE. We conclude the impact of differential gs kinetics depended on target light intensity, magnitude of change, gs prior to the change in light intensity, and particularly time of day. 相似文献
9.
A stomatal optimization theory to describe the effects of atmospheric CO2 on leaf photosynthesis and transpiration 总被引:1,自引:0,他引:1
Background and Aims
Global climate models predict decreases in leaf stomatal conductance and transpiration due to increases in atmospheric CO2. The consequences of these reductions are increases in soil moisture availability and continental scale run-off at decadal time-scales. Thus, a theory explaining the differential sensitivity of stomata to changing atmospheric CO2 and other environmental conditions must be identified. Here, these responses are investigated using optimality theory applied to stomatal conductance.Methods
An analytical model for stomatal conductance is proposed based on: (a) Fickian mass transfer of CO2 and H2O through stomata; (b) a biochemical photosynthesis model that relates intercellular CO2 to net photosynthesis; and (c) a stomatal model based on optimization for maximizing carbon gains when water losses represent a cost. Comparisons between the optimization-based model and empirical relationships widely used in climate models were made using an extensive gas exchange dataset collected in a maturing pine (Pinus taeda) forest under ambient and enriched atmospheric CO2.Key Results and Conclusion
In this interpretation, it is proposed that an individual leaf optimally and autonomously regulates stomatal opening on short-term (approx. 10-min time-scale) rather than on daily or longer time-scales. The derived equations are analytical with explicit expressions for conductance, photosynthesis and intercellular CO2, thereby making the approach useful for climate models. Using a gas exchange dataset collected in a pine forest, it is shown that (a) the cost of unit water loss λ (a measure of marginal water-use efficiency) increases with atmospheric CO2; (b) the new formulation correctly predicts the condition under which CO2-enriched atmosphere will cause increasing assimilation and decreasing stomatal conductance. 相似文献10.
Yusuke Mizokami Ko Noguchi Mikiko Kojima Hitoshi Sakakibara Ichiro Terashima 《Plant, cell & environment》2019,42(4):1257-1269
C3 photosynthesis is often limited by CO2 diffusivity or stomatal (gs) and mesophyll (gm) conductances. To characterize effects of stomatal closure induced by either high CO2 or abscisic acid (ABA) application on gm, we examined gs and gm in the wild type (Col‐0) and ost1 and slac1‐2 mutants of Arabidopsis thaliana grown at 390 or 780 μmol mol?1 CO2. Stomata of these mutants were reported to be insensitive to both high CO2 and ABA. When the ambient CO2 increased instantaneously, gm decreased in all these plants, whereas gs in ost1 and slac1‐2 was unchanged. Therefore, the decrease in gm in response to high CO2 occurred irrespective of the responses of gs. gm was mainly determined by the instantaneous CO2 concentration during the measurement and not markedly by the CO2 concentration during the growth. Exogenous application of ABA to Col‐0 caused the decrease in the intercellular CO2 concentration (Ci). With the decrease in Ci, gm did not increase but decreased, indicating that the response of gm to CO2 and that to ABA are differently regulated and that ABA content in the leaves plays an important role in the regulation of gm. 相似文献
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13.
The contribution of photosynthesis to the red light response of stomatal conductance 总被引:2,自引:0,他引:2
To determine the contribution of photosynthesis on stomatal conductance, we contrasted the stomatal red light response of wild-type tobacco (Nicotiana tabacum 'W38') with that of plants impaired in photosynthesis by antisense reductions in the content of either cytochrome b(6)f complex (anti-b/f plants) or Rubisco (anti-SSU plants). Both transgenic genotypes showed a lowered content of the antisense target proteins in guard cells as well as in the mesophyll. In the anti-b/f plants, CO(2) assimilation rates were proportional to leaf cytochrome b(6)f content, but there was little effect on stomatal conductance and the rate of stomatal opening. To compare the relationship between photosynthesis and stomatal conductance, wild-type plants and anti-SSU plants were grown at 30 and 300 micromol photon m(-2) s(-1) irradiance (low light and medium light [ML], respectively). Growth in ML increased CO(2) assimilation rates and stomatal conductance in both genotypes. Despite the significantly lower CO(2) assimilation rate in the anti-SSU plants, the differences in stomatal conductance between the genotypes were nonsignificant at either growth irradiance. Irrespective of plant genotype, stomatal density in the two leaf surfaces was 2-fold higher in ML-grown plants than in low-light-grown plants and conductance normalized to stomatal density was unaffected by growth irradiance. We conclude that the red light response of stomatal conductance is independent of the concurrent photosynthetic rate of the guard cells or of that of the underlying mesophyll. Furthermore, we suggest that the correlation of photosynthetic capacity and stomatal conductance observed under different light environments is caused by signals largely independent of photosynthesis. 相似文献
14.
气孔蒸腾中保卫细胞原生质的调控作用 总被引:4,自引:0,他引:4
气孔运动的机理一般公认为保卫细胞的渗透调节。作者所在研究小组近几年的工作表明:动物神经递质乙酰胆碱参与气孔运动的调节;植物细胞骨架微管、微丝在气孔运动中起重要作用。因面提出保卫细胞原生质在气孔蒸腾中的气孔蒸腾中的作用值得进一步研究。 相似文献
15.
The effects of blue light (BL) on leaf gas exchange of Populus × canadensis, a strong isoprene emitter, and Quercus ilex and Citrus reticulata, two monoterpene emitters with respectively small and large storage pools for monoterpenes, were studied. Leaves were initially exposed to a saturating photosynthetic photon flux density (PPFD) of white light (WL), which was then progressively reduced to perform WL-response curves. Leaves acclimated to saturating WL were then quickly exposed to equivalent BL levels to perform BL-response curves. Blue light did not significantly affect photosynthetic parameters in the light-limited portion of the PPFD-response curves in both P. × canadensis and Q. ilex. Whereas photosynthesis (A), stomatal conductance (gs), and mesophyll conductance (gm) were significantly decreased at high PPFDs of BL. A was similarly inhibited by BL in C. reticulata, but there was no significant effect of light quality on gs. Overall these results show that the negative effect of BL on photosynthesis is widespread in tree species with different leaf characteristics, and that this involves coordinated reductions in gs and gm. BL negatively affected isoprene emission and, to a lesser extent monoterpene emissions, in concert with photosynthetic inhibition. Interesting, both isoprene and monoterpene emissions were shown to be inversely dependent upon intercellular [CO2]. These results indicate that a change in light spectral quality, which can vary during the day, between days and within seasons, can alter photosynthesis and isoprenoid emissions, depending on the PPFD intensity. Such effects should be strongly considered in photosynthesis and volatile isoprenoid emission models. 相似文献
16.
Mesophyll conductance to CO2 (gm), a key photosynthetic trait, is strongly constrained by leaf anatomy. Leaf anatomical parameters such as cell wall thickness and chloroplast area exposed to the mesophyll intercellular airspace have been demonstrated to determine gm in species with diverging phylogeny, leaf structure and ontogeny. However, the potential implication of leaf anatomy, especially chloroplast movement, on the short‐term response of gm to rapid changes (i.e. seconds to minutes) under different environmental conditions (CO2, light or temperature) has not been examined. The aim of this study was to determine whether the observed rapid variations of gm in response to variations of light and CO2 could be explained by changes in any leaf anatomical arrangements. When compared to high light and ambient CO2, the values of gm estimated by chlorophyll fluorescence decreased under high CO2 and increased at low CO2, while it decreased with decreasing light. Nevertheless, no changes in anatomical parameters, including chloroplast distribution, were found. Hence, the gm estimated by analytical models based on anatomical parameters was constant under varying light and CO2. Considering this discrepancy between anatomy and chlorophyll fluorescence estimates, it is concluded that apparent fast gm variations should be due to artefacts in its estimation and/or to changes in the biochemical components acting on diffusional properties of the leaf (e.g. aquaporins and carbonic anhydrase). 相似文献
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Paphiopedilum and Cypripedium are close relatives in the subfamily Cypripedioideae. Cypripedium leaves contain guard cell chloroplasts, whereas Paphiopedilum do not. It is unclear whether the lack of guard cell chloroplasts affects photosynthetic induction, which is important for understory plants to utilize sunflecks. To understand the role of guard cell chloroplasts in photosynthetic induction of Paphiopedilum and Cypripedium, the stomatal anatomy and photosynthetic induction of Paphiopedilum armeniacum and Cypripedium flavum were investigated at different ratios of red to blue light. The highest stomatal opening and photosynthesis of intact leaves in P. armeniacum were induced by irradiance enriched with blue light. Its stomatal opening could be induced by red light 250 µmol m?2 s?1, but the magnitude of stomatal opening was lower than those at the other light qualities. However, the stomatal opening and photosynthesis of C. flavum were highly induced by mixed blue and red light rather than pure blue or red light. The two orchid species did not differ in stomatal density, but P. armeniacum had smaller stomatal size than C. flavum. The stomata of P. armeniacum were slightly sunken into the leaf epidermis, while C. flavum protruded above the leaf surface. The slower photosynthetic induction and lower photosynthetic rate of P. armeniacum than C. flavum were linked to the lack of guard cell chloroplasts and specific stomatal structure, which reflected an adaptation of Paphiopedilum to periodic water deficiency in limestone habitats. These results provide evidence for the morphological and physiological evolution of stomata relation for water conservation under natural selection. 相似文献
19.
《Environmental and Experimental Botany》2007,59(3):252-263
We analysed the impact of elevated CO2 on water relations, water use efficiency and photosynthetic gas exchange in barley (Hordeum vulgare L.) under wet and drying soil conditions. Soil moisture was less depleted under elevated compared to ambient [CO2]. Elevated CO2 had no significant effect on the water relations of irrigated plants, except on whole plant hydraulic conductance, which was markedly decreased at elevated compared to ambient CO2 concentrations. The values of relative water content, water potential and osmotic potential were higher under elevated CO2 during the entire drought period. The better water status of water-limited plants grown at elevated CO2 was the result of stomatal control rather than of osmotic adjustment. Despite the low stomatal conductance produced by elevated CO2, net photosynthesis was higher under elevated than ambient CO2 concentrations. With water shortage, photosynthesis was maintained for longer at higher rates under elevated CO2. The reduction of stomatal conductance and therefore transpiration, and the enhancement of carbon assimilation by elevated CO2, increased instantaneous and whole plant water use efficiency in both irrigated and droughted plants. Thus, the metabolism of barley plants grown under elevated CO2 and moderate or mild water deficit conditions is benefited by increased photosynthesis and lower transpiration. The reduction in plant water use results in a marked increase in soil water content which delays the onset and severity of water deficit. 相似文献
20.
Lia Ooi Takakazu Matsuura Shintaro Munemasa Yoshiyuki Murata Maki Katsuhara Takashi Hirayama Izumi C. Mori 《Plant, cell & environment》2019,42(2):437-447
Plants closing stomata in the presence of harmful gases is believed to be a stress avoidance mechanism. SO2, one of the major airborne pollutants, has long been reported to induce stomatal closure, yet the mechanism remains unknown. Little is known about the stomatal response to airborne pollutants besides O3. SLOW ANION CHANNEL‐ASSOCIATED 1 (SLAC1) and OPEN STOMATA 1 (OST1) were identified as genes mediating O3‐induced closure. SLAC1 and OST1 are also known to mediate stomatal closure in response to CO2, together with RESPIRATORY BURST OXIDASE HOMOLOGs (RBOHs). The overlaying roles of these genes in response to O3 and CO2 suggested that plants share their molecular regulators for airborne stimuli. Here, we investigated and compared stomatal closure event induced by a wide concentration range of SO2 in Arabidopsis through molecular genetic approaches. O3‐ and CO2‐insensitive stomata mutants did not show significant differences from the wild type in stomatal sensitivity, guard cell viability, and chlorophyll content revealing that SO2‐induced closure is not regulated by the same molecular mechanisms as for O3 and CO2. Nonapoptotic cell death is shown as the reason for SO2‐induced closure, which proposed the closure as a physicochemical process resulted from SO2 distress, instead of a biological protection mechanism. 相似文献