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1.
Summary Treatment of waterlogged tomato plants with benzyladenine relieved most of the symptoms of flooding injury. The effects of benzyladenine included maintenance of chlorophyll levels, reduced epinastic curvature of petioles, absence of adventitious roots, and stem growth greater than that of waterlogged control plants. 相似文献
3.
In May, greenhouse tomato ( Lycopersicon esculentum Mill.) plants near the end of their winter production cycle were shown to exhibit a diurnal photosynthetic decrease. In order to identify the physiological causes of this decline, we compared in May the photosynthetic characteristics of the fifth youngest leaves from tomato plants of different ages corresponding to a winter production (11-month-old plants) and to a spring production (5-month-old plants). Although the leaves were developed simultaneously under the same environmental conditions, only the ones from the winter production showed a diurnal decline of the in situ CO 2 assimilation rate (A CO 2). This was accompanied by a decline of internal CO 2 and stomatal conductance and by large accumulations of hexoses. When stomatal closure was relieved under saturated CO 2 concentration (5%) using a leaf-disc electrode system, the fifth leaves of both tomato cultures had similar maximum quantum efficiency of O 2 evolution (Φ max), light-saturated rate of O 2 evolution (P max) and quantum efficiency of photosystem II (PSII) photochemistry (ΔF/F' m, q P and q N ). We concluded that the diurnal decline of A CO 2 observed in winter tomato production during May originates from a stomatal limitation that is not dependent on environmental conditions but rather related to the developmental stage of the plants. 相似文献
5.
Summary When young tomato plants were transferred from nutrient solution to mineral-free water, reductions in transpiration, water content of the shoots and stomatal aperture were not accompanied by a reduction in the relative water content or an increase in the suction pressure of the leaves. The relative water content of the leaves was increased and the suction pressure was little affected.Following transfer of the plants to mineral-free water, the mineral content of the shoots and the osmotic pressure of expressed leaf sap were reduced. It was concluded that mineral salts were necessary for maintaining the osmotic pressure of the leaf cell sap and that this was achieved, at least in part, by maintaining the mineral concentration of the sap. The amount of water that could be taken up by leaves and their turgor pressure were related to the osmotic pressure of the sap and calculations of turgor pressure showed that it was less in the leaves of plants with their roots in mineral-free water than in the leaves of plants in nutrient solution.Evidence was obtained that in leaflets detached from plants with their roots in mineral-free water, stomatal closure could occur at a higher water content than in leaflets detached from plants in nutrient solution, indicating a further role of minerals in leaf water relations. It is suggested that this role may be related to the properties of the cell walls. 相似文献
6.
The hypothesis that ABA produced by roots in drying soil is responsible for stomatal closure was tested with grafted plants constructed from the ABA-deficient tomato mutants, sitiens and flacca and their near-isogenic wild-type parent. Three types of experiments were conducted. In the first type, reciprocal grafts were made between the wild type and sitiens or flacca. Stomatal conductance accorded with the genotype of the shoot, not the root. Stomates closed in all of the grafted plants in response to soil drying, regardless of the root genotype, i.e. regardless of the ability of the roots to produce ABA. In the second type of experiment, wild-type shoots were grafted onto a split-root system consisting of one wild-type root grafted to one mutant (flacca or sitiens) root. Water was withheld from one root system, while the other was watered well so that the shoots did not experience any decline in water potential or loss of turgor. Stomates closed to a similar extent when water was withheld from the mutant roots or the wild-type roots. In the third type of experiment, grafted plants with wild-type shoots and either wild-type or sitiens roots were established in pots that could be placed inside a pressure chamber, and the pressure increased as the soil dried so that the shoots remained fully turgid throughout. Stomates closed as the soil dried, regardless of whether the roots were wild type or sitiens. These experiments demonstrate that stomatal closure in response to soil drying can occur in the absence of leaf water deficit, and does not require ABA production by roots. A chemical signal from roots leading to a change in apoplastic ABA levels in leaves may be responsible for the stomatal closure. 相似文献
7.
Summary The spatial and temporal variation of lead conductance ( g) in Eucalyptus pauciflora was analysed with respect to photon flux area density ( I), temperature ( T), water vapour concentration deficit ( w), and leaf water potential () at four different sites between 940 m and 2,040 m altitude in the Snowy Mountains of south-eastern Australia. Along this altitudinal gradient the precipitation/evaporation ratio increases from 1 to 4. The results show that gas diffusion in this tree species is primarily controlled by I and w at all sites, independently of the specific soil moisture regime. Even under dry midsummer conditions with predawn leaf water potentials of-1 MPa at the lowest altitude, had no striking effect on g.The humidity threshold for the onset of stomatal closure does not vary greatly between the study sites (12.2±1.3 Pa kPa -1). The highest and lowest values observed for , the osmotic potential at water saturation (from pressure/volume curves), the mean and maximum g and stomatal dentity, all increase with elevation. The highest (least negative) osmotic potentials were obtained at all sites in midsummer. It therefore appears that there is no osmotic adjustment to drought in the seasonal course. The maximum difference between osmotic potentials obtained at the lowest and highest sites is 0.46 MPa. In general osmotic potential varies less than has been reported for other plant species exposed to varying water regimes. This may be the consequence of the pronounced feed-forward response of the stomata to evaporative demand, which led to only moderate tissue desiccation, never exceeding the turgor loss point. E. pauciflora is a tree species with a very conservative utilisation of soil water, which adjusts to drought via stomatal control of water loss, rather than via osmotic properties.These results explain previous reports of the comparatively high susceptibility of E. pauciflora to severe drought and its positive influence on the hydrological balance of mountain ecosystems in the Australian Alps. 相似文献
8.
Stomatal resistance (r L) and leaf water potential (Υ L), soil moisture and the course of meteorological factors were measured in irrigated and non-irrigated sugar beet canopies during three years. By means of the canopy water balance equation, theoretical analysis of observed dependencies of stomatal resistance upon leaf water potential was made. The changes of r L were not induced by the change of (Υ L) but by that of external and internal factors, (Υ L) correlates with. Therefore the empirical dependence of stomatal resistance upon leaf water potential cannot be generalized. 相似文献
9.
Wild-type and abscisic acid (ABA) -deficient ( sitiens) tomato plants were used to analyse the effects of abscisic acid (ABA), butyric acid (BA), jasmonic acid (JA) and linolenic acid (LA) on assimilation and transpiration rates in detached leaves taking up those substances into the transpiration stream. BA did not affect assimilation and transpiration rates. ABA decreased assimilation and transpiration in both wild-type and ABA-deficient mutants. JA reduced the assimilation rate in both lines but induced a significant reduction of transpiration in the wild type only. The response to LA in both lines was slower than that to JA. 相似文献
10.
Cotton ( Gossypium hirsutum L.) plants were grown in sand culture on nutrient solution containing adequate or growth-limiting levels of P. When water was withheld from the pots, stomata of the most recently expanded leaf closed at leaf water potentials of approximately −16 and −12 bars in the normal and P-deficient plants, respectively. Pressure-volume curves showed that the stomata of P-deficient plants closed when there was still significant turgor in the leaf mesophyll. Leaves of P-deficient plants accumulated more abscisic acid (ABA) in response to water stress, but the difference was evident only at low water potentials, after initiation of stomatal closure. In leaves excised from unstressed plants, P deficiency greatly increased stomatal response to ABA applied through the transpiration stream. Kinetin blocked most of this increase in apparent sensitivity to ABA. The effect of P nutrition on stomatal behavior may be related to alterations of the balance between ABA and cytokinins. 相似文献
11.
Potted two-year-old lemon plants (Citrus limon (L.) Burm. fil.) cv. Fino, growing under field conditions were subjected to
drought by withholding irrigation for 13 d. After that, plants were re-irrigated and the recovery was studied for 5 d. Control
plants were daily irrigated maintaining the soil matric potential at about -30 kPa. Young leaves of control plants presented
higher leaf conductance (g1) and lower midday leaf water potential (Ψmd) than mature ones. Young leaves also showed higher
leaf water potential at the turgor loss point (Ψtlp) than mature leaves. In both leaf types g1 decreased with increased vapour
pressure deficit of the atmosphere. From day 1 of the withholding water, predawn and midday leaf water potentials (Ψpd and
Ψmd) decreased, reaching in both cases minimum values of -5.5 MPa, with no significant differences between mature and young
leaves. Water stress induced stomatal closure, leaf rolling and partial defoliation. No osmotic adjustment was found in response
to water stress in either leaf type, but both were able to enhance the cell wall elasticity (elastic adjustment). After rewatering,
leaf water potential recovered quickly (within 2 d) but g1 did not.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
Cultured cells of tomato, Lycopersicon esculentum Mill. cv VFNT-cherry, have been selected for resistance to water stress (low water potential) imposed by the addition of polyethylene glycol to the culture medium. The ability of nonselected cells to grow in media with low water potentials changes dramatically with the age of the cells (with respect to days following inoculation) whereas there is little effect of the age of selected cells on growth over the same media water potentials. The increased resistance of selected cells has limited stability in the absence of stress, indicating that resistance is established by a slow reversible adaptive process. Increased resistance (growth) in the presence of water stress appears to result from considerable osmotic adjustment by the cells. Growth cycle-dependent changes in resistance of nonselected cells are correlated with osmotic potential changes which are associated with the normal cell growth pattern in culture. Lowered osmotic potential is maintained by selected cells throughout the entire growth cycle and may explain the growth cycle independence of growth of selected cells on polyethylene glycol-containing media. Osmotic adjustment of resistant cells at stationary phase can be as much as 40 bar. Turgor is maintained by resistant cells (as high as 21 bar) in media with low water potentials at least partly at the expense of cell expansion. 相似文献
13.
Abstract Experiments with isolated roots of wheat plants suggested that when water uptake rates are low, low concentrations of abscisic acid (ABA) may increase the flux of water into roots. This increase was recorded despite an ABA-stimulated reduction in the hydraulic conductance of the whole root system. Hydraulic conductances were measured under steady-state conditions. A system is described where the stomatal behaviour and water movement through roots of a single intact plant may be concurrently monitored. Experiments with intact plants confirmed that application of ABA could increase the rate of water movement into roots when uptake rates were low. No such increase was observed at high flux rates. Application of ABA to roots caused partial stomatal closure and caused conductance to oscillate around a reduced mean value. An ABA-stimulated increase in the turgor sensitivity of stomata is postulated and the significance of this effect is discussed. 相似文献
14.
Stomatal resistance was measured daily with a stomatal diffusion porometer during a 4-week period in leaves of bean ( Phaseolus vulgaris L., var. Bush Blue Lake) and barley ( Hordeum vulgare L., var. Liberty) plants having roots equally split between two differentially salinized nutrient solutions. The stomatal conductance (reciprocal of stomatal resistance) of plants with half their roots in saline solutions was intermediate between the stomatal conductances of plants grown in nonsaline solutions and those grown in saline solutions. 相似文献
15.
Potassium deficient (−K) and potassium sufficient (+K) plants were exposed to four days of water stress. Well watered −K and
+K plants had comparable rates of transpiration. But +K plants had a larger leaf area and depleted the soil moisture to a
greater extent on day 1 of stress. For days 2 and 3 their transpiration rate, leaf water potential and relative water content
fell below those of −K plants. Well watered −K plants had a significantly lower rate of photosynthesis than +K plants. Photosynthesis
of −K plants was more sensitive to reduction in plant water potential than that of +K plants. Reduction of photosythesis in
−K leaves was due to impairment of photosynthetic capacity and not to stomatal closure. Growth was significantly reduced in
−K plants. 相似文献
16.
It has been found that the stomatal behaviour of C 3 and C 4 plants can be predicted from the assumption that they increase transpiration whenever the increase δW in daily water loss is offset by a gain of at least λδW in carbon assimilation, where the minimum acceptable marginal conversion efficiency λ is determined by long term ecological factors, and is essentially constant within the course of a day. This paradigm is here extended to plants with Crassulacean acid metabolism (CAM). During daytime assimilation the results are the same as for C 3 and C 4 metabolisms. However night-time assimilation can be inhibited by the accumulation of malate in the cell vacuoles. In this event our model predicts that in a constant environment the stomatal conductance remains proportional to the square root of the mesophyll conductance as the latter declines. This is intermediate between keeping a constant stomatal conductance and keeping a constant intercellular CO 2 concentration (as tends to occur in the C 3/C 4 model when illumination varies), and results in an increasing intercellular CO 2 concentration towards the end of the night. This prediction accords with the Agave data of Nobel & Hartsock 1979. The model also predicts the allocation of time between C 3 and CAM for different degrees of water stress. The results agree qualitatively with observation, even though physiological changes (other than stomatal conductance) are not included in the model. 相似文献
17.
As the nerve-mediated signaling in animals, long-distance signaling in plants is a prerequisite for plants to be able to perceive environmental stimuli and initiate adaptive responses. While intracellular signal transduction has been attracting considerable attentions, studies on long-distance signaling in plants has been relatively overlooked. Stomatal movements are well recognized as a model system for studies on cellular signal transduction. It has been demonstrated that the stomatal movements may be frequently tuned by long-distance signaling under various environmental stimuli. Stomatal movements can not only respond to persistent stress stimuli but also respond to shock stress stimuli. Stomatal responses to drought stress situations may be best characterized in terms of interwoven networks of chemical signaling pathways playing predominant roles in these adaptive processes. In cases of shock stress stimuli, stomatal movements can be more sensitively regulated through the long-distance signaling but with distinctive patterns not observed for drought or other persistent stresses. Here, the fundamental characteristics of stomatal movements and associated long-distance signaling are reviewed and the implications for plant responses to environmental stresses are discussed.Key words: stomatal movement, long-distance signaling, environmental stresses, abscisic aci, pH signaling, hydraulic signaling, cytokinins, acetylcholine, heat-shock, electric signal 相似文献
18.
Three-week-old seedlings of one drought-susceptible tomato cultivar ( Lycopersicon esculentum cv. “New Yorker”) and two drought-resistant species of tomato ( Solanum pennellii and Lycopersicon chilense) were subjected to various degrees of PEG 8000-induced water stress from ?0.017 to ?1.0 MPa for a duration of 24 h so that their early responses to water stress could be compared. Such a comparison would determine if there was a relationship to root cytokinin levels following sudden induction of water stress in the drought-resistant species. Transpiration rates of leaves were monitored throughout the 24-h period, shoots were evaluated for leaf water potential (LWP), and roots were extracted for levels of t-zeatin riboside ( t-ZR) and dihydrozeatin riboside (DHZR) using a monoclonal antibody enzyme immunoassay. Transpiration rates were evaluated gravimetrically by difference every 6 h up to 24 h. Transpiration rate decreased with increasing PEG levels and passage of time in all three species, measured at 6 and 12 h, logarithmically in the case of the two Lycopersicon species and linearly in the case of Solanum. From 12–18 h (while plants were in darkness), transpiration rate was a function of the level of PEG only and not time in all three species. When light resumed from 18–24 h, only 5. pennellii showed no further decrease in transpiration rate over time with increasing PEG. Drought-susceptible L. esculentum had a stronger linear decrease in LWP with increasing PEG 8000 concentration than the other two species. L. esculentum also had a higher initial transpiration rate than did either of the drought-resistant species. The two drought-resistant species showed less change in LWP with 5. pennellii having a small decrease and L. chilense having little change. Only S. pennellii exhibited a decrease in root t-ZR levels, which may imply a role for root cytokinin within the first 24-h exposure to water stress in this species. L. esculentum exhibited no change in root t-ZR. The levels of t-ZR in L. chilense were less than that of L. esculentum but showed only a slight decrease with increasing PEG. S. pennellii and L. chilense, although both drought-resistant tomato species, showed different patterns of response with respect to pattern of decline in transpiration rate, LWP, and root t-ZR levels. 相似文献
19.
Most herbaceous plants employ thermodynamically active mechanisms of phloem loading, whereas in many trees, the mechanism is passive, by diffusion. Considering the different water transport characteristics of herbs and trees, we hypothesized that water relations play a role in the adoption of phloem loading strategies. We measured whole-plant hydraulic conductance (K(p)), osmolality, concentrations of polar metabolites, and key inorganic ions in recently mature leaves of 45 dicotyledonous species at midafternoon. Trees, and the few herbs that load passively, have low K(p), high osmolality, and high concentrations of transport sugars and total polar metabolites. In contrast, herbs that actively load sucrose alone have high K(p), low osmolality, and low concentrations of sugars and total polar metabolites. Solute levels are higher in sugar alcohol-transporting species, both herbs and trees, allowing them to operate at lower leaf water potentials. Polar metabolites are largely responsible for leaf osmolality above a baseline level (approximately 300 mm) contributed by ions. The results suggest that trees must offset low K(p) with high concentrations of foliar transport sugars, providing the motivating force for sugar diffusion and rendering active phloem loading unnecessary. In contrast, the high K(p) of most herbaceous plants allows them to lower sugar concentrations in leaves. This reduces inventory costs and significantly increases growth potential but necessitates active phloem loading. Viewed from this perspective, the elevation of hydraulic conductance marks a major milestone in the evolution of the herbaceous habit, not only by facilitating water transport but also by maximizing carbon use efficiency and growth. 相似文献
20.
The responses of water relations, stomatal conductance (g s) and growth parameters of tomato ( Lycopersicon esculentum Mill. cv. Royesta) plants to nitrogen fertilisation and drought were studied. The plants were subjected to a long-term, moderate
and progressive water stress by adding 80 % of the water evapotranspirated by the plant the preceding day. Well-watered plants
received 100 % of the water evapotranspirated. Two weeks before starting the drought period, the plants were fertilised with
Hoagland’s solution with 14, 60 and 110 mM NO 3
− (N14, N60 and N110, respectively). Plants of the N110 treatment had the highest leaf area. However, g s was higher for N60 plants and lower for N110 plants. At the end of the drought period, N60 plants showed the lowest values
of water potential (Ψ w) and osmotic potential (Ψ s), and the highest values of pressure potential (Ψ p). N60 plants showed the highest Ψ s at maximum Ψ p and the highest bulk modulus of elasticity. 相似文献
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