Effect of Half and Whole Root Drying on Photosynthesis, Nitrate Concentration, and Nitrate Reductase Activity in Roots and Leaves of Micropropagated Apple Plants

Half or whole root systems of micropropagated `Gala' apple (Malus ×domestica Borkh.) plants were subjected to drought stress by regulating the osmotic potential of the nutrient solution using polyethylene glycol (20% w/v) to investigate the effect of root drying on NO3- content and metabolism in roots and leaves and on leaf photosynthesis. No significant difference in predawn leaf water potential was found between half root stress (HRS) and control (CK), while predawn leaf water potential from both was significantly higher than for the whole root stress (WRS) treatment. However, diurnal leaf water potential of HRS was lower than CK and higher than WRS during most of the daytime. Neither HRS nor WRS influenced foliar NO3- concentration, but both significantly reduced NO3- concentration in drought-stressed roots as early as 4 hours after stress treatment started. This reduced NO3- concentration was maintained in HRS and WRS roots to the end of the experiment. However, there were no significant differences in NO3- concerntation between CK roots and unstressed roots of HRS. Similar to the effect on root NO3- concentration, both HRS and WRS reduced nitrate reductase activity in drought-stressed roots. Moreover, leaf net photosynthesis, stomatal conductance and transpiration rate of HRS plants were reduced significantly throughout the experiment when compared with CK plants, but the values were higher than those of WRS plants in the first 7 days of stress treatment though not at later times. Net photosynthesis, stomatal conductance and transpiration rate were correlated to root NO3- concentration. This correlation may simply reflect the fact that water stress affected both NO3- concentration in roots and leaf gas exchange in the same direction.

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Growth and Water Relations of Littleleaf Linden Trees Established in Irrigated Buffalograss and Kentucky Bluegrass

HortScience ◽

10.21273/hortsci.40.5.1529 ◽

2005 ◽

Vol 40 (5) ◽

pp. 1529-1533 ◽

Cited By ~ 3

Author(s):

J. Ryan Stewart ◽

Roger Kjelgren ◽

Paul G. Johnson ◽

Michael R. Kuhns

Keyword(s):

Water Stress ◽

Stomatal Conductance ◽

Water Potential ◽

Leaf Water Potential ◽

Kentucky Bluegrass ◽

Leaf Water ◽

Diameter Growth ◽

Predawn Leaf Water Potential ◽

Trunk Diameter ◽

Second Year

Although transplanted trees typically establish and grow without incident in frequently irrigated turfgrass, their performance in precisely irrigated turfgrass in an arid climate is not known. We investigated the effect of precision irrigation scheduling on growth and water relations of balled-and-burlapped littleleaf linden (Tilia cordata Mill. `Greenspire') planted in buffalograss (Buchloë dactyloides [Nutt.] Engelm. `Tatanka') and kentucky bluegrass (Poa pratensis L.). Over 2 years, trees in turfgrass were irrigated either by frequent replacement based on local reference evapotranspiration, or precision irrigated by estimating depletion of soil water to the point of incipient water stress for each turfgrass species. Predawn leaf water potential and stomatal conductance of trees were measured during first-year establishment, and predawn leaf water potential was measured during a mid-season water-deficit period during the second year. Trunk diameter growth and total tree leaf area were measured at the end of each year. Values of predawn leaf water potential and stomatal conductance of trees in precision-irrigated buffalograss were lower (–0.65 MPa, 25.3 mmol·m–2·s–1) than those of trees in the other treatments near the end of the first growing season. The longer interval between precision irrigations resulted in mild water stress, but was not manifested in growth differences among trees across treatments during the first season. During the water-deficit period of the second year, there was no evidence of stress among the trees regardless of treatment. At the end of the second season, total leaf area of trees grown in precision-irrigated kentucky bluegrass (1.10 ± 0.34 m2) was 46% of that of trees grown in buffalograss (2.39 ± 0.82 m2) that were irrigated frequently. Trunk diameter growth of trees in frequently irrigated kentucky bluegrass (1.91 ± 2.65 mm) was 29% of that of the trees grown in buffalograss (6.68 ± 1.68 mm), regardless of irrigation treatment, suggesting a competition effect from kentucky bluegrass. We conclude that frequent irrigation of balled-and-burlapped trees in turfgrass, particularly buffalograss, is more conducive to tree health during establishment than is maximizing the interval between turfgrass irrigation. Regardless of irrigation schedule, kentucky bluegrass appears to impact tree growth severely during establishment in an arid climate.

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Gas Exchange and Growth of Two Transplanted, Field-grown Tree Species in an Arid Climate

HortScience ◽

10.21273/hortsci.35.4.763 ◽

2000 ◽

Vol 35 (4) ◽

pp. 763-768

Author(s):

Thayne Montague ◽

Roger Kjelgren ◽

Larry Rupp

Keyword(s):

Stomatal Conductance ◽

Gas Exchange ◽

Vapor Pressure ◽

Water Potential ◽

Leaf Water Potential ◽

Pressure Difference ◽

Leaf Water ◽

Arid Climate ◽

Vapor Pressure Difference ◽

Predawn Leaf Water Potential

Gas exchange and growth of transplanted and nontransplanted, field-grown Norway maple (Acer platanoides L. `Schwedleri') and littleleaf linden (Tilia cordata Mill. `Greenspire') trees were investigated in an arid climate. In the spring of 1995, three trees of each species were moved with a tree spade to a new location within a field nursery and three nontransplanted trees were selected as controls. Predawn leaf water potential, morning-to-evening stomatal conductance and leaf temperature, leaf-to-air vapor pressure difference, midday stomatal conductance and photosynthetic rate, and growth data were collected over a 2-year period. After transplanting, weekly predawn leaf water potential indicated that transplanted trees were under greater water stress than were nontransplanted (control) trees. However, predawn leaf water potential of maple trees recovered to control levels 18 weeks after transplanting, while that of transplanted linden trees remained more negative than that of controls. In 1995, stomatal conductance and photosynthetic rates were lower throughout the day for transplanted trees. In 1996, gas exchange rates of transplanted maple trees recovered to near control levels while rates for transplanted linden trees did not. Sensitivity of stomata to leaf-to-air vapor pressure difference varied with species and with transplant treatment. Each year transplanted trees of both species had less apical growth than did control trees. Although gas exchange and apical growth of transplanted trees was reduced following transplanting, recovery of gas exchange to control rates differed with species.

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Leaf water potential and stomatal conductance of field-grown faba beans (Vicia faba L.) and oats (Avena sativa L.)

Plant and Soil ◽

10.1007/bf02377142 ◽

1986 ◽

Vol 93 (1) ◽

pp. 17-33 ◽

Cited By ~ 17

Author(s):

U. Müller ◽

K. Grimme ◽

C. Meyer ◽

W. Ehlers

Keyword(s):

Stomatal Conductance ◽

Water Potential ◽

Vicia Faba ◽

Leaf Water Potential ◽

Avena Sativa ◽

Leaf Water ◽

Vicia Faba L ◽

Faba Beans

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Photosynthesis Response of Sunlit and Shade Pepper (Capsicum annuum) Leaves at Different Positions in the Canopy Under Two Water Regimes

Functional Plant Biology ◽

10.1071/pp9940377 ◽

1994 ◽

Vol 21 (3) ◽

pp. 377 ◽

Cited By ~ 16

Author(s):

A Alvino ◽

M Centritto ◽

FD Lorenzi

Keyword(s):

Water Potential ◽

Capsicum Annuum ◽

Leaf Water Potential ◽

Co2 Exchange ◽

Leaf Water ◽

Predawn Leaf Water Potential ◽

Water Regimes ◽

Water Potentials ◽

Sun And Shade ◽

Shade Leaves

Pepper (Capsicum annuum L.) plants were grown in 1 m2 lysimeters under two different water regimes in order to investigate differences in the spatial arrangements of the leaves and to relate this to daily assimilation rates of leaves of the canopy. The control regime (well-watered (W) treatment) was irrigated whenever the accumulated 'A' pan evaporation reached 4 cm, whereas the water-stressed (S) treatment was watered whenever the predawn leaf water potential fell below -1 MPa. During the growing cycle, equal numbers of sun and shade leaves were chosen from the apical, middle and basal parts of the canopy, corresponding to groups of leaves of increasing age. The CO2 exchange rate (CER) was measured at 0830, 1230 and 1530 hours on 8 days along the crop cycle, on leaves in their natural inclination and orientation. Leaf water potentials were measured on apical leaves before dawn and concurrently with gas exchange measurements. Control plants maintained predawn leaf water potential at -0.3 MPa, but S plants reached values lower than -1.2 MPa. Midday leaf water potentials were about twice as low in the S plants as in the controls. Water stress reduced LA1 during the period of crop growth, and dry matter production at harvest. Stressed apical leaves appeared to reduce stress by changing their inclination. They were paraheliotropic around midday and diaheliotropic at 0830 and 1530 hours. The CER values of the S treatment were significantly lower than those of the W treatment in apical and middle leaves, whereas the CER of basal leaves did not differ in either treatments. In the S treatment, reduction in the CER values of sunlit apical leaves was more evident in the afternoon than at midday or early in the morning, whereas basal leaves were less affected by water than basal stress leaves if sunlit, and negligibly in shaded conditions.

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Interactions between leaf water potential, stomatal conductance and abscisic acid content of orange trees submitted to drought stress

Brazilian Journal of Plant Physiology ◽

10.1590/s1677-04202004000300005 ◽

2004 ◽

Vol 16 (3) ◽

pp. 155-161 ◽

Cited By ~ 38

Author(s):

Mara de Menezes de Assis Gomes ◽

Ana Maria Magalhães Andrade Lagôa ◽

Camilo Lázaro Medina ◽

Eduardo Caruso Machado ◽

Marcos Antônio Machado

Keyword(s):

Abscisic Acid ◽

Water Stress ◽

Stomatal Conductance ◽

Water Potential ◽

Leaf Water Potential ◽

Acid Content ◽

Stomatal Closure ◽

Leaf Water ◽

Orange Trees ◽

Abscisic Acid Content

Thirty-month-old 'Pêra' orange trees grafted on 'Rangpur' lemon trees grown in 100 L pots were submitted to water stress by the suspension of irrigation. CO2 assimilation (A), transpiration (E) and stomatal conductance (g s) values declined from the seventh day of stress, although the leaf water potential at 6:00 a.m. (psipd) and at 2:00 p.m. (psi2) began to decline from the fifth day of water deficiency. The CO2 intercellular concentration (Ci) of water-stressed plants increased from the seventh day, reaching a maximum concentration on the day of most severe stress. The carboxylation efficiency, as revealed by the ratio A/Ci was low on this day and did not show the same values of non-stressed plants even after ten days of rewatering. After five days of rewatering only psi pd and psi2 were similar to control plants while A, E and g s were still different. When psi2 decreases, there was a trend for increasing abscisic acid (ABA) concentration in the leaves. Similarly, stomatal conductance was found to decrease as a function of decreasing psi2. ABA accumulation and stomatal closure occurred when psi2 was lower than -1.0 MPa. Water stress in 'Pera´ orange trees increased abscisic acid content with consequent stomatal closure and decreased psi2 values.

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A model of stomatal closure driven by nonlinearities in soil-plant hydraulics

10.5194/egusphere-egu21-12524 ◽

2021 ◽

Author(s):

Fabian Wankmüller ◽

Mohsen Zarebanadkouki ◽

Andrea Carminati

Keyword(s):

Hydraulic Conductivity ◽

Stomatal Conductance ◽

Water Potential ◽

Leaf Water Potential ◽

Environmental Conditions ◽

Plant Traits ◽

Stomatal Closure ◽

Leaf Water ◽

Optimization Models ◽

Soil Conditions

Predicting plant responses to drought is a long-standing research goal. Since stomata regulate gas-exchange between plants and the atmosphere, understanding their response to drought is fundamental. Current predictions of stomatal behavior during drought mainly rely on empirical models. These models may suit well to a specific set of plant traits and environmental growth conditions, but their predictive value is doubtful when atmospheric and soil conditions change. Stomatal optimization offers an alternative framework to predict stomatal regulation in response to drought for varying environmental conditions and plant traits. Models which apply this optimization principle posit that stomata maximize the carbon gain in relation to a penalty caused by water loss, such as xylem cavitation. Optimization models have the advantage of requiring a limited number of parameters and have been successfully used to predict stomatal response to drought for varying environmental conditions and species. However, a mechanism that enables stomata to optimally close in response to water limitations, and more precisely to a drop in the ability of the soil-plant continuum to sustain the transpiration demand, is not known. Here, we propose a model of stomatal regulation that is linked to abscisic acid (ABA) dynamics (production, degradation and transport) and that allows plants to avoid excessive drops in leaf water potential during soil drying and increasing vapor pressure deficit (VPD). The model assumes that: 1) stomatal conductance (gs) decreases when ABA concentration close to the guard cells (CABA) increases; 2) CABA increases with decreasing leaf water potential (due to higher production); and 3) CABA decreases with increasing photosynthesis (e.g. due to faster degradation or transport to the phloem). Our model includes simulations of leaf water potential based on transpiration rate, soil water potential and variable hydraulic conductances of key elements (rhizosphere, root and xylem), and a function linking stomatal conductance to assimilation. It was tested for different soil properties and VPD. The model predicts that stomata close when the relation between assimilation and leaf water potential becomes nonlinear. In wet soil conditions and low VPD, when there is no water limitation, this nonlinearity is controlled by the relation between stomatal conductance and assimilation. In dry soil conditions, when the soil hydraulic conductivity limits the water supply, nonlinearity is controlled by the excessive drop of leaf water potential for increasing transpiration rates. The model predicts different relations between stomatal conductance and leaf water potential for varying soil properties and VPD. For instance, the closure of stomata is more abrupt in sandy soil, reflecting the steep decrease in hydraulic conductivity of sandy soils. In summary, our model results in an optimal behavior, in which stomatal closure avoids excessive (nonlinear) decrease in leaf water potential, similar to other stomatal optimization models. As based on ABA concentration which increases with decreasing leaf water potential but declines with assimilation, this model is a preliminary attempt to link optimization models to a physiological mechanism.

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