Stomatal closure ofPelargonium×hortorumin response to soil water deficit is associated with decreased leaf water potential only under rapid soil drying

The water relations of white clover and paspalum as monocultures and components of a mixed pasture were studied on a normal and a modified soil profile during the interval between 2 successive irrigations. Responses of individual species were similar in monocultures and mixed pastures. On the normal profile white clover was the first species to react to soil water deficit when the rate of leaf elongation fell by 33% to about 10 mm/day after 30 mm of cumulative evaporation minus rainfall (E - R). This was followed by a reduction in dawn and midday leaf water potential at around 50 mm E - R. After 65 mm E - R, leaf elongation had ceased. In contrast, paspalum showed no signs of water shortage until 70-80 mm E - R. At this stage both the rate of leaf elongation and midday leaf water potential fell. After 90 mm E - R the dawn leaf water potential fell and by 120 mm E - R leaf elongation was negligible. Modification of the profile increased soil water availability by allowing more extraction of water at depth in the profile. This delayed the onset of water stress by about 40 mm E - R in both species. These observations show that the common irrigation interval of 60-90 mm E - R in northern Victoria is likely to restrict pasture yields because it causes a period of soil water deficit stress, especially for white clover, and the development of leaf area is impeded, increasing the time taken for canopies to recover maximum productivity after grazing. To overcome these limitations farmers will have to water more frequently or modify the soil profile to provide pastures with a better water supply.

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Water status and gas exchange of umbu plants (Spondias tuberosa Arr. Cam.) propagated by seeds and stem cuttings

Revista Brasileira de Fruticultura ◽

10.1590/s0100-29452007000200032 ◽

2007 ◽

Vol 29 (2) ◽

pp. 355-358 ◽

Cited By ~ 2

Author(s):

José Moacir Pinheiro Lima Filho

Keyword(s):

Stomatal Conductance ◽

Gas Exchange ◽

Water Potential ◽

Soil Water ◽

Water Deficit ◽

Leaf Water Potential ◽

Leaf Gas Exchange ◽

Leaf Water ◽

Soil Water Deficit ◽

Stem Cuttings

The experiment was carried out at the Embrapa Semi-Árido, Petrolina-PE, Brazil, in order to study the physiological responses of umbu plants propagated by seeds and by stem cuttings under water stress conditions, based on leaf water potential and gas exchange measurements. Data were collected in one-year plants established in pots containing 30 kg of a sandy soil and submitted to twenty-day progressive soil water deficit. The evaluations were based on leaf water potential and gas exchange data collection using psychrometric chambers and a portable infra-red gas analyzer, respectively. Plants propagated by seeds maintained a significantly higher water potential, stomatal conductance, transpiration and photosynthesis under decreasing soil water availability. However, plants propagated by stem cuttings were unable to maintain a favorable internal water balance, reflecting negatively on stomatal conductance and leaf gas exchange. This fact is probably because umbu plants propagated by stem cuttings are not prone to formation of root tubers which are reservoirs for water and solutes. Thus, the establishing of umbu plants propagated by stem cuttings must be avoided in areas subjected to soil water deficit.

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Evaporation from Lucerne Under Advective Conditions in the Sudan I. Factors Affecting Water Losses and Their Measurement

Experimental Agriculture ◽

10.1017/s0014479700100420 ◽

1965 ◽

Vol 1 (1) ◽

pp. 23-32

Author(s):

J. P. Hudson

Keyword(s):

Water Potential ◽

Soil Water ◽

Water Deficit ◽

Leaf Water Potential ◽

Experimental Work ◽

Leaf Water ◽

Soil Water Deficit ◽

Water Losses ◽

Factors Affecting ◽

Sudan I

SummaryIt is suggested that irrigation should ideally be based on two sets of measurements, i.e. of conditions in the leaf and of cumulative evaporation rates respectively, on the assumption that the question 'When to irrigate ? ’ can best be answered from a knowledge of leaf water potential and the daytime behaviour of stomata, and the question ‘How much water to apply?’ from a knowledge of the current soil water deficit. It is emphasized that there is no unique or fixed relation between leaf water potential and soil water deficit, and since neither can be deduced from the other it is advisable to measure both in critical experimental work on irrigation. Various methods of measuring leaf water potential and evaporation rates are discussed, and their value in experimental work assessed.

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Relationship Between Root/Soil Hydraulic Properties and Stomatal Behaviour in Sugarcane

Functional Plant Biology ◽

10.1071/pp9890241 ◽

1989 ◽

Vol 16 (3) ◽

pp. 241 ◽

Cited By ~ 21

Author(s):

NZ Saliendra ◽

FC Meinzer

Keyword(s):

Stomatal Conductance ◽

Water Potential ◽

Soil Water ◽

Leaf Water Potential ◽

Water Status ◽

Hydraulic Conductance ◽

Leaf Water ◽

Soil Drying ◽

Root Hydraulic Conductance ◽

High Soil Moisture

Stomatal conductance, leaf and soil water status, transpiration, and apparent root hydraulic conductance were measured during soil drying cycles for three sugarcane cultivars growing in containers in a greenhouse. At high soil moisture, transpiration and apparent root hydraulic conductance differed considerably among cultivars and were positively correlated, whereas leaf water potential was similar among cultivars. In drying soil, stomatal and apparent root hydraulic conductance approached zero over a narrow (0.1 MPa) range of soil water suction. Leaf water potential remained nearly constant during soil drying because the vapor phase conductance of the leaves and the apparent liquid phase conductance of the root system declined in parallel. The decline in apparent root hydraulic conductance with soil drying was manifested as a large increase in the hydrostatic pressure gradient between the soil and the root xylem. These results suggested that control of stomatal conductance in sugarcane plants exposed to drying soil was exerted primarily at the root rather than at the leaf level.

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An Analysis of the Effects of Repeated Short-Term Soil Water Deficits on Stomatal Conductance to Carbon Dioxide and Leaf Photosynthesis by the Legume Macroptilium atropurpureum Cv. Siratro

Functional Plant Biology ◽

10.1071/pp9810347 ◽

1981 ◽

Vol 8 (3) ◽

pp. 347 ◽

Cited By ~ 24

Author(s):

MJ Fisher ◽

DA Charles-Edwards ◽

MM Ludlow

Keyword(s):

Stomatal Conductance ◽

Water Potential ◽

Soil Water ◽

Water Deficit ◽

Leaf Water Potential ◽

Leaf Water ◽

Mathematical Function ◽

Leaf Photosynthesis ◽

Short Term ◽

Macroptilium Atropurpureum

The response was measured of stomatal conductance and leaf photosynthesis to changing leaf water potential in the legume siratro subjected to a sequence of I-week cycles of increasing soil water deficit followed by watering. The response of stomatal conductance was described using a continuous mathematical function, which is more robust and accurate than the usual discontinuous linear function used to analyse such data. After seven successive cycles of water deficit, there was no apparent adjustment of the short-term response of leaf conductance to leaf water potential.

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Net photosynthesis, water use efficiency, leaf water potential and leaf rolling as affected by water deficit in tropical upland rice

Australian Journal of Agricultural Research ◽

10.1071/ar9891171 ◽

1989 ◽

Vol 40 (6) ◽

pp. 1171 ◽

Cited By ~ 47

Author(s):

M Dingkuhn ◽

RT Cruz ◽

JC O'Toole ◽

K D÷rffling

Keyword(s):

Water Use Efficiency ◽

Water Potential ◽

Water Deficit ◽

Water Use ◽

Leaf Water Potential ◽

Upland Rice ◽

Stomatal Closure ◽

Leaf Water ◽

Leaf Rolling ◽

Use Efficiency

Growth and production of tropical upland rice is often impeded by drought. Little is known on varietal response of CO2 assimilation to water deficit under tropical field conditions. A drought-susceptible semidwarf (IR20) and a drought-resistant traditional (Azucena) rice were grown in a dryland field experiment with sprinkler irrigation during the dry season in the Philippines. Differential irrigation was imposed for 11 days during vegetative growth using a line source sprinkler. Net photosynthesis, leaf conductance, transpiration, leaf rolling and leaf water potential were determined during the stress cycle at pre-noon and afternoon, with all measurements on the same leaf. No varietal differences in maximum photosynthetic rate and in the relationship between photosynthesis and leaf conductance were observed. In both rices, partial stomatal closure and nonstomatal inhibition reduced assimilation rates in the afternoon. Leaf water deficits restricted gas exchange through at least three apparently independent mechanisms: leaf rolling, reduced stomatal conductance and non-stomata1 inhibition which became evident only at severe degrees of stress. Stomata1 closure and leaf rolling were more sensitive to water deficit in Azucena which maintained higher leaf water potential throughout the stress cycle. Both stomatal closure and leaf rolling improved water use efficiency at moderate stress while nonstomatal inhibition of photosynthesis reduced water use efficiency.

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Leaf Gas Exchange and Water Relations of Lupins and Wheat. I. Shoot Responses to Soil Water Deficits

Functional Plant Biology ◽

10.1071/pp9890401 ◽

1989 ◽

Vol 16 (5) ◽

pp. 401 ◽

Cited By ~ 43

Author(s):

IE Henson ◽

CR Jensen ◽

NC Turner

Keyword(s):

Stomatal Conductance ◽

Water Potential ◽

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Leaf Water Potential ◽

Stomatal Closure ◽

Turgor Pressure ◽

Leaf Conductance ◽

Leaf Water

The effects of a progressive increase in soil water deficit on the leaf conductance and gas exchange of lupin (Lupinus cosentinii) and wheat (Triticum aestivum) were investigated in pot experiments in a temperature-regulated glasshouse, using a coarse, sandy soil characteristic of the Western Australian wheatbelt. Transpiration rates decreased rapidly in both species after water was withheld, mainly as a result of stomatal closure. Photosynthesis declined also, but to a lesser extent than conductance. Leaf extension in lupin was equally as sensitive to a decrease in leaf water potential and soil water potential as stomatal conductance. Stomatal closure served to maintain the water potential of lupin leaves to within 0.1 MPa of that of control (watered) plants as the soil water content decreased from 0.14 to 0.06 m3 m-3 and as the leaf conductance and the relative transpiration rate fell to less than 50% of control values. Maintenance of leaf water potential with decreasing soil water content and stomatal conductance was less evident in wheat. In both lupin and wheat, leaf conductance decreased linearly with soil water content and curvilinearly with bulk soil matric potential, indicating that water uptake was restricted at similar water contents and matric potentials in both species. Diurnal measurements on lupin indicated a substantial reduction in stomatal conductance after water was withheld, even when the leaf water potential at midday was reduced by only 0.1 MPa and no change could be detected in the bulk leaf turgor pressure. Conductance in lupin was reduced even though the soil matric potential decreased in only part of the rooting zone. This, together with the absence of any significant change in the leaf water potential, turgor pressure, or relative water content in lupin during the initial stages of stomatal closure, suggests that a soil or root factor initiates the reduction in leaf conductance - and hence regulates the shoot water status - in response to soil drying.

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Increased Tolerance of Citrus (Citrus tangerina) Seedlings to Soil Water Deficit after Mycorrhizal Inoculation: Changes in Antioxidant Enzyme Defense System

Notulae Botanicae Horti Agrobotanici Cluj-Napoca ◽

10.15835/nbha4129218 ◽

2013 ◽

Vol 41 (2) ◽

pp. 524 ◽

Cited By ~ 5

Author(s):

Qiu-Dan NI ◽

Ying-Ning ZOU ◽

Qiang-Sheng WU ◽

Yong-Ming HUANG

Keyword(s):

Antioxidant Enzyme ◽

Soil Water ◽

Water Deficit ◽

Mycorrhizal Fungi ◽

Enzyme System ◽

Arbuscular Mycorrhizal ◽

Temporal Variations ◽

Soil Drying ◽

Soil Water Deficit ◽

Antioxidant Enzyme System

Arbuscular mycorrhizal fungi (AMF) can enhance tolerance of plants to soil water deficit, whereas morphological observations of reactive oxygen species and antioxidant enzyme system are poorly studied. The present study thereby evaluated temporal variations of the antioxidant enzyme system in citrus (Citrus tangerina) seedlings colonized by Glomus etunicatum and G. mosseae over a 12-day period of soil drying. Root colonization by G. etunicatum and G. mosseae decreased with soil drying days from 32.0 to 1.0% and 50.1 to 4.5% in 0-day to 12-day, respectively. Compared to the non-AM controls, the AMF colonized plants had significantly lower tissue (both leaves and roots) hydrogen peroxide (H2O2) and superoxide anion radical (O2â€¢â€“) concentrations during soil water deficit, whereas 1.03â€“1.92, 1.25â€“1.84 and 1.18â€“1.69 times higher enzyme activity in superoxide dismutase, peroxidase (POD) and catalase. In situ leaf H2O2 and root POD location also showed that AM seedlings had less leaf H2O2 but higher root POD accumulation. Furthermore, significantly higher root infection and antioxidant enzymatic activities in plants colonized with G. mosseae expressed than with G. etunicatum during the soil drying. These results demonstrated that the AMs could confer greater tolerance of citrus seedlings to soil water deficit through an enhancement in their antioxidant enzyme defence system whilst an decrease level in H2O2 and O2â€¢â€“.

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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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