Influence of Water Stress on Water Relations and Growth of a Tropical (C4) Grass, Panicum maximum var. trichoglume

1975 ◽  
Vol 2 (4) ◽  
pp. 581 ◽  
Author(s):  
TT Ng ◽  
JR Wilson ◽  
MM Ludlow
Keyword(s):  
Growth Rate ◽  
Water Stress ◽  
Water Potential ◽  
Water Content ◽  
Soil Water ◽  
Leaf Area ◽  
Soil Water Content ◽  
Relative Growth Rate ◽  
Leaf Water ◽  
Relative Growth

The effects of recurring cycles of short-term water stress on the water relations and growth of P. maximum var. trichoglume in pots of soil were investigated under controlled conditions. As soil water content decreased there was an increase in the resistance to water movement in the soil-plant system. Leaf stomatal resistance increased and concomitantly transpiration rate decreased when soil water content fell below 37 % (soil water potential of - 1 .0 bars) and leaf water potentials were less than - 6 bars. The leaf water potential at wilting (- 8 to - 10 bars) and the relation between leaf water potential and relative water content changed with leaf position on the tiller. The death of early-formed leaves on the plants was accelerated by water stress but, in contrast, the later-formed leaves died more rapidly in the control (unstressed) treatment so that finally the control plants had a higher proportion of dead leaves. Plant growth was reduced at soil water contents above the permanent wilting point. Reduction in net assimilation rate was the main determinant of lower relative growth rate of stressed plants over the initial cycles of stress but subsequently, as leaf area expansion was reduced, leaf area ratio also had a significant influence. Water stress influenced growth directly, and also indirectly via its effect on plant development (ontogeny). Two techniques were used to separate the direct from the indirect effects on relative growth rate Some published data which suggest a stimulation of growth rate after the relief of stress are re-interpreted and the effect is shown to be due mainly to differences in ontogeny between stressed and control treatments

WATER EXTRACTION PATTERNS AND DEVELOPMENT OF PLANT WATER DEFICITS IN CORN

1985 ◽  
Vol 65 (4) ◽  
pp. 921-933 ◽  
Author(s):  
L. M. DWYER ◽  
D. W. STEWART
Keyword(s):  
Zea Mays ◽  
Water Stress ◽  
Water Potential ◽  
Water Content ◽  
Soil Water ◽  
Leaf Area ◽  
Water Use ◽  
Zea Mays L ◽  
Leaf Water ◽  
Plant Water

Water extraction patterns and plant water deficits for corn (Zea mays L.) were measured and related to development of aboveground biomass, leaf area and root density under different irrigation schedules in controlled chambers. A multi-layer transpiration model, based on an Ohm’s Law analogy, simulated the water uptake processes and predicted leaf water potential and soil water content through time. Comparison of measurements and model predictions of plant and soil water status tested our understanding of the principles involved in plant water use which resulted in growth differences. The experiment involved 48 planted cylinders plus controls; half were well-watered and maintained at or above field capacity and half were allowed to dry to near the wilting point. Over 6 wk, water stress reduced above-ground biomass and leaf area, but enhanced root growth over that of well-watered plants. This reflected the preferential allocation of photosynthate to the root when soil water became limiting. Measured leaf water potentials fell below the level for stomatal closure of the chamber population. The model also predicted a degree of water stress (midday leaf water potential of −1.48 MPa) that would increase stomatal resistance and restrict transpiration and photosynthesis. Measurements and predictions of soil water content over time were generally in good agreement. The model is therefore considered useful in describing water use patterns under controlled conditions.Key words: Zea mays L., transpiration, water use modelling, plant water stress, dry matter partitioning

scholarly journals Relationships Among Water Potential Components, Relative Water Content, and Stomatal Resistance of Field-Grown Peanut Leaves1

1984 ◽  
Vol 11 (1) ◽  
pp. 31-35 ◽  
Author(s):  
J. M. Bennett ◽  
K. J. Boote ◽  
L. C. Hammond
Keyword(s):  
Water Potential ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Leaf Water Potential ◽  
Relative Water Content ◽  
Leaf Water ◽  
Peanut Crop ◽  
Relative Water ◽  
Volumetric Soil Water

Abstract Limited data exist describing the physiological responses of peanut (Arachis hypogaea L.) plants to tissue water deficits. Detailed field experiments which accurately define the water status of both the plant and soil are required to better understand the effects of water stress on a peanut crop. The objectives of the present study were 1) to describe the changes in leaf water potential components during a drying cycle, and 2) to define the relationships among soil water content, leaf water potential, leaf turgor potential, relative water content, leaf-air temperature differential, and leaf diffusive resistance as water stress was imposed on a peanut crop. During a 28-day drying period where both rainfall and irrigation were withheld from peanut plants, midday measurements of the physiological parameters and volumetric soil water contents were taken concurrently. As soil drying progressed, water extraction from the upper soil depths was limited as soil moisture approached 0.04 m3m-3. Leaf water potentials and leaf turgor potentials of nonirrigated plants decreased to approximately −2.0 and 0 MPa, respectively, by the end of the experimental period. Leaf water potentials declined only gradually as the average volumetric soil water content in the upper 90 cm of soil decreased from 0.12 to 0.04 m3m-3. Further reductions in soil water content caused large reductions in leaf water potential. As volumetric soil moisture content decreased slightly below 0.04 m3m-3 in the upper 90 cm, leaf relative water content dropped to 86%, leaf water potential approached −1.6 MPa and leaf turgor potential decreased to 0 MPa. Concurrently, stomatal closure resulted and leaf temperature increased above air temperature. Osmotic potentials measured at 100% relative water content were similar for irrigated and nonirrigated plants, suggesting little or no osmotic regulation.

Growth and yield of rice cultivars under sprinkler irrigation in south-eastern Queensland. 3. Water extraction and plant water relations dash comparison with maize and grain sorghum

1988 ◽  
Vol 28 (2) ◽  
pp. 249 ◽  
Author(s):  
S Fukai ◽  
P Inthapan
Keyword(s):  
Water Potential ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Leaf Water Potential ◽  
Osmotic Potential ◽  
Root Length ◽  
Dry Matter ◽  
Root Length Density ◽  
Leaf Water

Several physiological responses were compared, under irrigated and water-stressed conditions, in an attempt to explain the reasons for the greater reduction in dry matter production of rice compared with maize and sorghum in a water-limiting environment. Leaf water potential and leaf rolling were determined weekly, soil water profiles and root length density twice, and leaf osmotic potential once during a long dry period. Root length density of rice was at least as high as that of maize and sorghum in the top 0.6 m layer of soil in both the wet and dry trials. There was no difference in water extraction among the 3 species from this layer, while rice extracted less water than did the other species from below 0.6 m. High variability among replicates precluded any conclusion being drawn regarding root length in the deeper layer. Leaf water potential, measured in the early afternoon, was consistently lower in rice than in maize and sorghum, even when soil water content was high, indicating high internal resistance to the flow of water in the rice plants. The low leaf water potential in rice was accompanied by low osmotic potential, and this assisted in maintenance of turgor and dry matter growth when soil water content was relatively high. As soil water content decreased, however, leaf water potential became very low (less than - 2.5 MPa) and, for rice, leaves rolled tightly.

Photosynthesis and Stomatal-Conductance Responses of Johnsongrass (Sorghum halepense) to Water Stress

Weed Science ◽  
1985 ◽  
Vol 33 (5) ◽  
pp. 635-639 ◽  
Author(s):  
Bryan L. Stuart ◽  
Daniel R. Krieg ◽  
John R. Abernathy
Keyword(s):  
Water Stress ◽  
Stomatal Conductance ◽  
Water Potential ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Osmotic Potential ◽  
Grain Filling ◽  
Leaf Temperature ◽  
Sorghum Halepense

The influence of water stress on johnsongrass [Sorghum halepense(L.) Pers. ♯ SORHA] physiology was evaluated in a semiarid environment. Stomatal conductance of johnsongrass responded to more negative leaf water potential and increasing leaf temperature. The sensitivity of the leaf temperature effect was dependent on the soil water content. At low soil water content, conductance was limited by low water potential, and increasing leaf temperature had little effect. Conductance of CO2was related to net photosynthesis in a curvilinear manner, with conductance levels greater than 0.3 mol·m-2· s-1being in excess of that necessary for maximum photosynthesis. At both high conductance levels and low levels associated with increased water stress, intercellular CO2concentration increased, indicating nonstomatal limitations to photosynthesis. Decreased osmotic potential provided the highest correlation with the linear decline of photosynthetic rate as stress intensified. The expression of osmotic adjustment in johnsongrass is reported during grain filling. Plants in the milkdough stage of grain filling had approximately 0.3 MPa lower osmotic potential at any relative water content than those at anthesis.

scholarly journals Drought Responses among Seven Southwestern Landscape Tree Taxa

2002 ◽  
Vol 127 (2) ◽  
pp. 211-218 ◽  
Author(s):  
Coye A. Balok ◽  
Rolston St. Hilaire
Keyword(s):  
Growth Rate ◽  
Water Potential ◽  
Relative Growth Rate ◽  
Water Relations ◽  
Leaf Water ◽  
Cuticular Wax ◽  
White Oak ◽  
Relative Growth ◽  
Fraxinus Velutina ◽  
Wax Content

Identification of tree taxa that can thrive on reduced moisture regimes mandated by xeriscape programs of the southwest United States could be facilitated if responses to drought of those taxa are determined. Leaf water relations, plant development, and cuticular wax content of seven taxa maintained as well-irrigated controls or exposed to drought and irrigated based on evapotranspiration were studied. Leaf water potential of drought-stressed Fraxinus velutina Torr. (Arizona ash), Koelreuteria paniculata Laxm. (golden rain tree), Quercus macrocarpa Michx. (bur oak), and Quercus muehlenbergii Engelm. (chinkapin oak) were lower at predawn than the controls. Drought-stressed plants of F. velutina, K. paniculata, and Quercus lobata Née (California white oak) had more negative midday water potential than the control plants. Drought reduced stomatal conductance to as little as 17%, 23%, and 45% of controls in F. velutina, K. paniculata, and Q. macrocarpa, respectively. Drought-stressed plants of F. velutina, K. paniculata, Q. macrocarpa, and Q. muehlenbergii had reduced transpiration rates. Fraxinus velutina had both the highest net assimilation rate (NAR) and relative growth rate (RGR) regardless of irrigation treatment. Mean specific leaf weight (dry weight (DW) of a 1-cm2 leaf disc divided by the weight), trichome density, stomatal density, leaf thickness, and cuticular wax content varied among species but not between irrigation treatments. Leaves of Q. buckleyi Buckl. (Texas red oak) had one of the highest stomatal densities, and also had leaves which were among the waxiest, most dense, and thickest. Abaxial leaf surfaces of F. velutina were the most pubescent. Across species, drought led to lower ratios of leaf surface area to root DW, and leaf DW to root DW. Quercus buckleyi plants subjected to drought had the highest root to shoot DW ratio (3.1). The low relative growth rate of Q. buckleyi might limit widespread landscape use. However, Q. buckleyi may merit increased use in landscapes on a reduced moisture budget because of foliar traits, carbon allocation patterns, and the relative lack of impact of drought on plant tissue water relations.

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