Water Relations in Cowpea and Pearl Millet Under Soil Water Deficits. II. Water Use and Root Distribution

1992 ◽  
Vol 19 (6) ◽  
pp. 591 ◽  
Author(s):  
CL Petrie ◽  
AE Hall
Keyword(s):  
Water Potential ◽  
Water Content ◽  
Soil Water ◽  
Pearl Millet ◽  
Water Use ◽  
Root Length ◽  
Root Distribution ◽  
Root Length Density ◽  
Leaf Water ◽  
Predawn Leaf Water Potential

Pearl millet [Pennisetum americanum (L.) Leeke] develops lower predawn leaf water potentials than cowpea [Vigna unguiculata (L.) Walp.] when plants are subjected to progressive soil dehydration. Water use and root distribution were studied as possible explanations for this difference using plants grown in pots and in tubes in a glasshouse. In experiments grown in pots, weights of each container were measured daily after initiation of the dry treatment to determine water use, and roots and soil were sampled at the end of the experiment to determine root length density and soil water content. In experiments conducted in 1 m long tubes, plants were grown in either Turface Plus or a Turface Plus/sand mixture which had a high water-holding capacity and could be easily separated from roots. Roots and rooting medium were sampled during the dry treatment. Water content and root length density in the same sample were measured, and root distributions at various depths were determined. Pearl millet (millet) did not use more bulk water than cowpea by the time the difference in predawn leaf water potential developed. Millet root length density was at least twice as great as cowpea, and the decline in predawn leaf water potential was greater in millet, even when its root system was more extensive than that of cowpea.

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.

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

Root length density and soil water distribution in drip-irrigated olive orchards in Argentina under arid conditions

2009 ◽  
Vol 60 (3) ◽  
pp. 280 ◽  
Author(s):  
Peter S. Searles ◽  
Diego A. Saravia ◽  
M. Cecilia Rousseaux
Keyword(s):  
Water Content ◽  
Root System ◽  
Soil Water ◽  
Soil Water Content ◽  
Root Length ◽  
Root Length Density ◽  
Soil Depth ◽  
Drip Line ◽  
North West ◽  
Intensively Managed

Several studies have evaluated many above-ground aspects of olive production, but essential root system characteristics have been little examined. The objective of our study was to evaluate root length density (RLD) and root distribution relative to soil water content in three commercial orchards (north-west Argentina). Depending on the orchard, the different drip emitter arrangements included either: (1) emitters spaced continuously at 1-m intervals along the drip line (CE-4; 4 emitters per tree); (2) 4 emitters per tree spaced at 1-m intervals, but with a space of 2 m between emitters of neighbouring trees (E-4); or (3) 2 emitters per tree with 4 m between emitters of neighbouring trees (E-2). All of the orchards included either var. Manzanilla fina or Manzanilla reina trees (5–8 years old) growing in sandy soils, although the specific characteristics of each orchard differed. Root length density values (2.5–3.5 cm/cm3) in the upper soil depth (0–0.5 m) were fairly uniform along the drip line in the continuous emitter (CE-4) orchard. In contrast, roots were more concentrated in the E-4 and E-2 orchards, in some cases with maximum RLD values of up to 7 cm/cm3. Approximately 70% of the root system was located in the upper 0.5 m of soil depth, and most of the roots were within 0.5 m of the drip line. For each of the three orchards, significant linear relationships between soil water content and RLD were detected based on 42 sampling positions that included various distances from the trunk and soil depths. Values of RLD averaged over the entire rooting zone and total tree root length per leaf area for the three orchards were estimated to range from 0.19 to 0.48 cm/cm3 and from 1.8 to 3.5 km/m2, respectively. These results should reduce the uncertainty associated with the magnitude of RLD values under drip irrigation as intensively managed olive orchards continue to expand in established and new growing regions.

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.

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