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Functional Plant Biology Functional Plant Biology Society
Plant function and evolutionary biology
RESEARCH ARTICLE

Comparison of Water Relations and Osmotic Adjustment in Sorghum and Cowpea Under Field Conditions

KA Shackel and AE Hall

Australian Journal of Plant Physiology 10(5) 423 - 435
Published: 1983

Abstract

Seasonal and diurnal patterns of xylem pressure potential, Ψx, and osmotic potential, Ψs, were compared using contrasting genotypes of sorghum [Sorghum bicolor (L.) Moench] and cowpea [Vigna unguiculata (L.) Walp.] under frequently imgated 'wet' and water-limited 'dry' field conditions. Generally, differences in Ψx and Ψs among genotypes within each species were small compared with differences between the two species. Sorghum exhibited a larger diurnal range and larger differences between wet and dry treatments for Ψx, Ψs, and estimates of bulk leaf turgor than did cowpea. Seasonal and drought- induced osmotic adjustment occurred in sorghum, but not in cowpea. Diurnal patterns of leaf conductance indicated that, under the dry treatment, cowpea avoided the occurrence of large plant water deficits by substantial reductions in leaf conductance, especially at midday, whereas sorghum maintained moderate values of leaf conductance throughout the day. Cowpea exhibited a larger diurnal range of leaf conductance and larger differences between wet and dry treatments than did sorghum. Differences were not observed between the species in overall soil water depletion or in root activity as estimated from profiles of soil water depletion until senescence occurred in cowpea. Sorghum genotypes that had been selected on the basis of differences in Ψs did exhibit significant differences in average values of leaf conductance and total soil water depletion, but the genotype that had the lowest Ψs (M35-1) also had the lowest leaf conductance and the least soil water depletion.

https://doi.org/10.1071/PP9830423

© CSIRO 1983

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