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Leaf responses to soil water deficits: Comparative sensitivity of leaf expansion rate and leaf conductance in field-grown sunflower (Helianthus annuus L.)

V.O. SADRAS, F.J. VILLALOBOS, E. FERERES and D.W. WOLFE
Plant and Soil
Vol. 153, No. 2 (June (II) 1993), pp. 189-194
Published by: Springer
Stable URL: http://www.jstor.org/stable/42938973
Page Count: 6
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Leaf responses to soil water deficits: Comparative sensitivity of leaf expansion rate and leaf conductance in field-grown sunflower (Helianthus annuus L.)
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Abstract

The relative importance of changes in leaf expansion rate (LER) and leaf conductance (g₁) in the control of crop transpiration depends primarily on their sensitivity to soil water deficits. The aim of this paper was to quantify the responses of LER and g 1 to soil water deficits in sunflower (Helianthus annuus L.) under conditions of moderate (spring) and high (summer) evaporative demand. Soil water content, g l5 and LER were measured in dryland (DRY) and daily-irrigated (WET) crops established on a deep sandy-loam (Typic Xerofluvent) in a Mediterranean environment. There was no difference between g l of DRY and WET plants (p > 0.20) in contrast with a highly significant difference in LER (p < 0.001). Even under the harsh conditions of the summer experiment, g₁ did not respond to water deficit in a ten-day period in which LER of DRY plants was reduced to approx. 30% of that measured in WET controls. This field study indicates that g₁ plays at most a minor role in the control of sunflower transpiration in the pre-anthesis period and confirms the importance of leaf expansion in the regulation of gas exchange of expanding canopies subjected to soil water deficits.

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