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Role of Gas Exchange, Leaf Water Status, and Carbohydrate Partitioning During the Early Vegetative Stage on Drought Tolerance in Cowpea
Author(s) -
Verbree David A.,
Singh Bir B.,
Payne William A.
Publication year - 2014
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci2013.07.0437
Subject(s) - cultivar , biology , transpiration , vigna , drought tolerance , stomatal conductance , photosynthesis , water content , agronomy , water use efficiency , horticulture , botany , geotechnical engineering , engineering
Two contrasting responses to water stress have been reported among drought‐tolerant cowpea ( Vigna unguiculata L. Walp.) cultivars. In Type 1 response, growth was arrested, moisture was conserved, and the unifoliates and trifoliates desiccated at approximately the same time. In Type 2 response, the unifoliates desiccated early and leaf moisture was conserved in the trifoliates to allow growth to continue slowly for the youngest trifoliate. The objective of this study was to evaluate these contrasting responses to water stress among six previously identified tolerant and susceptible cultivars and to elucidate the physiological basis for drought tolerance in cowpea with respect to gas exchange, leaf water status, and carbohydrate partitioning. Six cultivars previously identified as differing in type and level of drought tolerance were planted in a greenhouse with drought stress initiated 11 d after planting. Gas exchange, dry weight partitioning, and water status measurements were taken on each cultivar every 3 to 5 d during water stress. Water stress reduced net photosynthesis (A net ), stomatal conductance (g sw ), and transpiration, increased intercellular CO 2 concentration (C i ), but had no effect on leaf water content (LWC) of the trifoliates in all cowpea cultivars regardless of the type or level of drought tolerance. Results suggest that reduced A net under water stress was likely due to end‐product inhibition rather than stomatal limitation to CO 2 diffusion. This study found no evidence that the overall plant water status was improved by unifoliate senescence in certain drought‐tolerant cultivars as previously postulated. Rather, this appears to be a general stress response exhibited by certain cultivars.