Drought and pot size effects on transpiration efficiency and carbon isotope discrimination of cowpea accessions and hybrids [Vigna unguiculata]
1994
Ismail, A.M. | Hall, A.E. | Bray, E.A. (California Univ., Riverside (USA). Dept. of Botany and Plant Sciences)
Cowpea accessions and hybrids were grown in the field and subjected to wet or dry treatments with 3 different pot sizes. The experiment was conducted twice, giving similar results. The dry treatment resulted in decreases in C isotope discrimination (delta), and increases in seasonal transpiration efficiency (WUE) and ABA concentration in the xylem sap. Under drought, genotypes with higher WUE had higher xylem ABA, and the hybrids exhibited greater increases in ABA concentration in response to the dry treatment than either parent. Partial confounding was present in that the hybrids had substantial leaf area and water-use rate, and may have experienced greater soil drought in some conditions than some parents, with interacting effects of pot size. Plants in larger pots produced more biomass and leaf area but with changes in xylem ABA. Concentration of ABA in the xylem sap was correlated with delta and WUE for genotypic and drought treatment effects but not for pot size effects. Hybrids tended to have higher delta and lower WUE in relation to mid-parent means when grown in large wet pots than in small dry ones. Changes in hybrid performance with respect to delta and WUE were more consistent with changes in xylem ABA for drought treatment effects than for pot size effects. Another chemical signal might be involved in mediating pot size effects.
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