An association between flowering and reduced stomatal sensitivity to water stress in pearlmillet (Pennisetum americanum (L.) Leeke)
1983
Henson, I.E. | Mahalakshmi, V. | Alagarswamy, G. | Bidinger, F.R.
Stomatal sensitivity to water stress was investigated in pearl millet [Pennisetum americanum (L.) Leeke] in relation to stage of plant development, leaf water status and ABA content by sampling plants at midday. For the same leaf water potential (ψ), droughted plants with emerged panicles were found to have a greater leaf conductance (gL), indicative of greater stomatal opening, than plants sampled prior to panicle emergence. The difference between such flowering (F) and non-flowering (NF) plants in ψ at stomatal closure was estimated to be at least 0.6 MPa. This difference was considered unlikely to be the result of differential bulk leaf osmotic adjustment, and for most samples from both F and NF plants, bulk leaf turgor potential (ψp) was estimated to be zero. Stomatal closure in NF plants was associated in two genotypes (BJ 104 and line 112) with higher leaf ABA levels. Differences in ABA levels between F and NF plants were, however, smaller or absent in genotypes Serere 39 and B282. These genotypes were at lower ψ than BJ 104 and line 112 when sampled and showed smaller differences between F and NF plants in conductance. Lower ABA levels in F plants are ascribed either to effects of leaf ageing or to effects of flowering on ABA content of the leaf. Significant differences in gL in the absence of differences in ABA content are taken to imply changes in stomatal sensitivity to the hormone or in its access to the stomatal complex.
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