The maintenance of growth and turgor in pearl millet (Pennisetum glaucum [L.] Leeke) cultivars with different root structures and osmo-regulation under drought stress

Pearl millet (Pennisetum glaucum [L.] Leeke) is known to adapt to very dry conditions, however, the control of water loss and dehydration tolerance to drought is still not completely understood. Effects of water stress on root morphologies, osmotic relations, and stomatal conductance contributing to plant growth or turgor maintenance was investigated. Water stress was imposed by withholding water for 3 weeks at the seedling stage in a greenhouse. Irrigated treatments and two stress treatments were conducted in a tube culture experiment. One stress treatment was done by imposing water deficit, particularly in shallow areas of the soil (semi-drought), and the other was done by imposing widespread water deficit in the soil (drought). The genetic diversities in the total root length (TRL) were significantly related to the relative growth ratio of the shoot (RGR) within 4-21 days after withholding water in both stress treatments. On the other hand, osmotic adjustment was also strongly correlated with RGR and leaf turgor potential (LTP) in both stress treatments, but the effects of TRL and OA in terms of contributing to the variance in RGR was comparatively low under drought conditions. These results demonstrated that OA and TRL were dependent on the degree of water deficit, and these traits were the most important factors regarding turgor maintenance and plant growth under drought conditions during the seedling stage. (C) 2004 Elsevier Ireland Ltd. All rights reserved.