Drought-induced changes in shoot and root growth of young cotton plants

Abstract

An understanding of the response of plants to water deficits is important in efforts to model cotton (Gossypium hirsutum L.) growth, estimate irrigation needs, and breed drought-resistant cultivars. This study examined shoot and root growth of a long- and a short-season cotton cultivar after a brief drought and subsequent recovery period. Seeds were planted in fritted clay-filled pots in a growth room under fluorescent lights at about 27°C. Plants were divided at 36 d after planting into drought-treatment and watered-control groups. Plants were sampled after a 13-d drought and again after a 10-d recovery period. There were no treatment-by-genotype interactions. At the end of the drought and recovery, height, leaf area, number of nodes, and the dry weights of the leaves and stems were less in the drought-treated plants than in the controls. Root growth was not decreased in the drought-treated plants, compared with the controls, until the end of the recovery period, when the shoot:root ratio was less in the drought-treated plants than the controls. Most importantly, at the end of the drought and recovery the length of the taproot, but not its dry weight, was greater in the drought-treated plants than in the controls. This observation in both tested cotton genotypes suggests that increases in taproot length at the expense of root thickening after drought may be a common response in cotton. This response may permit cotton plants to survive drought by accessing water from deeper in the soil profile than the levels tapped during periods of adequate water supply. © The Cotton Foundation 1999.