Mechanisms of drought response in Populus.

Drought affects plant growth and has become a serious problem worldwide. Populus species have different drought tolerance and sensitivity abilities. In order to evaluate the mechanism of drought stress tolerance in different cultivated Populus species distributed in China, the response to drought in the morphology and physiology of three poplars clones, NL-895, NL-351 and NL-3412 was investigated. The growth, gas exchange capacity, water use efficiency, antioxidant enzyme activity and lipid peroxidation were measured in order to evaluate differences among different genotypes in responses to two watering regimes (80% and 30% of field capacity). Our results indicated that drought stress had serious adverse effects on the seedlings as the biomass, leaf area, nett photosynthetic rate (Pn) and chlorophyll content were decreased while the activities of antioxidative enzymes were increased and the relative electric conductivity and malondialdehyde (MDA) content were enhanced. The results showed Populus possessed an effective self-protective mechanism to relieve the inhibition of growth induced by water deficit through increasing waster use efficiency, adjusting osmotic membrane and decreasing plant growth. These findings deepened our understanding of drought-tolerance mechanism in Populus. [ABSTRACT FROM AUTHOR]