Comparison of Physiological and Biochemical Responses of Two Poplar Species under Drought Stress

Abstract

Drought stress is a crucial environmental factor for plant survival, and the development of drought-tolerant varieties is one of the goals of all cultivated plant researchers. In particular, the seedling stage is important for plant growth and development and is also the period most affected by drought. We investigated the initial response to drought stress in seedlings of two species of poplar (Populus alba × Populus davidiana and Populus davidiana) that phenotypically differed in drought tolerance. Comparative analysis in terms of shoot height, photosynthetic pigments, soluble sugars, antioxidants, proline, soluble protein, malondialdehyde (MDA), and hydrogen peroxide (H2O2) contents was used to measure the physiological and biochemical characteristics of drought stress, and drought-related genetic changes were also examined. Significant changes in shoot height, chlorophyll fluorescence, chlorophyll contents, MDA and H2O2 appeared more adversely in Populus alba × Populus davidiana than in Populus davidiana, whereas reductions in soluble protein, carotenoids, superoxide dismutase (SOD) and catalase (CAT), which are indicators related to drought tolerance, appeared less in Populus davidiana. The change pattern of genes related to electron transfer and H2O2 production were almost similar in the two species, and among the drought response genes, lipid transfer protein 3 (LTP3) was greatly upregulated only in Populus davidiana. In the initial response to drought stress of both poplars, Populus davidiana, which had good antioxidant maintenance, showed better drought tolerance than Populus alba × Populus davidiana, which had a faster response to osmotic balance control.