Physiological and metabolic responses of Salix sinopurpurea and Salix suchowensis to drought stress

Key message Physiological and metabolic analysis showed the difference in drought tolerance and revealed the common and specific metabolic regulations in Salix sinopurpurea and Salix suchowensis. Willows (Salix spp.) are important woody plants as promising sources for sustainable and renewable biomass. However, drought is highly detrimental to their growth and development. Deciphering the adaptation mechanism of willows to drought will provide a theoretical basis for the cultivation of drought-tolerant varieties. In this work, we investigated the physiological and metabolic responses to drought stress in Salix sinopurpurea and Salix suchowensis. The drought experiment was conducted on clonal plants from cuttings of the two willow species under greenhouse conditions. S. sinopurpurea exhibited higher drought tolerance, as evidenced by lower growth reduction, and higher leaf relative water content, water use efficiency and net photosynthesis rate than those of S. suchowensis under the same drought conditions. Metabolic profiling identified 67 and 64 differentially accumulated metabolites in S. sinopurpurea and S. suchowensis, respectively. These metabolites function as compatible solutes and energy reserves and in antioxidant protection to defend against drought stress. Carbohydrate, amino acid and lipid metabolic pathways were central in the metabolic regulations of the drought response in the two willow species. The accumulation of aspartate, glutamate, serine, threonine, and sedoheptulose particularly in S. sinopurpurea might equip this species with drought tolerance. Meanwhile, phenylalanine and phytosterols were specifically inhibited in S. suchowensis, which might be associated with its susceptibility to drought stress. Taken together, these results provide a framework for better understanding the metabolic responses of willow to drought stress.