Comparison of ultrastructural and physiological changes of potato (Solanum tuberosum L.) plantlets subjected to salt and modeling drought stresses

Salinity and drought are two severe abiotic stresses that affect plant growth and decrease food production worldwide. Compared to the field plants, test-tube plantlets could be more direct and fast to investigate the mechanism of stress adaptation. In the present study, the ultrastructural and physiological differences of potato (Solanum tuberosum L. c.v. Longshu No. 3'') plantlets in response to the gradient saline (0, 25, 50, 100, and 200 mM NaCl) and the modeling drought stresses with polyethylene glycol (PEG) at the concentrations of 0, 2, 4, 6, and 8 % were analyzed. The results show that the severe salt (200 mM NaCl) and the modeling drought stresses (8 % PEG) inhibited the plantlet growth. There are considerable differences in their ultrastructural alteration under salt and modeling drought adaptation: PEG caused the increase in the number of stacked chloroplast, plastoglobuli, and starch; NaCl induced the decrease in the number of chloroplast and plastoglobuli. Moreover, plantlet has higher free proline content, less malondialdehyde (MDA) content, and higher activities of catalase (CAT) and superoxide dismutase (SOD) under the gradient NaCl treatments than the gradient PEG treatments. The results of this study will provide theoretical and practical insights into characterizing the ultrastructural and physiological differences of plants adapting to various stressful environments.