Abstract:

The morphological, physiological and biochemical indexes associated with seed germination and seedling growth of Cercidiphyllum japonicum were measured under treatments of seven different polyethylene glycol (PEG) mass concentrations from 95 to 345 g·L^-1. The results showed that the suitable PEG concentration was in a range from 140 to 301 g·L^-1. In this range, the membrane-repair capacity and the drought resistance of seeds were improved, accompanied with the changes of the following indicators. The contents of three osmoregulation substances ［soluble protein, sugar and proline) and the activities of three protective enzymes (superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT)］ were increased, and the content of a final product of lipid peroxidation, malondialdehyde (MDA) was decreased. However, seed germination and seedling growth were inhibited in higher PEG mass concentrations under water stress. With increasing PEG mass concentrations, the contents of soluble sugar, proline and MDA, and the activities of two enzymes (SOD and CAT), were continuously raised, and the enzyme activity of POD was strongly inhibited. In addition, the content of soluble protein was increased first and then decreased in the condition. These results indicated that the seed germination and seedling growth were inhibited under the high PEG mass concentration (≥95 g·L^-1). The results suggest that C. japonicum seed is sensitive to drought stress.

Key words: Cercidiphyllum japonicum, PEG, seed priming, drought stress, seed germination, seedling growth