Effects of simulated drought by PEG-6000 on the germination of Hopea chinensis seeds under different temperature conditions

Abstract

Hopea chinensis is distributed in China and its seeds are typically reclacitrant. In order to investigate the germination adaptability of seeds to temperature and moisture, we carried out an experiment with three different constant temperatures (15, 20, 25 ℃) controlled by artificial climate incubators, and used six polyethylene glycol (PEG-6000) concentrations (0%, 5%, 10%, 15%, 25% and 35%) to simulate drought stress. The germination characteristics of these seeds were carefully examined. The results were as follows: (1) Temperature exerted a significant influence on seed germination. Regardless of the level of drought stress applied, higher temperatures positively affected the germination percentage, germination energy, germination index, radicle length, sprout length and vitality index of seeds, higher temperatures led to shorter germination delay and increased fluctuations in the germination duration. (2) Drought stress had a significant impact on seed germination. Under identical temperature conditions, increasing levels of drought stress resulted in decreasing of germination percentage, germination energy, germination index, germination duration, radicle length, sprout length and vitality index of seeds. Moreover, higher levels of drought stress led to longer germination delay of seeds. (3) The interaction between temperature and drought stress had a significant influence on seed germination. Under drought stress, seed germination exhibited different responses under different temperature conditions. Specifically, under conditions where a PEG-6000 concentration of 35% was applied as drought stress treatment, the germination percentage at temperatures of 20 ℃ and 25 ℃ were significantly higher than those observed at 15 ℃ (8.89% and 15.55% compared to lower percentage at 15 ℃). However, it was important to note that when subjected to both 35% PEG-6000 and a temperature of 15 ℃, the seeds no longer germinate. In summary, our results indicate that the suitable temperatures for seed germination are identified as being at 20 ℃ and 25 ℃. It is determined that the most favorable temperature for early seedling growth is 25 ℃. As the drought stress intensifies, the inhibitory effect on seed germination become stronger, the effect of drought stress on seed germination is higher than that of temperature. Additionally, moderate warming can help alleviate the inhibitory effect of drought stress on seed germination.

Keywords

• endangered plant
• hopea chinensis
• temperature
• drought stress
• seed germination