The effects of treating persimmon (Diospyros lotus) seeds with moist-chilling and growth regulators on seeds germination, the subsequent seedling characters and their induced drought tolerance

Abstract

The present experiment aimed at investigating the effects of seed pre-treatment with moist-chilling (mch), GA3, BA or their combinations on seed germination and subsequent drought resistance of the resulting seedlings. The obtained results indicated that increasing the moist-chilling period from 4 to 8 weeks progressively significantly increased the seeds germination percentages (average from 51.2% to 97.2%) and significantly decreased the time to 50% germination (T50) (average from 47days to 27.3 days). The control one (non-moist- chilled seeds) gave the lowest germination percentage (22.6%) and required the highest T50 (72.6 days). The 4 weeks-chilled seeds soaked in BA gave the most satisfactory results as it yielded high germination percentage (average 85.2%), low T50 (average 31.2 days) and saved about at least 4 weeks which would have otherwise being required for moist-chilling of the seeds. The best vegetative characteristics of 2.5-month-old persimmon seedlings were obtained from seeds treated with 8week-moist-chilling solely or with 4week- moist chilling followed by soaking in 20 ppm BA solution for 16 hr. After exposure the subsequent seedlings to 24 days drought period, the results revealed that increasing the moist-chilling period decreased proline content of the seedlings leaves and roots, while increased their leaf resistance to water vapour (LRWV) (9.9, 11.45 & 19.65 sec/cm for 0, 4, 8 weeks of mch, respectively). Generally, seeds pretreated with BA solely gave seedlings with significantly higher root proline content than those of the other treatments, and hence showing more drought resistance features. After the 24 days of drought, leaves of the seedlings resulting from either 4 or 8-weeks-chilled seeds had significantly higher values of chlorophyll (chl a, b) and total soluble carbohydrates (TSC) than those of their corresponding ones resulting from non-chilled seeds. In view of the above findings, the best combination that gave the most satisfactory results was soaking in BA of the seeds which were mois-chilled for 4 weeks.