Dormancy Characteristics and Breaking Methods of Vitex rotundifolia Seeds

Objective: Vitex rotundifolia, sandy plant and halophyte, naturally grows on the sandy beach coast front with arid and barren soil. In order to adapt to the adverse environment of strong wind and sea immersion, the seeds of V. rotundifolia have developed a deep dormancy. This study aimed to explore the dormancy characteristics of V. rotundifolia seed and the methods of breaking the seed dormancy, so as to provide theoretical basis to the propagation from seeds and large-scale production.Method: In this study, water absorption of the fruit and seed was measured. The sites and types of endogenous germination inhibitors were biologically identified, the mechanical barrier of the seed coat was broken with physical means (concentrated H2SO4, cutting peel), and the inhibitor concentration was reduced by low temperature stratification and GA3 treatment to study the possible types of and cause for dormancy, and methods of breaking dormancy of V. rotundifolia.Result:The results showed that: 1) Vitex rotundifolia had a thick pericarp, and the endocarp had a completely corked stone cell layer with a seed empty shell rate of 26%. The peel had obvious mechanical hindrance to the water absorption, and the seed had no water absorption barrier. 2) The water extract and methanol extract of the peel were able to significant inhibit the seed germination and seedling growth of Chinese cabbage. The inhibitory effect of water extract on the seed germination and seedling growth of Chinese cabbage was more obvious than that of methanol extract under the same concentration, that is, the activity of the water-soluble germination inhibitor is greater than that of the alcohol-soluble germination inhibitor. The GA3 treatment of peel water extract and methanol extract could significantly improve the seed germination rate, root length and seedling height of Chinese cabbage. The water extract and methanol extract of the seeds did not significantly inhibit the seed germination and seedling growth of Chinese cabbage, indicating that the presence of water-soluble and alcohol-soluble germination inhibitors in the pericarp of V. rotundifolia is the main cause of seed dormancy. 3) Seed dormancy was able to be broken down by low temperature stratification for 90 d, GA3, GA3+concentrated H2SO4, GA3+cutting peel, GA3+low temperature stratification for 30 d, GA3+low temperature stratification for 60 d and GA3+low temperature stratification for 90 d. The seed germination time under GA3+concentrated H2SO4 treatment was the shortest(14 days), and the germination rate was the highest(44%).Conclusion:The mechanical barrier and the endogenous inhibitor of the peel are the main factors affecting the dormancy of Vitex rotundifolia. Treatment with 500 mg•L-1GA3+concentrated H2SO4 can effectively release seed dormancy and increase germination rate. © 2020, Editorial Department of Scientia Silvae Sinicae. All right reserved.