Seed germination characteristics and drought resistance of six native trees from the dry-hot valley of Yunnan Province

Trema tomentosa , Osteomeles schwerinae , Vitex negundo , Phyllanthus emblica , Quercus franchetii and Sapindus delavayi are native Yunan trees which are highly adapted to the local dry-hot environmental conditions and play a crucial role in the restoration and improvement of the local environment. This study investigated their seed germination characteristics, germination inhibitors and optimal germination conditions, and evaluated the drought tolerance at the germination stage. The phenotypic characteristics of the seeds from four species exhibited significant differences. Water absorption in T. tomentosa , O. schwerinae , V. negundo , P. emblica , and Q. franchetii seeds increased with soaking time, while S. delavayi seed hulls hindered water absorption. Higher concentrations of seed coat extracts from T. tomentosa , Q. franchetii , P. emblica and S. delavayi more strongly inhibited root and seedling growth; for O. schwerinae , V. negundo and S. delavayi , seed coat extracts had greater inhibitory effects than endosperm extracts. Drought resistance during germination ranked: Q. franchetii > P. emblica > S. delavayi > T. tomentosa > O. schwerinae . This study can provide a theoretical basis for the introduction and cultivation of native trees and the selection and breeding of drought-resistant varieties suited to the dry-hot valley area of Yunnan.