Response of seed germination and seedling growth of different Pinus massoniana families to aluminum stresses

To investigate the response of Pinus massoniana seed germination and seedling growth to acidic aluminum stress, and to screen aluminum-tolerant or sensitive families, this study selected superior P. massoniana families from Guizhou as test materials. Ten aluminum concentration gradients（0 to 8.0 mmol·L^-1）were established to simulate acidic aluminum stress conditions and investigate their effects on seed germination and seedling growth. Then, Two-way ANOVA, principal component analysis, and cluster analysis were combined to evaluate each family`s aluminum tolerance and identify superior aluminum-tolerant lines. Results showed that both seed germination（five indicators, including germination energy and germination rate）and seedling growth（six indicators, including seedling height and fresh weight）first increased and then decreased as aluminum concentration increased. Growth under aluminum concentrations from 0.2 to 0.8 mmol·L^-1 exceeded that of the control, whereas growth was inhibited at concentrations above 0.8 mmol·L^-1. Hypocotyl length and radicle length were identified as sensitive indicators of P. massoniana seed adaptation to acidic aluminum stress, while root morphological indicators were sensitive for evaluating seedling adaptation to this stress. Overall, aluminum tolerance during seed germination was higher than during seedling growth. Based on the comprehensive evaluation of aluminum tolerance characteristics and hierarchical cluster analysis, five aluminum-tolerant families and five aluminum-sensitive families of P. massoniana were identified. These results provide valuable materials and a theoretical basis for the cultivation of P. massoniana seedlings and lay a foundation for further analysis of aluminum tolerance mechanisms in P. massoniana.