Natural Physiological Changes on Overwintering and Spring Recovery of Needles of Pinus densiflora Siebold & Zucc.

Overwintering and spring recovery of pine needles have important ecological significance. The natural changes in physiological state, photosynthetic function, material metabolism Pinus densiflora Siebold & Zucc. from the autumn 2020 to 2021 were assessed. rate (Pn) P. decreased first then increased, with maximum Pn observed autumn. After experiencing sub-zero temperatures winter, still performed weak photosynthesis at a temperature above zero. In spring, gradually recovered but could not recover maximum. Under winter 2020, plasma membrane permeability MDA content whereas chlorophyll Fv/Fm significantly. showed obvious characteristics freezing injury. During whole process, water remained low level (about 60%), which increase leaf age. cell sap concentration soluble sugar decrease air spring. Therefore, do improve frost resistance through osmotic adjustment. However, increasing carotenoid is helpful for tide over winter. protein contents implying they are This study expands our understanding mechanism contribution overwintering needles.