光周期对休眠诱导期桃树光合及PSⅡ光系统性能的影响

人工设置长日照和短日照2种光周期(以自然条件为对照)，测定6年生春捷桃树叶片光合参数和叶绿素荧光快速诱导动力学参数，研究诱导休眠期间光周期对北方落叶果树光合性能的影响.结果表明： 短日照条件下树体可提前进入休眠诱导期，长日照条件下则延后进入.休眠诱导期间，桃树叶片净光合速率(P_n)、气孔导度(g_s)降低，胞间CO₂浓度(C_i)升高，表明P_n降低的原因是非气孔限制；PSⅡ的最大光化学效率φ_Po(或F_v/F_m)、潜在活性（F_v/F_o）、PSⅡ反应中心捕获的光能用于Q_A^-下游的电子传递的能量比例(ψ_o)和光合性能指数(PI_ABS)均降低，表明光合电子传递链的电子传递能力受到抑制，其原因可能是PSⅡ反应中心受体侧Q_A^-下游的电子传递链受到了伤害.长日照有利于提高休眠诱导期的光合速率，减小PI_ABS下降幅度，减轻光系统的受害程度，短日照则明显加深、加速光合机构的损坏.光周期的诱导效应与休眠进程相关.

Effects of photoperiod on photosynthesis and PSⅡ performance in peach during dormancy induction.

Long-day and short day photoperiods were set artificially, with natural condition as the control, to examine photosynthetic parameters and chlorophyll fluorescence transient kinetics of 6-year-old ‘Chunjie’ peach cultivar (Prunus persica cv. Chunjie), and to investigate the effects of photoperiod on photosynthesis of the northern deciduous fruit trees. The tree advanced into the dormancy induction period under the short day condition, and delayed under the long day condition. In the dormancy induction period, the leaf net photosynthetic rate (P_n) and stomatal conductance (g_s) decreased, and the intercellular CO₂ concentration (C_i) increased, suggesting that the P_n decreased because of non stomatal limitation. Maximum quantum yield for primary photochemistry (φ_Po, or F_v/F_m), potential activity (F_v/F_o), probability that a trapped exciton moved an electron into the electron transport chain beyond Q_A^-(ψ_o) and performance index on absorption basis (PI_ABS) decreased in the dormancy induction period, suggesting that the electron transport capacity of photosynthetic electron transport chain was inhibited, possibly due to the damage to downstream electron transport chain (after Q_A^- acceptor) of PSⅡ reaction center. Long day photoperiod improved P_n in the dormancy induction period, and reduced the range of decline in PI_ABS and the injured degree of photosystem. Short day photoperiod deepened and accelerated the damage to photosynthetic apparatus significantly. The induced effect of photoperiod was associated with the dormancy processes.