高温胁迫对切花菊‘神马’光合作用与叶绿素荧光的影响

以切花菊品种‘神马’为试材，在40 ℃/35 ℃（昼/夜）与33 ℃/28 ℃高温下分别胁迫11 d，然后转入23 ℃/18 ℃恢复5 d，研究不同高温强度及恢复对菊花光合作用的影响.结果表明：33 ℃/28 ℃下净光合速率（P_n）逐渐降低，气孔导度（G_s）5 d后明显降低，两参数均可在23 ℃/18 ℃下恢复到对照的80%以上；40 ℃/35 ℃高温下P_n与G_s大幅度持续降低，胁迫前期，胞间CO₂浓度（C_i）上升，P_n的降低主要由非气孔因素导致；9 d后C_i与P_n同时降低，气孔限制成为P_n 降低的主要因素.高温使菊花叶片的PSⅡ潜在活性（F_v/F_o）、最大光化效率（F_v/F_m）、实际光化效率（Φ_PSⅡ）与天线转换效率 （F_v′/F_m′）降低，天线热耗散（D）增加，表明高温胁迫下菊花通过降低光能的捕获与通过PSⅡ的电子传递效率来保护反应中心免受伤害.33 ℃/28 ℃下光化学猝灭系数（q_P）呈先下降后上升趋势，推测此温度下受体端电子传递首先受到抑制；40 ℃/35 ℃下q_P持续增加，表明放氧复合体(OEC)可能是菊花光合系统中极端高温伤害的原初位点.

Effects of high temperature stress on photosynthesis and chlorophyll fluorescence of cut flower chrysanthemum (Dendranthema grandiflora 'Jinba')

Cut flower chrysanthemum (Dendranthema grandiflora ‘Jinba’) plants were treated with 40 ℃/35 ℃ or 33 ℃/28 ℃ (day/night) for 11 days and then transferred to 23 ℃/18 ℃ for 5 days to study the changes in their photosynthesis and fluorescence parameters under high temperature stress and normal temperature recovery. The results showed that on the 5^th day of 33 ℃/28 ℃ treatment, net photosynthesis (P_n) decreased gradually and stomatal conductance (G_s) decreased evidently; while after recovery for 5 days, both P_n and G_s resumed to 80% of the control. At 40 ℃/35 ℃,P_n and G_s decreased dramatically. The increase of intercellular CO₂ concentration (C_i) at the early stage under given high temperatures showed that the photosynthesis inhibition by high temperature stress was resulted from non-stomatal limitations. However, 9 days later, stomatal limitation became the mainly cause of photosynthesis inhibition. The intrinsic photochemical efficiency (F_v/F_m), quantum yield of PSⅡ(Φ_PSⅡ), and the efficiency of excitation energy capture by open PSⅡ reaction center（F_v′/F_m′） at 33 ℃/28 ℃ and 40 ℃/35 ℃ all decreased, with antenna heat dissipation increased, indicating that reaction center was protected by decreased light capture and efficiency of electron transfer through PSⅡ. The photochemical quenching (q_P) at 33 ℃/28 ℃ descended first and turned to rise then, suggesting that the electron transfer was firstly restrained by the stress. Contrastively, q_P rose continuously at 40 ℃/35 ℃, indicating that oxygen-evolving complex (OEC) was the location in chrysanthemum photosynthesis apparatus most sensitive to extreme high tempe rature.