芝麻与花生间作对芝麻功能叶光合荧光特性的影响

为了明确芝麻与花生间作提高芝麻产量的光合机理,于2017—2018年设芝麻与花生3∶6间作(IC 3∶6)、2∶4间作(IC 2∶4)、芝麻单作(SS)、花生单作(SP) 4个处理,研究了间作对芝麻功能叶气体交换参数、光合-光强和光合-CO₂响应曲线、快速叶绿素荧光诱导动力学曲线的影响.结果表明:间作芝麻产量的偏土地当量比大于1/3;与单作芝麻相比,芝麻与花生间作提高了芝麻功能叶的光饱和点(I_sat)、光饱和时的净光合速率(P_{n max})、最大电子传递速率(J_max)、磷酸丙糖利用率(TPU)、Rubisco最大羧化速率(V_{c max});提高了单位面积吸收(ABS/CS_o)、捕获(TR_o/CS_o)和电子传递(ET_o/CS_o)的能量、反应中心的数目(RC/CS_m)和传递到PSⅠ末端的量子产额(RE_o/CS_o);降低了可变荧光F_k占F_j-F_o振幅的比例(W_k)和可变荧光F_j占F_p-F_o振幅的比例(V_j),提高了PSⅡ反应中心捕获光能转化为电能的效率(Ψ_o)、PSⅡ将电子传递到PSⅠ受体侧末端的效率(Ψ_Ro)、电子传递链的电子传递效率(δ_R)、PSⅠ光化学活性(ΔI/I_o)和光系统间协调性(Φ_PSⅠ/PSⅡ).IC 3∶6下芝麻功能叶的净光合速率(P_n)、气孔导度(g_s)、蒸腾速率(T_r)、P_{n max}、J_max、V_{c max}、TPU、Ψ_o、Ψ_Ro和δ_R均高于IC 2∶4,其中P_n、g_s和T_r差异显著.这说明间作芝麻具有明显产量间作优势关键在于间作能促进其功能叶对光能的吸收、传递与转化,提高电子传递链性能,增强PSⅠ、PSⅡ性能和两者间协调性及CO₂羧化固定能力,从而提高净光合速率,其中IC 3∶6优于IC 2∶4.

The effects of sesame/peanut intercropping on photosynthetic fluorescence characteristics in functional leaf of sesame.

To unravel functional leaf photosynthetic mechanisms underlying enhanced yield of sesame in sesame/peanut intercropping, a field experiment was carried out in 2017 and 2018 with four treatments including (1) three-row sesame intercropped with six-row peanut (IC 3:6), (2) two-row sesame intercropped with four-row peanut (IC 2:4), (3) sole cropped sesame (SS), and (4) sole cropped peanut (SP). We measured the parameters of gas exchange, characteristics of photosynthetic response curve to light and CO₂, and characteristics of chlorophyll rapid fluorescence induction kinetic curves of the functional leaves of sesame. The results showed that the partial land equivalent ratio of intercropped sesame was greater than 1/3. The light saturation point (I_sat), maxi-mum net photosynthetic rate (P_{n max}), maximum electron transport rate (J_max), triose phosphate utilization rate (TPU), maximum carboxylation rate of Rubisco (V_{c max}) were increased significantly under intercropping. Further, absorption energy flux per CS (ABS/CS_o), trapping energy flux per CS (TR_o/CS_o), number of active reaction centers per CS (RC/CS_m), and electron transport flux per CS (ET_o/CS_o) in intercropped treatments were enhanced compared to that under sesame monoculture. However, the ratio between variable fluorescence F_k to amplitude F_j-F_o (W_k) and ratio between variable fluorescence F_j to amplitude F_p-F_o (V_j) in functional leaves of intercropped sesame were significantly decreased. The efficiency of converting light energy into electricity of PSⅡ reaction center (Ψ_o), electron transfer efficiency from PSⅡ to end acceptor of PSⅠ (Ψ_Ro), electron transfer efficiency of the electron transport chain (δ_R), PSⅠ photochemical activity, and the coordination between PSⅡ and PSⅠ in functional leaves of intercropped sesame were increased. The net photosynthetic rate (P_n), stomatal conductance (g_s), transpiration rate (T_r), P_{n max}, J_max, V_{c max}, TPU, Ψ_o, Ψ_Ro and δ_R were significantly higher in IC 3:6 than those in IC 2:4. We conclude that intercropping improves net photosynthetic rate and yield of sesame by increasing light absorption, electronic transmission, activity of PSⅡ donator/receptor sides, and CO₂ fixation, with stronger effects in IC 3:6 than IC 2:4.