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 (Isat), maxi-mum net photosynthetic rate (Pn max), maximum electron transport rate (Jmax), triose phosphate utilization rate (TPU), maximum carboxylation rate of Rubisco (Vc max) were increased significantly under intercropping. Further, absorption energy flux per CS (ABS/CSo), trapping energy flux per CS (TRo/CSo), number of active reaction centers per CS (RC/CSm), and electron transport flux per CS (ETo/CSo) in intercropped treatments were enhanced compared to that under sesame monoculture. However, the ratio between variable fluorescence Fk to amplitude Fj-Fo (Wk) and ratio between variable fluorescence Fj to amplitude Fp-Fo (Vj) in functional leaves of intercropped sesame were significantly decreased. The efficiency of converting light energy into electricity of PS2 reaction center (Ψo), electron transfer efficiency from PS2 to end acceptor of PS1 (ΨRo), electron transfer efficiency of the electron transport chain (δR), PS1 photochemical activity, and the coordination between PS2 and PS1 in functional leaves of intercropped sesame were increased. The net photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (Tr), Pn max, Jmax, Vc max, TPU, Ψo, ΨRo and δR 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 PS2 donator/receptor sides, and CO2 fixation, with stronger effects in IC 3:6 than IC 2:4.
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(Isat)、光饱和时的净光合速率(Pn max)、最大电子传递速率(Jmax)、磷酸丙糖利用率(TPU)、Rubisco最大羧化速率(Vc max);提高了单位面积吸收(ABS/CSo)、捕获(TRo/CSo)和电子传递(ETo/CSo)的能量、反应中心的数目(RC/CSm)和传递到PSⅠ末端的量子产额(REo/CSo);降低了可变荧光Fk占Fj-Fo振幅的比例(Wk)和可变荧光Fj占Fp-Fo振幅的比例(Vj),提高了PSⅡ反应中心捕获光能转化为电能的效率(Ψo)、PSⅡ将电子传递到PSⅠ受体侧末端的效率(ΨRo)、电子传递链的电子传递效率(δR)、PSⅠ光化学活性(ΔI/Io)和光系统间协调性(ΦPSⅠ/PSⅡ).IC 3∶6下芝麻功能叶的净光合速率(Pn)、气孔导度(gs)、蒸腾速率(Tr)、Pn max、Jmax、Vc max、TPU、Ψo、ΨRo和δR均高于IC 2∶4,其中Pn、gs和Tr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.
Keywords: PS1 photochemical activity; PS2 photochemical activity; intercropping advantage on yield; photosynthetic characteristic; sesame/peanut intercropping.