秸秆覆盖与施磷对西南冬小麦叶肉导度和CO_(2)同化效率的影响

Effects of straw mulching and phosphorus fertilization on mesophyll conductance and CO_(2) assimilation efficiency of winter wheat in southwest hilly regions of China

为探究西南麦区冬小麦旗叶叶肉导度(g_(m))与CO_(2)同化对土壤速效磷缺乏的响应。试验于2020—2022年在四川仁寿试验站进行秸秆覆盖和磷素水平的二因素裂区试验,以秸秆覆盖(SM)和不覆盖(NSM)为主区;三个磷水平0(P0)kg/hm^(2)、75(P75)kg/hm^(2)和120(P120)kg/hm^(2)为裂区,分析小麦旗叶光响应曲线、叶肉导度和CO_(2)同化对旗叶磷素水平的响应。结果表明:与NSM相比,SM下旗叶比叶重(LMA)、单位面积磷含量(PA)、单位质量磷含量(PM)和净光合速率(P_(n))分别提高4.1%、16.9%、12.2%和6.9%,且随着施磷量的增加,旗叶的LMA、PA、PM和P_(n)呈增加趋势。秸秆覆盖与施磷显著提高旗叶最大净光合速率(P_(nmax))和表观量子效率(AQY),增加旗叶的光合潜能。施磷显著提高旗叶光系统Ⅱ实际光化学效率(ΦPSII),最大羧化效率(V_(cmax))、核酮糖-1,5-二磷酸羧化酶(Rubisco)活力、胞间CO_(2)浓度(C_(i))、叶绿体CO_(2)浓度(C_(c))、气孔导度(g_(s))和g_(m),P75和P120较P0分别提高16.8%—23.8%、27.9%—35.3%、30.9%—61.7%、1.4%—3.6%、4.8%—13.1%、9.0%—10.2%和16.0%—16.9%,P75和P120无显著差异。秸秆覆盖与施磷降低旗叶的气孔限制(L_(s))和叶肉限制(L_(m)),生化限制(L_(b))是光合速率的主要限制因子。综上所述,秸秆覆盖配施75kg/hm^(2)磷肥可提高西南冬小麦旗叶磷素含量、光系统Ⅱ实际光化学效率、叶肉导度和CO_(2)同化效率,降低气孔限制和叶肉限制,从而提高旗叶净光合速率。

To explore the response of mesophyll conductance(g_(m))and CO_(2) assimilation of wheat flag leaves to soil available phosphorus(P)deficiency in the southwest wheat production region.During the years of 2020 to 2022,the experiment was conducted in the Renshou experiment station.Straw mulching(SM)and no mulch(NSM)were the main plots.Three P levels of 0(P0)kg/hm^(2),75(P75)kg/hm^(2) and 120(P120)kg/hm^(2) were set as the split plots.The responses of light response curve,mesophyll conductance and CO_(2) assimilation efficiency to P levels of flag leaves of wheat were analyzed.The results show that the leaf mass per area(LMA),P content per unit area(PA),P content per unit mass(PM)and net photosynthetic rate(P_(n))of flag leaf under SM were 4.1%,16.9%,12.2%and 6.9%respectively,greater than that in NSM,and the LMA,PA,PM and P_(n) of flag leaf increased with the increase of phosphorus fertilization rate.Straw mulching with phosphorus increased the maximum net photosynthetic rate(P_(nmax))and apparent quantum efficiency(AQY)of flag leaves and increased the photosynthetic potential of flag leaves.Phosphorus fertilization significantly improves the actual photochemical efficiency of photosystem Ⅱ(ΦPSII),the maximum carboxylation efficiency(V_(cmax)),ribulose 1,5-diphosphate carboxylase(Rubisco),intercellular CO_(2) concentration(C_(i)),chloroplast CO_(2) concentration(C_(c)),stomatal conductance(g_(s))and g_(m) of flag leaf.These value under P75 and P120 were 16.8%—23.8%,27.9%—35.3%,30.9%—61.7%,1.4%—3.6%,4.8%—13.1%,9.0%—10.2%and 16.0%—16.9%higher than that under P0,respectively.There was no significant difference between P75 and P120.Straw mulching and phosphorus fertilization decreased stomatal limitation(L_(s))and mesophyll limitation(L_(m)),and biochemical limitation(L_(b))was the main limiting factor of photosynthetic rate in flag leaves.In conclusion,straw mulching combined with 75 kg/hm^(2) can improve the phosphorus content,resulting in the enhancement of the actual photochemical efficiency of photosystem Ⅱ,mesophyll conductance and CO_(2) assimilation efficiency of flag leaves of southwest winter wheat,reduce stomatal restriction and mesophyll restriction,and thus increase the net photosynthetic rate of flag leaves.