In order to study the effect of seed coating agent on photosynthetic characteristics of cotton seedlings under low temperature,we used "Xinluzao 57" as material with pot culture method,the temperature is set to 10,18 ℃ and the stress time are set to 0,1,2,3 day,from three aspects of photosynthetic pigments,photosynthetic gas exchange parameters and chlorophyll fluorescence kinetics to investigate the relieving effect of seed coating agent on low temperature damage of cotton seedlings.The results show:(1) compared with the uncoated cotton seedlings,seed coating can improve the cotton seedling chlorophyll a,b and carotenoid contents under low temperature stress,but at normal temperature,seed coating agent had no significant effect on the photosynthetic pigment contents of the cotton seedlings.(2) Compared with uncoated cotton seedlings,after 10 ℃ and 18 ℃ low temperature treatment for 3 d,coated cotton seedlings net photosynthetic rate (Pn),transpiration rate (Tr),stomatal conductance (Gs) increased 33.71％,52.00％,96.63％ and 38.57％,55.17％ and 103.42％,respectively,intercellular carbon dioxide concentration (Ci) reduced by 15.15％ and 11.12％,respectively.(3) Compared with uncoated cotton seedlings,after 10 ℃ and 18 ℃ low temperature treatment for 3d,the absorption of light energy in the unit reaction center (ABS/RC) of the coated cotton seedlings increased 0.41％ and 1.56％,respectively.The energy used to restore the QA (TRo/RC) and the capture of energy for electron transfer (ETo/RC) increased 2.97％,0.47％ and 4.27％ and 1.67％,respectively.The reaction center for exciton electron transfer and to promote the reduction of QA exciton ratio (ψo) increased 0.18％ and 2.16％,respectively.The absorption of light energy for the quantum yield (5Eo) and the performance index (PIABS) of electron transfer increased 2.25％,2.42％ and 19.32％ and 5.94％,respectively.The results,indicated that coating agent treatment can improve the content of photosynthetic pigments in cotton seedlings,regulate stomatal opening,enhance the fixation and utilization of CO2,increase the energy of photosynthetic absorption and capture,and induce reasonable distribution of photosynthetic energy,maintain the absorption,capture and transformation of light energy in the photosynthetic organs,thus mitigate the damage caused by low temperature stress.%为研究种衣剂对低温下棉花幼苗光合特性的影响,以“新陆早57号”为材料,采用室内盆栽培养法,温度设置为10℃和18℃,胁迫时间为0、1、2、3d,分别从光合色素、光合气体交换参数以及叶绿素荧光动力学三方面探讨种衣剂对棉花幼苗低温伤害的缓解作用.结果表明:(1)与未包衣棉苗相比,种衣剂可提高低温胁迫下棉花幼苗的叶绿素a、b及类胡萝卜素含量,但在常温下种衣剂对棉苗的光合色素含量均无显著影响.(2)与未包衣棉苗相比,包衣棉苗在10℃和18℃处理3d后,净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)分别依次提高33.71％、52.00％、96.63％和38.57％、55.17％、103.42％,胞间二氧化碳浓度(Ci)分别降低了15.15％、11.12％.(3)与未包衣棉苗相比,包衣棉苗在10℃和18℃处理3d后,单位反应中心吸收的光能(ABS/RC)分别增加了0.41％、1.56％,捕获用于还原QA的能量(TRo/RC)和捕获用于电子传递的能量(ETo/RC)分别增加了2.97％、0.47％和4.27％、1.67％,反应中心用于电子传递的激子与用来推动QA还原激子的比率(ψo)分别增加了0.18％、2.16％,吸收的光能用于电子传递的量子产额(ΦEo)和性能指数(P IABS)分别增加了2.25％、2.42％和19.32％、5.94％.研究认为,种衣剂包衣处理可以提高低温下棉花幼苗的光合色素含量、调节气孔开度,增强CO2的固定能力和利用率,提高光合吸收及捕获的能量,并诱导光合能量合理分配,维持光合器官对光能的吸收、捕获、转化状况,从而减轻低温胁迫带来的伤害.
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