混合盐胁迫对栾树光合生理指标的影响

Effect of Mixed Salt Stress on Photosynthetic Physiological Indexes of Koelreuteria paniculata

该研究以2年生栾树扦插苗为材料,采用盆栽实验方法,设置梯度为0(CK)、100(S_(100))、200(S_(200))、300(S_(300))、400(S_(400))和500(S_(500))mmol·L^(-1)的摩尔质量比1∶1配制成的NaCl和NaHCO_(3)混合盐溶液,分析混合盐胁迫对栾树幼苗光合作用和叶绿素荧光特性的影响,以探讨栾树对混合盐胁迫的生理适应机制,为栾树在盐碱地区的引种与推广栽培提供理论依据。结果表明:(1)随着混合盐胁迫程度的增加,栾树出现叶片发黄焦枯、卷曲、根系减少、植株死亡等表观症状。(2)随着混合盐胁迫程度的增加,栾树的叶长、叶宽生长量整体呈下降趋势;栾树的叶长、叶宽生长量在S_(100)和S_(200)处理下较CK变化不显著,但其叶长生长量在混合盐浓度达到300 mmol·L^(-1)时较CK显著下降,叶宽生长量在混合盐浓度达到400 mmol·L^(-1)时较CK显著下降。(3)栾树幼苗叶片的叶绿素含量、PSⅡ实际量子产量(Yield)、光化学淬灭系数(qP)和PSⅡ最大量子产量(F_(v)/F_(m))在S_(100)处理下较CK无显著变化;当混合盐浓度达到200 mmol·L^(-1)时,除F_(v)/F_(m)外均较CK显著下降;当混合盐浓度达到300 mmol·L^(-1)时,F_(v)/F_(m)较CK也显著下降。(4)随着混合盐胁迫程度的增加,栾树幼苗叶片的净光合速率(P_(n))、气孔导度(G_(s))、蒸腾速率(T_(r))整体呈下降趋势;在混合盐胁迫0~30 d时,S_(100)-S_(300)处理的栾树幼苗叶片的P_(n)、C_(i)、G_(s)整体变化趋势一致;随着盐胁迫程度增大,P_(n)、G_(s)整体呈下降趋势,C_(i)整体呈上升趋势。研究发现,在100 mmol·L^(-1)混合盐胁迫下,栾树生长指标和生理指标变化不明显,表现出一定的耐盐性,此时光合作用主要受气孔限制的影响;当混合盐浓度达到200 mmol·L^(-1)时,栾树幼苗叶片的生长指标、叶绿素含量、光合生理指标整体显著降低,最终导致植株生长受到抑制,此时光合作用的主要影响因素是非气孔限制和光化学活性失活。

In order to provide a theoretical basis for introduction and cultivation of Koelreuteria paniculata in saline alkali areas,this paper studied effects of mixed salt stress on the photosynthesis and chlorophyll fluorescence characteristics of K.paniculata seedlings and its adaptation mechanism.The paper performed pot experiment at the six gradients of 0(CK),100(S_(100)),200(S_(200)),300(S_(300)),400(S_(400))and 500(S_(500))mmol·L^(-1),which were prepared by mixing NaCl and NaHCO_(3) at molar mass ratio of 1∶1,and 2-year-old K.paniculata cuttings were used in the pot experiment.The results showed that:(1)with the increase of stress degree,K.paniculata seedlings showed some apparent symptoms,such as yellowing,scorching,curling,root reduction,plant death and so on.(2)With the increase of stress degree,leaf length increment and leaf width incremen of K.paniculata seedling increased.The leaf length increment and leaf width increment of K.paniculata seedling were no difference with the control group when mixed salt concentration was 100 and 200 mmol·L^(-1),but the leaf length increment began to decrease significantly when mixed salt concentration reached 300 mmol·L^(-1),and the leaf width increment began to decrease significantly compared with control group when mixed salt concentration reached 400 mmol·L^(-1).(3)The chlorophyll,PSⅡactual quantum(Yield),photochemical quenching coefficient(qP)and maximum quantum yield of PSⅡ(F_(v)/F_(m))of K.paniculata seedling leaves were no difference with the control group when mixed salt concentration was 100 mmol·L^(-1),but the indexes except maximum quantum yield of PSⅡ(F_(v)/F_(m))began to decrease significantly when mixed salt concentration reached 200 mmol·L^(-1),and the indexes except maximum quantum yield of PSⅡ(F_(v)/F_(m))began to decrease significantly compared with control group when mixed salt concentration reached 300 mmol·L^(-1).(4)With the increase of mixed salt stress,net photosynthetic rate(P_(n)),stomatal conductance(G_(s))and transpiration rate(T_(r))of K.paniculata seedlings decreased as a whole;When mixed salt stress was 0-30 days,and mixed salt concentration was 100-300 mmol·L^(-1),changes of net photosynthetic rate(P_(n)),intercellular CO_(2) concentration(C_(i))and stomatal conductance(G_(s))of K.paniculata seedling leaves were same.With the increase of stress degree,net photosynthetic rate(P_(n))and stomatal conductance(G_(s))decreased,and intercellular CO_(2) concentration(C_(i))increased.These results showed that:when the mixed salt concentration was 100 mmol·L^(-1),the growth indexes and physiological indexes of K.paniculata did not change significantly,showing a certain ability to tolerate mixed salt stress.At this time,stomatal restriction was the main factor.The growth indexes,chlorophyll content and photosynthetic physiological indexes of K.paniculata seedling leaves decreased significantly as a whole when mixed salt concentration reached 200 mmol·L^(-1),resulting in the inhibition of plant growth.At this time,non-stomatal restriction and photochemical activity inactivation were main factors affecting photosynthesis.