甜高粱对镉胁迫的生理生化响应及镉富集研究

Physiological and Biochemical Responses of Sweet Sorghum to Cadmium Stress and Its Cadmium Accumulation

为阐明镉胁迫对甜高粱生理生化指标的影响以及镉富集特征,以辽甜1号为研究材料,采用5种不同浓度镉溶液(0、50、100、200、300μmol·L^-1)模拟胁迫环境,测定并分析了镉胁迫下幼苗的生长指标、抗氧化酶活性、同工酶、光合参数、荧光参数、光响应曲线及镉富集率的变化。结果表明:①镉胁迫下,甜高粱鲜重、株高、地上部及地下部干重显著降低。②伴随胁迫浓度的增加,超氧化物歧化酶(superoxide dismutase,SOD)先升高后降低,过氧化物酶(peroxidase,POD)活性显著升高,过氧化氢酶(catalase,CAT)活性显著降低,抗坏血酸过氧化物酶(ascorbate peroxidase,APX)先降低后升高再降低。胁迫早期SOD、POD酶谱多条带伴随胁迫浓度的增加而加深,出现了新的S2、P2条带;而CAT、APX酶谱无新的条带出现。③镉胁迫下叶片叶绿素含量,净光合速率、气孔导度、和蒸腾速率、叶片原初光能转化效率、光合电子传递量子效率、光化学淬灭系数,最大净光合速率、表观量子效率、暗呼吸速率、光饱和点显著降低,而胞间CO 2浓度、非光化学淬灭系数、光补偿点则升高。④伴随胁迫浓度的增加,地上部、地下部的镉浓度升高,而地上部、地下部及单株富集率降低。因此,镉胁迫是通过抑制甜高粱的光合作用而使其生物量降低;甜高粱通过调控其抗氧化酶基因表达以维持其细胞正常代谢;低浓度镉胁迫有利于甜高粱富集镉,高浓度镉胁迫使甜高粱不可逆损伤,生物量降低,导致甜高粱对镉的富集率下降。

In order to clarify the effects of cadmium stress on physiological and biochemical indexes of sweet sorghum and the characteristics of cadmium enrichment,Liaotian 1 and 5 different concentrations of cadmium solution(0,50,100,200,300μmol·L^-1)were used to simulate the stress environment.The growth index,antioxidant enzyme activity,isoenzyme,photosynthetic parameters,fluorescence parameters,light response curve and cadmium enrichment rate of seedlings under stress were measured and analyzed.The results showed that:①The cadmium stress significantly decreased the fresh weight,plant height,shoot and shoot dry weight of sweet sorghum.②With the increase of stress concentration,superoxide dismutase(SOD)increased first and then decreased,peroxidase(POD)activity increased significantly,catalase(CAT)activity decreased significantly,and ascorbate peroxidase(APX)became lower first,then increase and then lower.In the early stage of stress,multiple bands of SOD and POD zymograms were deepened with the increase of stress concentration,and new S2,P2 bands appeared,while no new bands appeared in CAT and APX zymograms.③Leaf chlorophyll content,net photosynthetic rate(P n),stomatal conductance(G s),and transpiration rate(T r),leaf primary light energy conversion efficiency(F v/F m),photosynthetic electron transport quantum efficiency(φPSⅡ),photochemistry quenching coefficient(qP),maximum net photosynthetic rate(P max),apparent quantum efficiency(Q),dark respiration rate(R d),light saturation point(LSP)decreased significantly,and intercellular CO 2 concentration(C i),non the photochemical quenching coefficient(NPQ)and the light compensation point(LCP)increased.④With the increase of stress concentration,the cadmium concentration in the aboveground and underground parts increased,while the enrichment rates of aboveground,underground and single plant decreased.Therefore,cadmium stress reduced biomass by inhibiting photosynthesis of sweet sorghum.Sweet sorghum maintained its normal cell metabolism by regulating the gene expression of its antioxidant enzymes.The low concentration of cadmium stress was beneficial to enrichment of cadmium in sweet sorghum,and the high concentration of cadmium stress caused sweet sorghum irreversible damage,and the biomass reduced,resulting in a decrease in the enrichment rate of cadmium in sweet sorghum.