干旱缺钾对油菜内源激素、光合作用和叶绿素荧光特性的影响

Effect of potassium deficiency on endogenous hormones,photosynthesis and characteristics of chlorophyll fluorescence in Brassica napus under drought stress

为了解钾肥对抗旱的生理影响,以抗旱性不同的两个油菜品种川油36(敏感)和油研57(耐旱)为材料,采用水培试验,调查干旱缺钾对油菜内源激素、光合作用和叶绿素荧光特性的影响。设置缺钾(0.01 mmol/LK_(2)SO_(4))和正常钾肥(1.0 mmol/LK_(2)SO_(4))两个梯度,加入7%的PEG6000模拟干旱,分别记为LK和NK处理。结果发现,干旱胁迫严重抑制油菜生长,不同钾肥水平对油菜生长和激素水平影响显著,与NK处理相比,LK处理下油菜生物量和叶片吲哚乙酸(IAA)、细胞分裂素(CTK)和油菜素内酯(BR)含量显著降低,而脱落酸(ABA)含量显著增加。干旱胁迫下钾肥水平对油菜光合作用影响显著,与NK相比,LK处理下油菜净光合速率、气孔导度、核酮糖-1,5-二磷酸羧化酶(RuBP羧化酶)活性、磷酸烯醇式丙酮酸羧化酶(PEPC)活性均显著降低。干旱胁迫下光系统I(PSI)P700最大变化(Pm)和光下P700最大变化(Pm')显著降低,LK处理下Pm'显著低于NK处理,而PSI受体侧限制非光化学量子产量[Y(NA)]显著高于NK处理。干旱胁迫导致光系统Ⅱ(PSⅡ)最大光化学量子产量(Fv/Fm)显著降低,与NK处理相比,LK处理下Fv/Fm和PSⅡ调节性能量耗散[Y(NPQ)]显著降低,然而非调节性能量耗散[Y(NO)]显著增加。LK处理下抗旱品种油研57叶片IAA含量、CTK含量、叶绿素含量、净光合速率和Fv/Fm显著高于川油36,表现出更高的生物量。综上,干旱缺钾会诱导ABA积累,抑制生长促进类激素IAA、CTK和BR的合成,抑制油菜生长。干旱缺钾条件下,RuBP羧化酶和PEPC酶活性显著降低,同时PSI受体侧过度还原,PSⅡ调节性能量耗散减弱,非调节性能量耗散量子产量增加,造成PSI和PSⅡ活性下降,导致油菜光合作用降低并限制油菜生长。

To better understand the effect of potassium deficiency on rapeseed(Brassica napus L.),hydroponic experiment was carried out using 2 cultivars Chuanyou 36(sensitive)and Youyan 57(tolerant)exposed to 7%PEG6000 simulated drought stress.Two potassium(K)levels were set as 0.01 and 1.0 mmol/L K_(2)SO_(4),referred to LK and NK respectively.Drought stress hindered rapeseed growth seriously,and K levels affected the growth and endogenous hormone levels significantly.Compared to NK,LK caused a more dramatic decrease in biomass and content of indole acetic acid(IAA),cytokinin(CTK)and brassinolide(BR)in leaf,while abscisic acid(ABA)increased significantly.LK decreased photosynthesis significantly under drought,including net photosynthetic rate,stomatal conductance,enzyme activity of ribulose 1,5-bisphosphate carboxylase(RuBP carboxylase)and phosphoenolpyruvate carboxylase(PEPC).The maximum change of photosystem Ⅰ(PSI)P700(Pm)and P700 under light(Pm')decreased significantly under drought.Under LK,Pm'was significantly lower,while nonphotochemical quantum yield by acceptor side limitation of PSⅠ[Y(NA)]was significantly higher.The maximum photochemical quantum yield(Fv/Fm)of photosystem Ⅱ(PSⅡ)decreased significantly under drought.Fv/Fm and quantum yield of regulated energy dissipation[Y(NPQ)]decreased significantly under LK treatment,while non-regulatory energy dissipation[Y(NO)]increased significantly.Drought tolerant cultivar Youyan 57 kept higher level of IAA,CTK,chlorophyll,net photosynthetic rate,and Fv/Fm than those of Chuanyou 36 under LK,with larger biomass.In summary,K deficiency could induce accumulation of ABA and inhibit synthesis of IAA,CTK and BR,then inhibited rapeseed growth under drought.It decreased growth and of photosynthesis under drought by decreasing activities of RuBP carboxylase and PEPC,over reducing acceptor side limitation of PSⅠ and quantum yield of regulated energy dissipation of PSⅡ,increasing quantum yield of nonregulated energy dissipation,resulted in decrease of PSI and PSⅡ activities.