硅对干旱胁迫下生菜幼苗生长及光合特性的影响

以抗性不同的2个生菜品种"玻璃生菜"和"罗莎红"为试材,采用营养液栽培,用15%聚乙二醇模拟干旱,研究外源施加1.0 mmol·L^-1的Na₂SiO₃作为硅供体对干旱胁迫的缓解效应,以期探讨硅对干旱胁迫下生菜幼苗生长及光合特性的影响。结果表明:与对照相比,干旱胁迫导致生菜幼苗株高、根长、植株鲜质量、干质量等生长指标降低;叶绿素a、叶绿素b、类胡萝卜素及总叶绿素含量降低;净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)显著下降,胞间CO₂浓度(Ci)显著上升;PSⅡ最大光化学效率(Fv/Fm)、PSⅡ实际光化学效率(Ф_PSⅡ)、光合电子传递效率(ETR)和光化学淬灭系数(qP)显著降低,而非光化学淬灭系数(NPQ)显著增加。外源添加适量浓度的Si,可不同程度提高生菜幼苗生长势及干鲜质量;也提高生菜光合色素含量及光合能力;同时对改善PSⅡ反应中心活性、提高叶绿素荧光参数也有促进作用。可见,外源添加一定浓度的Na₂SiO₃可缓解干旱胁迫对生菜幼苗的伤害,提高生菜叶片对光能的捕获与转化能力,增强光合效率,促进生菜生长。

Effects of Si on Growth and Photosynthetic Characteristics of Lettuce Seedlings Under Drought Stress

Two lettuce varieties with different resistance,‘Glass lettuce’and‘Rosa red’,were cultivated in nutrient solution and 15%polyethylene glycol was used to simulate drought.The alleviating effect of exogenous Na₂SiO₃ with 1.0 mmol·L^-1 as silicon donor on drought stress was studied,in order to explore the effects of silicon on the growth and photosynthetic characteristics of lettuce seedlings under drought stress.The results showed that compared with the control group,drought stress reduced the growth indexes of lettuce seedling such as plant height,root length,fresh weight and dry weight.The contents of chlorophyll a,chlorophyll b,carotenoid and total chlorophyll decreased.Net photosynthetic rate(Pn),stomatal conductance(Gs)and transpiration rate(Tr)decreased significantly,and intercellular CO2 concentration(Ci)increased significantly.PSⅡphotochemical efficiency(Fv/Fm),the largest PSⅡactual photochemical efficiency(Ф_PSⅡ),photosynthetic electron transport efficiency(ETR)and light chemical quenching coefficient(qP)significantly reduced,rather than the coefficient of photochemical quenching(NPQ)increased significantly.The growth potential and fresh dry weight of lettuce seedlings could be increased by adding proper concentration of Si.The photosynthetic pigment content and photosynthetic capacity of lettuce were also improved.At the same time,it could also improve the activity of PSⅡreaction center and chlorophyll fluorescence parameters.It could be seen that exogenous addition of a certain concentration of Na₂SiO₃ could alleviate the damage of drought stress on lettuce seedlings,improve the ability of lettuce leaves to capture and transform light energy,enhance the photosynthetic efficiency and promote the growth of lettuce.