复合盐碱胁迫对蓖麻早期幼苗光合生理的影响

Synergistic effects of salt and alkaline stresses on the photosynthetic physiology of early seedlings of Ricinus communis

摘要:

【目的】 探究复合盐碱胁迫对蓖麻早期幼苗生长阶段子叶与真叶光合能力的影响。【方法】 以能源草蓖麻（Ricinus communis）为供试材料，将 2种中性盐NaCl、 Na2 SO4 与 2种碱性盐NaHCO3 、 Na2 CO3 以不同的摩尔比例混合，模拟土壤复杂的盐碱逆境条件。按照碱性盐比例递增的顺序设置 A~F 6组试验组，同时每个组设置3种盐浓度（25、50、100 mmol/L）。在本试验模拟出的18种盐度和碱度下，对蓖麻早期幼苗光合生理指标和叶绿素荧光参数进行测定。【结果】 随着盐碱胁迫的加深，除子叶胞间CO2 浓度外，蓖麻真叶与子叶的光合生理参数和叶绿素荧光参数整体均呈现出下降趋势。尤其是光合速率，在盐浓度大于25 mmol/L时，下降显著（P＜0.05）。真叶气孔导度，子叶的蒸腾速率、光合速率、实际光化学速率和光化学淬灭系数大幅下降。这类变化在高浓度盐碱胁迫下表现更为显著， 如在最高浓度胁迫下（F4 ），子叶的光化学淬灭系数较上一浓度梯度（F3 ）下降47%，而真叶为22%。 【结论】 复合盐碱胁迫对蓖麻幼苗子叶和真叶的光合作用都存在严重影响，而从子叶受胁迫程度比真叶程度大这一现象推测子叶在蓖麻幼苗响应盐碱胁迫中发挥更加重要的作用，使真叶受到的胁迫降低从而更好地维持植物的生长发育。

Abstract:

【Objective】 To investigate the effects of complex saline-alkali stress on the photosynthetic capacity of cotyledons and true leaves in Ricinus communis seedlings during the early growth stage.【Method】 The early seed ings of the energy plant Ricinus communis were taken as research material. To simulate the complex saline-alkali stress conditions of soil，NaCl and Na2 SO4 were induced using different molar ratios. Similarly，alkaline stress was simulated by mixing NaHCO3 and Na2 CO3 with different molar ratios. Six groups（A to F）with six alkali concentra tion treatments were designed，and three salt concentrations （25，50，100 mmol/L） were applied within each group. The photosynthetic physiological indexes and chlorophyll fluorescence parameters of Ricinus communis were mea sured under 18 kinds of salinity and alkalinity.【Result】 Increasimh salt and alkali stress led to a general declinein pho tosynthetic physiological parameters and chlorophyll fluorescence parameters in both true leaves and cotyledon of Ricinus communis，with the exception of intercellular CO2 concentration in cotyledon. Notably，photosynthetic rate de creased significantly when the salt concentration exceeded 25 mmol/L. The stomatal conductance of true leaves ex hibited a more pronounced decline，while the transpiration rate，photosynthetic rate，?PSⅡand qP of cotyledon leaf decreased more significantly，especially under high salt and alkali stress. Such changes are more pronounced under high salt stress conditions，such as at the highest concentration （F4） of stress. At the highest stress level （F4） the qP of cotyledons decreased by 47% compared to the previous concentration gradient （F3），while the decrease in true leaves was 22%.【Conclusion】The findings suggest that the mixed salinity-alkalinity stresses significantly impacts growth and physiological function of both cotyledon and true leaves in Ricinus communis seedlings. The greater sem sitivity observed in cotyledon suggests that cotyledon plays a more important role in response to mixed salinity alkalinity stresses of Ricinus communis seedlings，thereby reducing the stress on true leaves to better maintain the growth and development of plants.