干旱胁迫对黄瓜幼苗生长、光合生理及气孔特征的影响

Effects of drought stress on growth,photosynthetic physiological features and stomata characters of cucumber seedlings

采用盆栽方式研究不同干旱程度（对照的基质含水量为田间持水量的70%-80%,轻度胁迫的基质含水量为田间持水量的40%-50%,重度胁迫的基质含水量为田间持水量的20%-30%）对2个不同黄瓜品种（千秋五号和千春七号）的形态指标、叶片气体交换参数、叶绿素荧光参数、生理生化指标和气孔特征的影响。结果表明：干旱胁迫下,2个品种的生长都受到显著抑制,叶片相对含水率、净光合速率（Pn）、气孔导度（Gs）和蒸腾速率（Tr）显著降低;在轻度干旱胁迫下,光合速率的下降主要是由气孔因素引起;而在重度干旱胁迫下,胞间CO2含量（Ci）升高,表明此时光合速率的下降是由非气孔因素引起的。干旱胁迫下,PSⅡ光化学量子效率（ΦPSⅡ）、光化学猝灭系数（qP）、光合电子传递速率（ETR）和PSⅡ吸收的光能用于光化学反应的份额（P）也都显著下降,而非光化学猝灭系数（NPQ）和用于天线热耗散的份额（D）显著增加。光合色素含量呈下降趋势,叶片中丙二醛（MDA）含量、游离脯氨酸（Pro）含量、超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）的活性显著升高。叶片气孔密度,开放气孔的比例,开度大小都呈下降趋势,胁迫后的叶片下表皮气孔变圆并且下陷,表皮毛的密度增加。试验显示,千春七号比千秋五号表现出更强的抗旱性。

The responses of morphological indexes,photosynthetic gas exchange,chlorophyll fluorescence,physiological indexes and stomata characters to different water stress（70%-80% of field capacity as no stress,40%-50% of field capacity as light stress,20%-30% of field capacity as high stress） in seedlings of two cucumber cultivars（var.＇Qianqiu No.5＇ and var.＇Qianchun No.7＇）.The growth of the two cultivars was inhibited under the drought stress.The water stress resulted in progressively decreases in relative water content of leaves,net photosynthesis rate（Pn）,stomatal conductance（Gs）,transpiration rate（Tr）,the actual photosynthesis efficiency of PSⅡ in the light（ΦPSⅡ）,the electron transport rate（ETR）,photochemical quenching（qP） and proportion of PSⅡ photochemistry（P）,but the non-photochemical quenching（NPQ） and proportion of antenna heat dissipation（D） increased.The intercellular CO2 concentration（Ci） decreased at light stress,but increased at high stress,which indicated that the decline of Pn was considered as a result of stomatal restriction under light stress,but non-stomatal restriction under high stress.The leaf pigment decreased,but increased for the contents of malon-dialdehyde,the proline as well as the activities of superoxide dismutase,peroxidase and catalase.The density of leaf stomata,open stomata proportion decreased progressively.The stomata were of smaller,low density,and most closed.Density of trichomes decreased.The cucumber cv.＇Qianchun No.7＇ was more drought-tolerant than var.＇Qianqiu No.5＇.