【作者】 晋晓彤；

【导师】 郭富常；

【作者基本信息】 天津大学 ， 蔬菜学， 2009， 硕士

【摘要】 温度、光照及氮素营养等环境条件都与黄瓜叶片的生长发育有密切关系,在实际生产中常因高温、强光及氮素缺乏等环境胁迫而引起黄瓜早衰,影响生产效益,如春夏黄瓜的开花结果和产量不足越冬黄瓜的1/4。为了明确认识环境胁迫引起黄瓜早衰的生理现象,把握栽培条件对黄瓜生长发育的影响,本实验以黄瓜栽培品种“津春5号”幼苗为材料,观测了高温、强光及不同氮营养条件下黄瓜幼苗叶片的活性氧过氧化氢（H₂O₂）和超氧阴离子（ O 2?）、衰老指标丙二醛（MDA）、叶绿素和可溶性蛋白质、反映光合机能的气孔导度、胞间CO2浓度、净光合速率及蒸腾速率的变化。昼17℃～36℃,夜17℃高温处理黄瓜幼苗的试验结果表明,与昼17℃～28℃,夜17℃对照比较,高温条件下黄瓜幼苗叶片的H₂O₂含量和O 2?生成速率高,子叶及叶片的MDA积累多,叶绿素和可溶性蛋白质含量少,净光合速率低。说明高温可以促进活性氧的产生和积累,诱发叶细胞大量发生膜脂过氧化及叶绿素、蛋白质降解,并对光合速率产生抑制,从而加速了黄瓜幼苗叶片的衰老。6月中下旬到8月上旬的遮光试验结果表明,与遮光率50%光量子流通密度在1000μmol·m-2·s-1左右的处理相比,无遮光光量子流通密度在2000μmol·m-2·s-1左右的强光处理显著促进了黄瓜幼苗叶片的O 2?和MDA生成、叶绿素和蛋白质的降解,也使净光合速率降低。说明夏季的强光可显著引起黄瓜幼苗叶片老化,造成植株早衰。与不施氮肥的处理比较,育苗期间三次施氮素0.4 g·kg-1的中氮处理,叶片的H₂O₂、O 2?及MDA的生成少,叶绿素和可溶性蛋白质含量的水平高,净光合速率大。但在育苗期间三次施氮素0.8 g·kg-1的高氮处理却观测到叶片H₂O₂、O 2?的生成多,MDA的含量高,净光合速率较低的现象。说明氮素营养特别是缺少氮素营养也是影响黄瓜早衰的一个重要因素。更多还原

【Abstract】 Some environmental conditions are closely related to the growth of cucumber leaves, such as temperature, light and nitrogen. In the actual production, premature senescence occurs in cucumbers under high temperature, excessive-light and low nitrogen stress. For example, the flowers and fruit yield of cucumbers in summer are less than 1/4 of that in winter. In order to determine the physiologic phenomenon of premature senescence caused by environmental stress and the effect of cultivation conditions on the growth of cucumbers, we took“Jinchun NO.3”as test materials and observed the physiological indices including Reactive Oxygen Species （ROS） contents, such as contents of hydrogen peroxide （H₂O₂） and superoside （ O 2?）, senescence indices such as contents of malondialdehyde （MDA）, chlorophyll and protein and also stomatal conductance, intercellular CO2 concentration, net photosynthesis rate and transpiration rate in cucumber seedlings.Compared with the indices in control （17℃～28℃in daytime, 17℃at night）, the contents of H₂O₂, MDA and O 2? generating rate of cucumber seedlings in high temperature stress （17℃～36℃in daytime, 17℃at night） were higher, Chlorophyll and protein contents, and net photosynthesis rate were lower. It indicated that high temperature accelerated the senescence of cucumber seedlings by promoting the accumulation of ROS, inducing membrane lipid peroxidation, dagrading chlorophyll and protein, and decreasing photosynthesis rate.Compared with the treatment of shading rate of 50%, no light shading treatment （photosynthetic photo flux density was 2000μmol·m-2·s-1） prominently promoted the generation of O 2? and MDA, reduced chlorophyll and protein contents, and decreased net photosynthesis rate of cucumber seedling leaves. The results showed that strong light could induce the premature senescence of cucumber seedlings.The contents of H₂O₂, MDA and O 2? generating rate of cucumber seedlings by middle nitrogen treatment, in which nitrogen applied rate was 0.4 g·kg-1, were lower than that in control by no nitrogen treatment. But the net photosynthesis rate and the contents of chlorophyll and protein were higher than that in control. However, high nitrogen treatment with a nitrogen applied rate of 0.8 g·kg-1 increased the contents of H₂O₂, O 2? and MDA, decreased the net photosynthesis rate of cucumber seedlings. These results indicated that the lacking of nitrogen was the most important reason for senescence in cucumber seedlings.更多还原