Effects Of Suboptimal Temperature And PFD Treatments On Growth Characters And Nitrogen Metabolism Of Cucumber Seedlings

Sunlight greenhouse and plastic greenhouse is the main vegetable cultivation facilities inwinter season in north China. Suboptimal environmental conditions (15¹8℃/10¹2℃，200³00μ mol m^-2s^-1)such as low temperature, weak light, etc always happen in thefacilities. This long-term cultivation environment contributes to cucumber physiologicalmetabolism disorders and absorption of mineral nutrition and distribution, which affects thegrowth and development of the cucumber yield and quality. It has become restricting the mainfactors of cucumber high yield and good quality that the long-term cultivation environmentcontributes appears in winter and earlier spring. Besides nitrogen is necessary to the formationof plant growth and quality which is one of the major mineral elements. A series ofphysiological and biochemical changes in cumcumbers are caused by the absorption ofnitrogen and transportation which may be affected by the suboptimal environmentalconditions.This project has studies the nitrogen content, related enzyme activity of cucumbernitrogen uptake and transport and other physiological characteristics changes etc insuboptimal environmental conditions, which in order to reveal physiological and molecularmechanism of nitrogen uptake and transport in cucumber. The main research results are asfollows:1. During suboptimal temperature and suboptimal PFD different treatments, plant height,fresh and dry weight and root shoot ratio significantly decreased，so the cucumber seedlingsgrowth has been inhibited, while the chlorophyll content increased and, photosynthesis ratereduced significantly. Therefore, it influenced the normal physiological metabolism ofcucumber plant activities by suboptimal temperature and suboptimal PFD differenttreatments.2. Compared with control plants, NR, GOGAT and GDH activity reduced; while GS activityincreased in suboptimal temperature and suboptimal PFD different treatments. Besides nitratecontents are evidently higher than those of control processing.3. The activities of Ca²⁺-ATPase and H⁺/K⁺-ATPase are evidently higer in suboptimal PFDand different temperature treatments while the activities of H⁺/K⁺-ATPase decrease and the activities of Ca²⁺-ATPase increase with the reducing of light intensity in suboptimaltemperature and different PFD treatments.4. The contents of N, P, K, Ca and Mg in cucumber seedlings have significantly reducedduring suboptimal temperature and suboptimal PFD different treatments, which indicated thatthat temperature and light stress are led to the reducction of mineral elements in plant body.