Properties Of Nitrogen Absorption And Transport Of Cucumber During The Fruiting Period Under Suboptimum Temperature And Suboptimum PFD

Sunlight greenhouse and plastic greenhouses are main facilities for vegetables cultivationin the winter and early spring of north China. Because of lacking the heating and lightingequipments, a long-period condition of suboptimum temperature and suboptimum PFD existin cultivation facilities, causing the physiological mechanism of cucumber imbalanced.Therefore, the growth, development, yield and quality of cucumber inhibited. This hasbecome the main limiting factors for the high yield and quality vegetable cultivation.Cucumber of “ZHONG NONG No.106” in fruiting period was used. Effects ofsuboptimum temperature and suboptimum PFD on growth and N absorption and transport ofthe cucumber plants during the fruiting period were studied, and effects of nitrogen level andN absorption and transport of the cucumber plants during the fruiting period undersuboptimum temperature and suboptimum PFD were probed. By measuring grouth, quality,mineral nutrient content, N metabolism related enzyme activity and the expression ofNitrogen transporters gene, the mechanism of N absorption and transport of the cucumberplants during the fruiting period under suboptimum temperature and suboptimum PFD wasprimarily clarified. Our result provide theoretical basis for improving the cucumber adaptivephysiological and molecular mechanisms, regulation the cucumber growth and developmentunder suboptimum temperature and suboptimum PFD. The main results are as follows:1. Effects of suboptimum temperature and suboptimum PFD on growth and N absorptionand transport of the cucumber plants during the fruiting period: compared with the normaltemperature and light intensity (T1) treatment, cucumber plants under the suboptimumtemperature and light intensity (T2) and the low temperature and weak light (T3) conditionsshowed remarkable decrease on the plant height, leaf area, fruit size and yield. The cucumberroot activity, chlorophyll content, fruit quality and glutamine synthetase, glutamate synthase,glutamate dehydrogenase activity were decreased with the decreased temperature and lightintensity decreasing. Under the suboptimum temperature and light intensity condition, the Ncontent of the cucumber during the fruiting period in the roots, leaves and fruits were declined.The suboptimum temperature and light intensity (T2) and the low temperature and weak light(T3) treatment down-regulated the expression of Nitrogen transporters protein gene of thecucumber during the fruiting period, and the expression of Nitrogen transporters gene weresuppressed by lower temperature and light intensity. The results indicated that thesuboptimum temperature and light intensity may decrease N content by suppressing nitrogentransport protein gene expression, and then inhibit the growth of cucumber. 2. Effects of nitrogen level on growth and N absorption and transport of the cucumberplants during the fruiting period under suboptimum temperature and suboptimum PFD:compared with the normal nitrogen level (A1), under the1.5times of nitrogen level (A2)treatment, the plant height, leaf area, fruit size and yield of the cucumber were significantlyincreased. The cucumber root activity, chlorophyll content, fruit quality and glutaminesynthetase, glutamate synthase, glutamate dehydrogenase activity were highest under the1.5times of nitrogen level, with the lowest in2times nitrogen level treatment. Under the1.5times of nitrogen level condition, the N content and the expression of Nitrogen transportersgene of the cucumber during the fruiting period in the roots, leaves and fruits were up-reulated. The results indicated that the1.5times of nitrogen level condition may increase Ncontent by promoteing nitrogen transport protein gene expression, and then enhance thegrowth of cucumber.