Effects Of Treatment Of Exogenous Substances On Cold Resistance Of Cucumber Seedlings

Cucumber is one of the typical cold sensitive plants that is widely cultivated in the world, and planting area shows a rising trend,bacause of the wide distribution. Cucumber is easily effected by low temperature in North China winte and made quality and output falled. Therefore, how to solve the chilling injury of cucumber problem have become the focus in recent years. Predecessors did lots of research on exogenous substances treatment of seeds and seedli ngs of cucumber, and tried to find the new method, but did not work well. The test selected t he weak cold resistance of cucumber variety "Jinyou No.1" and strong cold resistance of cucumber variety "Jinzao No.1" as the experimental material, the treatment of Cucumber seedlings with salicylic acid（SA）、calcium chloride（CaCl₂） and spermidine（Spd） is an important role in improving the chilling tolerance of cucumber seedlings.The varieties "Jinyou No.1" and "Jinzao No.1" as the experimental materials, in three leaves and one half leaf period with foliar application to cucumber leaves the way of applying single solution or different concentrations of the compound in aqueous solution, Using orthogonal test screening the best combination, studying the effect of ex ogenous substances on cucumber seedling anti cold ability, seeking the optimal combination of improving the resistance of cucumber seedlings, and provide a theoretical basis for the production practice. Obtain the following main results:（1） The treatment of exogenous substancesreduced the chilling injury index decreased relative conductivity andmalondialdehyde content remarkably. Calcium chloride plays an important role of the three kinds of exogenous substances. Results show that the optimum concentration of salicylic acid was 120mg/L,the optimum concentration of calcium chloride was 1000 mg/L, the optimum concentration of spermidine was80mg/L.（2） According to the results of single optimum concentration experiment designing orthogonal test,the result shows that the best and actual combination was the concentration of salicylic acid was 180mg/L, theconcentration of calcium chloride was 1000 mg/L and the concentration of spermidine was 40mg/L mixed. On the basis of the range analysis the best and theoretica lly combination was the concentration of salicylic acid was 180mg/L,theconcentration of calcium chloride was 1000 mg/L and the concentration of spermidine was 120mg/L mixed and the concentration of salicylic acid was 180mg/L,theconcentration of calcium chloride was 1000 mg/L and the concentration of spermidine was 40mg/L mixed.（3）The combination A3B2C1 and A3B2C3 can significantly improve cold resistance of cucumber seedlings and decrease injury index obviously.（4） We found the combination A3B2C1 and A3B2C3 not only improved the low temperature of Cucumber Seedlings of protective enzyme activity, enhanced plant resistance to cold, while increasing the osmotic adjustment and soluble sugar, soluble protein and proline content of the cell osmoregulation ability was enhanced obviously, and the leaf relative conductivity decreased, malondialdehyde content decreased, slowing the rate of declining of chlorophyll, maintain the normal light photosynthetic rate.（5） The height, stem diameter,leaf area of the combination A3B2C1 and A3B2C3 were increased dramaticlly.（6） The yield of the combination A3B2C1 and A3B2C3 were increased markedly.（7） Analysing the injury index、physiological and biochemical indexes、morphological index and yield of the combination A3B2C1 and A3B2C3, combination A3B2C3 is the best treatment of the experiment.