Effects Of Exogenous Substances On The Cold Resistance Of Pepper Seedlings At Low Temperature

Pepper,as the main vegetable in protected cultivation in northern China,is often injured by low temperature,which affects its growth and development,leads to the reduction of pepper yield and quality,and seriously restricts the production efficiency of protected pepper.Therefore,how to improve the low temperature resistance of pepper seedlings is an urgent problem to be solved in protected cultivation of pepper production.In this experiment,’ Longjiao No.2’ and’ California Extra-large Horn King’chillies were used as test materials.Light incubator was used to simulate low temperature conditions.Spermidine,spermidine,salicylic acid and chitosan with different concentrations were sprayed on leaves.Their physiological,growth and morphological indexes were measured.Their effects on chilling resistance of chillies seedlings were compared and studied to provide theoretical basis for chillies seedling cultivation in winter and spring low temperature seasons in Hebei.The main research results are as follows:1.Under low temperature stress,the proline content,soluble protein content and soluble sugar content of pepper seedlings are significantly higher than those of the control with the extension of time,which indicates that spraying spermine,spermidine,salicylic acid and chitosan with appropriate concentration can effectively improve the resistance of pepper to low temperature and slow down the damage of low temperature to pepper.2.With the extension of low temperature stress time,electrolyte permeability,MDA content and chilling injury index of pepper seedlings all increased,which were still lower than those of the control,indicating that certain concentrations of spermine,spermidine,salicylic acid and chitosan can reduce electrolyte permeability,MDA content and chilling injury index of the two varieties,thus reducing the degree of chilling injury to pepper.3.After low temperature stress,the SOD and POD activities of pepper seedlings generally showed a trend of rising first and then declining,but they were higher than that of the control,which indicated that certain concentrations of spermine,spermidine,salicylic acid and chitosan could protect the stability of the film and thus improve the cold resistance of pepper.4.After 7 days of low temperature stress and 3 days of recovery,the plant height and stem of the pepper seedlings of the two varieties were significantly higher than those of the control,indicating that spraying spermine,spermidine,salicylic acid and chitosan with appropriate concentrations can promote the growth of plants.5.After low temperature stress,the chlorophyll content and root activity of pepper seedlings decreased,but were still higher than that of the control,indicating that spermine,spermidine,salicylic acid and chitosan with appropriate concentrations can alleviate the degradation rate of chlorophyll,promote the growth of roots and protect the damage of low temperature to pepper.6.By analyzing the membership function of chilling resistance,it is found that the exogenous substances that improve chilling resistance of pepper seedlings are spermidine,spermine,salicylic acid and chitosan in descending order.The best inducing concentrations were 0.5mmol/L spermidine,0.1mmol/L spermine,2mmol/L salicylic acid and 50mg/L chitosan respectively.