Effects Of Several Exogenous Substances On Physiological Characteristics Of Fraxinus Mandshurica Seedling In Responses To Low Temperature

The Fraxinus mandshurica was an important precious hard hardwood species of China Northeast forest. The low damage had a significant impact on survival rate and preservation rate of Ash afforestation. Thus, it was important that mastering the chilling injury of Fraxinus mandshurica and revealing the mechanism of their victimization and change on the cold temperature stress, and on this basis proposing effective measures for prevention and control technologies to nurture and protect the plantation of Fraxinus mandshurica. The Fraxinus mandshurica seedling was used to study the effects of five different exogenous substances on the defense system of seedling leaveseffects under the artificial low temperature or fall natural temperature reduction. The relative conductivity, soluble protein and soluble sugar content, SOD and POD activity, photosynthetic rate and other physiological indicators were measured. In this paper, the effects of exogenous substances on physiological characteristics of Fraxinus mandshurica seedling in responses to low temperature were studied to obtain an dose formulation that could increase cold resistance of Fraxinus mandshurica. The results were as follows:1.0μmol·L-1 and 2.0μmol·L-1 concentration of brassinolide could effectively alleviate the change of electrolyte leakage amount, increase the content of soluble protein and the activity of protective enzymes, but 2.0μmol·L-1 concentration processing was not conducive to the soluble sugar accumulation of leaf at low temperatures. The low concentrations of 0.7μmol·L-1 processing had no significant effect for all the physiological indexes. Under natural cooling, the 1.0μmol·L-1 processing to maintain the conductivity was better than the other two concentrations. Comprehensive comparison, the 1.0μmol·L-1 concentration of brassinolide was better.Sodium nitrophenolate could increase the intracellular soluble content of seedling leaves at room temperature, but had no significant effect on the stability of membrane permeability and the protective enzymes under artificial low temperature stress. Sodium nitrophenolate had no effect on the conductivity under the natural cooling process and did not show a cold tolerance effect for seedling.10mg·L-1 concentration of ABA was best, which could effectively alleviate the change of electrolyte leakage amount, enhance the protective enzymes and the content of osmotic adjustment matter. 30mg·L-1 and 60mg·L-1 ABA demonstrated a degree of side effects on the conductivity, soluble protein content and POD activity under artificial low temperature. Under natural cooling,10 mg·L-1 ABA in maintaining the stability of membrane permeability was better. Comprehensive comparison, the 10mg·L-1 concentration of ABA was better.1mmol·L-1 concentration of spermidine was better on cold intimidate, which could ease the decline of leaves conductivity at 0℃and enhance osmotic adjustment matter content and SOD activity.5mmol·L-1 concentrations was not more remarkable than 1mmol·L-1 in terms of soluble protein and soluble sugar. Low concentrations of 0.5mmol·L-1 was not significant for the physiological indices. Comprehensive comparison, lmmol·L-1 concentration was better.50mg·L-1 concentration of GA treatment was helpful to the cold resistance of Fraxinus mandshurica, a certain degree to delay the decreace of leaf conductance, increase osmotic adjustment matter content, to some extent enhance the activity of protective enzymes SOD and POD. 100mg·L-1, 150mg·L-1 treatment showed some inhibition and result was not satisfactory. Comprehensive comparison, 50mg·L-1 concentration was better.The five kinds of cold dose combination were preparated on the base of above results. In the autumn natural cooling process, the formulation that could improve the cold resistance of Fraxinus mandshurica was determined, that 10mg·L-1ABA,1.0μmol·L-1 brassinolide, 1mmol·L-1 spermidine, 50mg·L-1 GA.