Effects Of K,Ca And Substance As SA On Cold Resistance Of Fraxinus Mandshurica

Under natural conditions, plants grown in temperate zone often exposed to low temperature injury in spring night. Low temperature injury is a serious natural global disaster in production of agriculture and forestry. Fraxinus mandshurica is a kind of precious hard-leaved species in China's Northeast forest zones. It belongs to classⅡin National plant protection. It is an important industrial wood species fostered now. Finding in the process of foster, low temperature plays an important inhibition on survival of Fraxinus mandshurica and growth of the seedlings. Therefore, studying the changes of their cold resistance index, and proposing effective prevent measures make great significance.Three-year-old seedling of Fraxinus mandshurica was used as plant material in this paper. The response to low temperature stress was studied of nutrients potassium, calcium and growth regulator salicylic acid, betaine on Fraxinus mandshurica's physiological indicators, seeking to find effective concentrations of substances and appropriate to improve cold tolerance of Fraxinus mandshurica. The paper also analyzed the effects of salicylic acid, betaine, 6-Benzylaminopurine, paclobutrazol on photosynthetic characteristics of seedlings under the low temperature in natural. The content study and conclusions are as follows:1. Experiments using MINITAB statistical analysis software designed two factors and five levels universal rotational. Interaction of K, Ca has 13 treat groups. Water improved Hoagland nutrient solution. Through analyzed 5 physiological indicators and regression equation, we got an optimal combination of K, Ca:under the low temperature condition, the best concentration of K is 4.61-8.27 mmol·L-1. And the best concentration of Ca is 4.55-7.10mmol·L-1. High and low concentrations of K, Ca ratios are bad to cold resistance physiological indicators of Fraxinus mandshurica, it is more sensitive on Ca concentration. In addition, relative electrical conductivity increased slightly in the chilling stress than normal temperature, while is significantly reduced under the ice. The accumulation of soluble protein under chilling stress was slower than freezing stress. Soluble sugar has increased in both stresses. Under chilling stress, SOD activity was first decreased and then increased. POD activity was first increased and then decreased. Both of enzyme activity has been reduced in freezing stress.2. Under low temperature stress, foliar application of salicylic acid, betaine to Fraxinus mandshurica seedlings can improve the cell's osmotic adjustment by the accumulation of soluble protein, soluble sugar. It also can reduce cell membrane damage caused of lipid peroxidation by the increased of SOD, POD activity. Spraying exogenous substances 3-6 days before the cold stress can play a larger role, and the general efficacy continued until 10 days after spraying. Under low temperature, the influence time of exogenous SA, BT on protective enzymes is greater than osmotic adjustment. Comparative Analysis to the Comparison, we determined the best concentration was SA: 1.0-5.0 mmol·L-1, BT: 5.0-10.0 mmol·L-1, and BT was obviously better than SA in the relative conductivity, soluble protein content, POD activity.3. We sprayed four growth regulators of salicylic acid, betaine,6-Benzylaminopurine, paclobutrazol to Fraxinus mandshurica seedlings in natural low temperature. The results to photosynthetic characteristics show that:With the natural temperature decrease, the chlorophyll content of comparison group decreased, net photosynthetic rate (Pn) also decreased. They are closely related. Exogenous addition of growth regulators under low temperature can regulate the content of chlorophyll and net photosynthetic rate. The most effective concentration were SA: 5.0 mmol·L-1, BT: 10.0 mmol·L-1, 6-BA:200 mg·L-1, PP333: 100 mg·L-1. The order of degree:BT> SA> 6-BA> PP333。The reduce degree of transpiration rate (Tr) was greater than photosynthetic rates, stomatal conductance (Gs) decline was more slowly, while intercellular CO2 concentration (Ci) showed slight upward trend.Comprehensive view, the best nutrients and growth regulators filtered to improve the cold tolerance of Fraxinus mandshurica seedlings was: 4.55-7.10mmol·L-1 of calcium and 10.Ommol·L-1 of betaine. This test determined cold tolerance physiological indicators of Fraxinus mandshurica seedlings under the normal temperature, 4℃chilling stress, -7℃freezing stress, also verified photosynthetic characteristics in natural low temperature.The study is systematic.