Mechanism Of Increasing The Frost-resistance Of Fraxinus Mandshurica And Tilia Amurense Seedlings Treated By K～+ And Ca～(2+) And Growth-regulating Agents

This paper mainly studied the frost-resistance of Fraxinus mandshurica and Tilia amurense seedlings which were treated by different concentrations of K+ . Ca2+ and two growth-rugulating agents. In this paper,use sand pots,in green house,to study seedlings the permeability of cell membrane content of MDA content of soluted sugar and free prolin under -10 low temperature treatment. Five nutrient solution levelsxoncentration of 50%,100%,150%,200%,250% were designed in the experiments.The results show that the permeability of cell membrane of Fraxinus mandshurica seedlings decreased and had better result than in Tilia amurense seedlings while K+ concentration was high. High concentration of K+ inhibited content of MDA in Fraxinus mandshurica seedlings and the regularity was clear but the infulence to Tilia amurense seedlings was not obvious but the time of action was longer. High concentration of K+ can also increase the content of soluted sugar but has better result to Tilia amurense seedlings than Fraxinus mandshurica seedlings and increase the content of free prolin in Fraxinus mandshurica seedlings,but had no influnce to Tilia amurense seedlings. Comparing with K+ treatment,Ca2+ increasing the frost-resistance of Fraxinus mandshurica and Tilia amurense seedlings was not obvious. Ca2+ concentration of 150% can effectively decrease the permeability of cell membrane and the content of MDA in Fraxinus mandshurica seedlings but high concentration of Ca2+ can increase the content of the soluted sugar. High concentration of Ca2+ (specially 200%) can obviously decrease the permeability of cell membrane in Tilia amurense seedlings but the result of 150% Ca2+increasing content of soluted sugar had notable result. Every concentration of Ca2+ influncing content of free prolin had no obvious regulation.GA3 and NAA can delay the time of germination of Fraxinus mandshurica and Tilia amurense seedlings but the result is not notable. GAs of 150% can delay germination of Tilia amurense seedlings 4 days and only Iday to Fraxinus mandshurica seedlings. High concentration of NAA can delay the germination of Fraxinus mandshurica and Tilia amurense seedlings but the seedlings which were treated can not grow normally.From the observation of ultrastructure of Fraxinus mandshurica and Tilia amurense seedlings,we can see that chloroplasts in different cells of the same leaf under the same treatment time or in the same cell suffered different damage. Amylum grains in both seeedlings' cells increased under low temperature and there were many leaf fat balls in Tilia amurense leaves. In the observation,the number of mitochondrion was little and difficult to observe..