Variation Of Drought-resistance And Cold-resistance Among Species And Provenances In Lespedeza Michx.

As forage plant, lespedeza has high feeding value, a certain extent ability of drought resistance and cold resistance as well. In order to improve the ability of resistance, the multiple physiological characteristics, including osmotic adjustment materials, relative permeability of membrane and so on, are studied to evaluate the endurance of lespedeza under drought and cold stress conditions. From two hierarchies, species and provenances, the differences of tolerance ability in physiological and biochemical traits are evaluated. The purpose of this dissertation is to select some species and provenances with strong ability of drought-resistance and cold-resistance, as well as several indices system adapting to selection. With the above research and analysis from geographic variation rule of resistances, this thesis will provide theoretic basis for the selection and popularization of this forage genus with strong drought and cold resistance in northeast and northwest regions. The results are found as follows.L. potaninii and L. cyrtobotrya rank the top of the list of ability of drought resistance in species, L .thunbergii is the last one. As for cold resistance in species, L. cyrtobotrya and L. bicolor are the top of all, while L. cuneata and L .thunbergii take second place. In the taxis of both drought resistance and cold resistance ability among provinances of L. biolor, the provenance from Da Qingshan is the first and that from Song Xian is the last. Besides, among L. cuneata the provenance fromTian Shui has the strongest ability of drought resistance, that fromYan Chi takes sencond place. The result shows that there are different mechanisms of resistance in different species. The ability to stress-resistance is effected by kinds of factors, and it needs a comprehensive evaluation relating diversified indices, not only one index which would be far enough to evaluate the intensity of abilities accurately. Finally, the variation of resistance in provenances of Lespedeza is type of cline which is a reflection of climate changes from cold to warm and dry to wet in the distribution area of this species.