Comparative analysis on proline content in the leaves of the ancient trees in northwest of Guangxi Karst Area

The habitats of plants in karst area are different from that in the mountain and hilly land formed in clastic rocks. Special habitat brings up different group of plant. The plants in karst area have different physiological and ecological adaptability features. Different ages of leaves are collected from the common tree species, including C. Camphora, F.virens Ait.var.sublanceolata, F.microcarpa var.pusillifolia, O.fragrans.B.polycarpa, L.formosana and D.longan, which distribute in northwest Guangxi. And then proline content in the leaves is determined by the method of sulfosalicylic acid extraction-ninhydrin coloration. By comparative analysis on the proline content in different leaf-samples, correlation between proline content and tree age, the living conditions of the trees and other ecological factors are studied, so as to provide scientific basis for biological protection of the old trees. The result shows that different tree species have different proline content in their leaves; the same species leaves with different ages had different proline content. With the growth of tree-age, there are some fluctuations in proline content in the leaves. The variation of proline content in the old leaves is similar to the new ones, and the proline content usually increase at first and then decrease. Lastly, it is proposed that proline content in the leaves should be used as the reference index of for tree protection.