Abstract: pectral analysis of Pb and Zn contents in annual growth rings of 2 back pine(Pins thunbergii Parl.)and 3 masson pine(Pinus massoniana Lamb)trees grown on a polyrnetal mine and its surrounding area of the Xixia Mountain in Nanjing shows that the length of periodicy plays a primary role in the periodic variations of Pb and Zn in tree rings. The synchronous variation of Pb with precipitation is dominated by long periodicy,while that of Zn by short periodicy.The ratio of orthogonal positive to orthogonal negative correlations of Pb and Zn variation,which is1/4 behind that of precipitation, varies with trees,Significant correlations between element and precipitation account for 0.30-0.60.For both of the element and precipitation sequences,their maximum and minimum delay time,and their corresponding periodicy vary with trees and elements.

Key words: rice, sowing date, low-light stress, photosynthetic rate, yield.