Relationship Of Leafblade Element Contents And Tree Growth Of Triploid Chinese White Poplar

Based on completely randomized block experiment design, two hybrid clones of triploid populus tomentosa were chosen as the research objects and an ordinary populus tomentosa as control(S10), the effects of plant density grandients on growth of different strains of populus tomentosa were investigated, and the seasonal variation of leafblade element contents as well as relationship of leafblade element contents and the growth of two hybrid clones of triploid populus tomentosa (S6 and S8) were also determined. Seven density gradients including 2m×2m, 2m×3m, 2m ×3.5m, 2m×4m, 2m×5m, 3m ×3m and 3m×4m were set, annual growth increment of tree hight and breast diameter as well as element contents of leafblades were selected as indexes indicating the growth characteristics of populus. The results indicated that plant density has no significant effects on populus tomentosa growth and the contents of leafblades at the initial stage of the experiment. Annual growth increments of the tree hight and the breast diameter of two triploid populus tomentosa were significantly higher than those of control(p < 0.05), but there were no significant difference between the two triploid populus tomentosa(p >0.05). The element contents of leafblades changed with the season variety and different elements of leafblades characterized by different variation rule. The contents of nitrogen, phosphorus, potassium and copper of leafblade of the two triploid populus tomentosa were higher at the initial growth stage when compare with other elements, but decreased gradually and showed lower level at the end of growth period. Therefore, the variation contents of nitrogen, phosphorus, potassium and copper of leafblade of the two triploid populus tomentosa presented decreasing trend during growth period. The contents of calcium, magnesium, nickel, molybdenum and cobalt were high in the middle period of tree growth but lower at the initial and the end of the growth period, while the contents of iron and zinc were just in the opposite. The manganese content of leafblades changed little during the growth period. But for sodium and boron, their contents increased with the changing of season. The difference of element contents of leafblades directly led to the difference between elements when absorbing by tree. It is suggested that the mutual promotion existed between elements absorbing by trees when they positively correlated with each other, on the contrary, the negatively correlations means antagonistic action existed between elements during absorbing by trees. Correlation analysis indicated that some elements promoted each other but some presented antagonistic action. There were close relationships between annual growth increments of the tree high and the breast diameter and elements during growing season of triploid populus tomentosa, the correlation analysis of them can provide useful information for diagnosing the nutrients demands of triploid populus tomentosa. Therefore, stepwise regression analysis...