Abstract:

Effects of nutrients and acidity on production of tannin and other organic matters in branchlets of Casuarina equisetifolia seedlings were studied. The results showed that, nitrogen fertilizer application significantly decreased total phenolics, TP, extractable condensed tannins (ECT), nitrogen contents and ECT ∶N ratios. The result lends support to source-sink theory such as the carbon-nitrogen balance (CNB) theory and the growth-differentiation (GDB) theory. Phosphorus fertilizer application had no significant effects on TP and ECT contents. TP contents increased, and ECT contents remained unchanged with the increasing of pH. But starch, chlorophyll a, carotenoid, nutrient contents and chlorophyll a/b ratios decreased significantly. Accordingly, TP ∶N and ECT ∶N ratios significantly increased. The discrepancy of relationship between nutrition with TP or ECT indicated that the biosynthetic route of different tannins were different. In this study, there was no significant correlation between TP and N, or ECT and N, which did not support protein competition model (PCM). TP ∶N and ECT ∶N ratios were higher under nutrient deficiency conditions, which was one of the important nutrient conservation strategy for C. equisetifolia.

Key words: Casuarina equisetifolia, nitrogen fertilizer, phosphorus fertilizer, pH value, tannin