Seasonal Variation on Ecological Stoichiometry of Carbon, Nitrogen and Phosphorus in Azolla Cultivars

Ecological stoichiometry of different Azolla cultivars as affected by the seasons was studied. In the lab, 8 Azolla cultivars were used to determine the seasonal variations on yield, contents of C, N, P as well as stoichiometry of the plants. The results showed the yield increased initially, reached a peak as the temperature rose in the summer, and followed by a decline. The highest average annual yield of 244.25 g·tray^-1 was observed on A. microphylla Minyu No. 1 (4087), the second highest of 240.43 g/tray on A. microphylla (4018) A. filiculoides (1001) A. microphylla (4018) MH3-1, and the third of 232.14 g·tray^-1 on A. caroliniana Willd (3001). The C content in them was low at first but gradually increased later to arrive at the highest at 44.40% in the spring. The contents of N and P increased firstly to their maximum, 4.50% and 0.86%, respectively, in the summer, then decreased. The C, N and P contents of A. caroliniana Willd (3001), A. filiculoides lamarck (1001) and A. Mexicana Schlecht et cham (2002) were higher than those of the other cultivars. As the temperature varied, the ratios of C:N, C:P and N:P decreased in the beginning to their lowest values in the summer and followed by an increasing trend. The ratios varied between 7.93-18.20, 41.05-225.18 and 5.16-23.90, respectively, in different seasons. Under the experimental conditions, A. caroliniana Willd (3001) was found superior to others on yield and contents of C, N and P.