Effects of nitrogen on photosynthetic characteristics of ‘Tifton85’ Bermudagrass

This study investigated the effects of different water nitrogen levels (0.05, 0.5, 1, 2.5, 5, 10, 20, or 40 mmol·L-1) on photosynthesis and fluorescence in ‘Tifton85’ (Cynodon dactylon×C. nlemfuensis) Bermudagrass in hydroponic experiments. The results showed that the leaf and stem dry weight increased, while root dry weight decreased, as the nitrogen content increased; the plant dry weight increased as nitrogen content increased, but there was no significant difference at high nitrogen levels. The plant dry weight was positively correlated with net photosynthetic rate(Pn), and Pn was positively correlated with the leaf nitrogen content. When nitrogen was lower than 5 mmol·L-1, the decrease of leaf nitrogen content induced the Gs to decrease, and eventually led to a decrease of Pn. When nitrogen was higher than 5 mmol·L-1, the Ci decreased, and then Fv/Fm and Fv/Fo both decreased, and so the increase of Pn slowed down. The above results showed that suitable nitrogen rates could improve Pn, and therefore improve the yield of ‘Tifton85’ Bermudagrass.