The Diurnal Variation of Photosynthesis of Water Hyacinth Leaves in Different Positions in Summer of Nanjing and Its Ecological Factors

In order to provide effective measures for farming and cultivation of water hyacinth in Jiangsu region,using Li-6400 portable photosynthesis system,the net photosynthetic rate(Pn) and other photosynthetic parameters of 1th,3rd and 6th leaf from artificial planting water hyacinth were selected,and then measured respectively at different times of the sunny day.Then the correlation analysis was made between the environment conditions such as air temperature and light intensity and all the photosynthetic parameters,The results were as follows: Pn of different leaf positions showed a single peak curve in a day in June,but those were a bimodal curve in July and August.Pn of all the leaves of water hyacinth were suffering a remarkable inhibition at noon during the whole summer,showing that the photosynthetic characteristics of water hyacinth is pertain to C 3 plant.At the same time,the diurnal variations of stomatal conductance(Gs) were similar to those of Pn at the similar period.The diurnal variation of Pn and Transpiration rate(Tr) were very similar in June.However, the diurnal variation between Pn and Tr was different in July and August,which showed a single peak,and the peak appeared at 15:00.The diurnal variation between Pn and Intercellular CO 2 concentration(Ci) was converse;while the Pn of leaves at different positions were of some differences,the Pn of the 6th leaf was significantly lower than that of the 1th and the 3rd leaf,while photosynthetic capacity of the 3rd leaf was the highest of the leaves,due to their different developmental stages of leaves.Correlation analysis showed that the photosynthetic performance of the plants during different months of summer was closely related to their environmental factors.