Comparative study on photosynthetic characteristics responses of 5 garden shrubs under NaCl stress

Five garden shrubs commonly used in Southern China coastal areas were selected as research materials, including Thevetia peruviana, Pittosporum tobira, Duranta repens, Hibiscus rosa-sinensis and Lantana montevidensis. Different gradients of salt content from 100 mmol/kg and 300 mmol/kg were applied in the planted soil, to analyze the changes in photosynthesis and chlorophyll fluorescence dynamics index in different stress duriation for 20 d and 40 d. With the prolongation of salt stress time, the Pn, Gs and Ci of the 5 shrubs decreased gradually, and further strengthened with the increase of stress concentration. The NPQ and Y（NO）of 5 shrubs increased gradually, and were further strengthened with the increasing trend of stress concentration. Under the stress of 100 mmol/kg concentration, the Tr decreased with the increase of time gradually. Under the stress of 300 mmol/kg, the Y（NO）of Duranta repens increased first, and the other shrubs decreased gradually. The Y（Ⅱ）of Lantana montevidensis decreased and the other shrubs decreased gradually, and the Y（Ⅱ）of 5 shrubs decreased gradually under the concentration of 300 mmol/kg. The results showed that the salt tolerance of these 5 shrubs was: Thevetia peruviana＞ Pittosporum tobira ＞Hibiscus rosa-sinensis＞ Lantana montevidensis＞Duranta repens.