Responses of photosynthetic and physiological parameters in Campsis radicans to soil moisture and light intensities
Using CIRAS-2 portable photosynthesis system, the light response process of photosynthetic and physiological parameters of three-year-old Campsis radicans leaves, such as net photosynthetic rate ( Pn), transpiration rate ( Tr), water use efficiency (WUE) and light use efficiency ( LUE ) were measured under different soil moisture conditions. Their response patterns were analyzed. Soil moisture and light intensity needed by the growth and development of Campsis radicans were selected. The results show that Pn, Tr, WUE and LUE of Campsis radicans leaves had a critical response to the level of soil moisture and the variation of photosynthetic active radiation ( PAR) . The non-rectangular hyperbola model was used to simulate light-response curve and the convexity was about 1. With the increases of mass water content of soil ( Wm, ranged from 5.5% to 19.4%) and soil relative water content ( Wr, ranged from 20.1% to 71.1%),the light compensation point was declined while light saturation point,the maximum Pn and apparent quantum yield were increased. When Wm was 19.4% , the light compensation point was at the minimum (21.61 /μmol/m2 per second) and the light saturation point was at the maximum (1 400 μmol/m2 per second) . In order to maintain the normal plant growth and have high Pn, LUE and WUE synchronously, the range of Wm was from 13.5% to 19.4% and the range of W, was from 49.5% to 71.1%. The optimum Wm and Wr were 19.4% and 71.1%, respectively. The maximum of Wm and Wr were 7.7% and 28.2 % for the normal growth of Campsis radicans , respectively. The high adaptability of Campsis radicans to light condition was founded. The high Pm, and WUE were recorded when the PAR ranged from 800 to 1 600 μmol/m2 per second and the light saturation point ranged from 800 to 1 400 μmol/m2 per second. The peak value of LUE was found when the PAR ranged from 100 to 300 μmol/m2 per second.
Campsis radicanssoil moisturephotosynthetic active radiationnet photosynthetic ratewater use efficiency
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