Effect of water stress on citrus photosynthetic characteristics
2012
Xie, Shenxi | Liu, Qiang | Xiongk Xingyao | Lovatt, C.J.
In south China, rainfall is unequally distributed in different seasons; therefore, water deficit is one of the serious environmental stresses that affect citrus growth, fruit production and quality. It is important for citrus production to understand the relationship between water stress and photosynthetic characteristics. In this research, effect of water stress on citrus photosynthesis characteristics was systematically studied using Yamasitaka, Newhall orange and Sha-tian pomelo as materials Chlorophyll content of citrus was significantly decreased by water stress. There was a positive relationship between relative water content of soil and the volume of chlorophyll a and chlorophyll b. Compared with chlorophyll b, chlorophyll a was more easily damaged by water stress. Under the greatest drought stress treatment, 20% of field capacity (FC), the net photosynthetic rates (Pn) of Sha-tian pomelo, Newhall orange, Yamasitaka were 3.44, 1.21, and 1.47 µmol m-2 s-1, respectively, which were decreased over 90% compared with the well-watered control. There were positive relationships between relative water content of soil, Pn, Transpiration rate (Tr), stomatal conductance (Gs). Under well water conditions, the diurnal variation of Pn of Sha-tian pomelo, Yamasitaka and Newhall orange had bimodal curve, but the value and apparent time of peak rates differed among three cultivars. There was an obvious "noon break" or midday depression phenomenon. Under water stress, the diurnal Pn of Sha-tian pomelo had one peak while Yamasitaka, Newhall orange had present two peaks. The diurnal Pn of Yamasitaka was bimodal curve, under well water, 60 and 40% FC treatments. However under 20% FC treatment, Yamasitaka had a single curve.
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