Photosynthetic regulation of C₄ desert plant Haloxylon ammodendron under drought stress

• Published in: Plant growth regulation 2007-02, Vol.51 (2), p.139-147
• Main Authors: Su, Peixi, Cheng, Guodong, Yan, Qiaodi, Liu, Xinmin
• Format: Article
• Language: English
• Subjects: Arid environments; Assimilation; Desert plant; Desert plants; Drought; Humidity; Moisture content; Photochemical efficiency; Photochemicals; photoinhibition; Photosynthesis down regulation; Soil moisture; Soil water; Solar energy; water stress
• ISSN: 0167-6903; 1573-5087
• DOI: 10.1007/s10725-006-9156-9

About 20-year-old desert plants of C₄ species, Haloxylon ammodendron, growing at the southern edge of the Badain Jaran Desert in China, were selected to study the photosynthetic characteristics and changes in chlorophyll fluorescence when plants were subject to a normal arid environment (AE), moist atmospheric conditions during post-rain (PR), and the artificial supplement of soil water (SW). Results showed that under high radiation, in the AE, the species down-regulated its net assimilation rate (A) and maximum photochemical efficiency of PS II (Fv/Fm), indicating photoinhibition. However, under the PR and SW environments, A was up-regulated, with a unimodal diurnal course of A and a small diurnal change in Fv/Fm, suggesting no photoinhibition. When the air humidity or SW content was increased, the light compensation points were reduced; light saturation points were enhanced; while light saturated rate of CO₂ assimilation (A max) and apparent quantum yield of CO₂ assimilation (ΦC) increased. ΦC was higher while the A max was reduced under PR relative to the SW treatment. It was concluded that under high-radiation conditions drought stress causes photoinhibition of H. ammodendron. Increasing air humidity or soil moisture content can reduce photoinhibition and increase the efficiency of solar energy use.