Seasonal variations in gas exchange and chlorophyll fluorescence in the leaves of five mango cultivars in southern Yunnan, China

Southern Yunnan Province marks the northern border of the East Asian tropics and is one of the major areas for growing mango (Mangifera indica L.) and other tropical crops in China. Here, daily temperatures in Winter (cold dry season,) are 8 degrees - 10 degrees C lower than in the hot - dry and hot - wet seasons. Moreover, cold winds occasionally affect the region, causing injury to mango and other tropical fruit trees. Hence, there is a need to select and breed cold-tolerant mango cultivars to be grown here. To compare the physiological sensitivity of mango cultivars to lower temperatures in Winter, we measured gas exchange, chlorophyll fluorescence, lipid peroxidation, and membrane leakage in five mango cultivars in three distinct seasons between 2004 and 2005. Maximum net CO2 assimilation (A(max)) was high and varied little among the five cultivars [17 - 18 mu mol CO2 m(-2) s(-1)] in the hot - wet season. Amax and photochemistry were significantly reduced in all cultivars in the cold - dry season, with increases in malondialdehyde content, membrane leakage, and non-photochemical quenching, with a carry-over effect into the subsequent hot - dry season. These physiological changes were greater in the cultivars 'Zill' and 'Tainong' than in 'Guire7','Hong-Xiangya', and 'Choke Anand', with sustained photo-inhibition in the cold - dry season found only in the two former cultivars. Our results show that photosynthesis in mango in Southern Yunnan can be strongly suppressed in the cold - dry season, and that the cultivars 'Guire7', 'Hong-Xiangya' and 'Choke Anand' are more cold - tolerant than 'Zill' and 'Tainong'.