The river valleys in Yunnan Province are characterized by a hot-dry climate because of the rain-shadow effect of mountains and host a valley-type savanna. Few studies have been carried out on the ecological adaptation of plants from Chinese savannas. Photosynthetic thermotolerance (PT) is important for plant survival and associated withecological adaptations of plants in tropical and sub-tropical savannas
Prof. Cao Kunfang and his team of Xishuangbanna Tropical Botanical Garden (XTBG) carried out a study in a valley savanna (23041′N, 101059’E, altitude 770 m) of the Yuanjiang River (the upper Red River). They evaluated the photosynthetic thermotolerance (PT) and associated leaf traits (leaf life span, leaf mass per unit area (LMA) and foliar Ca concentration [Ca]) of 24 woody savanna species (representing about 80 % of the savanna woody flora in this county) from south-west China.
They hypothesized that (1) species with leaf flushing in the hot-dry season show greater PT than those with leaf flushing in the rainy season; and (2) PT correlates positively with leaf life span, LMA and [Ca].
Their study found that the PT of the woody savanna species with leaf flushing in the hot-dry season was greater than that of those with leaf flushing in the rainy season. Thermotolerance was positively associated with leaf life span and [Ca] for all species irrespective of the time of flushing. The associations of PT with leaf life span and [Ca] were evolutionarily correlated. Thermotolerance was, however, independent of LMA.
Their results suggest that woody species from Chinese savannas are adapted to hot-dry habitats. This is the first time that PT has been shown to be associated with earlier leaf emergence, persistence (longer leaf life span) and increased Ca concentration across a large number of woody savanna species.
The study entitled “Photosynthetic thermotolerance of woody savanna species in China is correlated with leaf life span” has been published in Annals of Botany, 110 (5): 1027-1033, doi: 10.1093/aob/mcs172
