Non-structural carbohydrate (NSC), mainly soluble sugar and starch, is the greatest fraction of the mobile carbon pool in plants, and acts as a buffer for insufficient source activity under stress. It is important to quantify the change of NSC in a day as an indicator of environmental stress.

However, NSC dynamics under drought and the response mechanisms of NSC to drought remain unclear, especially in water-limited savanna ecosystems. 

Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences conducted a precipitation exclusion (PE) experiment to stimulate different drought intensities in a savanna ecosystem in Yuanjiang valley in SW China.  

They chose three dominant species of the Chinese savanna ecosystem, Lannea coromandelica, Polyalthia cerasoides and Heteropogon contortus to examine the influence of drought on NSC variation across the growing season. 

The precipitation exclusion experiment revealed that drought inhibited the growth of three dominant species in the Yuanjiang savanna ecosystem. The NSC in both organs of all three dominant species showed no obvious variation throughout the growing season under two PE treatments, whereas the diurnal change of NSC in the leaves of all three species increased under PE treatments. 

They also suggested that the carbon balance in plants in stressful environments may depend not only on carbon reserves but also on the relative change in NSC. 

Thus, relative change in NSC is a more sensitive and effective indicator than carbon reserves in evaluation of plant carbon balance. 

The study entitled "Carbohydrate dynamics of three dominant species in a Chinese savanna under precipitation exclusion" has been published in Tree Physiology.