COS 50-1
A global analysis of the concentration and dynamics of non-structural carbohydrates in plants: does it matter under global change?
Forests store significant amounts of C globally. Evidence points to increasing climate-change induced drought as a primary driver of recent tree and forest mortality, thus generating an urgent need to predict how forests will cope with increasing stress. Although plants store non-structural carbon (NSC) to buffer against times of carbon deficit, the role and regulation of NSC remains unclear. For instance, there is a strong debate on how abundant NSC pools in woody plants build up over time. NSC accumulation may simply reflect excess carbon supply via photosynthesis relative to demand. Stored NSC, however, may serve multiple critical functions, in which case plants should tightly regulate it to prevent excessive depletion. Over evolutionary scales, such regulation may occur both at the supply (photosynthesis) and demand (e.g. growth) end. Here, we assembled a new global database to examine broad patterns of seasonal NSC variation across organs, life forms and biomes. We compiled seasonal data (at least three measurements over a minimum of four months) for ca. 200 wild species under natural conditions. Our goal is to examine broad patterns of variation to help us elucidate the potential role and regulation of NSC.
Results/Conclusions
On average, NSC account for ca. 6-10% of dry plant biomass. NSC and starch concentrations do not vary significantly with biome, but plants from Mediterranean biomes have higher soluble sugars (SS) relative to plants from temperate or tropical biomes. On average, seasonal NSC minimums are high (above 50% of the average). NSC, starch and SS vary strongly seasonally. In temperate and boreal biomes there is a strong depletion of SS during the growing season followed by an increase during winter months. In Mediterranean biomes, the strongest high SS peak occurs during the dry period. Importantly, with the exception of tropical biomes, the decrease of SS during the growing season is generally accompanied with increases in starch (especially in stems and leaves) despite constant or even decreasing NSC concentrations. These results suggest that plants maintain or accumulate starch during the growing season, even under high growth demand. Our results tentatively suggest that, on a seasonal basis, plants put aside storage C compounds while growing. Our results are also consistent with an important role of NSC in osmotic regulation to cope with winter cold and summer drought.