Changes in carbohydrates induced by drought and waterlogging in Castanea sativa

Key message Two months of drought or waterlogging conditions did not induce carbon starvation in Castanea sativa . Carbohydrate dynamics in treated plants provide evidence of why this species adapts well to dry but not to waterlogging conditions. Drought and flooding events, which cause water and oxygen deprivation in tree roots, are expected to occur more frequently due to climate change. The effects of drought and waterlogging on physiology, growth and N content of Castanea sativa Mill. were explored. Through a manipulative experiment, we induced growth-limiting conditions in C. sativa seedlings to identify differences in the dynamics of soluble sugars, starch and total non-structural carbohydrates (NSC) in leaves, stems and roots. Two-year-old seedlings were subjected for 2 months to regular watering, drought and waterlogging treatments. Drought and waterlogging induced similar effects on plants, including reduced stomatal conductance, net photosynthesis and growth. However, chlorophyll degradation was detected only in plants subjected to waterlogging. N content and C/N ratios differed between treatments and were highest in leaves of drought stressed plants and roots of control plants, respectively. Under drought, starch was rapidly depleted to yield soluble sugars and afterwards remained constant, and no change in total NSC was observed, probably allowing plants to reverse drought-induced xylem embolisms. Under waterlogging, a net gain of NSC over time in plant stems and roots was observed, suggesting that plants were unable to utilise them. This is the first study to report different strategies of carbon use in C. sativa trees subjected to drought and waterlogging. NSC dynamics in C. sativa plants provide evidence of why this species adapts well to dry but not to waterlogging conditions.