Photosynthetic parameters and carbon reserves of a resurrection plant Reaumuria soongorica during dehydration and rehydration

The effects of dehydration and subsequent rehydration on photosynthetic parameters and carbon reserves were investigated in the resurrection plant Reaumuria soongorica. Dehydration was imposed by withholding water and covering plants with a PVC sheet when it rained, over a period of 53 days, by which time all leaves had been shed. Thereafter, plants were watered at 7-day intervals. The diurnal course of the net photosynthetic rate (Pn) was bimodal under well-watered conditions. After a period of withholding water, the second peak disappeared, and Pn, instantaneous water use efficiency (WUE), stomatal conductance (gs) and intercellular CO₂ concentration (Ci) decreased, but sugar, starch and non-structural carbohydrate (NSC) reserves increased. It was concluded that under the conditions of high temperature and dehydration, the reduction of Pn should be mainly attributed to gs. On rehydration Pn, gs, Ci and WUE increased slightly in the stem. Accompanying new leaf production, carbon reserves in the stem decreased. This indicated that carbon reserves in the stem have two important ecological roles, survival during dormant periods and support of vegetative regrowth following rehydration.