Design and set up of a plant growth chamber for stable isotope labeling to investigate carbon attraction toward fruit sinks and plant reserves upon and after drought stress

Root orchestrates the defense adaptations to drought, acting as a sink of the carbon in competition with other plant organs during growth slowdowns. We aim to study C allocation kinetics in grapevine organs in a controlled drought system basing on pulse-chasing isotopic strategy. The isotope acts as a tracer of the floematic flows that are oriented towards different sinks during drought/rehydration cycles. Photosynthetic assimilation, stomatal regulation and respiration are checked in the various phases to size 13CO2 enrichment flows in the chamber. Maximum assimilation ranges from 9 to 12 μmol m-2 s-1, reduced by stomatal control 3 o 4 times at the end of the drought period. Light responses are evaluated to optimizing chamber illumination. Saturation of net photosynthesis occurs around 1000 μmol m-2 s-1 PPFD: thereafter photoinhibition impairment starts in old leaves, whereas young leaves experience half of maximum assimilation without drastic photoinhibition. Temperature effects on photorespiration are checked and considered. A model optimizing light and temperature is proposed for plants in the various stages of the experiment. Financial support: Cassa Risparmio Torino Foundation.