Changes in leaf water potential and photosynthesis of Bauhinia forficata Link under water deficit and after rehydration

To evaluate the influence of different intensities of water deficit and rehydration on water relations and gas exchanges of Bauhinia forficata Link, plants were grown in a greenhouse for three months under the following water regimes: daily watered (control) and watered every 7 (7D) and 15 days (15D) returning to daily watering on 7D and 15D treatments at 75 days of the experiment. Aiming to evaluate short-term responses to re-hydration, plants of 7D and 15D treatments were re-watered 2 days before measurements and sampling was carried out at the 45th day of experiment. At fortnightly intervals (15, 30, 45, 60, 75, and 90 days) soil moisture (Usoil), leaf water potential (Ψwf), photosynthesis in response to photosynthetically active radiation (A × PPFD) to obtain the maximum net photosynthesis (Amax), and light saturation point (PARsat) were evaluated. The water deficit has affected water relations and photosynthesis with the lowest values observed in the treatments Usoil 7D, and 15D respectively, coinciding with the lowest Ψwf and Amax. Changes in PARsat in response to water deficit were observed showing mean values of 665, 275 and 254 µmol photons m-2 s-1 in control, 7D and 15D respectively. The return of daily watering after 75 days of experiment, promoted the recovery of Amax (7.8 and 9.6 µmol CO2 m-2 s-1) and PARsat (588 and 643 µmol photons m-2 s-1) in 7D and 15D respectively with values higher than control plants (4.7 µmol CO2 m-2 s-1 and 631 µmol photons m-2 s-1), suggesting a strong dependence of photosynthesis of Bauhinia forficata to the soil water availability.