Photochemical activity in Dalbergia nigra (Vell.) Fr. Allem. seedlings submitted to water deficit

Abstract

In this study, we evaluated the influence of the daily variation of both intensity of photosynthetically active radiation (PAR) and temperature on chlorophyll a fluorescence parameters in Jacarandá-da-Bahia seedlings submitted to two treatments: T1 (control) and T2 (water deficit during seven days). It was used seedling with approximately 90 days old cultivated in plastic pots contend soil. After 45 days of acclimation, the treatments were applied. In T2, the water deficit was applied by total suspension of irrigation. The physiological evaluations were made a long of the day (from 6 a.m. to 6 p.m.). The water deficit caused a significant reduction of the maximal fluorescence and in area below the fluorescence curve. Furthermore, the water deficit improved the effects of the high temperature and PAR on the energetic connectivity (or grouping between photosystem II units) and of oxygen-evolving complex (OEC) stability, evidenced by the high and positive values of L-band and K-band in those daytimes with higher incidence. Finally, the effects of water deficit were more evident on the OEC stability.