Successive cycles of soil drying and wetting improve tolerance to drought in mangabeira

Ciclos sucessivos de secagem e umedecimento do solo melhoram a tolerância à seca em mangabeira

Abstract

The objective of this work was to evaluate biomass accumulation and photosynthesis in mangabeira, in response to water deficit and to successive soil drying and wetting cycles. Seedlings were grown in pots and subjected to the three following water regimes: soil at 35, 70, and 100% of field capacity (FC), followed by a drying-down period until photosynthesis (measured weekly) was close to zero. Then, the seedlings were rewatered until completing four drying-wetting cycles. The control treatment was a permanently well-irrigated soil. There was a decline in biomass accumulation under water deficit conditions. Photosynthesis responded to soil rewatering only at 70 and 100% FC and was null at 35% FC. The elapsed time for photosynthesis to reach a null value after rewatering increases with successive drying-wetting cycles. In soil at 100% FC, for photosynthesis to approach zero, it takes five weeks in the first and eight weeks in the last rewatering cycle. Photosynthesis improves with progressive drying-wetting cycles, particularly in soil at 100% FC. The pre-acclimation of mangabeira to drying-wetting cycles should be considered before transplanting the seedlings in the field, and pre-acclimation should be carried out initially with soil at its FC.

Index terms
Hancornia speciosa; photosynthesis; stomatal conductance; water deficit