Drought Stress Induces Flowering and Enhances Carbohydrate Accumulation in Averrhoa Carambola

Star fruit (Averrhoa carambola) is an important fruit tree in tropical and subtropical Asia. The tree blooms several times and fruits accordingly within one year. Controlling the flowering time and understanding the physiological mechanism of the induction of floral buds in A. carambola are indispensable to the industry. In this study, A. carambola potted trees were subjected to drought stress in a growth chamber. To avoid excessive drought stress and leaf abscission, trees were watered every 7 d and were sprayed with water every 2 d. The flowering rate was recorded, and the carbohydrate contents of the leaves, phloem, and xylem tissues were determined during the treatment and after re-watering. The results showed that drought stress increased the flowering rate in both drooping and water shoots, increased the relative conductivity, decreased the relative water content (RWC) of leaves. The total soluble sugar, sucrose, fructose, and glucose in leaves of the drooping shoots were increased. The starch contents in the xylem of both drooping and water shoots were also increased by the treatment. The results indicated that drought stress enhances carbohydrate accumulation in A. carambola. This study provides a potential way by water control to induce flowering without chemical in A. carambola.