Prevention of natural flowering in pineapple (Ananas comosus) by shading and urea application

Abstract

The year-round production of pineapple (Ananas comosus var. comosus) is often interrupted by natural flowering during winter in Taiwan. A stable and promising technique for preventing natural flowering is required. In this study, we have tested the effect of shading and urea application on the flowering of pineapple. Shading 90% of sun light(s) before mid-November delayed the natural flowering of pineapple and the delay was affected by the plant age. For pineapples planted less than 11 month before mid-November, applying 1% urea plus shading treatment (SN) completely inhibited natural flowering. All the flowering-inhibited plants could be forced to flower by applying calcium carbide. Long-term shading might result in a decreased number of fruitlets within a fruit. However, 6 weeks of recovery before forcing flowering was sufficient for plants to produce fruits with quality equal to that of the control plants. In winter, pineapple plants that were prone to flowering tended to accumulate more leaf starch and increase their C/N ratio. The SN treatment increased the leaf nitrogen concentration and thus effectively maintained a low leaf C/N ratio. Furthermore, flowering-inhibited plants exhibited a constantly low level of leaf starch during the winter and their flowering forced by calcium carbide did not accompany with leaf starch accumulation.