Inducing Flushing in Citrus Cultivars and Changes in Polyphenols Associated With Bud Break and Flowering

Abstract

The presence of leaves in citrus inhibit axillary bud break which were released, in several citrus cultivars, as soon as leaves were removed. Since even the presence of small petiole alone was as effective in inhibiting bud growth in Satsuma trees as the whole leaf, this indicates that the supply of sugars or photosynthesis play little role in regulating bud break in Owari Satsuma trees. It appears that physical injury through complete defoliation may trigger hormonal stimulation that in turn initiates the metabolic processes leading to bud break. Majority of bud break from defoliation developed vegetative growth, but, as anticipated, chilling treatment in defoliated plants resulted in majority of buds breaking into flowers. Since differentiation of buds into vegetative or reproductive structures occur in the absence of leaves it indicates that in grapefruit, and possibly other citrus cultivars, metabolic processes leading to flowering occur within the resting bud tissue. Changes in the levels of specific polyphenols occur when buds begin to sprout as vegetative shoot, marked by increase in chlorogenic acid and naringenin levels. When buds develop into reproductive structures then such developmental change accompany dramatic rise in the levels of hesperidin, naringenin, and Apigenin-7-glucoside. In general, the results clearly show a strong inhibition of axillary bud sprouting even with the presence of a small portion of the leaf. Very distinct changes in the levels of specific polyphenols were associated with bud sprouting to vegetative shoot and when it develops into flower.