Changes of phenolic compounds and non-structural carbohydrates on alternate bearing cycle in ‘Kinnow’ mandarin trees

In this study we have demonstrated the variations of carbohydrates and phenolic compounds present in the leaves and stems of ‘Kinnow’ mandarin (Citrus reticulata Blanco) trees in alternate bearing cycle and the possible involvement of these compounds to flower bud formation process. The amounts of these compounds were determined in the leaves and stems of “on” and “off” trees  monthly  from Nov. 2010 until Mar. 2011 coinciding with citrus trees floral bud induction and differentiation in northern hemisphere. The experiments were designed as a randomized complete block with three replications and two trees per each replication. Results showed that the presence of fruits on “on” trees inhibited flower bud formation, decreased total sprouted buds and resulted in the reduction of vegetative growth of these trees. The endogenous levels of soluble sugars and total non-structural carbohydrates in leaves and the starch contents of stems were affected by fruiting state of trees. Variations of total phenol contents in the leaves and stems related to presence or absence of fruits on trees. The phenolic contents of the stems were significantly lower in non-bearing trees than in fruit-bearing ones. Among the five phenolic compounds analyzed, the pattern of changes in the contents of chlorogenic acid, caffeic acid and naringin were different in two types of trees. Similar trend was observed for the amounts of all phenolic compounds in the stems of bearing and non-bearing tress.