Changes of free polyamines in the leaves and stems of ‘Kinnow’ mandarin tree as affected by alternate bearing

In order to investigate the seasonal changes and the possible role of the free polyamines in the leaves and stems on the alternate bearing habit of the ‘Kinnow’ mandarin (Citrus reticulata Blanco) trees, a comparative study was conducted to analyze the levels of free polyamines  (putrescine, spermidine and spermine) in the leaves and stems tissues of “on” and “off” trees during the flower bud formation period.  Samples were taken from trees in one month interval period in a commercial orchard in the City of Darab, Fars Province from Nov. 2010 till Mar. 2011 according to the stages of flower bud phenology in citrus.  The experiments were designed as a randomized complete block with three replications and two trees per each replication. The experiments were designed as a randomized complete block with three replications and two trees per each replication. Total polyamines (putrescine, spermidine and spermine) levels in leaves were higher in “off” trees than in “on” trees throughout the experimental period but only the differences of spermine contents were significant during the most of season. The contents of spermidine and spermine in the stems of “off” trees were significantly higher than in “on” trees most of the season. Putrescine levels and polyamine ratio (putrescine/spermidine+spermine) in the stems were significantly higher in “on” trees than in “off” ones. Time of sampling had no significant effect on the stem total polyamines, putrescine and polyamine ratio in “off” trees. Results could not show a relationship between polyamine fluctuations in stems and leaves with processes of flower bud formation in mandarin trees.