Inhibition of flowering in vivo by existing fruits and applied growth regulators in Citrus unshiu

Abstract

In the Satsuma mandarin (Citrus unshiu Marc.) the presence of the fruit results in a gradual inhibition of flowering and of bud sprouting. This inhibitory effect starts several months before the onset of the winter rest period and lasts until the end of the accumulation of carotenoids in the fruit peel, more than one month after the completion of fruit growth. During all this time and until natural bud sprouting, flowering and bud sprouting are inhibited by exogenous gibberellic acid. Peak responses to this growth regulator coincide with periods of maximal rates of flowering inhibition by the fruit. Kinetin and abscisic acid, applied at the time of peak response to gibberellic acid, inhibited flowering and reduced the number of shoots developed through the reduction of the number of shoots formed per sprouted node, but failed to reduce the number of nodes which sprouted. The same pattern of sprouting was obtained in trees treated with gibberellic acid during the winter rest period or several months earlier. It is concluded that some step leading to flowering and which determines the differences in sensitivity of the buds to this growth regulator has taken place already at this early date.

Regulation of Floral Induction in Citrus

“…In satsuma mandarin, the presence of fruit on the tree results in a gradual inhibition of floral induction. Early thinning of fruit increases flower number in the following spring (Garcia-Luis et al, 1986;Iwasaki, 1959;Okuda et al, 1996) and the number of fruit on the tree is negatively correlated with flower number in the following year (Nishikawa et al, 2012).…”

“…In citrus, GA inhibits both floral induction and evocation (Garcia-Luis et al, 1986;Goldschmidt et al, 1985;Inoue, 1990a;Monselize and Halevy, 1964). Inhibitors of GA biosynthesis have been demonstrated to promote flowering (Monselize and Halevy, 1964;Ogata et al, 1995).…”

Physiology of citrus fruiting

“…The probability of fruit set, represented as a downward arrow, is inversely related to the number of flowers within the shoot. PHYSIOLOGY OF CITRUS FRUITING shortage that provokes the presence of fruit and/or to the release of signaling compounds, mainly gibberellins from the ripe fruits (Monselise, 1985;Garcia-Luis et al, 1986;Erner, 1988;Koshita et al, 1999).…”

The Effect of the Time of Fruit Harvest on Flower Formation and Carbohydrate Contents in Shoots of Wase Satsuma Mandarin Trees

“…In these trees, the flower induction seemed to be retarded in comparison with the summer shoots flushed after fruit removal and pruning in July. The presence of fruit load largely reduces flower formation in citrus trees (Garcia-Luis et al, 1986;Valiente and Albrigo, 2004), so that the flowering response to the low temperature is more marked for buds of defruited trees (Garcia-Luis and Kanduser, 1995).…”

“…Flower induction in satsuma mandarin trees occurs in response to low temperature (Garcia-Luis et al, 1992;Inoue, 1990). The most important period for the flower induction is about mid-November, as the number of flowers in the following spring is markedly decreased by defoliation, and increased by ringing or defruiting before mid-November (Agusti et al, 1992;Garcia-Luis et al, 1986;Iwahori et al, 1990;Iwasaki, 1959). However, the effects of fruit load and harvest timing on the progression of flower formation from harvest to the following spring have not been sufficiently explored.…”