No abstract

Fruit splitting in the mandarin orange cultivar 'Nova' is related to the presence of an open stylar end in the fruit. This opening arises from a cavity present at the bas e of the style, and is formed in a variable proportion of fruits. The cells at the bottom of this style cavity form a rind-like tissue which develop into a navel structure. The size of this navel is larger in open-stylar end bearing fruits and, accordingly, in split fruit. The number of split fruit per tree is unrelated to the number of fruit set. The application of gibberellic acid ( GA 3 ) has a variable effect on set and splitting depending on its timing. This hormone increases fruit splitting when applied at flowering, but reduces it when applied shortly after the end of the June drop. It has only a minor effect on fruit set.

The anatomy of the fruit has been compared in three prone-to-split mandarin hybrids (Nova, Ellendale and Murcott), several cultivars of clementine mandarin (Fino, Clementina de Nules and Orogrande), and in Owari satsuma mandarin. The fruit of the hybrids is oblate to subglobose and usually presents an open stylar end disrupted by a navel formed by the ¯oral meristem, which is conserved near the apex of the fruit. In the non-prone-to-split clementines as well as in Owari satsuma, the ¯oral axis protrudes inside the style, and the ¯ower meristem is lost through abscission shortly after petal fall. The abaxial side of the carpels fuses with the ¯ower axis forming at the stylar end of the fruit a solid tissue which externally has a small scar at the place of style abscission. Most of the fruits in these cultivars have no navel. In addition, the fruit of clementine is slightly oblate or globose. The relevance of these anatomical characteristics as regards to splitting is supported by the differences between the split and non-split fruits in Nova, the split fruit being more oblate in shape and having a bigger navel than non-split fruit. However, the effect of applied growth regulators on fruit splitting could not be correlated with their effect on the anatomy of the fruit. Additional factors not contemplated in the study also in¯uence fruit splitting.

No abstract

A winter gibberellic acid (GA3) spray consistently reduced flower formation, but had a variable effect on the amount of first-grade fruit in the early harvest of `Clausellina' satsuma (Citrus unshiu Marc.), and in the long term these applications had no significant effect on the value of the crop. Auxin applications increased the amount of first grade-early harvested fruit, and increased crop value as compared to hand-thinned trees. No significant differences in yield or fruit grade could be found among the different auxin applications tried, namely an application of 20 mg·L-1 2,4-dichlorophenoxyacetic acid (2,4-D) at flowering, or applications of 25 mg·L-1 naphthaleneacetic acid (NAA), or 50 mg·L-1 2,4-dicholorophenoxypropionic acid (2,4-DP) at the end of fruitlet abscission. Apart from their effect on size, the auxin applications had only a marginal effect on fruit quality.