Fruit size is a key parameter for quality and increases the profitability for export markets in citrus production in Turkey. Fruit size can be enhanced by several techniques such as girdling and thinning. Various plant growth regulators are known to affect the growth and size of citrus fruit. Thus the effects of synthetic auxin applications (2,4-DP and 3,5,6-TPA) at different physiological periods, girdling practices, pruning practices, foliar application of potassium and various combinations of these practices on the fruit size and yield, fruit retention rate, and leaf chlorophyll concentration and fluorescence of Star Ruby grapefruit cultivar were investigated.

As a result of pomological observations, treatments had different effects on fruit size and yield. The highest yield per tree were determined in Maxim (3,5,6-TPA) and Citrimax (2,4-DP) (605.33 and 601.83 kg/tree) treatments. The highest fruit diameter was determined from foliar spray of K (83.25 mm) on leafs whereas the lowest was obtained from control samples with 78.96 mm. The highest leaf chlorophyll concentration was determined in the leaf treated with foliar spray of K.

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Turgut Yesiloglu, Salih Koc, Berken Cimen
Fresenius Environmental Bulletin