Girdling effects on fruit set and quantum yield efficiency of PSII in two Citrus cultivars
Girdling effects on fruitlet abscission, leaf chlorophyll, chlorophyll a fluorescence and carbohydrate concentration in various flowering and vegetative shoots were studied during natural fruit drop in two Citrus cultivars. Irrespective of shoot type, girdling delayed fruitlet abscission, but only fruitlets borne on leafy shoots had increased final fruit set. Chlorophyll a fluorescence analysis revealed differences in quantum yield efficiency of photosystem II of light adapted leaves (ΦPSII) among shoot types and in response to girdling. In young leaves of vegetative shoots, girdling decreased ΦPSII, whereas ΦPSII increased from Day 30 after girdling in young leaves of leafy flowering shoots; however,ΦPSII did not change in mature leaves during fruit set in either control or girdled trees.