Effect of 2,4-D on Growth, Yield and Quality of Wax Apple (Syzygium samarangense, (Blume) Merrill & L.M. Perry cv. Jambu Madu) Fruits

In this study, we investigated the effects of 2,4-Dichlorophenoxy acetic acid (2,4-D) treatment on selected physiological parameters and fruit quality of wax apple fruits under field conditions.Foliar spray of 2,4-D at 0, 5, 10 and 20 mg L -1 concentrations were used from bud stage to the 3rd week of fruit development.Physiological parameters determined included net photosynthesis, stomatal conductivity, chlorophyll content and chlorophyll fluorescence.Net photosynthetic rate and photosynthetic efficiency via chlorophyll fluorescence significantly (p≤0.05)increased with 5 and 10 mg L -1 2, 4-D treatments.Furthermore, 5 mg L -1 2,4-D reduced bud and fruit drop, increased fruit weight and dry matter content in leaves.An improved fruit set, enhanced fruit growth, faster color development and advanced maturity were also recorded in treated plants.In addition, fruit yield increased by 39 and 48% with 5 and 10 mg L -1 2,4-D treatments, respectively.Fruit K + content, total sugar, protein content and chalcone synthase (CHS) activities increased with 2,4-D treatments.Increased leaf soluble protein and elevated sucrose phosphate synthase (SPS) activity were also observed in 5 mg L -1 treated plants.Positive correlation between photosynthesis rate and SPS activity of leaves (R 2 =0.98) and between CHS activity and color development of fruits (R 2 =0.98) were recorded in 5 mg L -1 treatments.The results also suggested that 5 and 10 mg L -1 2,4-D treatments are promising for enhancing plant productivity and fruit quality in wax apple trees under field conditions.