Hormonal changes during flowering in response to paclobutrazol application in mango cv. Alphonso under Konkan conditions

Abstract

Studies were conducted to investigate the effect of soil applied paclobutrazol (PBZ) on the hormonal composition of auxin (IAA), abscisic acid (ABA), cytokinins and gibberellins in 12 years old Alphonso mango trees during the year 2011. Paclobutrazol treatment decreased IAA contain in shoots by 4.3 and 28.2 % at 15 days before bud break and at bud break stage, respectively. Abscisic acid content in PBZ treated trees was 59.85 and 41.11 % higher in leaf and bud, respectively, as compared to untreated trees, during flowering period. Fifteen days before bud break, total cytokinin contents (zeatin, dihydrozeatin riboside, zeatin riboside, isopentenyl adenine, isopentenyl adenosine) in leaf and bud were 25.93 and 37.54 %, respectively less than untreated trees, but at bud break and 15 days after bud break it increased by 31.92 and 36.37 % in leaf and bud, respectively. Paclobutrazol treatment decreased gibberellin contents in shoots. Total gibberellin contents at bud break stage was 51.71 % less in treated trees as compared with untreated trees, while 55.58 % reduction was observed in treated trees from 15 days before bud break to bud break. While in untreated trees slight increment in total gibberellin contents was observed. These results indicated that, PBZ application though decreased gibberellin and IAA contents, but caused increases in ABA and cytokinins in mango shoots to elicit flowering responses.