Growth and Development of Young ‘Loring’ Peach Trees after Foliar Sprays of Paclobutrazol and GA3

Abstract

Abstract Container-grown ‘Loring’/Lovell seedling peach trees [Prunus persica (L.) Batsch] trained to four current-season extension shoots (ES) were treated with 60, 240, or 960 mg of foliar-applied paclobutrazol (PBZ)/liter 8 weeks after shoot growth began, followed 2 weeks later by a 50-mg spray of gibberellic acid (GA3)/liter. PBZ reduced both the post-treatment increment in trunk cross-sectional area (𝚫TCA) and current-season shoot length (𝚫ES) by up to 26% and 43%, respectively, as compared to control. GA3 increased 𝚫TCA by 45% and stimulated an increase in 𝚫ES, especially on the trees treated with PBZ at 0 and 60 mg·liter-1. PBZ had reduced the total length of lateral shoots (LS) developing on the ES by up to 48% and 38% as compared to control by 2 and 14 weeks, respectively, after PBZ application. However, the GA3 application increased the total LS length by 38%. The ES positioned at the two most basal locations on the tree trunk produced a 31% increase in LS length per ES, but there was no interaction between ES location and PBZ or GA3 influence on the final growth parameters. Total plant dry weight and root: shoot ratio were not affected by PBZ, but GA3 increased plant dry weight 38% and decreased the root: shoot ratio. Chemical name used: β -[(4-chlorophenyl) methyl]- α-(1,1-dimethylethyl)-l-H-l,2,4-triazole-1-ethanol (paclobutrazol).