Sensitivity of Peach Seedling Vegetative Growth to Paclobutrazol

Abstract

‘Nemaguard’ peach seedlings [Prunus persica (L.) Batsch] were grown for 21 days in nutrient solution cultures containing a range (0 to 3.4 μM) of paclobutrazol concentrations. Shoot growth rate and total extension growth were reduced by all paclobutrazol treatments. Within 2 days of treatment, paclobutrazol at 3.4 μM significantly reduced the growth rate, as did the 3.4 × 10−2 μM concentrations after 5 days. Increases in paclobutrazol concentrations decreased leaf area and leaf, stem, and shoot weights. However, specific leaf weight increased as paclobutrazol concentration increased. Leaf expansion was more sensitive to paclobutrazol treatments than stem elongation. As paclobutrazol concentration increased, root extension growth was reduced, but roots were thicker and produced more laterals near the tip. Compared with the control, paclobutrazol at 3.4 × 10−1 and 3.4 × 10−2 μM significantly increased the root: shoot ratio. Chemical name used: β-[(4-chIorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

Paclobutrazol and Root Zone Water Content Influence Peach Seedling Behavior

“…The details of PBZ treatment on plant fresh and dry weight response and leaf number were similar to that reported by others (Early and Martin, 1988;Steffens et al, 1983) and mirrored what might be expected from plants shorter than controls (data not shown). PBZ treatment at 100% FC resulted in the greatest growth restriction compared to control growth at 100% FC (Fig.…”

“…The smaller, PBZ-treated plants, with proportionally greater root : shoot ratios than controls, used less water at Davis and Bologna. The root systems resulting from PBZ treatment were more branched, with larger root diameter, as also reported by others (Atkinson, 1986;Williamson et al, 1986;Early and Martin, 1988). These root-zone features resulting from PBZtreatment should place a greater proportion of the roots in contact with the soil.…”

“…1). In agreement with Early and Martin (1988), shoot growth was restricted more by PBZ than was root growth. This feature of PBZ response may be important in water use features.…”

“…Controls at 100% FC in Davis contained a leaf area of 713 and Bologna 300 cm2; whereas PBZ treatment significantly reduced leaf area (135 and 99 cm2, respectively). Early and Martin (1988) showed a steady decline in peach leaf area as PBZ concentration increased.…”