Paclobutrazol, Root Growth, Hydraulic Conductivity, and Nutrient Uptake of `Nemaguard' Peach

Abstract

Paclobutrazol (PBZ) was supplied in nutrient solution culture to `Nemaguard' peach rootstock [Prunus persica × P. davidiana] at concentrations of 0, 0.001, 0.01, 0.1, and 1.0 mg·liter -1 . PBZ increased root: shoot ratio and decreased root length by ≈ 5-fold over the range of PBZ concentrations tested. Root tip diameter, stele diameter, and width of the root cortex were not significantly affected by PBZ. Root hydraulic conductivity decreased log-linearly with increasing PBZ concentration; however, this decrease did not affect midday leaf conductance or net photosynthetic rate. Foliar levels of N, P, K, Fe, and Mo were reduced, whereas levels of Ca, Mg, B, and Mn were increased by PBZ. The magnitude of changes in foliar nutrition were proportional to the degree of growth suppression. Chemical name used: (2RS,3RS)-l-(4- chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)pentan-3-ol (paclobutrazol).