Effects of gibberellin and gibberellin biosynthesis inhibitor (paclobutrazol) applications on radish (Raphanus sativus) taproot expansion and the presence of authentic hormones

Abstract

Radish (Raphanus sativus L), is a taproot plant that undergoes noticeable organ size modification during plant growth and development. Paclobutrazol (PBZ) inhibits gibberellin biosynthesis and stimulates the proliferation and expansion of plant root cells in growth and developmental stages. Our study aims to examine the effects of PBZ treatment on the storage organ of plant. Four treatments were applied at the pre-cortex splitting stage of "Nau-yh" radish plant. Foliar spray treatments including PBZ (50 mg/L), gibberellic acid (GA3, 150 mg/L) and a mix of GA3+PBZ (150+50 mg/L) were applied. The results revealed considerable improvement in taproot growth and decreases development in aerial parts after 48 days of the growth. Paclobutrazol treatment showed enhanced growth parameters, most notably, root weight was 33% higher than GA3 treatment, 28% higher than the control (H2O), and 23% higher than the PBZ+GA3 treatment. PBZ also significantly promoted xylem development in tuberous root of radish. In contrast, the GA3 treatment inhibited tuberous root growth and enhanced shoot growth in plants. Furthermore, mass spectrometry assay confirmed the absence of gibberellins in paclobutrazol-treated plants, whereas auxin was found in all treatments. Our study provides the first evidence on the applicability of PBZ in root size expansion of radish plant.