Paclobutrazol induced growth retardation of mango seedlings

Mango seedlings of polyembryonic cv. Bappakai were given soil-drenching treatment of paclobutrazol (PBZ) at 0, 0.34, 0.85 or 1.71 mM. Observations were recorded on morphological characters at weekly interval and on leaf water potential (Ψ_w) and levels of chlorophyll, total phenols and endogenous plant growth substances [ABA, cytokinins (t-ZR and DHZR) and IAA] at a monthly interval one month after PBZ treatment. There was reduction in seedling vigour after 2 months of PBZ treatment, the effect being more prominent at 1.71 mM. The fresh weights of root, leaves and stem also showed reduction. The Ψ_w was less negative and total phenols and chlorophyll content showed increase in response to PBZ application. The contents of leaf ABA and cytokinins (t-ZRand DHZR) were higher in treated seedlings. Thus it was suggested that PBZ induced growth retardation in mango seedlings is associated with increased levels of ABA and cytokinins together with higher Ψ_w and phenols in leaves.