Differential Assimilation of Nutrients and Plant Vigor in Paclobutrazol and Ethephon Treated Guava (Psidium guajava L.) Trees

The guava (Psidium guajava L.) trees of cv. ‘L-49’ were sprayed with an inhibitor of gibberellin bio-synthesis, paclobutrazol (PBZ)[(2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)pentan-3ol] and a growth inhibitor and ripening hormone, ethephon [(2-chloroethyl) phosphonic acid]@ 500 ppm and 1000 ppm each during March (2007 and 2008) to examine the effect on foliar nutrient assimilation. Both chemicals, particularly PBZ significantly restricted the plant growth and improved the N, P, Zn and Fe assimilation. However, leaf K concentration was reduced with PBZ treatments. The foliar concentration of N, P and Zn improved immediately after fruit harvest. However, concentration of leaf K decreased and leaf Fe content remained unchanged immediately after fruit harvest. Although, nutrient assimilation was registered significantly higher in all treated plants, the influence of paclobutrazol, particularly 1000ppm application markedly increased the nutrient assimilation and restricted the tree growth.