Arsenio D. Ramos and Antonio L. Acedo, Jr.
Rejuvenation pruning has been proven effective in bringing back vigor and productivity of old coffee trees. The effectiveness of the present rejuvenation techniques however could be probably enhanced by the application of tree growth regulators with known reinvigorating or tree health enhancing effect such as Paclobutrazol but has not been tried so far. The present study aimed to evaluate some physiological and biochemical responses of the rejuvenated coffee trees to timing and level of PBZ application prior to cutting.
Plants applied with PBZ 2 months prior to pruning had higher leaf internal CO concentration compared to those applied 1 month prior to 2 pruning. Net photosynthesis, transpiration rate, PAR/LAI, chlorophyll content, and leaf N, P, K, Ca and Mg contents did not differ with time of PBZ treatment. Application of 0.5-1.0 g a.i. PBZ per meter canopy span significantly increased transpiration rate, internal COconcentration and 2 chlorophyll content but did not affect the rate of photosynthesis, PAR/LAI, leaf N, P, K, Ca and Mg contents.
Keywords: rejuvenation pruning, Paclobutrazol, growth retardant, physiological and biochemical responses