Carbohydrate cycling in relation to shoot growth, floral initiation and development and yield in the avocado

Abstract Carbohydrate levels, shoot growth, floral initiation and yield were studied in 10 avocado trees of the cultivar ‘Fuerte’ over 2 years from March 1976 to April 1978. There were two main vegetative growth flushes per year, one in spring and one in summer. Floral initiation occurred in autumn, flowering was in late winter/spring and the fruit matured in winter. Thus one vegetative flush coincided with the end of flowering and the other occurred just prior to floral initiation. Carbohydrate levels were lowest after the summer vegetative flush and just prior to floral initiation in autumn. Levels increased over winter during the period of floral development and reached maximum levels in early spring, just prior to flowering. A steep decrease in carbohydrate levels, particularly starch, occurred during flowering, shoot growth and fruit development. The trees showed a marked biennial bearing cycle. The heavy yield in 1977 followed high levels of starch during the previous year and resulted in much lower levels being accumulated during the following winter and spring. The yields in 1976 and 1978 were low. Biennial bearing appeared to be closely related to the carbohydrate reserves of the trees.