Nutrition 83
Ghanta et al. (1992) conducted an experiment to study the effect of foliar applica-
tion of micronutrients, namely, B (0.1%), Mn (0.25%) and Cu (0.25%) applied singly
and in combination at 2 and 3 months after transplanting on growth, flowering, yield
and quality of papaya cv. Ranchi. All the micronutrients significantly increased the
growth of plant, numbers of leaves produced per plant and length of petiole (5th leaf).
Application of the micronutrients hastened flowering by 2–10 days. Combined appli-
cation of Mn and Ca produced the highest yield, 97.44 t/ha compared with 67.01 t/ha
in control. All the micronutrients increased individual fruit weight, fruit size and
pulp thickness of fruit and reduced the seed content of fruit. Combined spraying of
Mn and Cu showed best response in increasing the T.S.S. (9.67%) total sugar (6.84%),
reducing sugar (6.29%), sugar/acid ratio (58:46), ascorbic acid (56.79 mg/100 g pulp)
and total carotene (46.36 mg/100 g dry pulp) content of fruit.
The effects of mineral and elemental uptake of fertilisers by the plants are, how-
ever, significant and variable. High calcium uptake in fruit has been shown to reduce
respiration rates and ethylene production, delay ripening, increase firmness and
reduce the incidence of physiological disorders and decay, all of which result in
increased shelf life.
FIGURE 6.3 (See colour insert.) Symptoms of boron toxicity on the leaves.