Optimum ratio of calcium and boron in the nutrient solution or in castor bean shoot for fruit yield and seed oil content
2012
Franco, Henrique Coutinho Junqueira | Junior, José Lavres | Oliveira, Adilson de | Matias, Gean Carlos Silva | Cabral, Cleusa Pereira | Malavolta, E. (Eurípedes)
Calcium (Ca) and boron (B) have been reported as the major macro- and micronutrient required for castor bean plant yield. The objective of this study was to determine the Ca:B ratios (in the growth media and plant tissue) for fruit yield and shoot dry weight of the castor bean (Ricinus communis L.), grown in a nutrient solution, and to evaluate Ca and B supply on concentration and total uptake of Ca, potassium (K), magnesium (Mg), and B, as well on the seed oil content. The treatments were arranged in a 3 × 3 factorial fashion, consisting of three rates of Ca (40, 80, and 160 mg L⁻¹) and three of B (0.32, 0.96, and 1.60 mg L⁻¹). Calcium and B rates increased the shoot and root dry weight and fruit yield at a Ca:B ratio in the nutrient solution of 166 and 100, respectively. Symptoms of B deficiency were observed in plants supplied with 0.32 mg B L⁻¹, regardless of the Ca concentration in the nutrient solution. Plants which showed visual symptoms of Ca deficiency cultivated with 40 mg Ca L⁻¹ presented concentration of Ca in plant tissue up to 10 g kg⁻¹. The concentration and total Ca and B uptake increased with the rates of them. Notwithstanding, the shoot Ca accumulation was improved by B rates. In addition, there were no decreases in K and Mg uptake due to Ca rates. Furthermore, addition of 80 mg L⁻¹ of Ca and 1.60 mg L⁻¹ of B in the growth media increased the seed oil content. The Ca:B ratio in the diagnostic leaf associated with the highest plant dry weight (shoot and root) and fruit yield, was 500 (16 to 20 g kg⁻¹ of Ca, and for 30 to 40 mg kg⁻¹ of B).
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