Accumulation and Distribution of Nutrients in Fruits of Castor Bean (Ricinus communis L.)

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Abstract
The nutrition of developing fruits of Ricinus communis was studied near Perth, Western Australia, where the species grows as a weed on poor sandy soil. Fruits required 60 days to mature and dehydration of the capsule began 20 days before the seeds ripened. Mature seeds accumulated 49 per cent of the fruit dry matter and over 80 per cent of its P, Zn and Cu, 50–80 per cent of its Mg, N, Fe and Mn, 41–46 per cent of its S and Ca and 11–21 per cent of its K and Na. Losses of nutrients from capsules during fruit ripening were: Zn, 73 per cent, P, 42 per cent, Cu, 23 per cent and Mn, 8 per cent. Dry matter, N, K, S, Ca, Mg, Na and Fe were not withdrawn from capsules. Apparent retranslocation from capsules could have provided from 6–28 per cent of the Zn, Mn, P and Cu in mature seeds. Seeds from plants on poor sandy soil were small but had adequate levels of nutrients when compared with those from plants growing on a fertile loam. Concentrations of all nutrients except P were higher in young capsules than in young seeds, but levels of N, P, Mg, Fe, Zn and Cu were higher in mature seeds than in mature capsules. The intake of most nutrients by fruits was out of phase with dry matter accumulation, especially in capsules, and the elements appeared to accumulate in fruit parts independently of each other. Glutamine accounted for over 85 per cent of the amino-N in phloem sap destined for fruits. Potassium made up over 90 per cent of the inorganic cations in phloem exudate. Of the minor elements in the exudate, Fe was present at highest concentration and Cu at the lowest. The results showed that retranslocation from the capsule made a very small contribution to the nutrition of seeds. It is suggested that R. communis would require a sustained supply of soil nutrients to ensure maximum seed yield, partly due to the restricted retranslocation of most nutrients from capsules.