Sequential defoliations influencing the development and yield components of castor plants (Ricinus communis L.)

Castor plants (Ricinus communis) cv. BRS Nordestina were submitted to biweekly defoliations in order to evaluate the influence on development and yield components. Leaf area was calculated from the length of the main vein of each leaf. Defoliation treatments of 0, 15, 30, 45 or 60% of the total leaf area were applied. Each raceme was individually harvested and the date was recorded. Castor plants were able to completely regrow its leaf area when the defoliation occurred during the vegetative stage; however, this initial damage reduced the maximum leaf area obtained by the plant. Maturation of fruits occurred earlier when plants were subjected to defoliation. Defoliation treatments did not influence the number of fruits per raceme, but caused a steep reduction of the number of racemes per plant. Adaptations in the yield components were observed in the number of seeds per plant and in the seed oil content, but not in the mean seed weight. Any level of defoliation repeated along the plant growth cycle was found to cause a reduction of the oil yield. The loss of 1 m2 of leaf area caused the reduction of 37.8 g of castor seed or 24.4 g of castor oil.