Industrial Crops and Products 32 (2010) 400–404 Contents lists available at ScienceDirect Industrial Crops and Products journal homepage: www.elsevier.com/locate/indcrop Sequential defoliations influencing the development and yield components of castor plants (Ricinus communis L.) Liv S. Severino a,b,∗ , Maria A.O. Freire a , Amanda M.A. Lucena a , Leandro S. Vale a a Embrapa Algodão, Rua Oswaldo Cruz, 1143, CEP 58428-095, Campina Grande, PB, Brazil b Texas Tech University, Lubbock, TX, United States article info Article history: Received 5 March 2010 Received in revised form 1 June 2010 Accepted 3 June 2010 Keywords: Oilseed crop Leaf area Physiology Source and sink Regrowth abstract 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 m 2 of leaf area caused the reduction of 37.8 g of castor seed or 24.4 g of castor oil. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Castor (Ricinus communis L.) is cultivated mostly for production of oil for the chemical industry (Barnes et al., 2009), but there is increasing interest about this crop as an alternative for biodiesel purposes in several countries (Baldwin and Cossar, 2009; Hall et al., 2009). In the agronomical side, the main advantage of castor is its high tolerance to drought and wide adaptation around the world (Weiss, 1983). In the industrial side, castor oil is different in many aspects from any other oil because it consists largely (up to 90%) of an unusual fatty acid, ricinoleic (O’Brien, 2000). The ricinoleic fatty acid present in castor oil finds many uses in the textile, petroleum and lubricant fields because it exhibits certain characteristics not found in other oils, such as high hydroxyl value, high specific grav- ity, greater viscosity, and ability to hydrogenate to an unusually high melting point, i.e., 86–88 ◦ C(O’Brien, 2000). Defoliation studies are a traditional method for simulating dam- age to the plant leaf area caused by several unwanted factors such as pest attack, diseases, gusty winds and hail (Pickle and Caviness, 1984; Gazzoni and Moscardi, 1998; Shafiullah et al., 2000; Chen et al., 2002; Reichert and Costa, 2003; Endan et al., 2006). Defoliation can also be the consequence of agricultural practices like leaves ∗ Corresponding author at: Texas Tech University, TX, United States. Tel.: +1 806 4702472. E-mail addresses: liv@cnpa.embrapa.br, liv.severino@ttu.edu (L.S. Severino). broken by machinery traffic, the side effect of herbicides and plant growth regulators, or even experimental procedures. There are dif- ferences in the physiological effect made by artificial defoliation and the action of real damaging factors on cultivated crops. Emu- lating the attack of insects is complex due to details like selective defoliation, effect of saliva, incomplete consumption and fertiliza- tion from frass (Chen et al., 2002). Nevertheless, defoliation studies are useful for comprehension of several phenomena affecting leaf area, sink source relationship and the modeling of plant growth and production (Gazzoni and Moscardi, 1998; Endan et al., 2006; Ahmadi and Joudi, 2007). Assimilating carbon through photosynthesis is the primary function of a leaf. Therefore, when the total leaf area of a plant is reduced by an external factor, a reduction in the yield is expected due to the decreased capacity of that plant to accumulate dry mat- ter. However, many studies on crops like soybean (Glycine max), peanut (Arachis hypogea) and wheat (Triticum aestivum) concluded that severe defoliation on the early vegetative stage of the growth cycle did not compromise the final yield and in some cases resulted in a slight increase on production (Pickle and Caviness, 1984; Endan et al., 2006; Ahmadi and Joudi, 2007). Leaf photosynthesis depends on the intensity of the intercepted solar radiation. As the plant canopy consists of several layers that partially overlap and shade one another, when light is attenuated, less photosynthesis can be realized in the inner layers (Larcher, 2003). However, leaf function is not only photosynthesis, but it also act as transitory storage tissue. Primary accumulation of pho- 0926-6690/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.indcrop.2010.06.007