Termos para indexação: Helianthus annuus, casa-de-vegetação, nutrição vegetal, produção de aquênios, teor de óleo.

The objective of this work was to study under greenhouse conditions, the effect of the interaction between boron rates and phases of water stress on total dry matter production, achene production, oil content and development of sunflower tillage in dystrophic Red Yellow Latosol of medium texture. The experimental design consisted of casual blocks, using factorial scheme 4x4, with four replicates. The treatments studied were: Four boron rates: 0, 0,25, 0,5 e 2,0 mg kg -1 , applied through the boric acid form, and four period of soil water content: without water stress for the whole cycle, with water stress during the whole cycle, with stress after beginning of flowering and with water stress after beginning of grain filling. The results showed that independently of the presence or not of water stress, the 0,5 mg dm -3 of B was the best rate which presented the highest total dry matter production, achenes production and oil production. The absent water in soil after beginning of flowering and beginning of achenes filling resulted in small production of total dry matter, of achenes and of oil.