Development of sunflower plants under different conditions of water supply

Usually the lack or excess of water in the soil is harmful to plant development. Therefore, our objective was to evaluate the growth of sunflower plants under different water holding capacities (WHC). Trials were conducted in a greenhouse with plants of the sunflower cultivar Embrapa 122/V-2000. The experimental design was a randomized complete block with four treatments: 60%, 80% and 100% of WHC and a flooding level with four replications. Plants were evaluated weekly between stages V6 (with six leaves and 4.0 cm tall) to R4 (flowering). We evaluated the plant height, stem diameter, leaf chlorophyll content, leaves, stems, shoot and root dry matter, number of leaves, leaf area, and the relationship between root and shoot dry matter. The results showed that the sunflower plants had greater height and stem diameter when subjected to higher WHC. Under water stress the increased chlorophyll content was limited, and in treatments with high water availability the content initially increased, but decreased in later evaluations. Although the root/shoot ratio of dry matter was observed to be higher for treatment 60% of WHC, the dry matter of stem, root and leaf, number of leaves and leaf area on 60% of WHC resulted in smaller values. Therefore, improved development of these plants was observed when exposed to 80 and 100% of the WHC.