Characterization of Proteins from Sunflower Leaves and Seeds: Relationship of Biomass and Seed Yield

INTRODUCTION Sunflower (Helianthus annuus L., Asteraceae), currently cultivated for its seeds, is the world’s fourth largest oil-seed crop. World seed production was 25.2 million tonnes (t) during 1995/1996 from approximately 50 million ha of cultivated land. In the US, during 1999, sunflower seed production was 1,971,205 t from 1,438,000 ha, according to the National Agricultural Statistics Service, U.S. Department of Agriculture. Sunflower meal is a potential source of protein for human consumption (Sosulski 1979) due to its high nutritional value and lack of antinutritional factors (Smith 1968). About 3 to 7 t of plant biomass per ha, including 10% of the flowerhead, is left in the field and represents biomass that may have other uses (Marechal and Rigal 1999). Information on the biochemical and biophysical composition of sunflower seed proteins is limited and there are fewer reports dealing with leaf proteins. The majority of seed proteins are globulins (Gheyasuddin et al. 1970) with sedimentation constants of about 11S (Joubert 1955). The reported molecular masses are 300,000–350,000 Da for the sunflower globulins (Sabir et al. 1973). The major seed storage globulin in several sunflower species (heliantinin) has been studies by Anisimova (1992) who found three main groups of polypeptides: one with basic polypeptides of 20,000 Da molecular mass and two with acidic polypeptides (30,000 and 40,000 Da). However, the composition was highly variable. In Mexico, approximately 80% of oil-seeds for human food are imported so increasing sunflower production is an option to reduce this deficit. The Universidad Autónoma Agraria, Antonio Narro (UAAAN) has developed sunflower cultivars for the semi-arid regions. Understanding the relationship between biomass and seed yield and their correlation with leaf and seed proteins is important for plant selection. The objectives of this paper were to characterize the leaf and seed proteins from six sunflower cultivars and relate these to biomass and seed yield.