Water Stress in Sunflower (Helianthus annuus L.) 3. Responses of Cypsela Size

Abstract

Six water stress treatments were applied before, during and after anthesis of the sunflower inflorescence. The effects of these stresses on leaf and inflorescence size, cypsela number, pericarp and embryo weight were examined. Water stress accelerated leaf senescence and reduced leaf number. Leaf area and inflorescence diameter were reduced in some treatments. Total cypsela weight may be related to leaf area. All stress treatments reduced pericarp weight at all positions. Embryo weight at central positions was similarly affected. Post-anthesis stress did not affect embryo weight at peripheral positions. The effects of water stress on embryo weight may involve a critical stage in development but this differs from that envisaged for leaves.