Water Stress in Sunflower (Helianthus annuus L.) 2. Effects on Leaf Cells and Leaf Area

Abstract

Three water stress treatments were applied at early, mid and late stages of vegetative development in sunflower. The effects of these stresses on leaf area, cell frequency, number of cells per leaf and palisade cell area were examined. Final leaf area was reduced in all stress treatments. The largest reduction occurred in leaves that were unfolding or about to unfold at the commencement of stress. At full expansion of these leaves cell frequency had increased, cell number had decreased and cell area had decreased. These results help to explain the effects of stress on final leaf area, especially the reduced area of the lower leaves that are most sensitive to water stress.