Photosynthetic parameters were studied in plants experiencing repeated stress from seedling to seed filling and one stress cycle only at seed filling stage in sunflower with a view to understand the phenomenon of photosynthetic acclimation. The rates of PS II electron transport and net photosynthesis appeared to be almost equally affected in both single and repeated stress treatments at mild and moderate levels of moisture stress. However, at severe stress, reduction in PS II and net photosynthesis was comparatively less in plants under repeated stress treatment. PS I remained relatively high throughout at all the levels of leaf desiccation. Stomatal conductance was found fairly low in repeatedly stressed leaves upto - 18 bars but at-24 bars, it became almost equal to plants stressed at seed filling stage. Similar was the case with recovery. PS I, PS II and net photosynthesis exhibited fairly high recovery in repeatedly stressed plants as compared to plants with single stress treatment.
