Alleviation of Water Stress on Photosynthesis in Oilyplants

Stressful environments such as salinity and drought was assessed on photosynthesis, the most fundamental and intricate physiological process of three oil plants canola (BrassicanapusL.), safflower (Carthamustinctorius L.) and sunflower (Helianthus annusL) grown in different sites in Egypt (Suez road; North Coastal area; El-Kantra East) , is also severely affected in all its phases by such stresses . The plants were subjected to a pot experiment in which pots contained an equal amount of each soil-type either alone or supplemented with composted plant residue (wheat straw and Eichhorniacrassipes) at three concentrations (0.25, 0.5, 1.0% v/v) as organic fertilizers and ammonium sulphate at three levels (5, 10, 15 g/pot) as inorganic fertilizer. Since the mechanism of photosynthesis involves various components, including photosynthetic pigments and photo systems, the electron transport system, and CO2 reduction pathways, any damage at any level caused by a stress may reduce the overall photosynthetic capacity of a three plants . All three soil types resulted in a decrease in photosynthetic pigments and Hill reaction as well as transpiration rate and leaf conductance for all three plants when grown in these different soil types compared to the control garden soil although these parameters improved when soils were supplemented with organic fertilizers rather than inorganic ones. In addition leaf temperature of stressed plants was increased and decreased when grown in different soil and when soil were supplemented with fertilizers respectively compared with the control.

Keywords: Photosynthesis, canola, safflower, sunflower, stress, organic and inorganic fertilizers.