WHEAT YIELD AND ANTIOXIDANT ENZYMES RELATIONSHIP UNDER DIFFERENT SOIL WATER CONTENT

The objectives of this study were to examine the relationship between wheat yield cultivars (Sakha 93 and Giza 168) and antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) and phenylalanine ammonia-lyase (PAL) activities  under different soil water content i.e. low, moderate and high content by irrigation at 80% ETo (1280m³/fed.), by 100% ETo (1600m³/fed.) and120% ETo (1920m³/fed.), respectively. Two lysimeter experiments were carried out in two successive seasons i.e. 2006/2007 and 2007/2008 to estimate  wheat yield and one experiment in plastic bags carried out of the greenhouse to determine the antioxidant enzymes of 28 days wheat plant under three different soil water content i.e. providing wheat seedlings with aforementioned treatment.  Exposing wheat cultivars i.e. Giza 186 or Sakha 93 to water stress by irrigation at 80% ETo (1280 m³/fad.) exerted an increase in CAT, SOD, POD, APX and PAL over those irrigated at 100% ETo (1600 m³/fad.) or at 120% ETo (1920 m³/fad.), but the previous enzyme activities in the tissue of Saka 93 surpassed of that of Giza 168 cultivar. spike weight and weight of 100 grain/plant of Sakha 93 cultivar overcome that of Giza 168 at low soil moisture content (80% ETo), whereas opposite results were obtained at high and moderate water content (120% and 100% ETo) in the first growing season (2006/2007) and spike weight/plant in second growing season (2007/2008). There was a proportional relationship between increasing soil moisture content and grain yield/plant but the difference between moderate water content 100% ETo (1600 m³/fed.) and high water content 120% ETo (1920 m³/fed.) was not significant. Providing 28 days wheat plant with low water content, decreased wheat yield/plant and its attributes comparing with moderate water content for the two studied cultivars. The current study indicates that Sakha 93 cultivar was the most tolerant cultivar compared with Giza 168.