Storage reserve mobilization, gluconeogenesis, and oxidative pattern in dormant pistachio (Pistacia vera L.) seeds during cold stratification

Effects of cold stratification on enhancing germination capacity of pistachio (Pistacia vera L.) kernels was investigated through the study of storage reserve mobilization, gluconeogenesis, and enzymatic antioxidant defense system in both cotyledon and embryonic axis organs. Every week, imbibed pistachio seeds were cold stratified at 5 degrees C for increasing periods up to 42 days. Stratifying seeds for 42 days significantly increased their germination potential. Lipid hydrolysis in both organs during cold stratification was accompanied by increased isocitrate lyase activity and the accumulation of starch and soluble sugars. Total protein mobilization occurred in cotyledons rather than embryonic axes but was accompanied by high proteolytic activity and accumulation of amino acids in both organs. However, the pattern of soluble proteins changes in both tissues was nearly identical. The activity of a typical protease at a particular pH was not detected in stratifying pistachio kernels, but rather different proteases might be activated depend on cold treatment period. Cold stratification also led to increased H2O2-scavenging enzymes activity and consequently decreased hydrogen peroxide and lipid peroxidation in pistachio kernels. These data suggest that beneficial effects of cold treatment in germination induction of pistachio kernels arise from prevention of processes causing seed deterioration by turning on cellular repair mechanisms and activating gluconeogenic processes, which subsequently enhance seed capability for germination.