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ŠUMARSKI LIST 11-12/2018 str. 39     <-- 39 -->        PDF

samples are indicative of very low lipid peroxidation level in these seeds (Jeng and Sung, 1994; Goel and Sheoran, 2003; Hampton et al., 2009), thus preserved membrane integrity (Demirkaya et al., 2010; Gomes et al., 2010) and protein structure (Sanders et al., 2009).
High concentrations of H2O2 result with oxidative stress, which may also lead to seed senescence (Vianello et al., 2007), loss in viability (Hampton et al., 2009) and morphological, biochemical degradations of seeds. H2O2 concentration is significantly high in ANA and NIK samples of Taurus cedar. The lowest H2O2 levels, on the other hand, were detected in AND ad KAS seed samples (Table 1). The varying H2O2 content is primarily ascribed to the differences in the growth environments (Jeng and Sung, 1994; Güney et al., 2013). Also the detection of low H2O2 content in the locations with high enzymatic activities is associated with the function of CAT, GuPX and APX activities in inhibition of ROS synthesis (Lehner et al., 2008).
Seeds contain enzymes in addition to carbonhydrates, fats, hormones, minerals, proteins and aminoacids (Hare et al., 2003; Bewley et al., 2013). These compounds protect cells, tissues and organs through preventing the damages induced by ROS and lipidperoxidation, or repairing damaged tissues, or suppressing ROS synthesis (Bailly et al., 2000).      
According to the enzymatic activity values obtained from Taurus cedar population samples, the highest APX and CAT enzyme activities were detected in POZ, the highest GuPX activity was detected in ANA and NIK samples, and the highest SOD enzyme activity was detected in FIN, KAS and NIK samples in descending order (Table 3). Various researchers reported that, APX and CAT enzymes inhibit H2O2 and ROS synthesis, thus reducing the possible damages of oxidative stress (Bailly, 2004). However, low MDA and high proline and protein contents were detected in these seeds. This finding is indicative of the completion of tissue differentiation and the necessity of H2O2 inhibition for testa or other tissues’ development (Corpas et al., 2015). It was verified in previous researches that hydrolytic enzymes released during seed development lead to peroxidation in cell and organelle membranes, thus resulting with increased MDA accumulation (McDonald, 2004). Low APX and GuPX activities in KAS samples led to reduced levels of H2O2 and MDA (Jeng and Sung, 1994; Caverzan et al., 2012). Protein amount was also affected by these enzymatic activities (Palma et al., 2002). The decrease in the protein content may also have stemmed from the increased proline amount. It was detected in previous researches that, proline amount triggered protein catabolism under arid and low temperature conditions (Hare et al., 2003; Sanders et al., 2009).
Varying enzyme activities in the seed samples are primarily ascribed to varying locations, thus climate and soil characteristics (Ertekin et al., 2015), seed storage conditions (Pukacka and Ratajczak, 2005; Pekşen and Palabıyık, 2013), and harvesting method. As indicated by the results of literature studies and evaluation of the obtained data, activities of the enzymes such as SOD, CAT; APX and GuPX can be used as indicators in the determination of seed quality (McDonald, 1998; Corbineau, 2012).
In addition to antioxidant enzymes, seeds also contain enzymes that control germination (Schmidt et al., 2007). It was reported in literature studies on seed germination that, seeds contain amylase (α and β) enzymes (Black et al., 1996) that breakdown starch into glucose, fructose and sucrose (Cochrane et al., 2000; Palma et al., 2002). The lowest α-amylase activities were detected in KAS and FIN samples, and the highest activities were detected in POZ and NIK samples of Taurus cedar populations (Table 2). According to numerous researchers, seed storage attributes are dependent on climate changes, soil characteristics, age and size of tissues and organs, and competitiveness (Price et al., 2003; Lehner et al., 2008).
The signal transduction and responses against stress conditions vary in roots and leaves of plants. H2O2 is effective in signal transduction and antioxidant enzyme activities. Plants are equipped with antioxidant defense system that control ROS levels; and this system comprise of defending elements such as SOD, CAT, GuPX, APX and The plants