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ŠUMARSKI LIST 11-12/2018 str. 38     <-- 38 -->        PDF

amount in this population is an indication of possible water deficiency stress in this region, thus increased resistance against water stress, and production of proline and glucose required for maintaining the osmotic potential (Ashraf and Foolad, 2007; Sharma et al., 2011) through protein catabolism (Tanner, 2008). This is also supported by the fact that, ANA population is in the transition zone from Mediterranean to steppe climate.
As an effective constituent in the growth and development of plants (Tanner, 2008; Verslues and Sharma, 2010) proline has an important role in the maintenance of intracellular redox balance, thus for establishment of hemostatic balance, preservation of conformational structure and form of protein, enzyme and DNA, maintenance of membrane integrity, prevention of ROS production (Ashraf and Foolad, 2007; Bhaskara et al., 2015) improvement of membrane resistance through inclusion in the secondary membrane (Verslues and Sharp, 1999; Karlsson et al., 2005), maintenance of turgor and osmotic balance (Hong et al., 2000; Gomes et al., 2010) transfer of metabolites (Kishor et al., 2005; Lehmann et al., 2010) and in physiologic processes such as germination (Hare et al., 2003). It is also important for glucose synthesis through its catabolism, and its being C, N and ATP source (Verbruggen and Hermans, 2008; Verslues and Sharma, 2010).
In the research, the highest proline amounts were detected in ANA and POZ samples. Both populations are in the transition zone from Mediterranean to steppe climate zone. The lowest proline amounts were detected in KAS and AND population samples which represent the optimal range (Table 1). The proline amount is thought to be related to and MDA content, APX, CAT, GuPX, SOD activities in AND and in MDA, GuPX, SOD KAS population. Numerous researchers suggest that proline and enzyme activities are directly effective on MDA amount (Sung, 1996; Pukacka, 1998; Sofoa et al., 2004). Detection of high proline content in POZ samples is associated with relatively high APX, CAT, GuPX and SOD activities. Detection of high proline content in POZ and ANA samples is also indicative of high water stress (Pukacka and Ratajczak, 2005; Verslues and Sharma, 2010) or very high temperatures in these regions. Under arid conditions proline accumulates in vacuole and cytoplasm, accordingly it may have been effective in the protection of the cellular components, chemical content and water/moisture rate of the seed, as well as preservation of the morphological, physiological and biochemical structure of embryonic cells (Ueda et al., 2007; Szabados and Savoure, 2010). Moreover, higher proline and H2O2 amounts were associated with increased lignin synthesis in the seed testa or membrane, thus leading to an increased resistance against stress (Zhao et al., 2008; Yang et al. 2009; 2013). In the present research, detection of high proline and H2O2 amounts in NIK population (with an isolated and marginal distribution) and ANA population (that is in the transition zone to steppe region) is indicative of stress resistance of the seed (Table 1). In literature, proline accumulation was detected in plant tissues under stress conditions. A significant correlation between frost resistance and proline amount was also reported (Ait Barka and Audran, 1997). Proline amount significantly increased in the plants that suffer stress throughout the cold-adaptation period (Hare and Cress, 1997). Up to 3 to 6 times higher proline amounts were reported in Citrus sp. plants as compared to non-acclimated plants (Yelenosky, 1979).
Age of the seed, sampling time, harvest and postharvest conditions are likely to increase ROS synthesis (Bewley, 1986; Bailly, 2004; Güney et al., 2013). Oxidative stress, on the other hand, can lead to peroxidation in organelle and plasma membranes, which in turn leads to MDA accumulation (El-Maarouf-Bouteau and Bailly, 2008; Cakmak et al., 2010). In this research, the highest MDA amount was detected in NIK and AND samples, the the lowest amounts were detected in FIN and KAS samples (Table 1). High MDA content in NIK and AND seed samples was attributed to low proline amount and low activities of some of the enzymes (Bailly et al., 1996; Bhaskara et al., 2015). High H2O2 amount in NIK population can also be effective in increased MDA amount (Bailly, 2004; Corpas et al., 2015). Detection of the lowest MDA levels in KAS and FIN