Study On Mechanism Of Effects Of Salt-stress To POD Activity Of Wheat

The wheat ( Triticum aestivum L.) cultivars pH82-2-2 was used to investigate the changes of peroxidase activity and isozyme in the living wheat seedlings and the wheat leaves in vitro under salt-stress and relationships betw -een salt-stress and gene expression, and make an initial study to the chan -ges of Salicylic Acid(SA)and Calcium nitric(Ca(NO3)2) and 6-benzyladenine (6-BA) on peroxidase activity and isozyme in salt-stress wheat seedlings.The main results were present as follows:1. Effects of salt-stress on peroxidase activity in early days of wheatThe wheat seedlings were irrigated with 200mmol/L NaCl solution every day after cultivated one day. Salt stress enhanced the activity of peroxidase and the content of malondialdelehyde(MDA) . When seedlings were stressed under salt,six POD bands (POD1, POD2, POD4, POD9 ,POD12, POD6(in roots)and POD11(in leaves))were induced and POD8 decreased, POD7 was absent (in leaves ).2. Effects of salt-stress on peroxidase activity at growing period of one leaf and one needle of wheatPeroxidase activity and the content of malondialdelehyde(MDA) was increated remarkably in treatment seedlings at the stage of one leaf and one needle of wheat,which were irrigated with 200mmol/L NaCl solution every day. The same bands of peroxidase stained thicker after 4 d and6 d and new POD bands were induced in roots only in 7 days.3. Effects of salt-stress on peroxidase activity at growing period of two leaves and one needle of wheatAt growing period of two leaves and one needle of wheat, and under the same condition with primary wheat. Peroxidase activity increased and came to maximum in one day and then declined to a varying extent in roots and leaves of wheat. Peroxidase activity and the content of malondi-aldelehyde (MDA) were higher than those of the non-NaCl treatment seedlings. The obvious change has taken place in the patters of peroxidase which the same bands stained thicker but no new POD bands were induced in in 0.5 d, new POD bands were induced in roots only in 1 d and 2 d.4. Effects of NaCl-treatment on peroxidase activity of wheat leaves in vitro Peroxidase activity increased and came to maximum in two days and then declined slowly in wheat leaves in vitro. Peroxidase activity declined after NaCl– treatment. Native-PAGE showed that the band numbers of peroxidase isozyme remained the same but the intensity of bands changes. The band numbers of peroxidase isozyme decreased with the extension of the time of NaCl-treatment, which is consistent with varying trends of Peroxidase activity. 5. Effect of salt-stress and 6-benzyladenine(6-BA),Calcium nitric(Ca(NO₃)₂),Salicylic Acid(SA)on POD of wheatSalt-stress did not alter the pattern of POD isozymes after treatment of 6-BA,Ca(NO₃)₂,SA, but POD bands stained thicker ,POD activity increased significantly. The results showed that the wheat was well to alleviate salt injury through enhancement of enzyme activityby after treating with 6-BA,SA,Ca(NO₃)₂.6. Effects of salt-stress on peroxidase isozyme gene expression in wheatWith treament of salt, changes of peroxidase isozyme were evident in root and leaf of wheat. The analysis showed that there are close relationships between salt-stress and gene expression. When investigating the effects of salt-stress on the expression of 12 alleles at 5 loci in specific tissues, it was found that some alleles expressed only under salt-stress, for example PX-2b et al; some alleles expressed in specific tissues, for example PX-1 and so on. These studies showed that the wheat may resist the salinity after being exposed to salt-stress by controlling the expression of relevant genes.