| The increasing saline land has become a threat on food security and ecological environment currently in China, which is also a global problem for human being. Oat is a salt-resistant crop, and it can be widely used as both food and forage. Therefore, it’s very valuable to explore the responding mechanism of oat to saline-alkali stress. A salt-tolerant cultivar Vao-9 and a salt-sensitive cultivar Baoyan 5 were planted in pots to study the effects of varied concentration of salt (0,25,50,75,100 mmol·L-1) and alkali (0,50,100,150,200 mmol·L-1) on organ, grain yield, photosynthetic characteristics, antioxidant system, as well as the proteom. By analyzing the effects of salt and alkali stresses on 235 varieties, we want to establish a method to screen the salt-tolerant oat cultivar. The results:1. Due to the varied levels of saline-alkali stress, the effects of salt, alkali stresses on dry matter accumulation, root-shoot ratio, as well as yield are different. Low saline stress (50mmol·L-1) showed no significant effect on yield and 100-seed weight, and increased the grain number per spike and dry matter. Moderate or severe saline-alkali treatments decreased yield, 100-seed weight and grain number on the main branch, as well as the dry weight of shoot and root, while had no significant effect on the spikelet number. Severe saline stress (200 mmol·L-1) decreased the root-shoot ratio, while moderate or severe alkali stress improved the root-shoot ratio. What’s more, alkali stress limited the shoot growth seriously at heading and grain filling stages.2. Salt and alkali stresss affected the photosynthetic characteristics in Oats. Low saline treatment (50mmol·L-1) improved the chlorophyll content and Pn, while decreased limiting value of stomata. In addition, the improvement of chlorophyll content and photosynthetic efficiency in Vao-9 was higher than in Baoyan 5. The two cultivars got improvement in chlorophyll content by 10.8%-34.4% and 6.5%-14.7% respectively, while the improvement of Pn by 7.9%-15.8% and 12.1%-18.2%, respectively. Moderate or severe salt-alkali stresses decreased chlorophyll content, photosynthetic efficiency and maximum net photosynthetic rate significantly (P<0.05). The apparent quantum yield increased at the heading stage. Under moderate and severe alkali stress, photosynthetic efficiency decreased due to non-stomatal limitation. Under salt stress, photosynthetic efficiency decreased due to stomatal limitation. Light saturation point and light compensation point was lower in Vao-9 than in Baiyan 5.3. Under salt and alkali stresses, the maximum contents of malonaldehyde (MDA) appeared at grain-filling stage. Compared to the control, the activities of superoxide dismutase (SOD) and catalase (CAT) increased significantly at grain-filling stage. It was reported that SOD and CAT could play important roles in remitting the damage from reactive oxygen. The SOD activity of Vao-9 increased by 11.4%-80.4%,12.8%-117.5%,10.4%-99.7%in leaves, stems and roots respectively compared to the control. The SOD activity of Baiyan 5 increased by 4.4%-34.7%, 8.6%-95.3%,6.3%-43.25% in leaves, stems and roots respectively. The CAT activity in leaves of Vao-9, Baiyan5 increases by 33.9%-110.4%,15.9%-59.3% respectively compared to the control, while by 14.6%-378.9%、12.9%-235.3% respectively in roots. The peroxidase (POD) activity reached the peak at the jointing stage. Soluble sugar accumulated in leaves obviously during tillering, jointing and grain-filling stages. The soluble sugar contents in the stem and root obviously decreased at grain-filling stage. Under low saline stress (50mmol·L-1), the relative water content in leaves increased. Under low and moderate salt-alkali stresses, root activity increased at tillering, jointing and heading stages.4. There was a significantly negative correlation (P<0.05) between root-shoot ratio and yield at heading and grain-filling stages under salte-alkali stresses, therefore yield decreased due to redundant roots. Chlorophyll content and photosynthetic rate had an significantly positive correlation with yield(P<0.01) and a significantly negative correlation with MDA(P<0.05). Lipid peroxidation damage reduced the yield by decreasing photosynthetic rate and chlorophyll content. Soluble sugar content in leaves (P<0.01) and stems (P<0.05) at tillering stage had a significantly negative correlation with yeild, while soluble sugar contents in stem (P<0.05) was positively correlated with yield at grain-filling stage (P<0.01). Photosynthetic rate had a extremely significant correlation with root activity (P<0.01). SOD was significantly correlated with CAT (P<0.01)5. Under the long-term salt stress,13 root proteins were identified by using MALDI-TOF MS. These proteins are involved in five types of biological processes:1) two fructose-bisphosphate aldolase (FBA), four alcohol dehydrogenase (ADH), an enolase (ENO), a UDP-glucuronic acid decarboxylase (UXS), and a Fl-ATPase alpha subunit (atpA) related to carbohydrate and energy metabolism; (2) a choline monooxygenase (CMO) related to stress and defense; (3) a lipase related to metabolism; (4) a polyubiquitin related to protein degradation, and (5) a 14-3-3 protein related to signaling. We also investigated the protein profiles of oat leaves in response to salinity and detected 30 reproducible protein spots by two-dimensional gel electrophoresis that were differentially expressed. Specifically, one protein was up-regulated and 29 proteins were down-regulated compared with the control. These 29 proteins were identified using MALDI-TOF mass spectrometry. These proteins were involved in 4 types of biological processes:photosynthesis, carbohydrate metabolism and energy, protein biosynthesis and folding and detoxification.6. GGE-Biplot was used to select the salt-alkali tolerant genotype and establish the selecting method.235 cultivars were used in total. We used cones combined with tray to plant oat, and this method could improve the planting efficiency. Under the salt-alkali stresses, high germination rate couldn’t demonstrate high yield. So it Is necessary to consider the germination rate and yield together. To identify production capacity, the best salt concentration is 150mmol·L-1, and the best alkali concentration is 75 mmol·L-1. The volume is 40L. Chlorophyll could be chosen as one physiological indexe to identify salt and alkali tolerance. |
PDF Full Text Request