Background Qinghai-Tibet Plateau is known for characteristics of high altitude, low rainfall and varying temperature, and the crops in this area are susceptible to abiotic stresses such as drought, basic salt and freeze-thaw that caused damages in different perspectives such as the permeability of biological membrane, osmotic adjustment, and antioxidant enzyme system. Hordeum vulgare L. is an indispensable crop in plateau and plays an important role in agricultural ecosystem as well.Result In this experiment, H. vulgare L. was used as experimental material and the physiological characteristics soluble protein (SP) content, malondialdehyde (MDA) content, antioxidant enzyme activity and relative water content (RWC) of seedlings were examined under freeze-thaw condition combined with drought and alkali stress.Conclusion Research results indicated that under the combined stresses of basic salt and drought, H. vulgare L. seedlings were damaged by lipid peroxidation, weakened superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities, while enhanced osmotic adjustment ability in plants cell. It was suggested that, in agricultural management, the simultaneous occurrence of two stresses, basic salt and drought, should be avoided in the early stage of H. vulgare L. planting to reduce the physiological stress on plants.
Secale cereale L. (rye) as an overwinter forage usually harvested in the autumn, widely grows in the northeastern China, where the temperature varies widely from day to night. In this area, the crop is confronted with not only freeze–thaw stress, but also the soil salinization. In this study, the rye seedlings under alkaline salt (AS) stress were subjected to both cutting treatment (CT) after growing for 7 days and freeze–thaw (FT) stress(10/−5°C) after 6 days regrowth. The changes of soluble protein (SP), malondialdehyde (MDA), relative water content (RWC), catalase (CAT) and superoxide dismutase (SOD) activities in seedlings were studied to analyze the physiological effects of FT and AS stress with CT. The results indicated, under the combined stress, the enzyme activity and RWC decreased and the soluble protein and MDA content increased. Cutting treatment led to the accumulated of MDA, increase of enzyme activity and decrease of RWC in seedlings. The finding from the study indicates that the CT could aggravate the membrane peroxidation under the combined stress of FT and AS and enhance the osmotic adjustment ability of rye and activated the antioxidant enzyme system. The rye having been cut is more sensitive to the compound stress.
The freeze-thaw (FT) and drought in early spring in Northeast China are two main ecological stresses to forage grasses. In this paper, Secale cereale L. grown under 2 d drought-stress (mild, moderate, and severe treat) with 5, 10 and 15% polyethylene glycol (PEG-6000) concentrations. The temperature gradient was set to 10, 5, 0, -5, 0, 5 and 10ºC after FT treatment. The content of protein, soluble sugar and MDA increased with a trend of combined stress>FT>drought stress, indicating that the damage of rye under single FT stress was higher than that under the single drought stress. Under drought stress, FT could aggravate the damage to rye. At T7 (10ºC) in the thawing stage, compared with the CK, the pattern of the decrease of RWC and chlorophyll and the increase of protein and MDA content was severe combined stress>FT>moderate combined stress>moderate drought stress. The results of this study showed that a proper drought treatment before FT stress could alleviate the physiological damage to the forage leaf.
Effects of grazing, cutting and decapitating on grass populations on the artificial grassland in the in subtropical region of China were studied. The results showed that moderate grazing and cutting could increase the adaptability of Dactylis glomerata and Lolium prenne due to decapitating. Decapitating could reduce the apical dominance and reproductive growth of grass, so the ecological effects grazing and cutting on grass could be realized by decapitating, and the population density, caloric value and energy accumulation of D. glomerata and L. prenne increased obviously. Apical dominance of grasses could lower the population density, energy accumulation and intra population competitive ability.
Increasing levels of sodium carbonate are major causes of grassland alkalinization in the Song-Nen Plain of northeast China. In winter-spring alternation, plants are often subjected to double stresses of alkaline salt and freeze-thaw. Here, Medicago sativa CV. Zhongmu No.1 seedlings were used to study the effects of laboratory-simulated basic salt (BS) and freeze-thaw (FT) stresses on the contents of osmoregulatory substances, biological membrane permeability, and antioxidant enzyme activity. The results showed that under individual BS-or FT-stress, the soluble protein in seedlings decreased by 9.6-20.2%, proline and MDA contents increased by 18.4-48.1 and 7.8-37.7%, respectively. Furthermore, the activities of SOD and POD increased by 6.2-24.9 and 4.8-30.3%, respectively. During the freezing and thawing cycles, both proline and MDA contents initially increased and then decreased; these observations contrasted with those for soluble protein content. Activities of SOD and POD increased in attempts to resist reactive oxygen species (ROS). Moreover, M. sativa CV. seedlings under combined stress of BS and FT showed significantly higher physiological responses than those under individual stress (BS-or FT-stress). The results of this study demonstrate the molecular basis for BS-and FT-stress tolerance by M. sativa. In turn, this could lead to strategies for further enhancement of these tolerances in the plant.
Crops are commonly subjected to freeze-thaw and salt stress factors simultaneously in Qinghai-Tibet Plateau. In the agricultural field, potassium fulvic acid can not only promote plant growth and increase crop yield but also enhance plant resistance to stress. In this study, the changes of osmotic adjustment substances, antioxidant enzyme activities and photosynthetic characteristics of barley seedlings under alkaline salt and freeze-thaw stress were investigated by laboratory simulation. The results showed that under single alkaline salt stress, the soluble protein content increased significantly (P < 0.05), and the malondialdehyde (MDA) content of seedlings increased by 63.1%; however, antioxidant enzymes activities and photosynthetic rate of barley seedlings decreased. Under combined stresses of alkaline salt and freeze-thaw, the soluble protein content, antioxidant enzyme activities, and photosynthetic rate of barley seedlings decreased; in contrast, the MDA content of seedlings increased. With the addition of potassium fulvic acid, the soluble protein content of seedlings increased, MDA content decreased significantly (P < 0.05), and enzyme activities tended to be stable. This study revealed that the addition of a proper amount of potassium fulvic acid could mitigate the damage of alkali salt and freeze-thaw stress on barley seedlings.
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