Four varieties of winter wheat with different return green rates were used to analyze the plasma membrane stability and the factors that affect winter wheat in the frigid region during winter. The removal of reactive ...Four varieties of winter wheat with different return green rates were used to analyze the plasma membrane stability and the factors that affect winter wheat in the frigid region during winter. The removal of reactive oxygen species, the degree of plasma membrane impairment, water composition and content, and the changes in cell viability in the crowns, which contain the growing point, were studied during the period from cold acclimation to the deep freezing. The results showed that electrical conductivity which reflects the degree of plasma membrane damaged under low temperature was significantly correlated with the free water and the total water content. The malondialdehyde （MDA） content, which reflects the degree of membrane peroxidation, was very significantly correlated with superoxide dismutase （SOD）, peroxidase, and ascorbic acid. During the deep freezing period, the SOD activity and glutathione （GSH） content of the winter wheat varieties were relative to their cold resistance. During this period, the MDA stability, SOD, GSH, and the total water and the free water content might be used to identify the cold resistance of winter wheat varieties.展开更多
By using atomic force microscope (AFM), the topography and function of the plasmalemma surface of the isolated protoplasts from winter wheat mesophyll cells were observed, and compared with dead protoplasts induced by...By using atomic force microscope (AFM), the topography and function of the plasmalemma surface of the isolated protoplasts from winter wheat mesophyll cells were observed, and compared with dead protoplasts induced by dehydrating stress. The observational results revealed that the plasma membrane of living protoplasts was in a state of polarization. Lipid layers of different cells and membrane areas exhibited distinct active states. The surfaces of plasma membranes were unequal, and were characterized of regionalisation. In addition, lattice structures were visualized in some regions of the membrane surface. These typical structures were assumed to be lipid molecular complexes, which were measured to be 15.8±0.09 nm in diameter and 1.9±0.3 nm in height. Both two-dimensional and three-dimensional imaging showed that the plasmalemma surfaces of winter wheat protoplasts were covered with numerous protruding particles. In order to determine the chemical nature of the protruding particles, living protoplasts were treated by proteolytic enzyme. Under the effect of enzyme, large particles became relatively looser, resulting that their width was increased and their height decreased. The results demonstrated that these particles were likely to be of protein nature. These protein particles at plasmalemma surface were different in size and unequal in distribution. The diameter of large protein particles ranged from 200 to 440 nm, with a central micropore, and the apparent height of them was found to vary from 12 to 40 nm. The diameter of mid-sized protein particles was between 40―60 nm, and a range of 1.8―5 nm was given for the apparent height of them. As for small protein particles, obtained values were 12―40 nm for their diameter and 0.7―2.2 nm for height. Some invaginated pits were also observed at the plasma membrane. They were formed by the endocytosis of protoplast. Distribution density of them at plasmalemma was about 16 pits per 15 μm2. According to their size, we classified the invaginated pits into two types―larger pits measuring 139 nm in diameter and 7.2 nm in depth, and smaller pits measuring 96 nm in diameter and 2.3 nm in depth. On dehydration-induced dead pro-toplasts, the degree of polarization of plasma membranes decreased. Lipid molecular layers appeared relatively smooth, and the quantity of integral proteins reduced a lot. Invaginated pits were still de-tectable at the membrane surface, but due to dehydration-induced protoplast contraction, the orifice diameter of pits reduced, and their depth increased. Larger pits averagely measuring 47.4 nm in di-ameter and 31.9 nm in depth, and smaller pits measuring 26.5 nm in diameter and 43 nm in depth at average. The measured thickness of plasma membranes of mesophyll cells from winter wheat examined by AFM was 6.6―9.8 nm, thicker in regions covered with proteins.展开更多
基金Supported by the Postdoctoral Science Foundation of Heilongjiang Province(2010RCB17)Doctoral Research Startup Foundation of Northeast Agricultural University(LBH-Z10266)+2 种基金New Rural Project of Heilongjiang Provincial Department of EducationProject of Education Department in Heilongjiang Province(12521035)Postgraduate Innovation Project of Education Department in Heilongjiang Province (YJSCX2012-036HLJ)
文摘Four varieties of winter wheat with different return green rates were used to analyze the plasma membrane stability and the factors that affect winter wheat in the frigid region during winter. The removal of reactive oxygen species, the degree of plasma membrane impairment, water composition and content, and the changes in cell viability in the crowns, which contain the growing point, were studied during the period from cold acclimation to the deep freezing. The results showed that electrical conductivity which reflects the degree of plasma membrane damaged under low temperature was significantly correlated with the free water and the total water content. The malondialdehyde （MDA） content, which reflects the degree of membrane peroxidation, was very significantly correlated with superoxide dismutase （SOD）, peroxidase, and ascorbic acid. During the deep freezing period, the SOD activity and glutathione （GSH） content of the winter wheat varieties were relative to their cold resistance. During this period, the MDA stability, SOD, GSH, and the total water and the free water content might be used to identify the cold resistance of winter wheat varieties.
文摘By using atomic force microscope (AFM), the topography and function of the plasmalemma surface of the isolated protoplasts from winter wheat mesophyll cells were observed, and compared with dead protoplasts induced by dehydrating stress. The observational results revealed that the plasma membrane of living protoplasts was in a state of polarization. Lipid layers of different cells and membrane areas exhibited distinct active states. The surfaces of plasma membranes were unequal, and were characterized of regionalisation. In addition, lattice structures were visualized in some regions of the membrane surface. These typical structures were assumed to be lipid molecular complexes, which were measured to be 15.8±0.09 nm in diameter and 1.9±0.3 nm in height. Both two-dimensional and three-dimensional imaging showed that the plasmalemma surfaces of winter wheat protoplasts were covered with numerous protruding particles. In order to determine the chemical nature of the protruding particles, living protoplasts were treated by proteolytic enzyme. Under the effect of enzyme, large particles became relatively looser, resulting that their width was increased and their height decreased. The results demonstrated that these particles were likely to be of protein nature. These protein particles at plasmalemma surface were different in size and unequal in distribution. The diameter of large protein particles ranged from 200 to 440 nm, with a central micropore, and the apparent height of them was found to vary from 12 to 40 nm. The diameter of mid-sized protein particles was between 40―60 nm, and a range of 1.8―5 nm was given for the apparent height of them. As for small protein particles, obtained values were 12―40 nm for their diameter and 0.7―2.2 nm for height. Some invaginated pits were also observed at the plasma membrane. They were formed by the endocytosis of protoplast. Distribution density of them at plasmalemma was about 16 pits per 15 μm2. According to their size, we classified the invaginated pits into two types―larger pits measuring 139 nm in diameter and 7.2 nm in depth, and smaller pits measuring 96 nm in diameter and 2.3 nm in depth. On dehydration-induced dead pro-toplasts, the degree of polarization of plasma membranes decreased. Lipid molecular layers appeared relatively smooth, and the quantity of integral proteins reduced a lot. Invaginated pits were still de-tectable at the membrane surface, but due to dehydration-induced protoplast contraction, the orifice diameter of pits reduced, and their depth increased. Larger pits averagely measuring 47.4 nm in di-ameter and 31.9 nm in depth, and smaller pits measuring 26.5 nm in diameter and 43 nm in depth at average. The measured thickness of plasma membranes of mesophyll cells from winter wheat examined by AFM was 6.6―9.8 nm, thicker in regions covered with proteins.
