渗透胁迫和CO~(++)对小麦幼苗内源多胺含量和乙烯产生的影响

抗旱和不抗旱的小麦幼苗叶片与根系,在1MPaPEG渗透胁迫下释出乙烯和生成内源腐胺、亚精胺和精胺的数量增加。当增加2mmol钴离子处理6h和12h后,乙烯生成显著受到抑制,而亚精肢和精胺呈现进一步增加。表明钴离子阻遏了氨基环烷羧酸向乙烯转变的途径,并为多胺合成提供了更多的底物,从而有利于提高小麦抗衰老和抗旱的能力,抗旱品种表现更为明显。     

Cascade transduction and production of the light-nitric oxide signal from shoots to roots in maize seedlings exposed to enhanced UV-B radiation

The biomasses, rate of apparent nitric oxide (NO)-release, nitric oxide synthase (NOS) activity as well as β-d-endo and exo-glucanase activity of the cell wall were analyzed and determined in the roots of maize seedlings. It was found that rhizospheric treatments of 2-phenyl-4,4,5,5-tetramethlimida-zoline-l-oxyl-3-oxide (PTIO), a NO scavenger, and radiation of enhanced ultraviolet-B (UV-B) to aerial parts of the seedling markedly inhibited the rate of NO release in roots, raised the activity of β-d-endo and exo-glucanase, and increased the biomasses of roots. The patent inhibitor, N-nitro-l-arginine (LNNA), of NOS was unable to inhibit NOS activity and NO generation. Inversely, reactive oxygen species (ROS) eliminator, N-acetyl-cysteine (NAC), stimulated the rate of NO release. There is no relationship between NOS activity and the rate of NO release. The latter showed a positive correlation with nitrate reductase (NR) activity, whereas it showed a negative correlation with the bio-masses and the activity of β-d-endo and exo-glucanase. All results implicated that NO was a by-product generated by NR catalysis, whereas NR activity was sensitively repressed by the systemic signal network (involved in ROS) induced by enhanced UV-B. It indicated that the downstream signal molecule of enhanced UV-B light is probably ROS which decreased NO generation through inhibiting NR activity. The endogenous NO generated by NR catalysis is perhaps such a messenger for restraining β-d-endo and exo-glucanase activity that the root growth was retarded.     

圆柏属常绿木本植物叶片抗氧化系统季节变化与抗冷冻的关系

测定分析圆柏属2种常绿木本植物叶抗氧化系统在冷冻适应过程中的季节变化。结果表明,叶能在组织结冰状况下生存与其具备完善的抗氧化保护系统有关,该系统能及时清除氧自由基、抑制膜脂过氧化、维持膜的完整性;冷适应期积累的活性氧可能诱导了抗氧化保护系统使叶片获得抗冻性。祁连圆柏的抗氧化系统比圆柏在抗冻性诱导中具有更广泛的适应策略。     

Effects of nitric oxide on growth of maize seedling leaves in the presence or absence of ultraviolet-B radiation

The leaves of maize seedlings were used to measure leaf biomass including leaf length, width and weight, and to examine the relationship between nitric oxide (NO) synthase activity in microsomes and cytosol to the exo- and endo-beta-glucanase activity during growth. It was found that ultraviolet-B radiation (UV-B radiation) strongly induced nitric oxide synthase (NOS) activity but caused both a decrease of leaf biomass and exo- or endo-beta-glucanase activity. In contrast, the NOS inhibitor and NO donor largely decreased the activity of NOS in non-irradiated seedlings. The inhibitor also reduced exo- and endo-beta-glucanase activity and leaf biomass while the donor increased the enzyme activity and leaf biomass under normal conditions. Alternatively, under ultraviolet-B, the additional inhibitor of NOS and NO donor appeared to compromise the effects of ultraviolet-B on glucanase activity and leaf biomass, making the relationship between NOS activity and glucanase activity negatively correlated. This suggests that the changes of NOS activity showed a positive correlation to glucanase activity and leaf biomass in the absence of ultraviolet-B, but a negative correlation to ultraviolet-B irradiation and NO donor treatment alone. It is assumed that exo- and endogenous NO is responsible for the up-regulation of regular growth and development without ultraviolet-B. Under UV-B radiation, however, it might function as a signaling molecule of ultraviolet-B inhibiting leaf growth of maize seedlings to carry out stress-signaling transduction.     

Seasonal changes in anthocyanin contents and in activities of xanthophyll and ascorbate–glutathione cycles in Sabina species derived from different environments

Qilian Juniper (Sabina przewalskii Kom.) and Chinese juniper [Sabina chinensis (Lin.) Ant.] are overwintering plants. S. przewalskii, a protected species in China, is distributed in subalpine and alpine area on the Qinghai-Tibet Plateau. S. chinensis is distributed in plain area. We investigated seasonal changes in photoprotective stress compounds such as anthocyanins, activities of three enzymes of ascorbate–glutathione pathway, as well as xanthophyll size and conversion in these species. Ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) levels were higher in the low-temperature months, which was associated with changes in anthocyanins and in de-epoxidation index [(A + Z)/(V + A + Z)]. Photochemical efficiency of PSII (Fv/Fm) was lower (<0.70) during winter and late autumn in both species. During the low-temperature months, S. przewalskii had higher levels of photoprotective stress compounds than S. chinensis. The results suggested that these two species possess cold-induced photoinhibition functions and show the inherent, season-dependent differences in the amounts of the stress-related compounds.     

Regulation of the plasma membrane during exposure to low temperatures in suspension-cultured cells from a cryophyte (Chorispora bungeana)

Summary. As the outermost boundary of the cell, the plasma membrane plays an important role in determining the stress resistance of organisms. To test this concept in a cryophyte, we analyzed alterations of several components in plasma membranes isolated from suspension-cultured cells of Chorispora bungeana Fisch. & C.A. Mey in response to treatment at 0 and −4 °C for 192 h. When compared with the controls growing at 25 °C, both the membrane permeability and fluidity showed recovery after the initial impairment. Linolenic acid and membrane lipid unsaturation increased by about 0.8-fold following cold treatments, although the kinetics of the increase varied with the temperatures examined. During the treatments, the plasma membrane H⁺-ATPase (EC 3.6.1.3) activity increased by 78.06% at 0 °C and 100.47% at −4 °C. However, the plasma membrane NADH oxidase (EC 1.6.99.3) activity only decreased when exposed to a lower temperature (−4 °C), and remained at 63.93% after being treated for 192 h. After the treatments, the physical properties of the plasma membranes of suspension-cultured cells, especially the −4 °C treated cells, were similar to those in the wild plants. These findings indicate that the specific mechanism of cold resistance of C. bungeana is tightly linked with the rapid and flexible regulation of membrane lipids and membrane-associated enzymes, which ensure the structural and functional integrity of the plasma membrane that is essential for withstanding low temperature. Correspondence: Lizhe An, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, People’s Republic of China.     

祁连圆柏和圆柏色素含量及其花青苷合成酶活性的季节性变化

以祁连圆柏(Sabina przewalskii)和圆柏(S. chinensis)为材料, 测定2种植物花青苷、类黄酮、紫松果黄素、叶绿素和 类胡萝卜素的含量及花青苷合成过程中关键酶苯丙氨酸解氨酶(PAL)和类黄酮糖基转移酶(UFGT)的活性, 并分析了各值的季节性变化。结果表明, 祁连圆柏和圆柏叶片中PAL及UFGT的活性、花青苷、类黄酮﹑紫松果黄素以及类胡萝卜素的含量在低温季节均明显高于其它季节; 叶绿素含量在低温季节低于其它季节; 并且祁连圆柏中花青苷含量及其合成酶PAL和UFGT的活性以及类黄酮、紫松果黄素和叶绿素含量始终高于圆柏。结果说明花青苷是圆柏属植物中具有抗冻特性的重要次生代谢物,是抵御低温和辐射胁迫的一种重要保护物质; 紫松果黄素等色素对圆柏属植物抵抗低温诱导的光抑制起重要作用。     

Met对渗透胁迫下小麦幼苗内源多胺含量和乙烯产生的影响

渗透胁迫下,小麦幼苗内源多胺含量和乙烯产生均明显增加,再用0．4mmoL甲硫氨酸掺人处理后,乙烯释出加速,精胺含量进一步增多,亚精胺含量变化不大,腐胺的含量几乎减少到胁迫前的水平。可见,渗透胁迫下,甲硫氨酸既可以在Met循环中以甲硫氨酸与腐胺联合生成亚精胺,进而再与亚精胺联合生成精胺,又可以S-腺苷甲硫氨酸分解生成5’-甲硫基腺苷和氨基环丙烷羧酸,最后由氨基环丙烷羧酸加氧生成乙烯。