菜心叶片中乙醇酸氧化酶的多种组分

乙醇酸氧化酶（EC．1．1．3．1,GO）是光呼吸中的关键酶,过去对其电泳行为和等电点的报告互不一致。Grodzinski和Col－man（1972）将菠菜、烟草等植物部分纯化的GO酶液在pH8．3的聚丙烯酰胺凝胶中电泳,活性染色后出现两条活性带,两者对FMN的依赖性有一定差异。Kerr和Groves（1975）对豌豆叶片部分纯化的GO酶液进行等电聚焦电泳,表明其pI值大于9．6.Behrends等（1982）将绿色黄瓜子叶的酶液经聚焦层析,发现GO活性分布在pH8．7附近。但Nishimura等（1983）发现在pH8．9的凝胶中南瓜子叶GO不迁移,而在pH4．5的凝胶中则出现一…     

Shoot regeneration from cultured leaves of Japanese pear (Pyrus pyrifolia)

Several experiments were conducted to investigate in vitro regeneration of adventious shoots from cultured leaves of Japanese pear (Pyrus pyrifolia). A protocol was developed and regeneration achieved from six cultivars. Leaves harvested from shoot cultures which had been preconditioned on B5 medium with 5 μM thidiazuron plus 0.25 μM gibberellic acid were placed on regeneration medium of the same composition. Frequency of regeneration per leaf was as high as 23% but cultivar and environmental factors influenced the result. More mature (basal) leaves regenerated more frequently than younger ones from the shoot tip. Leaf orientation during regeneration and photoperiod was not a strong influence but regeneration from leaf pieces was less than from uncut leaves. An alternative regeneration procedure was developed in which first, shoot cultures were grown on the preconditioning medium. Leaves of the intact shoot cultures were then induced to regenerate directly when adventitious shoots formed on leaves of the intact shoot culture leaves without excision. Adventitious shoots from both procedures developed into typical shoot cultures when transferred to shoot culture maintenance medium. This revised version was published online in June 2006 with corrections to the Cover Date.     

Soret absorption of intermediate(s) in protochlorophyllide to chlorophyllide photoreduction trapped at low temperature

Absorption spectra at ca 100 K from 400 to 750 nm and fluorescence emission spectra at 77 K from 600 to 750 nm were obtained from: 1) etiolated leaves of the H-ordeum vulgare L. (barley) mutant albozonata 2 and SAN 9789-treated Avena sativa L. (oat) with low levels of carotenoids, and 2) preparations of protochlorophyllide holo-chrome from Phaseolus vulgaris L. cv. Commodore (bean).
This allowed clear resolution for the first time of the Soret bands of the green pigments before and after light-induced accumulation of intermediate(s) in protochlorophyllide to chlorophyllide photoreduction and after conversion of the intermediate(s) to chlorophyllide by warming the samples to 233 K in darkness. Although the intermediate(s) differ(s) in absorption and fluorescence in the red wavelength region from both protochlorophyllide and chlorophyllide, the extinction in the Soret band is not distinguishable from that of chlorophyllide. These observations indicate that the C7-C8 double bond in ring IV of protochlorophyllide has been altered in intermediate(s) accumulated at low temperature in intense light, such that the transition state exhibits the character of a π complex.     

The stimulating effect of a cold dark-pretreatment on the etioplast/chloroplast transformation of angiosperms. III. Involvement of the excision factor and of cold-retarded aging processes?

Our question is whether the stimulating effect of a cold dark-pretreatment on the process of de-etiolation in primary leaves of wheat seedlings under subsequent continuous white light is essentially mediated by the retarding effect of highly lowered temperatures on the following processes: aging and/or senescence, realization of the so-called excision factor in detached leaves, decrease of the cytokinin level in detached leaves. The strong stimulating effect of a cold dark-preatreatment remains inspite of progressive aging in parts of the leaves and a strong decrease of the capability of chlorophyll accumulation in detached in contrast to attached leaves. The strong stimulatory effect of a cold dark-pretreatment is not diminished by application of cytokinin or gibberellic acid. The stimulating effect of a cold dark-pretreatment is detectable over several days under continuous light, but it is lost during a warm dark-phase of a few hours duration between the cold dark-pretreatment and the white light phase.     

Long-term patterns of mass loss during the decomposition of leaf and fine root litter: an intersite comparison

Decomposition is a critical process in global carbon cycling. During decomposition, leaf and fine root litter may undergo a later, relatively slow phase; past long-term experiments indicate this phase occurs, but whether it is a general phenomenon has not been examined. Data from Long-term Intersite Decomposition Experiment Team, representing 27 sites and nine litter types (for a total of 234 cases) was used to test the frequency of this later, slow phase of decomposition. Litter mass remaining after up to 10 years of decomposition was fit to models that included (dual exponential and asymptotic) or excluded (single exponential) a slow phase. The resultant regression equations were evaluated for goodness of fit as well as biological realism. Regression analysis indicated that while the dual exponential and asymptotic models statistically and biologically fit more of the litter type–site combinations than the single exponential model, the latter was biologically reasonable for 27–65% of the cases depending on the test used. This implies that a slow phase is common, but not universal. Moreover, estimates of the decomposition rate of the slowly decomposing component averaged 0.139–0.221 year⁻¹ (depending on method), higher than generally observed for mineral soil organic matter, but one-third of the faster phase of litter decomposition. Thus, this material may be slower than the earlier phases of litter decomposition, but not as slow as mineral soil organic matter. Comparison of the long-term integrated decomposition rate (which included all phases of decomposition) to that for the first year of decomposition indicated the former was on average 75% that of the latter, consistent with the presence of a slow phase of decomposition. These results indicate that the global store of litter estimated using short-term decomposition rates would be underestimated by at least one-third.     

Genetic networks regulated by ASYMMETRIC LEAVES1 (AS1) and AS2 in leaf development in Arabidopsis thaliana: KNOX genes control five morphological events

The asymmetric leaves 1 ( as1 ) and as2 mutants of Arabidopsis thaliana exhibit pleiotropic phenotypes. Expression of a number of genes, including three class-1 KNOTTED -like homeobox ( KNOX ) genes ( BP , KNAT2 and KNAT6 ) and ETTIN / ARF3 , is enhanced in these mutants. In the present study, we attempted to identify the phenotypic features of as1 and as2 mutants that were generated by ectopic expression of KNOX genes, using multiple loss-of-function mutations of KNOX genes as well as as1 and as2 . Our results revealed that the ectopic expression of class-1 KNOX genes resulted in reductions in the sizes of leaves, reductions in the size of sepals and petals, the formation of a less prominent midvein, the repression of adventitious root formation and late flowering. Our results also revealed that the reduction in leaf size and late flowering were caused by the repression, by KNOX genes, of a gibberellin (GA) pathway in as1 and as2 plants. The formation of a less prominent midvein and the repression of adventitious root formation were not, however, related to the GA pathway. The asymmetric formation of leaf lobes, the lower complexity of higher-ordered veins, and the elevated frequency of adventitious shoot formation on leaves of as1 and as2 plants were not rescued by multiple mutations in KNOX genes. These features must, therefore, be controlled by other genes in which expression is enhanced in the as1 and as2 mutants.     

Simultaneous determination of vitexin-4″-O-glucoside,vitexin-2″-O-rhamnoside,rutin and vitexin from hawthorn leaves flavonoids in rat plasma by UPLC–ESI-MS/MS

A sensitive and accurate ultra-performance liquid chromatography electrospray ionization tandem mass spectrometry (UPLC–ESI-MS/MS) method was developed and validated for the simultaneous determination of vitexin-4″-O-glucoside (VGL), vitexin-2″-O-rhamnoside (VRH), rutin (RUT) and vitexin (VIT) in rat plasma after intravenous administration of hawthorn leaves flavonoids (HLF). Following protein precipitation by methanol, the analytes were separated on an ACQUITY UPLC BEH C₁₈ column packed with 1.7 μm particles by gradient elution using a mobile phase composed of acetonitrile and water (containing 0.1% formic acid) at a flow rate of 0.20 mL/min. The analytes and diphenhydramine (internal standard, IS) were detected in the multiple reaction monitoring (MRM) mode by means of an electrospray ionization (ESI) interface (m/z 292.96 for vitexin-4″-O-glucoside, m/z 293.10 for vitexin-2″-O-rhamnoside, m/z 299.92 for rutin, m/z 310.94 for vitexin and m/z 166.96 for IS). The calibration curve was linear over the range 10–40,000 ng/mL for vitexin-4″-O-glucoside, 10–50,000 ng/mL for vitexin-2″-O-rhamnoside, 8–1000 ng/mL for rutin and 16–2000 ng/mL for vitexin. The intra- and inter-run precisions (relative standard deviation, RSD) of these analytes were all within 15% and the accuracy (the relative error, RE) ranged from −10% to 10%. The stability experiment indicated that the four analytes in rat plasma samples and plasma extracts under anticipated conditions were stable. The developed method was applied for the first time to pharmacokinetic studies of the four bioactive compounds of hawthorn leaves flavonoids following a single intravenous administration of 20 mg/kg in rats.     

Effect of Controlled Crossing on the Triglyceride and Fatty Acid Composition of Virgin Olive Oils

Our study reports the triglyceride (triacylglycerol, TAG) composition of five new Tunisian virgin olive oil cultivars obtained through controlled crossings of the cultivar (cv.) Chemlali Sfax. These cultivars have been selected among a progeny of 500 olive descendants, based on an evaluation of the fatty‐acid (FA) composition of their oils. Among these samples, two were derived from the crossing with the cv. Sigoise as pollinator (SM634) or pollen acceptor (SM1110) and the others from the crossing with the cv. Meski as pollen acceptor (SM513, SM514, and SM517). The five descendants were characterized by a good fat value, a balanced FA composition, and a high content of triolein, varying between 26.9 (SM514) and 45.46% (SM1110). They had an improved FA composition as compared to that of the cv. Chemlali Sfax and their fruits were slightly bigger. The principal component analysis suggested that the TAG variables were more suitable than the total FAs for an optimum classification of the cultivar samples analyzed. The cultivars obtained through the crossing with the cv. Sigoise (as pollen acceptor or pollinator) had a more favorable composition of FAs and TAG than those obtained through the crossing with the cv. Meski, which indicated that genetic factors had the most important influence on the quality of the virgin olive oils.     

秦岭南坡不同海拔林分凋落叶分解特征

采用野外放置凋落物分解袋法,对秦岭南坡林区不同海拔华山松(Pinus armandii)、油松(P.tabulaeformis)、锐齿栎(Quercus aliena var.acuteserrata)和华北落叶松(Larix principis-rupprechtii)凋落叶分解过程中N、P、C、粗脂肪、粗纤维和热值的变化规律进行比较研究.结果表明:(1)处于不同海拔的同一树种新鲜凋落叶的N、P、C、粗脂肪含量及其热值差异不显著(P＞0.05).(2)在一年的分解过程中,凋落叶N、P含量表现出逐渐富集的趋势,其中油松凋落叶N、P富集速度最快,分别达到165.60%和189.94%;凋落叶C、粗脂肪含量和热值、C/N、C/P、粗纤维/N在分解中逐渐下降,粗脂肪释放速率达到50.29%～77.82%.(3)分解一年后,不同海拔同一树种凋落叶N、P、C、C/N、C/P含量仍未表现出显著性差异(P＞0.05),但不同海拔凋落叶粗脂肪分解表现出极显著差异(P＜0.01),其中差距最大的锐齿栎凋落叶低海拔较高海拔粗脂肪释放率高19.38%;不同海拔华北落叶松和锐齿栎凋落叶粗纤维释放速率差异极显著(P＜0.01),而不同海拔油松、华山松凋落叶粗纤维释放无显著差异;处于高低海拔的华北落叶松和锐齿栎凋落叶热值分别为17.12和15.68 kJ·g-1、17.74和13.51 kJ·g-1,表现出极显著差异(P＜0.01),油松、华山松凋落叶表现出显著差异(P＜0.05).研究发现,一年中海拔差异所造成的降水、温度等因素的变化对各树种凋落叶中N、P、C的释放无显著影响,但对凋落叶分解过程中粗脂肪、热值、粗纤维/N的变化影响显著.     

NaCl胁迫对毛竹叶片的电阻抗图谱参数及膜透性的影响

以NaCl胁迫下毛竹（Phyllostachys edulis）实生苗叶片为材料,测定其电阻抗图谱参数和膜透性的变化,通过膜透性与电阻抗图谱参数间的相关性,来证明电阻抗图谱法研究竹子受胁迫程度的有效性。结果表明：随着盐浓度的升高,胞外电阻、胞内电阻和弛豫时间呈现先减小、后增加、再减小的特征,而弛豫时间分布系数表现恰好相反;叶片细胞膜相对透性逐渐增大,脯氨酸的含量先逐渐增大,然后减小。相关分析表明：胞内电阻、胞外电阻、弛豫时间与脯氨酸含量呈极显著负相关（p〈0.01）;胞外电阻、弛豫时间与膜相对透性呈显著负相关（p〈0.05）。电阻抗图谱参数能够有效地表示毛竹受NaCl胁迫的程度,电阻抗图谱法将是竹子逆境胁迫研究的一种有效方法。