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991.
A hydroponic trial was conducted to investigate effects of molybdenum (Mo) on ascorbate-glutathione cycle (AsA-GSH cycle)
metabolism in Chinese cabbage (Brassica campestris L. ssp. pekinensis). Mo was applied at four rates: 0, 0.01, 0.15 and 1.5 mg l−1. The concentrations of ascorbate, dehydroascorbate, reduced- and oxidized- glutathione, and activities of five key enzymes
in the AsA-GSH cycle were studied. The results showed that appropriate Mo application increased the fresh weight of Chinese
cabbage, but excess application of Mo (1.5 mg l−1 Mo) decreased the fresh weight. Total ascorbate and reduced ascorbate concentrations in the Chinese cabbage increased with
Mo application rates. Although no significant differences existed in DHA concentration between the different Mo regimes, but
it has an increase trend with the 0.01 mg l-1 Mo treatment, and then decreased with the Mo level increasing. No significant difference in GSH concentration was found between
the different Mo treatments. Compared with the control, the GSSG concentration decreased significantly in the 0.01 mg l−1 Mo treatment. The activities of APX, MDHAR, DHAR and GR increased due to Mo application. But the activity of AAO decreased
with increasing Mo application rates. It is hypothesized that Mo may promote the redox process and regeneration of ascorbic
acid, and affect the ability of anti-oxidation in the Chinese cabbage.
Responsible Editor: Jian Feng Ma. 相似文献
992.
Falke KC Flachenecker C Melchinger AE Piepho HP Maurer HP Frisch M 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2007,114(5):765-776
Selection and random genetic drift are the two main forces affecting the selection response of recurrent selection (RS) programs
by changes in allele frequencies. Therefore, detailed knowledge on allele frequency changes attributable to these forces is
of fundamental importance for assessing RS programs. The objectives of our study were to (1) estimate the number, position,
and genetic effect of quantitative trait loci (QTL) for selection index and its components in the base populations, (2) determine
changes in allele frequencies of QTL regions due to the effects of random genetic drift and selection, and (3) predict allele
frequency changes by using QTL results and compare these predictions with observed values. We performed QTL analyses, based
on restriction fragment length polymorphisms (RFLPs) and simple sequence repeats (SSRs), in 274 F2:3 lines of cross KW1265 × D146 (A × B) and 133 F3:4 lines of cross D145 × KW1292 (C × D) originating from two European flint maize populations. Four (A × B) and seven (C × D)
cycles of RS were analyzed with SSRs for significant allele frequency changes due to selection. Several QTL regions for selection
index were detected with simple and composite interval mapping. In some of them, flanking markers showed a significant allele
frequency change after the first and the final selection cycles. The correlation between observed and predicted allele frequencies
was significant only in A × B. We attribute these observations mainly to (1) the high dependence of the power of QTL detection
on the population size and (2) the occurrence of undetectable QTL in repulsion phase. Assessment of allele frequency changes
in RS programs can be used to detect marker alleles linked to QTL regions under selection pressure.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
993.
Endogenous embryo factors, which act mainly in the radicle, prevent germination in Tagetes minuta at high temperatures. These factors act to prevent cell elongation, which is critical for radicle protrusion under optimal conditions. Once the radicle has emerged both cell elongation and cell division are required for post-germination growth. Germination can be induced at high temperatures by fusicoccin, which rapidly stimulates cell elongation. In addition, priming seeds at 25 °C on polyethylene glycol (PEG) 6000 and mannitol could also induce germination on water at 36 °C, indicating that priming prevents radicle protrusion at a point subsequent to the point of control in thermoinhibited achenes. Flow cytometry studies revealed that DNA synthesis occurs during thermoinhibition and the inhibition of DNA synthesis during this process inhibits subsequent germination on water under optimal conditions, suggesting a protective role for DNA synthesis in thermoinhibited achenes of T. minuta. 相似文献
994.
Changes in leaf cuticular waxes of sesame (Sesamum indicum L.) plants exposed to water deficit 总被引:4,自引:0,他引:4
Sesame (Sesamum indicum L.) is one of the most important oilseed crops, having seeds and oil that are highly valued as a traditional health food. The objective of this study was to evaluate leaf cuticular wax constituents across a diverse selection of sesame cultivars, and the responses of these waxes to drought-induced wilting. Water-deficit was imposed on 18 sesame cultivars by withholding irrigation for 15d during the post-flowering stage, and the effect on seed yield and leaf waxes compared with a well-watered control. Leaf cuticular waxes were dominated by alkanes (59% of total wax), with aldehydes being the next-most abundant class. Compared to well-irrigated plants, drought treatment caused an increase in wax amount on most cultivars, with only three cultivars having a notable reduction. When expressed as an average across all cultivars, drought treatment caused a 30% increase in total wax amount, with a 34% increase in total alkanes, a 13% increase in aldehydes, and a 28% increase in the total of unknowns. In all cultivars, the major alkane constituents were the C27, C29, C31, C33, and C35 homologs, whereas the major aldehydes were the C30, C32, and C34 homologs, and drought exposure had only minor effects on the chain length distribution within these and other wax classes. Drought treatments caused a large decrease in seed yield per plant, but did not affect the mean weight of individual seeds, showing that sesame responds to post-flowering drought by reducing seed numbers, but not seed size. Seed yield was inversely correlated with the total wax amount (-0.466*), indicating that drought induction of leaf wax deposition does not contribute directly to seed set. Further studies are needed to elucidate the ecological role for induction of the alkane metabolic pathway by drought in regulating sesame plant survival and seed development in water-limiting environments. 相似文献
995.
Lactic acid is a versatile organic acid, which finds major application in the food, pharmaceuticals, and chemical industries.
Microbial fermentation has the advantage that by choosing a strain of lactic acid bacteria producing only one of the isomers,
an optically pure product can be obtained. The production of l(+) lactic acid is of significant importance from nutritional viewpoint and finds greater use in food industry. In view of
economic significance of immobilization technology over the free-cell system, immobilized preparation of Lactobacillus casei was employed in the present investigation to produce l(+) lactic acid from whey medium. The process conditions for the immobilization of this bacterium using calcium pectate gel
were optimized, and the developed cell system was found stable during whey fermentation to lactic acid. A high lactose conversion
(94.37%) to lactic acid (32.95 g/l) was achieved with the developed immobilized system. The long-term viability of the pectate-entrapped
bacterial cells was tested by reusing the immobilized bacterial biomass, and the entrapped bacterial cells showed no decrease
in lactose conversion to lactic acid up to 16 batches, which proved its high stability and potential for commercial application. 相似文献
996.
Physiology and biochemistry of source-regulated protein accumulation in the wheat grain 总被引:2,自引:0,他引:2
Barneix AJ 《Journal of plant physiology》2007,164(5):581-590
Wheat is unique among cereals for the baking qualities of its flour, which are dependent upon the type and concentration of its proteins. As a consequence, the grain protein concentration (GPC) is one of the main determinants of wheat international market price. More than 50-70% of the final grain N is accumulated before flowering and later remobilized to the grain, N fertilization being the common practice used to produce high GPC. However, after incremental additions of N fertilizer, GPC reaches a maximum and then remains constant, without any increase in N uptake or remobilization by the crop, thus decreasing the efficiency of N fertilizer. Although, the genetic and molecular mechanisms that regulate N uptake by the roots are being clarified quickly, the regulation and physiology of N transport from the leaves to the grain remains less clear. In this review, the possible regulatory points involved in N transport to the grain and the difficulties for increasing GPC are discussed. It has been demonstrated that protein synthesis in the grain is source-limited, and that the grain can accumulate protein limited only by the amino acids provided by the phloem. It has also been shown that there is no limitation in the amino acid/sugar ratios that can be exported to the phloem. On the other hand, NO(3)(-) uptake transporters are depressed when the plant concentration of some amino acids, such as glutamine, is high. It has also been shown that a high N supply increases cytokinins concentration, preventing leaf senescence and proteolysis. Based on this information, it is postulated that there are two main regulatory points during grain filling when plant N status is ample. On the one hand, the N uptake transporters in the roots are depressed due to the high amino acids concentration in the tissues, and N uptake is low. On the other, a high amino acids concentration keeps the cytokinins level high, repressing leaf protein degradation and decreasing amino acid export to the phloem. As a consequence, GPC cannot be increased despite the ample N supply. 相似文献
997.
Hossain MT Soga K Wakabayashi K Kamisaka S Fujii S Yamamoto R Hoson T 《Journal of plant physiology》2007,164(4):385-393
Effects of silicon on the mechanical and chemical properties of cell walls in the second leaf of oat (Avena sativa L.) seedlings were investigated. The cell wall extensibility in the basal region of the second leaf was considerably higher than that in the middle and subapical regions. Externally applied silicon increased the cell wall extensibility in the basal region, but it did not affect the extensibility in the middle and subapical regions. The amounts of cell wall polysaccharides and phenolic compounds, such as diferulic acid (DFA) and ferulic acid (FA), per unit length were lower in the basal region than in the middle and subapical regions of the leaf, and silicon altered these amounts in the basal region. In this region, silicon decreased the amounts of matrix polymers and cellulose per unit length and of DFA and FA, both per unit length and unit matrix polymer content. Silicon treatment also lowered the activity of phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) in the basal region. In contrast, the amount of silicon in cell walls increased in response to silicon treatment in three regions. These results suggest that in the basal region, silicon reduces the net wall mass and the formation of phenolic acid-mediated cross-linkages between wall polysaccharides. Such modifications of wall architecture may be responsible for the silicon-induced increase in the cell wall extensibility in oat leaves. 相似文献
998.
999.
Evidence suggests that dab and rainbow trout are able to quickly adjust their food intake to an appropriate level when offered novel diets. In addition day-to-day and meal-to-meal food intake varies greatly and meal timing is plastic. Why this is the case is not clear: Food intake in fish is influenced by many factors, however the hierarchy and mechanisms by which these interact is not yet fully understood. A model of food intake may be helpful to understand these phenomena; to determine model type it is necessary to understand the qualitative nature of food intake. Food intake can be regarded as an autoregressive (AR) time series, as the amount of food eaten at time t will be influenced by previous meals, and this allows food intake to be considered using time series analyses. Here, time series data were analysed using nonlinear techniques to obtain qualitative information from which evidence for the hierarchy of mechanisms controlling food intake may be drawn. Time series were obtained for a group of dab and individuals and a group of rainbow trout for analysis. Surrogate data sets were generated to test several null hypotheses describing linear processes and all proved significantly different to the real data, suggesting nonlinear dynamics. Examination of topography and recurrence diagrams suggested that all series were deterministic and non-stationary. The point correlation dimension (PD2i) suggested low-dimensional dynamics. Our findings suggest therefore that any model of appetite should create output that is deterministic, non-stationary, low-dimensional and having nonlinear dynamics. 相似文献
1000.