PVA和PEG(6000)预处理对大豆胚轴生长、蛋白质合成和ATP含量的影响

在低温吸胀阶段,经PVA(聚乙烯醇)和PEG(聚乙二醇6000)预处理的大豆胚轴蛋白质合成和ATP含量均比对照高。在萌发阶段,胚轴生长增快,蛋白质合成明显加快,ATP迅速被消耗,而对照胚轴则相反。试验结果表明,预处理大豆种子萌发和生长与其蛋白质合成、ATP水平和消耗能力有密切关系。     

Disproportionate allocation of mineral nutrients and carbon between vegetative and reproductive structures in Banksia hookeriana

We compared above-ground allocation patterns in mature shrubs of Banksia hookeriana from three 13-year-old populations, growing on nutrient-impoverished sands to determine whether C (dry mass) could be a substitute for mineral nutrients (N, P, K, Ca, Mg and NA). The percentage of reproductive structures to total above-ground growth (reproductive effort; RE) was integrated over nine successive reproductive cycles. Only 0.5% of above-ground dry mass was allocated to seeds compared with 31% to total RE. Allocations of N (24%) and P (48%) to seeds, and N (44%) and P (65%) to RE were much higher. Allocations of K, Ca, Mg and Na to seeds (<1–3%), and RE (21–35%) were closer to that of dry mass. Relative allocation (RA) is defined as the proportion of a nutrient element allocated to a structure relative to its dry mass. RA of P to seeds was 91 and N was 44, but for K, Ca, Mg and Na ranged from only 6 for K to<1 for Na. Thus P, and to a lesser extent N, provide a much more sensitive measure of the relative cost of reproduction than C in this nutrient-limited system.     

Molecular evolution of pteridophytes and their relationship to seed plants: Evidence from complete 18S rRNA gene sequences

Complete 18S ribosomal RNA sequence data from representatives of all extant pteridophyte lineages together with RNA sequences from different seed plants were used to infer a molecular phylogeny of vascular plants that included all major land plant lineages. The molecular data indicate that lycopsids are monophyletic and are the earliest diverging group within the vascular land plants, whereasPsilotum nudum is more closely related to the seed plants than to other pteridophyte lineages. The phylogenetic trees based on maximum likelihood, parsimony and distance analyses show substantial agreement with the evolutionary relationships of land plants as interpreted from the fossil record.     

芸苔属脱外壁花粉的分离与人工萌发

芸苔属青菜（Ｂｒａｓｓｉｃａ ｃｈｉｎｅｎｓｉｓ）与紫菜苔（Ｂ． ｃａｍ ｐｅｓｔｒｉｓｖａｒ． ｐｕｒｐｕｒｅａ）的花粉经低温水合、热激、渗激三步程序,分离出大量具萌发能力的脱外壁花粉,脱外壁率可高达６０％ 以上。在含有碳源与氮源及Ｒｏｂｅｒｔｓ培养基盐成分的碱性ＰＥＧ 培养基中,首次使芸苔属脱外壁花粉萌发,萌发率可达３３％ ～４１％ 。在扫描电镜下观察了花粉脱外壁与萌发的过程。讨论了不同植物花粉脱外壁的方法与花粉壁生物学特点的对应关系,以及外壁对花粉萌发的可能作用     

Life-history ofNeurospora intermedia in a sugar cane field

The life-history ofNeurospora in nature has remained largely unknown. The present study attempts to remedy this. The following conclusions are based on observation ofNeurospora on fire-scorched sugar cane in agricultural fields, and reconstruction experiments using a colour mutant to inoculate sugar cane burned in the laboratory. The fungus persists in soil as heat- resistant dormant ascospores. These are activated by a chemical(s) released into soil from the burnt substrate. The chief diffusible activator of ascospores is furfural and the germinating ascospores infect the scorched substrate. An invasive mycelium grows progressively upwards inside the juicy sugar cane and produces copious macroconidia externally through fire- induced openings formed in the plant tissue, or by the mechanical rupturing of the plant epidermal tissue by the mass of mycelium. The loose conidia are dispersed by wind and/or foraged by microfauna. It is suggested that the constant production of macroconidia, and their ready dispersal, serve a physiological role: to drain the substrate of minerals and soluble sugars, thereby creating nutritional conditions which stimulate sexual reproduction by the fungus. Sexual reproduction in the sugar- depleted cellulosic substrate occurs after macroconidiation has ceased totally and is favoured by the humid conditions prevailing during the monsoon rains. Profuse micro-conidiophores and protoperithecia are produced simultaneously in the pockets below the loosened epidermal tissue. Presumably protoperithecia are fertilized by microconidia which are possibly transmitted by nematodes active in the dead plant tissue. Mature perithecia release ascospores in situ which are passively liberated in the soil by the disintegration of the plant material and are, apparently, distributed by rain or irrigation water.     

Promoter regions of cysteine endopeptidase genes from legumes confer germination-specific expression in transgenic tobacco seeds

Cysteine endopeptidases, SH-EP from Vigna mungo and EP-C1 from Phaseolus vulgaris, act to degrade seed storage protein during seed germination. Using transgenic tobacco plants, expression of SH-EP and promoter activity of the EP-C1 gene were analyzed in transgenic tobacco plants. The promoters of the two genes in tobacco seeds showed germination-specific activation, although post-translational processing of SH-EP and regulatory regions of promoter of the gene for EP-C1 were found to differ between leguminous seeds and transgenic tobacco seeds.     

Bacterial expression of an active class Ib chitinase from Castanea sativa cotyledons

Ch3, an endochitinase of 32 kDa present in Castanea sativa cotyledons, showed in vitro antifungal properties when assayed against Trichoderma viride. The characterization of a cDNA clone corresponding to this protein indicated that Ch3 is a class Ib endochitinase that is synthesized as a preprotein with a signal sequence preceding the mature polypeptide. Bacterial expression of mature Ch3 fused to the leader peptide of the periplasmic protein ompT resulted in active Ch3 enzyme. A plate assay was adapted for semi-quantitative determination of chitinase activity secreted from cultured bacteria, which should facilitate the identification of mutants with altered capacity to hydrolyse chitin.     

Germination in spores of Dryopteris filix-mas: Regulation of rhizoid elongation as a second phytochrome-mediated response

Spore germination in Dryopteris filix-mas occurs via a cascade of cellular responses, and chlorophyll formation, mitosis or rhizoid elongation are commonly used as parameters to determine spore germination. Detailed investigations of these parameters led to the hypothesis that they are regulated by different, independent phytochrome-mediated responses. This concept could be confirmed, as is described in this paper which demonstrates that perception of light via phytochrome occurs within two different phases separated in time. Presence of the far-red absorbing phytochrome form, P_fr, for 36 h, induces chlorophyll formation and the first unequal cell division, by which a rhizoid initial and a protonemal initial are formed (first phytochrome-mediated response). However, rhizoid elongation requires a second period of P_fr, presence (second phytochrome-mediated response). There is a clear temporal distinction between the first and the second phytochrome-mediated response with respect to the coupling of P_fr to the transduction chain; P_fr is unable to induce rhizoid growth until 60 h after the start of the first red irradiation. The effectivity of P_fr for inducing the second response shows an optimum at ca 96 h after the beginning of the presence of P_fr; thereafter, it declines slowly. The fluence-response relationship and the presence of red/far-red reversibility demonstrate that rhizoid elongation is a low-fluence response mediated by phytochrome and is independent of the first phytochrome response.     

Changes in malondialdehyde content and in superoxide dismutase, catalase and glutathione reductase activities in sunflower seeds as related to deterioration during accelerated aging

Sunflower ( Helianthus annuus L.) seeds progressively lost their ability to germinate at 25°C, the optimal temperature for germination, after accelerated aging was carried out at 45°C (a temperature too high to permit germination) in water or at 76 or 100% relative humidity (RH). The deleterious effects of the high-temperature treatment increased with increasing seed moisture content. Incubation of seeds at 45°C in water resulted in electrolyte leakage, which indicated a loss of membrane integrity. A relationship between leakage and loss of seed viability could not be assumed, since no increase in electrolyte efflux occurred after aging al 100% RH. Accelerated aging induced accumulation of malondialdehyde, suggesting that seed deterioration was associated with lipid peroxidation. However, there was no direct relationship between lipid peroxidation and deterioration in membrane integrity. Loss of seed viability was also associated with a decrease in superoxide dismutase, catalase and glutathione reductase activities. Finally, the results obtained suggest that sunflower seed deterioration during accelerated aging is closely related to a decrease in the activities of detoxifying enzymes and to lipid peroxidation.     

Hydrolysis products of glucosinolates in Brassica napus tissues as inhibitors of seed germination

Enzymatic hydrolysis of glucosinolates, a class of compounds found in Brassica species, results in a number of products with potential to inhibit seed germination. To investigate the impact of both volatile and water-soluble allelochemicals, germination bioassays using Lactuca sativa seeds were conducted with root and combined leaf and stem tissues of Brassica napus. Tissues in which glucosinolates were hydrolyzed to remove volatile glucosinolate degradation products were compared with intact tissues and water controls. Only tissues containing glucosinolates produced volatiles that inhibited germination. Volatiles were trapped and identified using GC-MS. Volatiles produced in greater quanitity from intact tissues than from tissues without glucosinolates were almost exclusively glucosinolate hydrolysis products. Water-soluble components also inhibited germination. Chemical analysis of extracts confirmed the presence of glucosinolate hydrolysis products, but indicated the involvement of additional allelochemicals, especially in leaf and stem tissues. Results support the proposal that glucosinolate-containing plant tissues may contribute to reductions in synthetic pesticide use if weed seeds are targeted.Abbreviations ITC isothiocyanates - CN organic cyanides - OZT oxazolidinethione - iRoot intact root tissue - iL&S intact leaf and stem tissue - hRoot hydrolyzed root tissue - hL&S hydrolyzed leaf and stem tissue