中国十字花科(Cruciferae)的地理分布

在评述十字花科（Cruciferae）分类系统,分析主要性状演化趋势和科、属分布的基础上,提出中国十字花科植物可能是本土起源的观点,其起源中心和分布中心可能在以青藏高原为主体的西部高山和丘陵地区,起源时间至少在第三纪晚期以前,并认为中国十字花科植物自起源地（青藏高原）可能有3条主要的散布途径：第1条是自青藏高原向东北部,沿宁夏、陕西、内蒙古、山西、河北,到达东北大小兴安岭一带,并在蒙古高原及东北山地形成次分布中心;第2条自青藏高原向东,经重庆、湖南、湖北,沿长江流域分布,到达东部沿海一带;第3条自青藏高原向东南部,经贵州、广西、广东、福建,延伸到台湾。     

十字花科栽培蔬菜及野生近缘种资源对小菜蛾的抗性分析

小菜蛾是危害十字花科蔬菜最严重的害虫,造成蔬菜产业巨大经济损失。现有育种材料中抗小菜蛾的资源非常稀缺,制约了抗虫新品种的选育。本研究利用国家蔬菜种质资源中期库中近年收集的来自10个国家,42个种,218份十字花科栽培蔬菜及野生近缘种资源进行了小菜蛾抗性鉴定。这些资源的抗性水平从极抗到极感皆有分布,除极端抗/感材料较少外,总体上呈均匀分布。属间、种间、变种间的平均抗性差异显著。同种植物的不同种质间抗性分布亦广。栽培资源比野生资源具有相对更高的平均抗虫水平,但是后者高抗材料更多。北部欧洲等地是抗性资源分布相对集中的地理区域。本研究获得抗虫资源19份,其中高抗资源4份,这些材料对蔬菜抗虫育种和抗虫基因发掘具有重要应用价值。     

Degradation of glucosinolates of Nasturtium officinale seeds

Nasturtium officinale contains four glucosinolates, the major representative being 2-phenethylglucosinolate. On autolysis of seeds or leaves, isothiocyanates were the main products of glucosinolate degradation but no thiocyanate was detected. The application of heat during extraction caused an increase in nitrile formation to dominance over isothiocyanates. A (benzyl) thiocyanate-forming extract of Lepidium sativum seeds did not provoke generation of any thiocyanate from glucosinolates of N. officinale (or Barbarea praecox), but it did impose accentuated nitrile-forming properties on the systems. The conclusion is reached that some glucosinolate-containing Cruciferae are predominantly nitrile-producing and some predominantly isothiocyanate-producing, all other factors being constant.     

Some glucosinolates of Farsetia aegyptia and Farsetia ramosissima

Air-dried leaves of Farsetia aegyptia and F. ramosissima have been analysed for their glucosinolates; the former was shown to contain at least six but chiefly allylglucosinolate, whilst the latter contains at least five but mainly but-3-enylglucosinolate with some 4-(methylthio)butylglucosinolate. Without the addition of extraneous thioglucosidase enzyme, both species gave predominantly nitrile degradation products of glucosinolates; but if extra enzyme were added, corresponding isothiocyanates became the major products instead. Varying the pH from the natural level for the plant also considerably affected the ratios of glucosinolate products.     

Relationship of dehydration rate to drought avoidance,dehydration tolerance and dehydration avoidance of cabbage leaves,and to their acclimation during drought-induced water stress*

Abstract. Drought avoidance due to cuticular control increases with leaf number to a maximum in the intermediate leaves, decreasing to a minimum in the upper leaves. Dehydrated intermediate leaves do not rehydrate detectably when floated on water for several days. Excision of their petioles when submerged, permits full rehydration, presumably via the xylem. Stressing the plant by withholding water for 1–3 weeks fails to increase this already high resistance to water movement through the leaf surface. It does, however, markedly decrease the loss of water from the fully rehydrated (100% RWC) leaves during the first hour of dehydration, presumably due to a more rapid stomatal closure than in the non-stressed leaves. Dehydration tolerance increases with leaf number, without an intermediate maximum. The intermediate and upper leaves were markedly more tolerant of dehydration after drought-induced stress than when non-stressed. Dehydration tolerance in some cases, was inversely proportional to dehydration rate. It was possible, however, to equalize the rates of dehydration of drought-stressed and non-drought-stressed leaves without affecting the greater tolerance of the drought-stressed leaves. Dehydration avoidance by osmotic adjustment was markedly developed in the slowly dehydrated attached leaves of drought-stressed plants, but not in the rapidly dehydrated excised leaves. This is evidence of drought acclimation. It must, therefore, be concluded that the slow dehydration of the drought-stressed plants also leads to the increase in dehydration tolerance by permitting drought-induced acclimation. The overall drought resistance of cabbage leaves depends on the three components: drought avoidance, dehydration avoidance and dehydration tolerance. The latter two increase during acclimation but the cuticular control of drought avoidance does not.     

Effect of polyamines and guanidines on the growth,nitrogen assimilation and reserve mobilization in germinating radish seeds

Polyamines and guanidines enhanced the growth of radish seedlings grown in dark or light, irrespective of the supply of nitrogen. All the compounds inhibited ntirate reducatase and glutamine synthetase in the cotyledons of light-grown but not in dark-grown seeds. Nitrite reductase and glutamate dehydrogenase were not affected. Protease activity was enhanced by all the compounds in dark-as well as in light-grown seeds. Alanine aminotransferase activity was increased only in the light-grown seeds. The inhibition of nitrate reductase was not due to decreased nitrate uptake but was due to a decreased metabolic pool of nitrate and a decline in enzyme synthesis. The inhibition of glutamine synthetase and activation of alanine aminotransferase by the compounds was found only in the chloroplast fraction. The activation of protease was due to the release or activation of preexisting enzyme while that of alanine aminotransferase was dependent on the de novo protein synthesis which was abolished by cycloheximide.     

Physiology and costs of resistance to herbivory and disease in Brassica

We used artificial selection experiments to study genetic allocation costs and physiological mechanisms of resistance to herbivory and fungal disease. Genetic costs to resistance were present in some instances and absent in others. Genetic resistance to the fungal pathogen, Leptosphaeria maculans was cost-free, while resistance to Peronospora parasitica showed a negative genetic correlation between disease resistance and growth rate. Leptosphaeria resistant genotypes had 13% higher chitinase activity. Genetic increases in myrosinase activity were correlated with increased resistance to flea beetles (Phyllotreta cruciferae), but resulted in lower plant fecundity, presumably due to production costs of myrosinase. Genetic costs of resistance may maintain genetic variation in natural plant populations. These studies demonstrate the predictive and explanatory power of a functional approach to plant-herbivore and plant-pathogen interactions.     

Osmotic stress and abscisic acid reduce cytosolic calcium activities in roots of Arabidopsis thaliana*

Cytosolic Ca²⁺· ([Ca²⁺]_i, and elongation growth were measured in the roots of Arabidopsis thaliana. Exposure of plant tissues to high NaCl and abscisic acid (ABA) concentrations results in a reduction in the rate of growth, but the mechanism by which growth is inhibited is not understood. Both NaCl and ABA treatments are known to influence [Ca²⁺]_i, and in this study we measured the effects of salinity and ABA on [Ca²⁺]_i in cells from the meristematic region of Arabidopsis roots. The Ca²⁺-sensitive dye Fura-2 and ratiometric techniques were used to measure [Ca²⁺]_i in cells of the root meristem region. Resting [Ca²⁺]_i was found to be between 100 and 200 μmol m^?3 in roots of untreated plants. Resting [Ca²⁺]_i changed in response to changes in the [Ca²⁺] surrounding growing roots. An increase of external [Ca²⁺] increased [Ca²⁺]_i; conversely, a decrease of external [Ca²⁺] decreased [Ca²⁺]_i. Exposure of roots to NaCl caused a rapid reduction of [Ca²⁺]_i, a response that was proportional to the external NaCl concentration. Thus, as the NaCl concentration was increased, [Ca²⁺]_i in root meristematic cells decreased. Root elongation was also inhibited in proportion to the external NaCl concentration, with maximal inhibition occurring at 120 mol m^?3 NaCl. The [Ca²⁺]_i of root meristem cells also changed in response to ABA, and the magnitude of the effect of ABA was dependent upon ABA concentration. Treatment with 0.2 mmol m^?3 ABA caused a momentary increase in [Ca²⁺]_i followed by a decrease after 15 min, but 10 mmol m^?3 ABA caused an immediate decline in [Ca²⁺]_i. There was a strong positive correlation between [Ca²⁺]_i and root elongation rates. Experiments with the ABA-deficient Arabidopsis mutant aba-3 indicated that the reduction in [Ca²⁺]_i brought about by NaCl was unlikely to be mediated via changes in endogenous ABA. Experiments with solutes such as sorbitol, KCl and NaNO₃ indicated that the effects of NaCl could be mimicked by other solutes and was not specific for NaCl.     

Arbuscular mycorrhizal development in three crucifers

To determine the developmental patterns of arbuscular mycorrhizae (AM) in three crucifers (Brassicaceae) of differing life histories, we inoculated seedlings of the annual Capsella bursa-pastoris, biennial Hesperis matronalis, and the perennial Matthiola incana with Glomus intraradices. The plants were grown either alone or in a matrix of living roots of the mycotrophic grass Sorghum sudanense. The percent root length colonized was greatest in C. bursa-pastoris and least in H. matronalis. Colonization was greater in plants grown in the grass matrix than in plants grown alone, and colonization in grass matrix-grown plants continued to increase over the 90-day growth period, whereas colonization leveled off or decreased near the end of the growth period in crucifers grown alone. No arbuscules were observed in crucifer roots at any time, which suggests that AM in these crucifers is nonfunctional. Furthermore, the increase in colonization only in pots with both crucifers and active mycotrophic roots suggests that AM development in crucifer roots is primarily the consequence of progressive root senescence in the crucifer and continued inoculum spread from the mycotrophic plant.