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51.
Tissue culture techniques for the propagation and conservation of endemic or threatened plants can be used to complement the methods usually applied in ex situ conservation. Thus, Minuartia valentina (Caryophyllaceae), an endangered plant species endemic to the Valencia Community (Eastern Spain), was successfully regenerated through shoot proliferation from wild plants growing in their natural area. Nodal segments, 10~mm long, were cut from rametes of adult material, sterilised and established in vitro. Equally successful shoot multiplication was achieved on Murashige and Skoog (MS) medium with 80 mg l-1 phloroglucinol in combination with either 1 mg l-1 6-benzylaminopurine or 1 mg l-1 kinetin. Excised shoots were rooted in MS medium supplemented with an auxin (indole acetic acid, indole-3-butyric acid, or napththalene acetic acid). Shoots rooted well (96–100%) within three weeks in all auxin treatments. However, the use of napththalene acetic acid was discarded because this auxin delayed root differentiation, and induced adventitious root malformation. Rooted plantlets were transferred to pots and 85% of them acclimatized successfully four weeks after transfer to greenhouse conditions, where they exhibited normal morphology and growth.  相似文献   
52.
1. The Qilian Mountains represent one of the key livestock‐raising grasslands in China. The two main herbivore species raised in this area – yaks and sheep – are of critical economical value. Grasshoppers compete with these animals for available nutrients, creating multifaceted relationships between livestock, grasshoppers and plants. A clear understanding of such relationships is lacking and is urgently needed to guide conservation efforts. 2. This study aims to document the effects of yak and sheep grazing on grasshopper assemblages and to elucidate the underlying mechanisms of such effects. 3. It is shown here that yaks and sheep impact grasshopper assemblages differently. Grasshopper assemblages exhibited lower density, biodiversity, richness, and evenness of distribution in yak‐grazed pastures than in grazing‐free grasslands. Sheep‐grazed pastures exhibited a dramatically divergent picture, with elevated density, biodiversity and richness, and a slightly decreased evenness of distribution. Grasshoppers were generally larger in grazed pastures than in grazing‐free grasslands, especially in yak‐grazed plots. 4. The present study suggests that differences between yak and sheep pastures in plant assemblage structure and plant traits are probably the underlying forces driving the differences in grasshopper assemblage structure and grasshopper traits, respectively. 5. The study shows that the grasshopper habitat indicator species differ between yak and sheep pastures, raising the possibility that such indicators can be used to monitor grassland usage and degradation in the Qilian Mountains. 6. These results provide novel insights into the dynamic interactions of common domesticated herbivore species, grasshoppers and plants in Qilian Mountains, which augment current knowledge and may ultimately lead to better conservation practices.  相似文献   
53.
1. Generalist herbivores feed on a wide and diverse set of species, but fine‐scale foraging patterns may be affected by the interplay between the quality, quantity and spatial distribution of host plants. 2. The foraging patterns of a prevalent Neotropical herbivore, the leaf‐cutter ant Atta laevigata, in the Brazilian Cerrado savannas were examined in order to determine if patterns observed are in concert with central‐place foraging predictions. 3. The results showed that A. laevigata acts as a polyphagous but highly selective herbivore, with ant attacks often resulting in partial defoliation of less‐preferred species and full defoliation of preferred ones. It was found, for the first time, that there is a strong and positive relationship between the relative attack frequency on plants from preferred species and foraging distance to the nest. This suggests a balance between the quality of plant resources harvested and costs involved in their transportation. It was also observed that colonies focused their harvest on preferred species in months with low availability of young leaves. Consequently, high herbivory rate was more frequent in plants attacked far away from the nest and in dry months. 4. These assessments highlight the fact that Atta colonies may become more selective as foraging distance to the nest increases and in response to fluctuations in the availability of palatable resources throughout the year. The results also show some dissimilarities in the foraging behaviours of A. laevigata when compared with other locations, suggesting that widely distributed herbivores may modify foraging strategies across their geographic range.  相似文献   
54.
自然界中植物的生长发育受到各种环境变化的影响。为了响应外界各种环境条件,植物演化出一系列识别和传递环境信号的蛋白分子,其中比较典型的是植物细胞质膜上的类受体蛋白激酶(RLKs)。凝集素类受体蛋白激酶(LecRLKs)是类受体蛋白激酶家族中的一个亚族,它主要包含3个结构域:细胞外凝集素结构域、跨膜结构域和细胞内激酶结构域。根据细胞外凝集素结构域的不同,LecRLKs可分为3种不同类型:L、G和C型。近年来,研究表明LecRLKs在植物生物/非生物胁迫和发育调控中发挥非常重要的作用。该文综述了植物凝集素类受体蛋白激酶的研究历史、结构特点、分类以及生物学功能,并重点阐述凝集素类受体蛋白激酶在植物生物/非生物胁迫响应和调控发育方面的功能。对不同类型和不同功能的植物凝集素类受体蛋白激酶进行阐述将有利于对该类蛋白开展功能研究,并为作物改良提供有益借鉴。  相似文献   
55.
为明确昆虫抗冻蛋白基因转入甘薯(Ipomoea batatas)后是否能提升其抗冻能力,进而为培育甘薯抗冻育种材料奠定基础,将黄粉虫(Tenebrio molitor)抗冻蛋白基因TmAFP导入植物基因表达质粒,经农杆菌介导的遗传转化获得抗冻甘薯新材料。以甘薯品种Huachano为受体材料建立甘薯植株高效再生体系,并采用不同成分的体细胞胚成熟培养基培养胚性悬浮细胞。胚性愈伤组织对除草剂的敏感性测试结果表明,转基因阳性植株筛选的最适培养基为MS+0.2 mg·L–12,4-D+0.8 mg·L^–1 GAP+100 mg·L^–1 Carb。将表达质粒分别转化Huachano后共获得7个胚性愈伤团并最终获得42株再生抗性植株,其中转pSUIBEV3-AFP有23个株系,转pCAMBIA-AFP有19个株系,经PCR、Southern杂交和RT-PCR检测后证实TmAFP基因已整合至甘薯基因组中并获得表达。将转基因甘薯及对照植株在–1℃下处理15小时后转移至室温,结果表明,转基因甘薯植株的抗冻能力显著提升。  相似文献   
56.
Flowering plants display spectacular floral diversity and a bewildering array of reproductive adaptations that promote mating, particularly outbreeding. A striking feature of this diversity is that related species often differ in pollination and mating systems, and intraspecific variation in sexual traits is not unusual, especially among herbaceous plants. This variation provides opportunities for evolutionary biologists to link micro-evolutionary processes to the macro-evolutionary patterns that are evident within lineages. Here, I provide some personal reflections on recent progress in our understanding of the ecology and evolution of plant reproductive diversity. I begin with a brief historical sketch of the major developments in this field and then focus on three of the most significant evolutionary transitions in the reproductive biology of flowering plants: the pathway from outcrossing to predominant self-fertilization, the origin of separate sexes (females and males) from hermaphroditism and the shift from animal pollination to wind pollination. For each evolutionary transition, I consider what we have discovered and some of the problems that still remain unsolved. I conclude by discussing how new approaches might influence future research in plant reproductive biology.  相似文献   
57.
Nuclear genes that appear to encode both cytosolic and plastid isozymes of phosphoglucose isomerase (PGI), an essential glycolytic enzyme, have been isolated from three diploid species of the annual wild flower genus Clarkia (Onagraceae). The genes do not contain introns and are expressed to varying degrees in Escherichia coli when cloned in either Charon 35 phage or pUC plasmid vectors. The PGI proteins synthesized in E. coli form dimers, are catalytically active, and their electrophoretic mobilities are similar to those of appropriate Clarkia PGIs. The nucleotide sequence of a gene encoding a plastid isozyme of C. unguiculata is described.  相似文献   
58.
  1. Understanding the drivers of trait selection is critical for resolving community assembly processes. Here, we test the importance of environmental filtering and trait covariance for structuring the functional traits of understory herbaceous communities distributed along a natural environmental resource gradient that varied in soil moisture, temperature, and nitrogen availability, produced by different topographic positions in the southern Appalachian Mountains.
  2. To uncover potential differences in community‐level trait responses to the resource gradient, we quantified the averages and variances of both abundance‐weighted and unweighted values for six functional traits (vegetative height, leaf area, specific leaf area, leaf dry matter content, leaf nitrogen, and leaf δ13C) using 15 individuals of each of the 108 species of understory herbs found at two sites in the southern Appalachians of western North Carolina, USA.
  3. Environmental variables were better predictors of weighted than unweighted community‐level average trait values for all but height and leaf N, indicating strong environmental filtering of plant abundance. Community‐level variance patterns also showed increased convergence of abundance‐weighted traits as resource limitation became more severe.
  4. Functional trait covariance patterns based on weighted averages were uniform across the gradient, whereas coordination based on unweighted averages was inconsistent and varied with environmental context. In line with these results, structural equation modeling revealed that unweighted community‐average traits responded directly to local environmental variation, whereas weighted community‐average traits responded indirectly to local environmental variation through trait coordination.
  5. Our finding that trait coordination is more important for explaining the distribution of weighted than unweighted average trait values along the gradient indicates that environmental filtering acts on multiple traits simultaneously, with abundant species possessing more favorable combinations of traits for maximizing fitness in a given environment.
  相似文献   
59.
Abstract. 1. Eurytoma gigantea Walsh is a specialist parasitoid of the tephritid gallmaker Eurosta solidaginis (Fitch).
2. In the natural environment the incidence of parasitism by Eurytoma is greater in small galls than in large ones.
3. Laboratory experiments demonstrated that small galls are not more frequently discovered; however, oviposition attempts on small galls were more likely to be successful.
4. Eurytoma spends much time probing galls too big to penetrate; this leads to a decrease in foraging efficiency when many large galls are present.
5. The chance of successfully penetrating a gall depends on the thickness of the gall wall and the length of the parasitoid's ovipositor.
6. A simulation model was constructed which shows that a gallmak-er's chance of being parasitized depends on gall size, the number of parasitoids that discover the gall, and their ovipositor lengths.  相似文献   
60.
A simple, rapid, and inexpensive method for the preparation and purification of chloroplast DNA (cpDNA) from pea has been developed. The crucial step is the isolation of chloroplasts in a medium of high ionic strength (I congruent equal to 1.40 M). CpDNA from pea prepared according to this method has successfully been used for restriction enzyme mapping, Southern transfers, and cloning.  相似文献   
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