Effect of the Heavy Metals on Developmental Stages of Ovule,Pollen, and Root Proteins in <Emphasis Type="Italic">Reseda lutea</Emphasis> L. (Resedaceae)

Heavy metals are some of the most important environmental pollutants. Excessive amounts of heavy metals adversely affect plant growth and development. Also, the presence of elevated levels of heavy metal ions triggers a wide range of cellular responses including changes in gene expression and synthesis of metal-detoxifying peptides. The overall objective of this research was to elucidate some microscopic effects of heavy metals on the formation, development, and structure of pollen, ovule, and embryo and also root proteins in Reseda lutea L. For this purpose, the vicinity of Ahangaran lead–zinc mine (Hamedan, Iran) was chosen as a polluted area where amount of some heavy metals was several times higher than the natural soils. Flowers and young buds were collected from non-polluted and polluted plants, fixed in FAA₇₀, and studied during developmental stages by light microscopy. The results showed that heavy metals can cause some abnormalities during the pollen and ovule developmental process. The number of pollen grains was decreased, and their shape was changed. Increasing in thickness of the callosic wall and stabilizing of tapetum layer were observed in polluted plants. Asymmetrical formation of ovular integuments, degradation of egg apparatus, irregular formation of embryo sac, considerable vacuolation of embryonic cells, and degeneration of embryo in the late stage of heart-shaped embryo are the results of heavy metal pollution. For protein studies, young roots were harvested from plants exposed to pollution and non-exposed to pollution at the same time. Root proteins were extracted and studied by electrophoresis. The results revealed that some new proteins were synthesized in polluted samples that probably elevate plant tolerance to heavy metals.     

Investigating the Effect of Heavy Metals on Developmental Stages of Anther and Pollen in <Emphasis Type="Italic">Chenopodium botrys</Emphasis> L. (Chenopodiaceae)

Excessive amounts of heavy metals adversely affect plant growth and development. Whereas some regions naturally contain high levels of heavy metals, anthropogenic release of heavy metals into the environment continuously increases soil contamination. Preliminary studies have shown that Chenopodium botrys can grow in some heavy metal contaminated soils and is a high accumulator plant species for Cu and moderately accumulator plant species for Fe, Mn, and Zn, thus, was considered as an important species in this study. Based on that, in this species, we studied the individual effects of heavy metals on the formation, development, and structure of anther and pollen. To achieve this purpose, surrounding area of Hame-Kasi iron and copper mine (Hamedan, Iran) was chosen as a polluted area where the amount of some heavy metals was several times higher than the natural soils. Flowers and young pods were removed from non-polluted and polluted plants, fixed in FAA 70, and subjected to developmental studies. Analysis of anther development in plants from contaminated sites showed general similarities in the pattern of pollen formation with those from non-polluted ones, but also deviation from typical form of major stages of anther and pollen development was seen in plants from polluted ones. Stabilizing of tapetum layer, increasing in tapetum layer numbers, thickening callose wall in the microspore mother cell stage, changing the anther shape, and decreasing the size of anther were the effects of heavy metals. Reduction of pollen number was also seen in the plants collected from polluted area.     

Genetic structure of Suillus luteus populations in heavy metal polluted and nonpolluted habitats

The genetic structure of populations of the ectomycorrhizal basidiomycete Suillus luteus in heavy metal polluted and nonpolluted areas was studied. Sporocarps were collected at nine different locations and genotyped at four microsatellite loci. Six of the sampling sites were severely contaminated with heavy metals and were dominated by heavy metal-tolerant individuals. Considerable genetic diversity was found within the geographical subpopulations, but no reduction of the genetic diversity, current or historic, was observed in subpopulations inhabiting polluted soils. The genetic differentiation between the geographical subpopulations was low, and no evidence for clustering of subpopulations from polluted soils vs. subpopulations from nonpolluted soils was found. These results indicate that heavy metal pollution has a limited effect on the genetic structure of S. luteus populations, and this may be due to the high frequency of sexual reproduction and extensive gene flow in S. luteus, which allows rapid evolution of the tolerance trait while maintaining high levels of genetic diversity.     

Embryological features of Alhagi persarum (Fabaceae): Adapt to environmental constraints

Reproductive organs, in flowering plants, are sensitive to stressful environments. Alhagi persarum Boiss. & Buhse copes with the stresses and produce reproductive organs under difficult climatic conditions. Embryological characters of this plant were investigated for the first time using different microscopy and staining techniques. The results of this study showed unique reproductive characters and strategies in A. persarum that we named reproductive adaptation. These characters have roles in protection and nutrition of reproductive organs, some of which were visible in ovule: accumulation of phenolic compounds, presence of ovular endothelium with its cuticle coat, hypostase, postament, endosperm haustorium, presence of operculum, curvature of the embryonic axis. The other characters in the seed are macrosclereid cells with cuticle coat, double palisade layer and lignified tracheids in hilar groove. Thickness increasing of endothecium and exine are the adaptive characters in anther. Unlike many of the stress-sensitive plants, all developmental stages of the embryo sac, anther, pollen and pollen tube are without any defects in these stress-tolerant plants. Seed germination rate is low in this species that is due to the hardness of seed coat which causes seed deep exogenous dormancy. This dormancy is also a developmental program for stress tolerance to keep seed viability for a long time in difficult conditions.     

ScORK17, a transmembrane receptor-like kinase predominantly expressed in ovules is involved in seed development

The mRNA expression of the Solanum chacoense Ovule Receptor Kinase 17 (ScORK17), a receptor kinase of the LRR-VI subfamily, is highly specific to the female reproductive tissues. No LRR-VI subfamily members in any plant species have yet been attributed a function. A phylogenetic tree inferred using the kinase domain of LRR-VI subfamily members separated the family into two clades: one containing an average of 8.2 LRR per protein and a second clade containing an average of 2.7. In situ hybridization analyses showed that the ScORK17 signal was mainly detected in the single ovule integument and in the endothelium. Transient expression analysis also revealed that ScORK17 was N-glycosylated in planta. Overexpression of ScORK17 in S. chacoense did not produce plants with an altered phenotype. However, when heterologous transformation was performed with a full-length ScORK17 clone in A. thaliana, the resulting transgenic plants showed reduced seed set, mainly due to aberrant embryo sac development, thus supporting a developmental role for ScORK17 in ovule and seed development.     

Heterochrony and its role in sex determination of cryptically dioecious Consolea (Cactaceae) staminate flowers

Ovule development, megasporogenesis, and megagametogenesis were studied in six cryptically dioecious species of Consolea. All species showed uniform development typical for the Opuntioideae. Ovule development proceeds acropetally, but shows developmental asynchrony across floral morphs. At anthesis, female morph ovules are functional and available for fertilization, whereas staminate flower ovules are senescing and incapable of being fertilized. In occasional plants of some species, staminate flowers may reach anthesis with a few functional apical ovules capable of seed formation. Such plants are described as inconstant/leaky males. Ovule fertility differences across morphs are interpreted as resulting from heterochronic ovule development and senescence, although variation in embryo sac longevity cannot be ruled out. Significantly, ovule abortion follows a common pattern and timing in staminate flowers of both male morphs in all species. Thus, on the basis of this uniformity, a common origin for the cryptically dioecious breeding system in Consolea is hypothesized. Furthermore, staminate expression in Consolea appears to be controlled by a common, genetically determined heterochronic ovule developmental programme affecting the relative timing of ovule receptivity and flower opening. This is the first report of heterochrony as a mechanism of male sex determination.  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 156 , 305–326.     

Ovule morphology, embryogenesis and seed development in three Hylocereus species (Cactaceae)

Pre-embryonic and embryonic stages and seed developments were studied in the diploids Hylocereus monacanthus and Hylocereus undatus and the tetraploid Hylocereus megalanthus. Ovule morphology was similar among species except for micropyle entrance. H. monacanthus had the thickest and most robust suspensor. Embryo developmental time, measured from fertilization to maturity, was significantly more prolonged in H. megalanthus. Typical to Cactaceae, the seed coat was formed by one layer of sclerenchymatous cells, but was more lignified in H. megalanthus. Morphological features common to all species included (1) cellular type endosperm with independent patterns of development in the chalazal and micropylar zones, forming a haustorium layer from the chalazal zone to the embryo; (2) an endothelial layer surrounding the embryo sac almost complete; (3) a nucellar summit growing into the micropyle; and (4) a placental obturator and a funicle connecting the ovarian tissue to the ovule. Seed development was typically endospermic (exendospermic orthodox seeds). Anomalies included two egg cells in the same embryo sac, two embryos developing in the same ovule, and embryos developing from the chalazal pole region. Total seed number and seed viability were significantly lower in H. megalanthus than in the other two taxa. Embryos at different developmental stages were observed in aborted H. megalanthus seeds.     

Genetic variation and heavy metal tolerance in the ectomycorrhizal basidiomycete Suillus luteus

Twenty-one isolates of the ectomycorrhizal fungus Suillus luteus were screened for their tolerance to the heavy metals Zn, Cd, Cu and Ni, measured as inhibition of radial growth and biomass production. Two populations from even-aged pine stands were investigated: 10 isolates were obtained from an area polluted with high levels of Zn, Cd and Cu, and 11 isolates were obtained from a control population located in a nearby unpolluted area. RFLP patterns of the internal transcribed spacer region of the isolates confirmed the morphological identification of the carpophores. All isolates were maintained on basic medium without elevated metals to avoid phenotypically acquired metal tolerance. The in vitro Zn and Cd tolerance of the S. luteus isolates from the polluted habitat were significantly higher than the tolerances measured in the isolates from the nonpolluted site. This observation suggests that the elevated soil metal concentrations might be responsible for the evolution of adaptive Zn and Cd tolerance. Tolerance was maintained in an isolate not exposed to elevated metals for 3 yr. The two S. luteus populations did not differ in tolerance to Cu and Ni. The mechanisms for the adaptive Zn and Cd tolerance are not identical as there was no correlation between response to the two metals; the most Zn-tolerant isolate was the most sensitive for Cd in the metal-tolerant population. Zinc did not accumulate in basidiocarp tissue, whereas Cd levels in basidiocarps were significantly higher in the population on the polluted site. Inter-simple sequence-repeat fingerprints showed that 90% of the isolates were from different individuals. The genetic variation in the population from the unpolluted site was considerably larger than that observed at the polluted site.     

广西大新县锰矿区植物重金属污染的调查研究

调查分析了广西大新县锰矿污染的部分土壤及9种优势耐性植物对Mn、Zn、Ni的富集和吸收能力。其中,蜈蚣草对Mn、Zn、Ni有较强的吸收能力;五节芒、野茼蒿、酸模叶蓼、加拿大蓬对Mn的吸收较强;蔓生莠竹、马唐、海芋对Zn吸收较强;而五节芒、加拿大蓬对Ni亦有较强的吸收能力。虽然这些植物对三种重金属的吸收均未达到超富集植物的要求,但作为污染土壤上的优势耐受性植物仍具有一定的意义。     

Comparative ovule and megagametophyte development in Hydatellaceae and water lilies reveal a mosaic of features among the earliest angiosperms

Background and Aims: The embryo sac, nucellus and integuments of the early-divergentangiosperms Hydatellaceae and other Nymphaeales are comparedwith those of other seed plants, in order to evaluate the evolutionaryorigin of these characters in the angiosperms. Methods: Using light microscopy, ovule and embryo sac development aredescribed in five (of 12) species of Trithuria, the sole genusof Hydatellaceae, and compared with those of Cabombaceae andNymphaeaceae. Key Results: The ovule of Trithuria is bitegmic and tenuinucellate, ratherthan bitegmic and crassinucellate as in most other Nymphaeales.The seed is operculate and possesses a perisperm that developsprecociously, which are both key features of Nymphaeales. However,in the Indian species T. konkanensis, perisperm is relativelypoorly developed by the time of fertilization. Perisperm cellsin Trithuria become multinucleate during development, a featureobserved also in other Nymphaeales. The outer integument issemi-annular (‘hood-shaped’), as in Cabombaceaeand some Nymphaeaceae, in contrast to the annular (‘cap-shaped’)outer integument of some other Nymphaeaceae (e.g. Barclaya)and Amborella. The megagametophyte in Trithuria is monosporicand four-nucleate; at the two-nucleate stage both nuclei occurin the micropylar domain. Double megagametophytes were frequentlyobserved, probably developed from different megaspores of thesame tetrad. Indirect, but strong evidence is presented forapomictic embryo development in T. filamentosa. Conclusions: Most features of the ovule and embryo sac of Trithuria are consistentwith a close relationship with other Nymphaeales, especiallyCabombaceae. The frequent occurrence of double megagametophytesin the same ovule indicates a high degree of developmental flexibility,and could provide a clue to the evolutionary origin of the Polygonum-typeof angiosperm embryo sac.     

组织透明技术在植物解剖学和植物发育生物学实验教学中的应用

整体组织透明和组织切片技术是研究植物组织和器官的结构及其发育过程的常用实验手段。该文针对本科生植物学课程的侧根、胚珠(特别是胚囊)以及胚胎发育内容设计了相应的实验教学课程。该实验以拟南芥幼苗、不同发育时期的花蕾和种子为材料,经固定、脱色和组织透明,利用正置显微镜观察侧根、胚珠以及胚胎的发育过程。根组织经透明后,在显微镜下可以清晰地观察到从侧根原基的建成到侧根发生的八个发育阶段。各个发育时期的胚珠经组织透明后,在显微镜下可以清晰地观察到大孢子母细胞、功能性大孢子(FG1期)以及FG2~FG7期的胚囊。各个发育时期的种子经透明后,在显微镜下可以清晰地观察到胚胎发育的1细胞期、8细胞期、球形期、心形期、鱼雷期、拐杖期和成熟期。这些实验结果可以使学生对拟南芥等双子叶植物的侧根、胚珠以及胚胎发育过程有较为系统的了解。该实验方法在其他较小的双子叶植物中也适用。     

Evolution and patterning of the ovule in seed plants

The ovule and its developmental successor, the seed, together represent a highly characteristic feature of seed plants that has strongly enhanced the reproductive and dispersal potential of this diverse group of taxa. Ovules encompass multiple tissues that perform various roles within a highly constrained space, requiring a complex cascade of genes that generate localized cell proliferation and programmed cell death during different developmental stages. Many heritable morphological differences among lineages reflect relative displacement of these tissues, but others, such as the second (outer) integuments of angiosperms and Gnetales, represent novel and apparently profound and independent innovations. Recent studies, mostly on model taxa, have considerably enhanced our understanding of gene expression in the ovule. However, understanding its evolutionary history requires a comparative and phylogenetic approach that is problematic when comparing extant angiosperms not only with phylogenetically distant extant gymnosperms but also with taxa known only from fossils. This paper reviews ovule characters across a phylogenetically broad range of seed plants in a dynamic developmental context. It discusses both well-established and recent theories of ovule and seed evolution and highlights potential gaps in comparative data that will usefully enhance our understanding of evolutionary transitions and developmental mechanisms.     

Expression-based discovery of candidate ovule development regulators through transcriptional profiling of ovule mutants

Background  

Arabidopsis ovules comprise four morphologically distinct parts: the nucellus, which contains the embryo sac, two integuments that become the seed coat, and the funiculus that anchors the ovule within the carpel. Analysis of developmental mutants has shown that ovule morphogenesis relies on tightly regulated genetic interactions that can serve as a model for developmental regulation. Redundancy, pleiotropic effects and subtle phenotypes may preclude identification of mutants affecting some processes in screens for phenotypic changes. Expression-based gene discovery can be used access such obscured genes.     

微生物与重金属间的相互作用及其应用研究

从多方面阐述了微生物与重金属二者间相互作用,指出微生物在生长代谢过程中能淋滤、吸收和转化重金属,对重金属有一定的抗性和解毒作用;但是,一定浓度的重金属对微生物过程及其种群具有较大的毒性。影响微生物在环境介质中的活动,矿业工程生产工艺已充分利用微生物能淋滤,吸收和转化重金属等特性来处理低品位难浸矿石,环境保护领域也积极利用微生物对重金属的抗性和解毒作用来实现工业废弃物的处理以及被重金属污染土壤的修复。利用微生物的生物量及其活性可以评价环境中不同介质的重金属污染水平。     

Evaluation of Environmental Quality of Atmosphere by Determination of Element content in Plants and Soils in Tianjin

165 plants and 40 soil samples were collected at seven areas in Tianjin. The analysis of sulphur and heavy metals in these samples showed the polluted degree of the air. It is indicated that the plants at smeltery (polluted industry area) contain Zn, Cu, Cd, Pb highest and NJ, S higher. The content of heavy metals in these plants were 3 to 11 times higher than that of the background value. In business-traffic area and park, the amount of Zn, Cu, Ni, Cd in the plants were 1.5 to 3.5 times higher than the background value. In the other area, such as culture-education area, road and suburbs, the pollution is not significant, and in the clean area (Panshan), all elements in the plants are the lowest. As to the soils in polluted industry area (Smeltery), the amount of Ph, Cu, Cd, Zn and S was 725, 348, 9, 3 and 14 times higher than that of the background value respectively. Among them, most of Pb, Cu were deposited in surface layer. In soil of business-traffic area, Pb, Cu, Cd, Zn and S were 2 to 10 times higher than the background value, and in the soil of clean area, all elements are also the lowest. The stomata of plants which were blocked by the particles going down from the air resulted in increase in the stamotal diffusive resistance and the order of the resistance in the different places are as follows: polluted industry areas > parks > business-traffic areas > road > clean areas. These results are in agreement with the polluted state of the plants and soils in above mentioned areas.     

Maternal control of seed development

Maternal control of higher plant seed development is likely to involve female sporophytic as well as female gametophytic genes. While numerous female sporophytic mutants control the production of the ovule and the embryo sac true maternal effect mutations affecting embryo and endosperm development are rare in plants. A new class of female gametophytic mutants has been isolated that controls autonomous development of endosperm. Molecular analyses of these genes, known as FIS class genes, suggest that they repress downstream seed development genes by chromatin remodelling. Expression of the FIS genes in turn is modulated by parent specific expression or genomic imprinting which in turn is controlled by DNA methylation. Thus maternal control of seed development is a complex developmental event influenced by both genetic and epigenetic processes.     

Densities of microtime rodents along a pollution gradient from a copper-nickel smelter

Population densities of microtine rodents were studied along an air pollution gradient in the Kola Peninsula, Russia, by long-term and short-term trapping. The study area is affected by high sulphur dioxide and heavy metal emissions from the Severonikel copper-nickel smelter in Monchegorsk. The density of Clethrionomys rufocanus, the most abundant vole species in the area, was lowest close to the smelter and increased with distance up to the farthest, less polluted trapping sites. Clethrionomys glareolus, C. rutilus and Lemmus lemmus were absent from the most severely damaged area and were also scarce at the moderately polluted area 28 km south of the smelter. Although the population of C. glareolus has previously been cyclic at the moderately polluted area, we were unable to demonstrate any regular cycle. The most likely explanation for the low number of microtine rodents in the damaged and moderately polluted areas in a decrease in the quantity of important food plants: epiphytic lichens for C. glareolus and possibly C. rutilus, mosses for L. lemmus and seed plants, especially Vaccinium myrtillus, for C. rufocanus. Close to the smelter, direct toxic effects of heavy metals may also reduce population densities. The results show that pollutants may change the relative proportions of microtine species.     

Genomic pattern of adaptive divergence in Arabidopsis halleri, a model species for tolerance to heavy metal

Pollution by heavy metals is one of the strongest environmental constraints in human-altered environments that only a handful of species can cope with. Identifying the genes conferring to those species the ability to grow in polluted areas is a first step towards a global understanding of the evolutionary processes involved and will eventually improve phytoremediation practices. We used a genome-scan approach to detect loci under divergent selection among four populations of Arabidopsis halleri growing on either polluted or nonpolluted habitats. Based on a high density of amplified fragment length polymorphism (AFLP) markers (820 AFLP markers, i.e. ~1 marker per 0.3 Mb), evidence for selection was found for some markers in every sampled population. Four loci departed from neutrality in both metallicolous populations and thus constitute high-quality candidates for general adaptation to pollution. Interestingly, some candidates differed between the two metallicolous populations, suggesting the possibility that different loci may be involved in adaptation in the different metallicolous populations.     

无公害水稻生产的病虫草调控技术及其效应的研究

利用无公害农药和农业措施防治水稻主要病虫草试验结果表明,井·腊芽、井冈霉素和多抗霉素在水稻分蘖末期和孕穗末期各喷施1次,对纹枯病防效达75.16%～94.27%,优于化学杀菌剂三唑酮;春雷霉素和灭瘟素在叶瘟病发生初期及破肚期、齐穗期各喷施1次,对叶瘟防效为50.54%～72.67%,穗瘟为76.66%～87.42%,与化学杀菌剂三环唑相当.3种无公害农药在二化螟和稻纵卷叶螟1～2龄幼虫期使用,苏云金杆菌防效优于化学杀虫剂杀虫双,皂素·烟碱和苦参碱与杀虫双相当;皂素·烟碱和苦参碱在稻飞虱1～2龄若虫期使用,药后3～30d防效均在70%以上,低于化学杀虫剂吡虫啉.在水稻移栽前耕地2次,再配合施用适量的未腐熟有机质或人工除草,能控制杂草发生和提高产量.采用无公害农药和农业措施防治水稻病虫草,产量较常规化防区略有增加,稻谷中农药残留量较化防区低,符合绿色食品卫生指标要求.