四种石斛兰种胚发育进程研究

以玫瑰石斛、尖刀唇石斛、短棒石斛、兜唇石斛种子为材料,进行种胚非共生萌发研究,并对其种子形态和胚的发育进程进行了显微观察。结果表明:处于球形胚阶段的石斛兰种子,种胚吸胀后突破种皮,发育至吸收毛和芽生长点出现后,种胚形成原球体;种子萌芽后胚尚未成熟,只进入心形胚阶段。呈纺锤形种子的种皮两端形状不同,一端存在结点,呈弯曲状的尖形,另一端种皮呈收拢的圆口形。4种石斛兰种子,玫瑰石斛种子最长,为两端狭长的纺锤形;兜唇石斛种子最短,呈两端稍细的纺锤形。玫瑰石斛、短棒石斛、尖刀唇石斛种子胚培养需要5～10 d萌发;兜唇石斛种子和胚皆偏小,萌发需要30 d。石斛兰种胚和种皮吸水膨胀后,种胚向种皮的一端移动、脱出或种胚撕裂种皮中央后突破而出,形成裸胚。玫瑰石斛种子撕裂种皮后主要从种皮中央突破;短棒石斛、尖刀唇石斛、兜唇石斛部分种胚从种皮一端脱出,部分种胚则从中央撑破种皮脱出。充分膨胀、变绿后萌芽的裸胚,存在极性,顶部芽生长点萌动,下部出现成群散射状吸收毛。     

Polyembryony increases embryo and seedling mortality but also enhances seed individual survival in Handroanthus species (Bignoniaceae)

Polyembryony seems to be advantageous to mother plants in detriment of their siblings which face competition since the beginning of seed development. This competition may limit the turnover of embryos into seedlings and their survival ability. We analysed polyembryony frequency and embryo to seedling turnover in three Handroanthus species with sporophytic apomixis. We tested if the embryo number per seed affected seed and embryo morphometry, seedling survival ability and seed individual survival (i.e. survival of at least one seedling per seed). The number of embryos per seed was compared with seedling number at different developmental stages. All 14 populations showed high frequencies of polyembryonic seeds (21–91%). As the number of embryos per seed increased (up to eight embryos/seed), there was a reduction of mean embryo mass, area, seedling length, individual seedling survival ability, and embryo to seedling turnover. There was also an increase in embryo morphological anomalies. However, enhanced seed individual survival was also observed. Thus, the high frequency of polyembryonic seeds and the increase in seed individual survival support the idea that polyembryony represents an alternative reproductive mechanism which can favours these species.     

Xenia effect on seed and embryo size in cotton (<Emphasis Type="Italic">Gossypium hirsutum</Emphasis> L.)

The term xenia was coined to describe the effect of foreign pollen on the development and characters of the seed. To study its importance and consequences for various seed traits in cotton (Gossypium hirsutum L.), the effect of pollen genotype on seed and embryo weight was studied with seeds from 15 F1 hybrids. Cross-fertilization changed seed weight by up to 7.0% in relation to self-fertilization. Xenia effect significantly increased embryo weight of cross-fertilized seeds, by up to 14.4% in comparison to self-fertilized seeds. Seeds of some crosses had a lower hull content than corresponding selfed seeds. On average, the xenia effect was greater for embryo weight than for seed weight. However, in some crosses there was no difference between cross- and self-fertilized seeds for seed weight, embryo weight, moisture content and hull content. Positive xenia effects for seed weight and embryo weight may help us to establish uniform stands of vigorous hybrid seedlings, especially under unfavourable conditions. Also, larger seed and embryo weight, along with lower hull content, could result in higher oil yield. Therefore, careful choosing of genotypes as parents and of cross direction in the production of hybrid seed is very important in cotton.     

Tissue culture of parasitic flowering plants: Methods and applications in agriculture and forestry

Summary Parasitic flowering plants from 23 genera in 7 families (Convolvulaceae, Lauraceae, Loranthaceae, Orobanchaceae, Santalaceae, Scrophulariaceae and Viscaceae) have been cultured in vitro. These plants include both hemiparasites and holoparasites that parasitize stems and roots of angiosperms and gymnosperms. This review highlights relevant information on each genus with regard to its biology, distribution, host range, and tissue culture procedures. Tissue culture has been used to study aspects of the development, metabolism, reproduction, physiology and nutritional requirements of these plants under controlled conditions. Studies of host-parasite relationships, including potential roles of signals/receptors that influence host development and physiology, and factors influencing seed germination and haustorium formation, have been conducted. The effects of chemicals and herbicides on the physiology and biochemistry of parasite embryo and seedling development have been studied, as well as the influence of inhibitors or stimulants on seed germination. Tissue culture has provided a method for propagation and genetic improvement of plants with commercial value.     

The Growth-Substance Content of Dormant Fruits of Fraxinus excelsior L.

The growth-substance content of fruits of F. excelsior has beenexamined as part of an investigation into the causes of dormancyin this species. During the growth of the embryo within theimbibed seed, a neutral ether-soluble hormone, tentatively identifiedas indole aceto-nitrile, is utilized. After the embryo is fullygrown the seed and the excised embryo are still dormant unlesschilled. A watersoluble growth inhibitor is metabolically producedin both embryo and endosperm when the dry seed is imbibed. Thisinhibitor remains undiminished.in activity at all stages ofpretreatment of the seed, and is still present in the germinableembryo. Inhibitor is readily destroyed by an enzyme system presentin the seed tissues unless care is taken to extract at low temperatures.     

沙葱种皮特性、种胚及种子浸提液与种子休眠的关系

本文以沙葱休眠种子为试材,检测其种皮透水性、透气性、超微结构、种胚休眠及种子浸提液。结果表明,酸蚀种子吸水12h达饱和,吸水率是完整种子的2倍;其呼吸强度最大值是完整种子的1.36倍。酸蚀处理使种子表面结构破损,角质层脱落,种孔露出。沙葱种子离体胚接种培养后2～3d,种胚开始萌发,萌发率达85％。沙葱完整种子与粉碎种子的浸提液对白菜种子发芽率、苗高、根长均有抑制作用,且随着浓度的提高而增强。     

Sequential steps for developmental arrest in Arabidopsis seeds

The continuous growth of the plant embryo is interrupted during the seed maturation processes which results in a dormant seed. The embryo continues development after germination when it grows into a seedling. The embryo growth phase starts after morphogenesis and ends when the embryo fills the seed sac. Very little is known about the processes regulating this phase. We describe mutants that affect embryo growth in two sequential developmental stages. Firstly, embryo growth arrest is regulated by the FUS3/LEC type genes, as mutations in these genes cause a continuation of growth in immature embryos. Secondly, a later stage of embryo dormancy is regulated by ABI3 and abscisic acid; abi3 and aba1 mutants exhibit premature germination only after embryos mature. Mutations affecting both developmental stages result in an additive phenotype and double mutants are highly viviparous. Embryo growth arrest is regulated by cell division activities in both the embryo and the endosperm, which are gradually switched off at the mature embryo stage. In the fus3/lec mutants, however, cell division in both the embryo and endosperm is not arrested, but rather is prolonged throughout seed maturation. Furthermore ectopic cell division occurs in seedlings. Our results indicate that seed dormancy is secured via at least two sequential developmental processes: embryo growth arrest, which is regulated by cell division and embryo dormancy.     

Endosperm cellularization defines an important developmental transition for embryo development

The endosperm is a terminal seed tissue that is destined to support embryo development. In most angiosperms, the endosperm develops initially as a syncytium to facilitate rapid seed growth. The transition from the syncytial to the cellularized state occurs at a defined time point during seed development. Manipulating the timing of endosperm cellularization through interploidy crosses negatively impacts on embryo growth, suggesting that endosperm cellularization is a critical step during seed development. In this study, we show that failure of endosperm cellularization in fertilization independent seed 2 (fis2) and endosperm defective 1 (ede1) Arabidopsis mutants correlates with impaired embryo development. Restoration of endosperm cellularization in fis2 seeds by reducing expression of the MADS-box gene AGAMOUS-LIKE 62 (AGL62) promotes embryo development, strongly supporting an essential role of endosperm cellularization for viable seed formation. Endosperm cellularization failure in fis2 seeds correlates with increased hexose levels, suggesting that arrest of embryo development is a consequence of failed nutrient translocation to the developing embryo. Finally, we demonstrate that AGL62 is a direct target gene of FIS Polycomb group repressive complex 2 (PRC2), establishing the molecular basis for FIS PRC2-mediated endosperm cellularization.     

Abortive seed development in Ulmus minor (Ulmaceae)

Three genotypes of field elm ( Ulmus minor ) were studied to determine the structural basis of seed abortion in this species. In the non-abortive control, P-VV1, the pattern of seed development is similar to many flowering plants. The embryo progresses through defined morphological stages leading to developmental arrest as the seed matures. Storage products are abundant within embryo cells. Endosperm development is similar to the nuclear type; however, a more extensive cellularization of the endosperm occurs prior to it being crushed by the expanding embryo. For the abortive genotypes, M-SF1 and V-JR1, abnormalities in endosperm development are found. This is judged by the early cellularization and the massive synthesis of the PAS-positive material in the cellular endosperm. In these abortive genotypes, embryo development is delayed and storage products failed to accumulate within embryo cells. After seed desiccation, no living embryo tissue remains within the seed coat in the abortive genotypes.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 145 , 455–467.     

Study on fish embryo responses to the treatment of cryoprotective chemicals using impedance spectroscopy

Investigations using electrical impedance spectroscopy to measure the responses of fish embryos to the cryoprotective chemicals, methanol and dimethyl sulphoxide (DMSO), were carried out. Zebrafish (Danio rerio) embryos were used as a model to study the newly proposed technique. The normalised permittivity and conductivity changes of the embryos were measured continuously over a 20-min period in a customised embryo-holding chamber. The normalised permittivity and conductivity spectra were obtained during embryo exposure to different concentrations of methanol (1.0, 2.0 and 3.0 M) and DMSO (0.5, 1.0 and 2.0 M) solutions. The results showed significant permittivity and conductivity changes after embryo exposure to methanol and DMSO at the optimum embryo loading level (six embryos). Embryos in different concentrations of methanol and DMSO also resulted in quantitative responses shown in the normalised permittivity and conductivity spectra. The results demonstrated that fish embryo membrane permeability to cryoprotective chemicals could be monitored in real-time. The measurement of permittivity at a lower frequency range (10–10³ Hz) and conductivity at a higher frequency range (10⁴–10⁶ Hz) during fish embryo exposure to cryoprotective chemicals using impedance spectroscopy can be used as a new tool for the fast screening of most effective cryoprotective chemicals. The results from the present study also demonstrated the possibility of quantifying the level of cryoprotective chemicals penetrating the fish embryos.     

花生胚离体发育及渗调物质的影响

在无外源激素培养基上花生胚能继续发育．渗调物质如甘露醇可抑制胚早萌,维持胚性发育,促进贮藏蛋白质合成和累积．渗调物质对胚离体发育的调控与其提高胚内源ＡＢＡ含量有关．     

广东高州普通野生稻生殖特性的研究Ⅱ.胚囊育性、胚囊发育、胚胎发生和胚乳发育

利用整体染色激光扫描共聚焦显微镜术（WCLSM）,对采自广东省高州市6个地点共141个编号的高州普通野生稻的成熟胚囊育性和胚囊形成发育特点等进行研究。结果表明,供试的绝大多数高州普通野生稻材料成熟胚囊均存在不同程度的育性异常现象,包括雌性生殖单位退化、极核位置异常、极核数目异常、胚囊退化等。这些异常结构的胚囊由于没有正常的卵细胞,不能正常受精,影响子粒结实。141个编号平均异常胚囊频率为11．11％,最高异常率为67．86％。高州普通野生稻胚囊发育过程与正常栽培稻一致,属寥型。对一些结实率偏低材料的研究,发现在胚囊发育过程的不同时期存在一些异常现象,包括功能大孢子退化,二至八核胚囊发育异常等。对柱头上的花粉量调查,发现观察的69个编号中,多数编号柱头上花粉量偏少。研究表明,花粉量偏少影响受精是导致结实率偏低的最主要原因之一。本文对导致结实率偏低的综合因素进行了讨论。     

Growth Substances Separated from the Fruits of Cassia fistula

The growth substances of the seeds of Cassia fistula were studied and the changes in the relative levels in the endosperm and embryo (plus cotyledons) with development of the seed were noted. Indoleacetic acid was found to be the major auxin component of the seed almost throughout its growth and development, while acidic inhibitors possibly belonging to β-complex were also noted in bioassay tests. The main source of the IAA in the seed is the endosperm, although measurable amounts are also present in the embryo. While this IAA activity in the endosperm is detectable till maturity of the fruit, it decreases relatively in the embryo to fall to insignificance at maturity of the seed. However, there is indication of the binding of such IAA in the embryo or the cotyledon, which can be released by alkaline hydrolysis but not before the seeds are matured. No such bound auxin could be detected in the endosperm. The inhibitors, on the other hand, are more prominent in the embryo than in the endosperm, particularly with ageing of the fruit. The possible significance of these changes in the growth factors has been discussed in relation to the age of the seed and the development of the embryo inside it.     

黄连木果实中油体的发育

黄连木（Pistacia chinensis）是一种重要的木本油料植物,其果实中贮存着大量的油脂,这些油脂分子主要存在于果皮、种皮和胚的油体中。在光学显微镜下观察发现,果皮中油的积累开始于果实发育晚期,果皮开始变红时;种皮中油体的发育开始于果实发育早期;胚中油体的发育开始于球形胚时期。透射电子显微镜观察结果显示,种皮和胚中的油体形成于内质网,而果皮中的油体则分别由内质网、质体和液泡形成。尼罗红荧光标记显示,内质网形成的油体始终以独立单元的形式存在。种皮和胚中也贮藏蛋白体,但发育晚于油体。果皮、种皮和子叶中都贮存少量的淀粉粒。     

A Cascade of Sequentially Expressed Sucrose Transporters in the Seed Coat and Endosperm Provides Nutrition for the Arabidopsis Embryo

Developing plant embryos depend on nutrition from maternal tissues via the seed coat and endosperm, but the mechanisms that supply nutrients to plant embryos have remained elusive. Sucrose, the major transport form of carbohydrate in plants, is delivered via the phloem to the maternal seed coat and then secreted from the seed coat to feed the embryo. Here, we show that seed filling in Arabidopsis thaliana requires the three sucrose transporters SWEET11, 12, and 15. SWEET11, 12, and 15 exhibit specific spatiotemporal expression patterns in developing seeds, but only a sweet11;12;15 triple mutant showed severe seed defects, which include retarded embryo development, reduced seed weight, and reduced starch and lipid content, causing a “wrinkled” seed phenotype. In sweet11;12;15 triple mutants, starch accumulated in the seed coat but not the embryo, implicating SWEET-mediated sucrose efflux in the transfer of sugars from seed coat to embryo. This cascade of sequentially expressed SWEETs provides the feeding pathway for the plant embryo, an important feature for yield potential.     

Methods and strategies for detecting Solanum tuberosum dihaploids in interspecific crosses with S. phureja

The frequency of dihaploid production following the interspecific pollination of Solanum tuberosum clones with Solanum phureja has been investigated. Seventeen hybrid combinations were tested and the crosses differed significantly in the number of seed produced, the proportions that were viable and the proportions that were dihaploid. The overall frequency of dihaploid production was 62%. The dominant embryo spot marker of the pollinator (IVP 48) in conjunction with seed diameter was used to classify the seed samples. Number of days taken to germinate was also recorded. It was therefore possible to examine retrospectively the effect of selecting sub-sets of the seed based on the presence or absence of the embryo spot, seed size and germination time. A seed selection system based on the absence of the embryo spot in conjunction with seed greater than 1.25 mm in diameter resulted in 93.6% of the potential dihaploids being identified.     

Prediction of the coefficient of variation of carrot embryo length from a germination test

The value of the International Seed Testing Association (ISTA) germination test in estimating levels of variation in embryo length between carrot seed lots was examined. For the two groups of seed lots used, the coefficient of variation (c.v.) of embryo length ranged from 16 to 50%. The c.v. of embryo length was negatively correlated with the numbers of normal seedlings counted after 7 days of germination at 20°C, r_s= - 0·72 D.F. 12 and - 0·82, D.F. 15 for the two groups of seed lots used. Provided the relationship between these two characters is established for each laboratory, it is likely to be useful in identifying seed lots of potentially low c.v. of embryo length.