莲种子萌发和幼苗生长时期营养物质的代谢变化

莲子叶细胞中储存了丰富的营养物质, 主要为蛋白质、淀粉和淀粉质体DNA。这些贮藏物质为种子萌发和幼苗的生长提供必需的能量和养料。通过组织化学和显微镜观察, 研究莲从种子萌发到植株生长至具有4个节时, 子叶中贮藏物质消耗的全过程。在此过程中, 子叶中的贮藏物质不断降解,营养物质发生转运。蛋白体首先发生降解, 其大量降解主要发生在幼苗三叶期。淀粉质体降解时会聚 集成团, 之后体积逐渐减小, 最后完全降解。种子萌发后65天是子叶贮藏物质消耗末期, 淀粉质体DNA的含量比萌发后20天的三叶期明显减少。细胞壁的形态结构发生多种形式的变化, 细胞壁发生的这些变化与子叶细胞间物质的运输有关。含多糖的球形颗粒通过维管束在子叶中运输。     

淀粉质体遗传研究的现状与展望

淀粉质体来源于前质体,与叶绿体同源,具有其特有的遗传特性,是核外遗传的重要组成部分。本文综述了淀粉质体遗传研究方面取得的成果和进展。淀粉质体DNA发现于20世纪70年代,其含量随着组织发育的不同阶段有所变化,最后这些DNA作为贮藏的形式积累在质体中。淀粉质体基因组与叶绿体基因组同源性很高,但是不表达与光合作用有关的基因。现有的实验证据表明,淀粉质体基因组的表达调控发生在转录水平,与DNA甲基化有关。淀粉质体的发育受核基因组和质体基因组双重调控。组织发育到一定时期,淀粉质体中出现单核糖体和多聚核糖体;淀粉质体具有蛋白质合成体系。淀粉质体DNA及淀粉质体遗传的研究具有重要的理论和实际意义,对淀粉质体遗传进行深入的研究,将丰富核外遗传知识和理论。     

大豆子叶衰老的细胞学观察

以萌发后不同时期的大豆子叶为材料,通过普通光镜和荧光显微镜观察,分析了不同时期子叶细胞的结构变化及子叶细胞内蛋白质和淀粉含量的组织化学变化.结果表明,随着种子萌发时期的延长,子叶细胞内的蛋白质和淀粉含量逐渐减少,在子叶衰老过程中,细胞内蛋白质首先消耗殆尽,淀粉的消耗速度较蛋白质慢;大豆子叶细胞在萌发后第18天时出现典型的植物编程性死亡的形态学特征,子叶细胞内营养物质的消耗诱发子叶细胞发生细胞凋亡.     

冠果草种子萌发过程的组织化学动态

冠果草的种子中没有胚乳,营养物质贮藏在胚中,其成分主要是淀粉和蛋白质。胚各部分的物质积累情况差异较大,子叶和下胚轴细胞中的淀粉粒、蛋白体数目多、体积大,胚芽和胚根分生细胞中则只贮藏少量的淀粉粒、蛋白体。在种子萌发过程中,胚各部分的淀粉粒逐渐解体,至二叶幼苗期全部消失。蛋白体的降解有严格顺序,远离胚芽的细胞中蛋白体降解较早,胚芽附近细胞中的降解较晚,而且胚芽细胞中还有新的蛋白体形成。单个蛋白体的降解     

几种植物贮藏器官淀粉质体蛋白质和总蛋白质的电泳分析

在质体范畴对淀粉质体蛋白质的分析资料非常缺乏,尤其是在淀粉质体遗传方面做了许多工作后〔1～5〕,在质体水平上研究它的蛋白质显得尤为重要。对此,我们选了3种不同类型的植物,有蛋白质含量高的豆科植物(蚕豆),水生植物莲和鳞茎植物百合,分别从贮藏器官中分离淀粉质体,对其蛋白质进行了电泳分析,试图在讨论淀粉质体遗传和淀粉质体蛋白质分析方面提供一些资料。1　材料和方法1蚕豆(VicafabaL.)取成熟种子的子叶。2莲(NelumbonuciferaGaertn)采受精后生长到21d的种子(25d成熟),去掉胚芽用子叶。3取兰州地区栽培的百合〔(Liliumdavidilvar.w…     

去胚轴对花生子叶肽链内切酶和贮藏蛋白质降解的影响

从离体子叶与连体子叶在水中培养一段时间后的比较,看到它们之间在肽链内切酶活性和盐溶蛋白及花生球蛋白降解上的差异并不大,这表明去除胚轴对子叶肽链内切酶活性和贮藏蛋白降解的影响很轻微。亚胺环己酮（蛋白质合成抑制剂）不能完全抑制离体子叶肽链内切酶活性的提高,子叶的大部分大分子贮藏蛋白同样被降解。这表明,在花生种子萌发过程中降解大部分贮藏蛋白的子叶肽链内切酶并非人全部是在种子萌发是新合成的。子叶贮藏蛋白降     

去胚轴对花生子叶肽链内切酶和贮藏蛋白质降解的影响

从离体子叶与连体子叶在水中培养一段时间后的比较,看到它们之间在肽链内切酶活性和盐溶蛋白及花生球蛋白降解上的差异并不大,这表明去除胚轴对子叶肽链内切酶活性和贮藏蛋白降解的影响很轻微。亚胺环己酮(蛋白质合成抑制剂)不能完全抑制离体子叶肽链内切酶活性的提高,子叶的大部分大分子贮藏蛋白同样被降解。这表明,在花生种子萌发过程中降解大部分贮藏蛋白的子叶肽链内切酶并非全部是在种子萌发时新合成的,子叶贮藏蛋白降解和肽链内切酶活性基本不受胚轴调控,子叶与胚轴之间在调控关系上可能是一种新的调节类型。     

西瓜种子发育和萌发过程中子叶细胞超微结构的变化

西瓜种子子叶内贮存物质开始积累时,细胞质内有大量核糖体、质体、线粒体,内质网片段和囊泡,种子脱水期至成熟期,细胞器的数量减少,成熟种子子叶细胞的细胞壁不连续,几乎观察不到细胞器的存在,种子萌发过程中内质网,线粒体,质体的数目逐渐增多,叶肉细胞的质体发育成叶绿体,种子形成过程中,在子叶细胞大液泡分隔的同时,膨胀的内质网囊泡内积累蛋白质（直径0.1-0.4μm),这些小的蛋白质球体最终进入液泡形成大的蛋白体（直径1-3μm);萌发种子贮存蛋白质被水解的同时,一些脂体进入液泡并被分解,同时液泡融合;脂类物质开始积累的时间早于蛋白质,积累的量较蛋白质多,但在萌发种子中被彻底水解的时间晚于蛋白质,淀粉粒的数量在种子形成时减少,种子萌发时在表皮细胞和叶肉细胞内都重新合成。     

坛紫菜菌解液对植物生长和抗性指标的影响

利用琼胶降解菌处理坛紫菜粉末,降解其细胞壁多糖,释放内容物,并获得菌解液,研究不同稀释度坛紫菜菌解液对受体植物蚕豆出芽和生长,以及大豆和番茄幼苗抗性相关指标的影响.结果显示:(1)随琼胶降解菌处理时间的延长,菌解液中还原糖含量逐渐增高.(2)3.33%的菌解液对蚕豆种子萌芽促进效果最好,而2%的菌解液能增加蚕豆叶绿素含量,促进其幼苗生长.(3)3.33%的菌解液能有效提高大豆离体子叶的植保素含量,迅速增加番茄叶片表皮条的H2O2的释放量,提高苯丙氨酸解氨酶活性.研究表明,琼胶降解菌能使坛紫菜细胞壁中的营养物质释放,并产生某些激发物质,从而使坛紫菜菌解液能够促进受体植物的种子发芽和幼苗生长,并能有效诱导植物的抗性.     

粘液繁殖体种子的粘液质形成、分泌及释放相关基因

种皮粘液质是在种皮外层细胞的高尔基体内产生并分泌到胞腔内或细胞壁层的一种果胶类多糖物质.当干燥种子遇水后,粘液质即刻被释放形成透明胶质并完全包被整个种子.粘液质对种子的扩散定居、种子萌发以及幼苗的存活和生长均具有重要作用.粘液质作为一种模型研究细胞壁的产生及其形成的分子机制已经成为植物种皮发育与环境变化相适应关系的研究...     

Influence of microgravity on ultrastructure and storage reserves in seeds of Brassica rapa L.

Successful plant reproduction under spaceflight conditions has been problematic in the past. During a 122 d opportunity on the Mir space station, full life cycles of Brassica rapa L. were completed in microgravity in a series of three experiments in the Svet greenhouse. Ultrastructural and cytochemical analyses of storage reserves in mature dry seeds produced in these experiments were compared with those of seeds produced during a high-fidelity ground control. Additional analyses were performed on developing Brassica embryos, 15 d post pollination, which were produced during a separate experiment on the Shuttle (STS-87). Seeds produced on Mir had less than 20% of the cotyledon cell number found in seeds harvested from the ground control. Cytochemical localization of storage reserves in mature cotyledons showed that starch was retained in the spaceflight material, whereas protein and lipid were the primary storage reserves in ground control seeds. Protein bodies in mature cotyledons produced in space were 44% smaller than those in the ground control seeds. Fifteen days after pollination, cotyledon cells from mature embryos formed in space had large numbers of starch grains, and protein bodies were absent, while in developing ground control seeds at the same stage, protein bodies had already formed and fewer starch grains were evident. These data suggest that both the late stage of seed development and maturation are changed in Brassica by growth in a microgravity environment. While gravity is not absolutely required for any step in the plant life cycle, seed quality in Brassica is compromised by development in microgravity.     

Changes in Cell Fine Structure in the Cotyledons of Phaseolus vulgaris L. during Germination

When germination begins, the storage cells of Phaseolus vulgariscotyledons are packed with starch grains and protein bodies.Digestion of these reserves starts in cells furthest away fromthe vascular bundles and is practically completed in eight daysat 25° C. After the reserves are hydrolysed, the storagecells die. The changes in fine structure during the processof digestion and protoplasmic breakdown are described. Vascularbundle and epidermal cells survive till the cotyledons absciss,but in these tissues also profound changes occur in cellularorganization. The observations on fine structure are discussedwith reference to the metabolic activities of the cotyledons.     

On the Function of Seedcoats in Gibberellin-induced Hydrolysis of Starch Reserves during Avocado (Persea americana) Germination

Of all seed components investigated, the endogenous levels ofboth bound and free gibberellin (GA) are highest in embryo tissueof young immature avocado seeds. Experimentation with the gelatinaceousendosperm tissue of these seeds indicated that hydrolysis ofstarch reserves may be triggered by the embryo-contained GAacting on the ‘endosperm sheath’, a thin layer ofcells encompassing the endosperm. In the mature fruit when theendosperm and the encompassing layer are no longer present andin which starch reserves are present in the two stony cotyledons,the papery bi-integumental layer, commonly regarded as biologicallyinert, retains the ability to trigger starch hydrolysis uponcontact with GA. From these data and also based upon the findingsthat during germination levels of endogenous GA increase inembryo tissue and that exogenously applied GA₃ is effectivein induction of dormancy break it is proposed that in the avocadoseed an analogy, physiological but not anatomical, to the cerealendosperm system exists.     

Histocytological changes and reserve accumulation during somatic embryogenesis in Eucalyptus globulus

We recently described a protocol for Eucalyptus globulus somatic embryogenesis (SE). For its immediate use at industrial levels, some stages of the process require better control. In particular, SE germination rates are variable, decreasing SE efficacy. As reserves may play a central role in embryogenic processes, we followed histocytological changes and reserve fluctuations, during SE. For SE induction, explants of mature zygotic embryos were grown on Murashige and Skoog (MS) medium with 3 mg l⁻¹ α-naphthalene acetic acid and later transferred to MS without growth regulators (MS_WH). Samples of zygotic embryo cotyledons (explants), of globular and dicotyledonar somatic embryos, and of embling leaves were analysed for reserve accumulation and histocytological profiles. Cotyledon cells of zygotic embryos were rich in lipid and protein bodies, having almost no starch. After 3 weeks of induction, starch grain density increased in differentiated mesophyll regions, while in meristematic regions their occurrence was diffuse. In globular somatic embryos, starch accumulation increased with time (in amyloplasts), but protein bodies were absent. Cotyledonary somatic embryos had lower density of starch grains and absence of lipid and protein bodies. Embling leaves showed typical histological organisation. This is the first comprehensive study on histological and cytological changes during Eucalyptus SE with emphasis in reserve accumulation. With this work we demonstrate that the presently available SE protocol for E. globulus leads to reserve fluctuations during the process. Moreover, the reserves of somatic embryo cotyledons differ from those of their zygotic embryo counterparts, which reinforce the importance of reserves in the embryogenic process and suggests that manipulating external conditions, SE may be optimised giving suitable emblings production for industrial purposes.     

Changes in cell-wall polysaccharides in relation to seedling development and the mobilisation of reserves in the cotyledons of Lupinus angustifolius cv. Unicrop

Some 22% of the dry weight of the cotyledons of resting seeds of Lupinus angustifolius cv. Unicrop has been shown to be non-starch polysaccharide material comprising the massively thickened walls of the storage mesophyll cells. On hydrolysis this material released galactose (76%), arabinose (13%), xylose (4%), uronic acid (7%): only traces of glucose were detected indicating the virtual absence of cellulose from the walls. Changes in the amount and composition of this material following germination have been studied in relation to parameters of seedling development and the mobilisation of protein, lipid and oligosaccharide reserves. Starch, which was not present in the resting seed, appeared transitorily following germination: under conditions of continuous darkness starch levels were reduced. During the period of bulk-reserve mobilisation, 92% of the non-starch polysaccharide material disappeared from the cotyledons. The residual cell-wall material released galactose (14%), arabinose (19%), xylose (24%) and uronic acid (43%). The galactose and arabinose residues of the cotyledonary cell walls clearly constitute a major storage material, quantitatively as important as protein. The overall role of the wall polysaccharides in seedling development is discussed.     

Ultrastructural and Biochemical Changes in Cotyledon Reserve Tissues3

Changes in major protein, lipid and carbohydrate reserves duringthe germination of Citrus limon (L.) Burm. f. seeds have beenstudied. The rate of release of amino acids and soluble sugarshas been evaluated. Mobilization of protein reserves began 4 d after the onset ofimbibition. The main period of hydrolysis occurred between 8d and 24 d after the start of germination. Ultrastructural studies showed the presence of protein bodiesin quiescent cotyledon cells. These bodies virtually disappeared14 d after the start of germination. The nitrogenous compoundsthat were liberated and subsequently translocated were predominantlyin the form of asparagine, arginine, and proline. The cotyledonshad a lipid content representing 51.7% of their dry weight.Lipid reserves in quiescent cotyledons were laid down in theform of oil-bodies. These organelles rapidly disappeared asgermination progressed, and were replaced by vacuoles. The starch content of quiescent cotyledons is very low, butit increased considerably up to 20 d after germination started. Key words: Proteins, lipids, carbohydrates     

Mobilisation of storage reserves during germination and early seedling growth of sugar beet

The principal storage reserve of sugar beet seeds is starch, which is localised in the perisperm. Additional storage reserves include the seed proteins, albumins, globulins and glutclins, which are exclusively located in the embryo. Soluble sugars are also detectable in all the organs of the mature seed. The time-course of reserve mobilisation in the different organs of the sugar beet ( Beta vulgaris L. cv. Regina) seed during germination and early seedling growth is documented, with particular reference to changes in (a) activities of hydrolases: a-amylase, β-amylase, and α-glucosidases; (b) levels of carbohydrates and (c) proteins. Amylase activities increase substantially in both cotyledons, as well as the perisperm, whereas the increase in α-glucosidase activities is largely confined to the perisperm.     

Protein Bodies of Developing Seeds of Vicia faba

Changes in fine structure and starch, nitrogen, and solublesugar content were followed through to maturation in developingcotyledons of Vicia faba. Various ultrastructural changes wereobserved in the developing cotyledons, notably an increase inthe number of membrane-bound ribosomes which corresponded withthe onset of storage protein deposition. The build-up of storageprotein was shown to occur in the cytoplasm within membrane-boundvacuoles which subsequently became the protein bodies of themature seed, retaining the original tonoplast as the boundingmembrane of the protein body. Nuclei became lobed during thelater phases of maturation; phytoferritin was observed in plastidsof mature seeds. The deposition of reserves in the cotyledonswas complete by 85–90 days after flowering, followingwhich water was lost until the seed became hard and ‘ripe’by no days after flowering.     

Protein Bodies of Germinating Seeds of Vicia faba: CHANGES IN FINE STRUCTURE AND BIOCHEMISTRY

Changes in fine structure and starch, total nitrogen and solublesugar contents were followed during the first 3 weeks of germinationin Vicia faba cotyledons. Following hydration the reserves were mobilized and loss ofprotein from the cotyledons began after 4 days; concomitantfine structural changes included the swelling and coalescenceof protein bodies, the disappearance of their contents, andthe differentiation of the provascular tissue in the cotyledonwithin which ‘transfer cells’ developed. There wassome development of rough endoplasmic reticulum during the earlypart of germination. A pattern of protein-body degradation appeared in the cotyledonsduring germination, those cells nearest to the vascular bundlesand to the epidermis being the first to lose their reserves.After 3 weeks' growth the parenchyma cells of the cotyledonwere very vacuolate and typical of senescent tissue, while thevascular bundle cells still retained their contents and remainedactive-looking.