Effet du stress salin sur la germination et la croissance in vitro du pistachier (Pistacia vera L.)

In order to study the salinity tolerance of pistachio (Pistacia vera L.), embryos developed from mature seeds were isolated and cultured in vitro and subjected to different NaCl concentrations (0, 42.8, 85.5, 171.1 and 256.6 mM) for 30 days. The results showed that in vitro germination of embryonic axes was not affected by the salt concentration. However, the germinated embryo survival rates decreased from 100% for the control to 62.9% for the highest salt concentration (256.6 mM).In addition, the plantlet growth (length of aerial and root parts, number of leaf produced per embryo, as well as the production of total fresh and dry matter for both aerial parts and roots) showed significant differences according the various salt concentrations. To cite this article: B. Benmahioul et al., C. R. Biologies 332 (2009).     

Plant regeneration via direct embryo axis-like shoot and root formation from excised cotyledon explants of ginseng seedlings

Summary Cotyledon explants of Panax ginseng at various developmental stages were cultured on Murashige and Skoog (MS) medium with 0.5 μM indole butyric acid and 8.8 μM N⁶-benzyladenine. Upon culturing of cotyledon explants from mature zygotic embryos, 34% of the explants formed somatic embryos, and 46% formed adventitious shoots. In the cotyledon explants from 1-wk-old seedlings, embryo axis-like shoots and roots developed at a high frequency (79%) near the excised portion of the cotyledon base. The developmental pattern of embryo axis-like organ formation was structurally different from that of somatic embryos and adventitious shoots but similar to that of parts of the embryo axis of zygotic embryos. In the early stages of embryo axis-like organ formation, epicotyl-like shoot primordia were developed directly from the cotyledon base after 2 wk of culture; subsequently roots developed near the base of the epicotyl-like shoots and eventually regenerated into plantlets with both shoots and roots. The frequency of embryo axis-like organ formation declined as the growth of seedlings proceeded. In addition, the frequency of somatic embryo and adventitious bud formation rapidly declined with the age of the cotyledons. Plant regeneration via embryo axis-like organ formation might be a new pattern of morphogenesis in P. ginseng cotyledon culture.     

In vitro regeneration of Sophora toromiro from seedling explants

Embryonic axes with cotyledons, shoot-tips of embryonic axes, isolated cotyledons, as well as axillary buds and leaves from 20-year-old trees of Sophora toromiro, were evaluated for their capacity to trigger organogenesis and to regenerate plantlets under in vitro conditions. Embryonic shoot-tips were the only explants capable of regenerating plants. They developed rapidly in vitro in the presence of NAA and BA while in subculture roots were induced at the proximal end in the presence of 0.49 μM IBA within 40–60 days. Development was completed with a subculture phase under non-sterile conditions using a mixture of equal parts of sterilized vermiculite/sand/soil in growth chambers, before final acclimation in the greenhouse. In the presence of NAA, BA and GA₃, whole embryonic axes formed multiple shoots that branched when grown in 2.27 or 11.35 μM TDZ in subculture. Similarly, callus was initiated at the embryo axis base, developing into several new shoots in the presence of TDZ. Because of the relatively high shoot induction rate along the embryonic axis, this axis presents a valuable source of new juvenile explants. Growth and rhizogenesis was satisfactory only when organs from seed pods of the year or from the previous season were used. Experiments with isolated cotyledons produced callus only, while axillary buds and leaves did not show any responses in the presence of several growth regulators assayed. Inoculation of seedlings with various strains of rhizobia under in vitro conditions resulted in root outgrowths, but not in nodules that are typical of rhizobia infection. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of genotype on somatic embryogenesis from axes of mature peanut embryos

Genotypes representing the three botanical varieties of peanut (Arachis hypogaea L.) were assessed for somatic embryogenesis and subsequent plant conversion from mature zygotic embryo axes. Explants were initially cultured on Murashige and Skoog medium supplemented with 12.42 M 4-amino-3,5,6-trichloropicolinic acid. Individual somatic embryos wer isolated from explant tissue and used to initiate repetitive liquid cultures. There were significant differences among genotypes and varieties for somatic embryo formation and plant regeneration using a single media sequence. Botanical variety fastigiata had a lower embryogenic frequency and produced significantly fewer embryos than either hypogaea or vulgaris, which were similar in response.Abbreviations EA zygotic embryo axes - MS Murashige and Skoog (1962) medium - picloram 4-amino-3,5 - 6 trichloropicolinic acid     

Early embryonic development,including germ-disk stage,in the theridiid spider Achaearanea japonica (Bös. et Str.)

Early embryonic development, from the first cleavage to the germ-disk stage, in the theridiid spider Achaearanea japonica was examined by light and electron microscopy. The eggs are syncytial during the first four cleavages, and then invaginations of cell membranes fuse to generate the blastomeres at the sixteen-nucleus stage. The cleavage pattern is a modified type of total cleavage. It appears that radial bundles of microtubules that radiate from the perinuclear cytoplasm may participate in the migration of cleavage nuclei for the formation of the blastoderm. The large yolk granules are sequestered by cell membranes from the blastomeres or blastoderm cells into the interior of the embryo together with various organelles and glycogen granules. Most of the blastoderm cells converge in the upper hemisphere to form the germ disk, whereas a few cells remain in the lower hemisphere. The embryo at the germ-disk stage contains many spherical germ-disk cells. Almost no large yolk granules are found in these cells, but the flat remaining cells each contain several large yolk granules. These remaining cells may preserve a flat shape to cover the surface of the embryo that does not include the germ disk. © 1995 Wiley-Liss, Inc.     

The use of embryo culture for the recovery of plants from cassava (Manihot esculenta Crantz) seeds

Cassava fertility and seed viability are frequently low, which can be a disadvantage in a breeding programme. An embryo culture method is described whereby embryonic axes are excised from mature seeds and placed on a culture medium containing 1.23 M indolebutyric acid (IBA) at 30°C under continuous light. The number of plants recovered by embryo culture was much greater than the number recovered from conventional seed germination procedures.     

Drosophila embryo syncytial blastoderm cellular architecture and morphogen gradient dynamics: Is there a correlation?

During embryo development in many metazoan animals, the first differentiated cell type to form is an epithelial cell. This epithelial layer is modified by developmental cues of body axes formation to give rise to various tissues. The cells that arise are mesenchymal in nature and are a source of other tissue types. This epithelial to mesenchymal transition is used for tissue type formation and also seen in diseases such as cancer. Here we discuss recent findings on the cellular architecture formation in the Drosophila embryo and how it affects the developmental program of body axes formation. In particular these studies suggest the presence of compartments around each nucleus in a common syncytium. Despite the absence of plasma membrane boundaries, each nucleus not only has its own endoplasmic reticulum and Golgi complex but also its own compartmentalized plasma membrane domain above it. This architecture is potentially essential for morphogen gradient restriction in the syncytial Drosophila embryo. We discuss various properties of the dorso-ventral and the antero-posterior morphogen gradients in the Drosophila syncytium, which are likely to depend on the syncytial architecture of the embryo.     

Function of Node Unit in Photosynthate Distribution to Root in Higher Plants

Leaf-root interaction is a critical factor for plant growth during maturation and activity of roots is maintained by a sufficient supply of photosynthates. To explain photosynthate distribution among organs in field crops, the node unit hypothesis is proposed. One node unit consists of a leaf and an upper adventitous root, as well as the axillary organs and the lower adventitious root, which is adjacent to one node. Using ¹⁴C as tracer, the carbon distribution system has been clarified using spring wheat, soybean, tomato, and potato. The interrelationship among organs from the strongest to the weakest is in the following order: (1) within the node unit > (2) between the node unit in the same or adjacent phyllotaxy > (3) in the main root or apical organs, which are adjacent to the node unit. Within the node unit, ¹⁴C assimilated in the leaf on the main stem tended to distribute to axillary organs in the same node unit. The ¹⁴C assimilated in the leaf of axillary organs tended to distribute within the axillary organs, including adventitious roots in the axillary organ and then translocated to the leaf on the main leaf of the same node unit. In different organs of the node unit in the same or adjacent phyllotaxy, ¹⁴C assimilated in the leaf on the main stem was also distributed to the organs (node unit) belonging to the same phyllotaxy in dicotyledons, while in monocotyledons, the effect of phyllotaxy on ¹⁴C distribution was not clear. Among roots/apical organs and node unit, ¹⁴C assimilated in the upper node unit was distributed to apical organs and ¹⁴C assimilated in the lower node unit was distributed to roots. Thus the node unit hypothesis of photosynthate distribution among organs is very important for understanding the high productivity of field crops.     

薏苡胚发育及贮藏营养物质积累的研究

薏苡（Ｃｏｉｘ ｌａｃｒｙｍ ａ－ｊｏｂｉ）胚发育分下列各期：棒形胚前的原胚期、棒形胚期、胚芽鞘期、１叶期、２ 叶期、３叶期、４ 叶期、５ 叶期及６叶期成熟胚。３ 叶期胚具１ 条不定根（种子根）,４ 叶期具２ 条,５ 叶期及成熟胚期具３ 条。不定根与胚根排成１ 纵行。营养物质最先在盾片细胞中积累。开花后９ 天的１ 叶期胚,在盾片、胚芽鞘及胚轴细胞中积累了淀粉,以后遍及成熟胚的各部分。淀粉粒含量与器官发生及生长顺序成正相关,但发育后期,盾片细胞内的淀粉粒含量下降。开花后１０ 天,盾片细胞中形成含晶体的蛋白质体,晶体含蛋白质及植酸钙镁。以后,这种蛋白质体增多、增大。同时,又形成不含晶体的蛋白质体。一定时期,含晶体的蛋白质体消失,不含晶体的蛋白质体增多,直到胚成熟。开花后１３ 天,胚芽鞘上部细胞形成蛋白质体。以后遍及成熟胚的各部分,器官发生越早,所含蛋白质体越多、越大。开花后１０ 天,盾片细胞中产生了脂体,成熟胚的盾片细胞,含有大量的脂体。还观察了胚发育各期与颖果及盾片长度的对应关系     

MtZR1, a PRAF protein,is involved in the development of roots and symbiotic root nodules in Medicago truncatula

PRAF proteins are present in all plants, but their functions remain unclear. We investigated the role of one member of the PRAF family, MtZR1, on the development of roots and nitrogen‐fixing nodules in Medicago truncatula. We found that MtZR1 was expressed in all M. truncatula organs. Spatiotemporal analysis showed that MtZR1 expression in M. truncatula roots was mostly limited to the root meristem and the vascular bundles of mature nodules. MtZR1 expression in root nodules was down‐regulated in response to various abiotic stresses known to affect nitrogen fixation efficiency. The down‐regulation of MtZR1 expression by RNA interference in transgenic roots decreased root growth and impaired nodule development and function. MtZR1 overexpression resulted in longer roots and significant changes to nodule development. Our data thus indicate that MtZR1 is involved in the development of roots and nodules. To our knowledge, this work provides the first in vivo experimental evidence of a biological role for a typical PRAF protein in plants.     

Studies on Embryo Development and Deposition of Storage Reserves in Coix lacryma-jobi

Embryo development in Coix lacryma-jobi is classified into the following stages: proembryo before club-shaped, club-shaped, coleoptilar, I-leafed, 2-1eared, 3-1eared, 4-1eared, 5-leafed and 6-leafed (mature embryo). The 3-, 4-, 5-leafed embryos have 1, 2 and 3 adventitious roots (seminal roots) respectively, and the matrue also has 3. These seminal roots are arranged in a longitudinal row parallelling with the radicle. The storage reserves first deposit in the scutellar cells. 9 days after anthesis (l-leafed stage), the starch grains are accumulated in cells of scutellum, coleoptile and mesocotyle. When the embryo matures, starch grains are deposited throughout its cells. The increase in size and amount of starch grains correlates with the initiation and growth order of the embryonic organs. But the amount in the scutellar cells decreases from later to mature stage. 10 days after anthesis (2-leafed stage), protein bodies containing crystals, of protein and phytin are present in the scutellar cells. They subsequently become larger and abundant druses. At the same time some protein bodies without crystals are also formed. Later, the protein bodies containing crystals disappear, while those without crystals increase until the embryo matures. 13 days after anthesis (3- leafed stage) protein bodlies are formed in the upper coleoptile cells. Protein bodies are rich in the cells of mature embryo, but the earlier the organ of embryo occurs, the more and the larger protein bodies it contains. 10 days after anthesis, lipid bodies appear in the scutellar cells and increase in size and quantity rapidly as the embryo develops. The correlation of the length of caryopsis and scutellum with embryo development is also observed.     

Metabolism of amino acids in germinating yellow lupin seeds III. Breakdown of arginine in sugar-starved organs cultivated in vitro

The pathways of arginine transformations in organs of yellow lupin (Lupinus luteus L.) cultivated in vitro in the presence and absence of sucrose were investigated. Isolated embryo axes, isolated cotyledons and seeds deprived of their coat were cultured for 96 h on Heller medium with 60 mM saccharose (the fed variant, +S), without sugar (the starved variant, −S) and for 72 h without sugar, followed by 24 h in its presence (the transferred variant, −S→+S). Activities of arginine decarboxylase [EC 4.1.1.19], arginase [EC 3.5.3.1], and urease [EC 3.5.1.5] were assessed in extracts from isolated embryo axes. They were the highest in the sugar-starved variant. Supplementation of the medium with saccharose resulted in decrease in enzyme activities. The level of urea was higher (of ca. 20 %) in starved embryos than in embryos grown in the saccharose-containing medium. Moreover, participation of transamination in arginine catabolism was evidenced.     

Maturation and germination of Phaseolus vulgaris embryonic axes in culture

In this study of embryo development in Phaseolus vulgaris L., we found that immature embryonic axes placed in culture show a growth lag before germinating. The length of this lag phase varies according to axis age at excision, but is not affected by transfer to fresh medium, alteration of sucrose concentration between 0.5 and 2%, or whether the culture medium is liquid or agar-solidified. The lag phase was shortened by both actinomycin D and cordycepin treatment, and by treatment with 10^-5 to 10^-6 M benzyladenine. The effect of abscisic acid (ABA) varied with concentration: below a certain level, it had no effect on the lag phase, but above that level it inhibited, germination. This threshold concentration was 10^-7 M for 20-d-old axes but increased to 10^-5 M by the time the axes were 32 to 34 d old. To determine whether the axes were continuing their embryonic development during the lag phase, we tested them for desiccation-tolerance and for synthesis of phaseolin, a seed storage protein which is specific for embryos of P. vulgaris. The ability to germinate after rapid desiccation was acquired by axes at 26 d past anthesis; when axes younger than this were placed in culture, they developed desiccation-tolerance during the lag phase of growth, indicating that they were continuing embryonic maturation. Phaseolin was present in isolated axes, although at lower levels than in cotyledons. It accumulated during axis development in parallel with total protein, staying at about 1% of total protein content. When isolated immature axes were pulsed with ³H-or ¹⁴C-amino acids, they incorporated label into phaseolin, shown by precipitation with anti-phaseolin antibody. Isolated axes from mature seeds, however, did not synthesize detectable amounts of phaseolin. Immature axes cultured in vitro for a period of one to several days continued synthesizing phaseolin until the day prior to visible germination. Treatment of cultured axes with ABA increased the amount of precursor amino acids incorporated into protein, but had a small or no effect on the relative proportion of phaseolin synthesized. We conclude that P. vulgaris axes in culture continue to develop embryonically for a period of time which seems to be under intrinisc control by the axis. This contrasts with precocious germanation, a pattern of embryo behavior seen in many other species. When such embryos are excised from seeds while immature and placed in culture, they switch promptly from embryo development into germination. If ABA or water stress is responsible for preventing precocious germination, it may be that a high level of ABA is maintained or synthesized internally by embryonic axes of Phaseolus, while in other embryos the maternal environment supplies ABA and/or causes water stress.Abbreviations ABA Abscisic acid - BA benzyladenine     

Growth Capacity of Embryo Axes Excised from Dormant and Germinating Horse Chestnut Seeds and Their Response to Exogenous Abscisic Acid

In embryo axes excised from mature horse chestnut (Aesculus hippocastanum L.) seeds, both freshly-fallen and subjected to cold stratification, the ability for growth was studied. While excised axes were kept on water at 28°C for 3 days, their fresh weight and length increased, the polypeptide composition of soluble proteins changed, the content of some heat-stable polypeptides decreased, and the capacity for protein synthesis in vivo retained. All these processes were similar to those in the axes of intact seeds during stratification until radicle protrusion. Growth of excised axes accelerated with the increasing duration of stratification. Cycloheximide (50 mg/l) and -amanitin (7 mg/l) inhibited axis growth, but an inhibitor of ABA synthesis fluridone (5 mg/l) and a natural cytokinin dihydrozeatin (10^–5 M) did not influence the growth rate. The growth capacity of axes excised from dormant and germinating horse chestnut seeds indicates the absence of dormancy in the axes of mature seeds. ABA (10^–5 M) suppressed completely the growth of axes detached from seeds experiencing cold stratification but still not germinating, although protein synthesis was not inhibited. The axes excised from the seeds after radicle emergence were insensitive to ABA and grew actively in its presence. ABA-induced growth inhibition might be related to the suppressed synthesis of minor polypeptides required for growth or to the activated synthesis of some growth-retarding proteins. The conclusion was drawn that the excised axes could be used as a model for studying the processes preceding visible germination of recalcitrant seeds.     

Organ-dependent responses of Periploca sepium to repeated dehydration and rehydration

Plant responses to water deficit occur in a complex framework of organ interactions, but few studies focus on the effect of drought stress on all organs in a whole-plant. The effects of repeated dehydration and rehydration (DH) on physiological and biochemical responses in various organs of Periploca sepium Bunge (P. sepium) were investigated. The leaf relative water content decreased significantly during drought, but recovered and showed an increase when compared to well-watered control plants. The malondialdehyde (MDA) content increased in mature and old leaves, but decreased in young leaves, new stems and fine roots during drought, indicating that the young and vigorous tissues of a whole-plant are protected preferentially from the oxidative stress. Among all organs, the fine roots showed the highest levels of proline, total free amino acids (TFAA) and Na⁺, while the leaves showed the highest levels of total soluble sugars (TSS), soluble proteins (SP), Ca²⁺ and Mg²⁺. The response to DH differed in different organs, both in magnitude and in the type of solutes involved. Drought stress increased the contents of proline, TFAA, TSS, SP and K⁺ in all organs of P. sepium plants, while the accumulation amounts were obviously different among the organs. The storage starch in stems and roots plays an important role in providing carbohydrates for growth. Changes in Na⁺, Ca²⁺ and Mg²⁺ under DH presented a high degree of organ specificity. Our data indicates that response strategies are different between different organs; therefore, evidence the needs to integrate all the information in order to better understand plant tolerance mechanisms.     

<Emphasis Type="Italic">In vitro</Emphasis> germination and micropropagation of <Emphasis Type="Italic">Givotia rottleriformis</Emphasis> Griff.

The propagation of Givotia rottleriformis Griff. is difficult as a result of long seed dormancy associated with poor seed germination. The present study was undertaken to develop a protocol to overcome seed dormancy by culture of zygotic embryo axes and then develop an efficient method for micropropagation of Givotia. Best germination frequency (78.3%) was achieved from mature zygotic embryo axes isolated from acid-scarified fresh seeds when cultured on Murashige and Skoog (MS) medium (half-strength major salts) with 28.9 μM gibberellic acid (GA₃). Efficient plant conversion was achieved by transfer of 10-d-old germinated embryos to MS medium (half-strength major salts) supplemented with 1.2 μM kinetin (KN) and 0.5 μM indole-3-butyric acid (IBA). However, acid scarification of 1-yr-old seeds decreased the germination frequency of zygotic embryo axes in comparison to those obtained from non-acid-scarified seeds which germinated (96.2%) and converted into plants (80.3%) on MS basal (half-strength major salts) medium. Multiple shoot bud induction was achieved by culture of shoot tips derived from in vitro germinated seedlings on MS medium with 0.5 μM thidiazuron for 4 wk, and the shoots elongated after transfer to a secondary medium with 1.2 μM KN. A maximum number of 7.8 shoots per explant with an average shoot length of 3.2 cm was achieved after two subcultures on this medium. The in vitro regenerated shoots rooted (41.5%) on half-strength MS medium with 0.5 μM IBA. The in vitro generated seedlings and micropropagated plants were established in soil with a survival frequency of 70% and 60%, respectively.     

Regulation and the modification of axial properties in partial embryos of the nemertean, Cerebratulus lacteus

 Embryos acquire axial properties (e.g., the animal-vegetal, dorsoventral and bilateral axes) at various times over the course of their normal developmental programs. In the spiral-cleaving nemertean, Cerebratulus lacteus, lineage tracing studies have shown that the dorsoventral axis is set up prior to the first cleavage division; however, blastomeres isolated at the two-cell stage will regulate to form apparently perfect, miniature pilidium larvae. We have examined the nature of axial specification in this organism by determining whether partial embryos retain the original embryonic/larval axial properties of the intact embryo, or whether new axial relationships are generated as a consequence of the regulatory process. Single blastomeres in two-cell stage embryos were injected with lineage tracer, and were then bisected along the second cleavage plane at the four-cell stage. Thus, the relationship between the plane of the first cleavage division and various developmental axes could be followed throughout development in the ”half-embryos”. While some embryo fragments appear to retain their original animal-vegetal and dorsoventral axes, many fragments generate novel axial properties. These results indicate that axial properties set up and used during normal development in C. lacteus can be completely reorganized during the course of regulation. While certain embryonic axes, such as the animal-vegetal and dorsoventral axes, appear to be set up prior to first cleavage, these axes and associated cell fates are not irreversibly fixed until later stages of development in normal intact embryos. In C. lacteus, the process whereby these properties are ultimately determined is apparently controlled by complex sets of cell-cell interactions. Received: 11 October 1996 / Accepted: 21 February 1997