Plant regeneration from callus and protoplasts of Brassica nigra (IC 257) through somatic embryogenesis

A method to obtain plants from embryogenic callus of Brassica nigra and protoplasts of hypocotyl expiants is described. Callus was initiated on Murashige and Skoog medium containing kinetin (kn) and 2,4-dichlorophenoxy acetic acid (2,4-D). Lowering of auxin induced embryo formation. Supplementation with gibberellic acid (GA₃) enhanced embryogenic response tenfold. Passage through liquid medium devoid of growth regulators was essential for the growth of embryos. Secondary embryos were produced on transfer to solid basal medium. Embryogenic callus retained its morphogenic ability even after 12 subcultures. Both primary and secondary embryos produced fertile plants. Hypocotyl-derived protoplasts were also regenerated to plants following the same protocol. The survival of plants on transfer to soil was about 80%. The seeds from plants derived from callus and protoplasts were viable.Abbreviations 2,4-D 2,4-dichlorophenoxy acetic acid - NAA naphthalene acetic acid - IAA indole acetic acid - kn kinetin - GA₃ gibberellic acid     

Effects of water level fluctuation on the growth ofNelumbo nucifera Gaertn. in Lake Kasumigaura,Japan

Investigations were made of the growth ofNelumbo nucifera, an aquatic higher plant, in a natural stand in Lake Kasumigaura. A rise of 1.0 m in the water level after a typhoon in August 1986 caused a subsequent decrease in biomass ofN. nucifera from the maximum of 291 g d.w. m⁻² in July to a minimum of 75 g d.w. m⁻². The biomass recovered thereafter in shallower regions. The underground biomass in October tended to increase toward the shore. The total leaf area index (LAI) is the sum of LAI of floating leaves and emergent leaves. The maximum total LAI was 1.3 and 2.8 m² m⁻² in 1986 and 1987, respectively. LAI of floating leaves did not exceed 1 m² m⁻². The elongation rates of the petiole of floating and emergent leaves just after unrolling were 2.6 and 3.4 cm day⁻¹, respectively. The sudden rise in water level (25 cm day⁻¹) after the typhoon in August 1986 caused drowning and subsequent decomposition of the mature leaves. Only the young leaves were able to elongate, allowing their laminae to reach the water surface. The fluctuation in water level, characterized by the amplitude and duration of flooding and the time of flooding in the life cycle, is an important factor determining the growth and survival ofN. nucifera in Lake Kasumigaura.     

Nauclea diderrichii: rooting of stem cuttings,clonal variation in shoot dominance,and branch plagiotropism

Summary Nauclea diderrichii (De Wild, and Th. Dur.) Merill (Rubiaceae), an indigenous hardwood of West Africa, is increasingly being grown commercially. This study investigates the potential for vegetative propagation and clonal selection, and raises some fundamental questions about the physiology of apical dominance and of plagiotropism. Rooting ability was high, with up to 100% rooting in 2–4 weeks, when different Indole-3-butyric acid (IBA) concentrations and leaf areas were tested. Auxin applications greatly increased the numbers of roots per cutting. The decapitation of unbranched plants revealed clonal variation in apical dominance and also in the establishment of outright dominance by the two shoots formed from the outgrowth of the axillary buds of the opposite leaves at the top node. Regression analysis of the Dominance Ratio (length of dominant: length of the sub-dominant shoot at the time of achieving dominance) against overall lateral bud activity (r = 0.82), showed that when the two top shoots co-dominate they provide a more powerful source of Correlative Inhibition than when one of the top shoots dominates the other. The imposition of plagiotropism in the axillary bud occurred over a period of a few days as the terminal and axillary buds emerged from the stipule. Growth of accessory buds on intact plants and debranched cuttings was orthotropic. These results are discussed with regard to the role of the leaf in root formation and the understanding of dominance relationships, branching and crown development in trees.     

植物单盐毒害和离子拮抗机理研究Ⅰ.单盐和混合盐对植物原生质体膜某些特性、超氧物歧化酶和过氧化氢酶活性的影响

单盐(KCl, CaCl_2或MgCl_2)和混合盐(KC_1+CaCl_2或KCl+MgCl_2)对植物原生质体完整率、存活率和膜透性等均有明显影响。K~+、Ca~(2+)或Mg~(2+)等单种阳离子明显降低原生质体膜完整率和存活率而增加其物质渗漏量,其中以单价阳离子K~+的影响为甚。上述单种阳离子还明显降低小麦幼叶超氧物歧化酶(SOD)和过氧化氢酶活性。只有由单价和二价阳离子组成的平衡混合盐才能使原生质体维持较高的完整率、存活率和较正常的膜透性.并能使细胞维持较高的SOD和过氧化氢酶活性。 认为单盐毒害机理可能是首先引起细胞膜发生不正常的膜相变或细胞累积较多的有害氧自由基,引起膜脂发生过氧化或脱酯化而破坏膜结构。在离子平衡混合盐作用下,膜系才能维持正常液晶相,具有较高活性的SOD和过氧化氢酶等生物保护性酶系是离子拮抗作用之原因。     

Common antigenic determinants in the glycoproteins of plants,molluscs and insects

An antiserum raised against -fructosidase isolated from the cell walls of suspension-cultured carrot cells cross-reacts with many plant proteins and hemocyanin ofHelix pomatia. The shared epitope appears to be a small complex glycan with a (1–2)-linked xylose residue attached to the -linked mannose residue of the core of an asparagine-linked oligosaccharide. There is strong cross-reactivity with the proteins of many seed plants, molluscs and insects, and no cross-reactivity with the proteins of fungi, algae, mosses, ferns, or any of the vertebrates tested. Xylose-containing glycans appear to increase the immunogenicity of the proteins to which they are attached, and we suggest that they may be responsible for some allergic responses of people that are repeatedly exposed to plant or insect proteins.     

A role for haemoglobin in all plant roots?

Abstract. We have found haemoglobin in plant roots whereas previously it has been recorded only in nitrogen fixing nodules of plants. Haemoglobin occurs not only in the roots of those plants that are capable of nodulation but also in the roots of species that are not known to nodulate. We suggest that a haemoglobin gene may be a component of the genome of all plants. The gene structure and sequence in two unrelated families of plants suggests that the plant haemoglobins have had a single origin and that this origin relates to the haemoglobin gene of the animal kingdom. At present we cannot completely rule out the possibility of a horizontal transfer of the gene from the animal kingdom to a progenitor of the dicotyledonous angiosperms but we favour a single origin of the gene from a progenitor organism to both the plant and animal kingdoms. We speculate about the possible functions of haemoglobin in plant roots and put the case that it is unlikely to have a function in facilitating oxygen diffusion. We suggest that haemoglobin may act as a signal molecule indicating oxygen deficit and the consequent need to shift plant metabolism from an oxidative to a fermentative pathway of energy generation.     

Effects of auxins and cytokinins on epigenetic instability of callus-propagated Kalanchoe blossfeldiana Poelln.

A main problem in the vegetative propagation of ornamental plants in vitro is the epigenetic instability of cells removed from their organized environment. With calluses of leaf explants of Kalanchoe blossfeldiana Poelln., cv. Yucatan, the role of plant growth regulators (PGRs) in the occurrence of fasciation was studied.In various combinations of auxins and cytokinins, the auxin 2,4-D (2,4-dichlorophenoxyacetic acid) gave only deformed, inseparable shoot primordia. The most rapid callus induction with regeneration of well-developed sprouts was obtained with the natural IAA (indoleacetic acid) and Z (zeatin).As a first symptom of fasciation, aberration in decussate phyllotaxis can be observed. At increasing concentrations of IAA + Z, this symptom gradually decreased but fasciation proper increased. The optimum concentration was at 1 M for both PGRs. Reduction of exposure to the PGRs from six to three weeks reduced the epigenetic instability.     

Overwintering and growth regulator treatment effects on celery (Apium graveolens L.) flowering and seed production

Celery (Apium graveolens L.) plants cv. Jason overwintered in a polythene tunnel flowered earlier and grew taller than similar plants given a 10-week cold-treatment at 5°C prior to transplanting in the same tunnel in mid-February. However, there was no significant difference in the yield of seeds obtained from both treatments, plants grown at a density of 4m^-2 yielded less seeds than those at 2m^-2, though the yield per unit area was slightly higher from the high density treatment. Treatment with 100 mgl^-1 GA₃ applied twice just prior to flowering and during anthesis increased flower stalk, flower pedicel and stamen length but delayed flower opening and seed ripening and decreased seed set and seed yield. Treatment with a mixture of 1000 mgl^-1 GA₄ and GA₇ plus 1000 mgl^-1 ethephon on three occasions during seed ripening decreased seed yield and reduced seed germination though those seeds capable of germinating were less dormant than seeds from untreated plants. The size distribution of seeds was unaffected by any treatment other than the preseeding spray with GA₃ which reduced the percentage of medium-size seeds.     

Substance P analogues function as bombesin receptor antagonists and inhibit small cell lung cancer clonal growth

Human small cell lung cancer (SCLC) produces and secretes BN/GRP (bombesin/gastrin releasing peptide). Because BN stimulates the growth of SCLC cells and these cells have receptors for BN-like peptides, it is important to define agents which disrupt this self-promoting autocrine growth cycle. Here, substance P analogues were evaluated as BN receptor antagonists using SCLC cell lines. (D-Arg¹, D-Pro², D-Trp^7,9, Leu¹¹) substance P [(APTTL)SP] was one of the more potent analogues tested in inhibiting BN-like peptide receptor binding with an IC₅₀ value of 1 μM. Micromolar concentrations of (APTTL)SP antagonized BN receptor mediated elevation of cytosolic Ca²⁺ levels and decreased the colony formation in soft agarose. These data suggest that SP analogues function as SCLC BN receptor antagonists and may be useful in disrupting the autocrine growth function of BN-like peptides.