UNUSUAL DARK-GROWTH AND ANTHERIDIAL DIFFERENTIATION IN SOME GAMETOPHYTES OF THE FERN ONOCLEA SENSIBILIS

A fertile frond of O. sensibitis was found which yielded spores with unusual growth characteristics. About 25% of the gametophytes derived from the spores were able to undergo 2-dimensional development in darkness, in contrast to normal plants which are filamentous in darkness. When the aberrant spores were cultured in darkness under conditions of reduced ethylene concentration, the proportion of 2-dimensional plants rose to 75%, and, moreover, up to 50% of the gametophytes produced antheridia within 2 weeks. Under comparable conditions normal gametophytes produced no antheridia. The medium from antheridial cultures of the aberrant spores failed to induce the formation of antheridia in other plants.     

RHIZOID CELL DIFFERENTIATION IN THE FERN GAMETOPHYTE OF PTERIS VITTATA

A series of events in the differentiation of rhizoid cells in the gametophyte of Pteris vittata L. is described. Differential in vivo staining reactions make it possible to trace a sequence of stages from pre-mitotic nucleocytoplasmic staining (corona stage), through the events of mitosis, to formation of an internally segmented rhizoid cell which then grows out from the parent thallus cell. When the standard ribonuclease test is employed, basophilic protoplasmic staining due to pyronin is prevented in developmental stages up through early formation of the rhizoid cell. Staining in these stages is therefore assumed to be due to ribonucleic acid associated with protein synthesis. A new developmental phase starts just prior to the protrusion growth of this cell when an intensely pyroninophilic material appears at the membrane of the rhizoid cell nucleus and along cytoplasmic strands radiating to the peripheral regions of the cell. The staining of this newly synthesized material cannot be prevented by ribonuclease treatment, and it shows strong positive tests for protein and polysaccharide. As long as the rhizoid continues to grow, this material remains concentrated in the growing tip region. Material showing similar staining reactions is also found in the cells of the meristematic notch area. Although thallus cell walls do not stain, the rhizoid cell wall adsorbs basic stain, in some cases, metachromatically. Finally, it is suggested on the basis of observations reported here that the sometimes neglected role of the nucleus in theories of unequal cell division-differentiation should be re-examined.     

DIFFERENTIATION AND CONTINUITY OF THE PHLOEM IN THE LEAF INTERCALARY MERISTEM OF LOLIUM PERENNE

Serial transverse sections of the stem tip and leaf bases of immature perennial ryegrass leaves were examined to assess the effect of the intercalary meristem on assimilate movement. The development of procambial strands in very young leaves was followed, and the subsequent differentiation of proto- and metaphloem examined in both lamina and sheath. In major bundles the first two or three series of protophloem cells differentiated acropetally into the leaf and they or their crushed remnants could be recognized at all levels. A further three or four series of protophloem cells differentiated basipetally, as did the protophloem of all minor bundles and the metaphloem. The basipetal differentiation of the bulk of the phloem combined with crushing of older cells resulted in acute constriction or even complete local blockage of the functional phloem in the active meristematic region. This constriction of the phloem would tend to divert assimilates into the dividing cells both from the stem below and from the mature upper portion of the leaf. No constriction was found at the base of a mature sheath.     

中国产瓦韦属植物叶柄与根状茎的比较解剖研究

详细观察了已发表的60种瓦韦属植物叶柄和根状茎的横切面。瓦韦属植物叶柄维管束条数最多7条,最少2条,其中2个较粗,其余较细,排成一字型、三角型、四角型、半轮型等。根状茎上的维管束条数最少5条,最多16条,属于网状中柱,维管束不规则环形排列,夏绿种类厚壁组织较少或没有,常绿种类厚壁组织较多。叶柄与根状茎的研究对瓦韦属组的划分和种的确立有重要的参考价值。参考这些特征,瓦韦属相应地划分成六个组,即:大叶瓦韦组、扭瓦韦组、瓦韦组、革质叶瓦韦组、纸质叶瓦韦组、网眼瓦韦组。一些种类相应地进行了合并。     

THE ROLE OF LIGHT IN HISTOGENESIS AND DIFFERENTIATION IN THE SHOOT OF PISUM SATIVUM. II. THE LEAF

Thomson , Betty F., and Pauline Monz Miller . (Connecticut Coll., New London.) The role of light in histogenesis and differentiation in the shoot of Pisum sativum, II. The leaf. Amer. Jour. Bot. 49(4): 383–387. Illus. 1962.—Development of the form and anatomy of leaves was studied in plants of Pisum sativum grown in vermiculite under constant conditions and exposed daily to red or white light or kept in continuous darkness. The red light used had an intensity in the morphogenetically active red region of the spectrum of 70–75% that of the white light. Light had no effect on the manner of initiation or early development of leaf primordia. Quantitative data from older leaves showed that light has no effect on the pattern of later development but does affect the rate and extent of development. Under all light conditions, the length of the leaflet is closely correlated with the state of its internal anatomy. “Mature” etiolated leaves duplicate young stages of light-grown leaves. Mature leaves grown in red light duplicate not-quite-mature leaves grown in white light. The difference between white-light and red-light leaves is attributed here to light intensity and resembles that between sun and shade leaves.     

烟草花柄愈伤组织花芽分化的能力(简报)

来源于开花植株的外植体(如花柄、花序轴等)具有在离体培养条件下直接分化花芽的能力,这一现象已在数十种植物的组织培养中得到证实。但是,这种成花能力能否保留在由这些外植体形成的愈伤组织之中?已有报道在风信子、布罗瓦利亚花、石龙芮、大蒜、矮通泉草等值物的愈伤组织中得到无     

ACTION OF PURINE AND PYRIMIDINE ANALOGS ON THE GROWTH AND DIFFERENTIATION OF THE GAMETOPHYTES OF THE FERN ASPLENIUM NIDUS

The purine analogs, 8-azaadenine, 8-azaguanine, 8-azaxanthine and 8-azahypoxanthine, and the pyrimidine analogs, 2-thiocytosine, 5-fluorouracil, 2-thiouracil and 6-azauracil, inhibited the induction of 2-dimensional growth in the gametophytes of the fern Asplenium nidus L. In contrast, thymine analogs such as 5-fluorodeoxyuridine, 2-thiothymine, 6-azathymine and 5-bromouracil caused non-specific growth inhibitions without suppressing 2-dimensional growth. Subinhibitory concentrations of 8-azaxanthine, 8-azahypoxanthine, and 2-thiouracil promoted both 1-dimensional and 2-dimensional phases of growth of the gametophytes. Inhibitory effects of the analogs were observed on treatment of the spores or of gametophytes of different ages. Gametophytes growing in the analogs for different periods of time recovered from inhibition on transfer to the basal medium.     

SHOOTLESSNESS,VELAMENTOUS ROOTS,AND THE PRE-EMINENCE OF ORCHIDACEAE IN THE EPIPHYTIC BIOTOPE

Roots of representative epiphytic orchids were examined for anatomical detail, desiccation resistance and evidence of CAM activity. Those “shootless” taxa examined (Campylocentrum pachyrrhizum (Reichenb. f.) Rolfe, Harrisella porrecta Reichenb. f.) Fawc. & Rendle, and Polyradicion lindenii (Lindl.) Cogn. ex Urban) and a semi-shootless type (Kingidium taeniale (Lindl.) P. F. Hunt) bear thinner or eroded velamina and greater volumes of cortical intercellular space than do those of the leafy forms tested (Campylocentrum sellowii (Reichenb. f.) Rolfe, Encyclia tampensis (Lindl.) Small, Epidendrum radicans Pavon ex Lindl., Phalaenopsis amabilis (L.) Blume, Rangaeris amaniensis (Krzl.) Summerhayes and Vanda parishii (Reichenb. f.)). Shootless species also bear a more elaborate aeration apparatus at the velamen-cortex interface. Structurally distinct cortical cells located in this region may regulate gas exchange across the exodermis. Velamen thickness varies greatly among the ten species, as does the development of outer tangential walls of U cells in the underlying exodermis. Desiccation resistance under laboratory conditions was more closely related to root surface-to-volume ratio (S/V) than to any other measured anatomical parameter, including velamen development. Modes of carbon gain and the possible pathway for movement of fungus-borne carbon into an orchid's pool of assimilates are described, as is the possible significance of these processes to survival in forest canopy habitats.     

烟草愈伤组织分化和芽原基形成期间呼吸代谢途径的改变

接种在继代培养基上的柳叶烟草愈伤组织,未观察到组织分化和芽原基形成。在分化培养基上生长的愈伤组织,接种后第6天可见拟分生组织和管胞分化,9—12天有芽原基形成,15—18天可观察到苗端结构。根据碘乙酸、Na_3PO_4和丙二酸抑制试验,以及3-磷酸甘油醛脱氢酶与琥珀酸脱氢酶活性测定结果,初步表明烟草愈伤组织呼吸中存在有EMP、HMP和TCAC代谢途径.在发生输导组织和芽原基分化的愈伤组织中(接种后第6—12天),HMP途径的运行程度较高;而芽原基的继续生长(培养12天以后),则与EMP途径的增加有关;分化培养基上生长的愈伤组织,始终较继代培养愈伤组织具有较高的FCAC活性水平。     

OBSERVATIONS ON LEAF AND BUD FORMATION IN HYDROCHARIS MORSUS-RANAE

Regular sequences of leaf and bud formation occur in several members of the Hydrocharitaceae, including Hydrocharis, in which buds are normally formed in the axil of every second leaf of the phyllotactic spiral. Leaf inception begins by periclinal divisions of the inner cells of the 2-layered tunica. Bud formation, which occurs in the apical meristem itself, immediately following the inception of the subtending leaf primordium, begins by divisions in various planes in the corpus, the 2 tunica layers remaining continuous throughout. The young bud meristem soon gives rise to a lateral bud, before leaf formation begins upon it. Because of these and other features, this species is one of considerable morphogenetic interest. Morphogenesis of the whole plant, and in particular the factors controlling the regular sequence of leaf and bud formation, have been and are being investigated experimentally.     

生长素极性运输抑制剂(TIBA)对烟草离体花柄花芽分化的影响

在只含6-BA(2mg/L)的MS培养基上,烟草花柄外植体形态学基端膨大,上着生再生花芽,而花柄中部大多都形成愈伤组织。添加IAA(2,10,20 mg/L)后,花柄基端膨大的现象依然存在,但再生花芽的分布并不限于基端,在花柄中部、顶端都可见再生花芽。花柄外植体中部愈伤组织的形成也随添加的IAA和IAA浓度升高而受到抑制。在上述培养基中添加生长素极性运输抑制剂TIBA后,无一花柄中部能形成愈伤组织,再生花芽的形态变化也很大,有具锥形花柄的花芽、喇叭叶和一些难于确定由何种器官衍生而来的喇叭状器官。这些异于正常形态的器官发生,显然与花柄外植体中生长素极性运输受抑制有关,本文对它们的形成机理作了一些推测。     

HOST-PLANT SWITCHES AND THE EVOLUTION OF CHEMICAL DEFENSE AND LIFE HISTORY IN THE LEAF BEETLE GENUS OREINA

Insect-plant interactions have played a prominent role in investigating phylogenetic constraints in the evolution of ecological traits. The patterns of host association among specialized insects have often been described as highly conservative, yet not all specialized herbivorous insect lineages display the same degree of fidelity to their host plants. In this paper, we present an estimate of the evolutionary history of the leaf beetle genus Oreina. This genus displays an amazing flexibility in several aspects of its ecology and life history: (1) host plant switches in Oreina occurred between plant families or distantly related tribes within families and thereby to more distantly related plants than in several model systems that have contributed to the idea of parallel cladogenesis; (2) all species of the genus are chemically defended, but within the genus a transition between autogenous production of defensive toxins and sequestration of secondary plant compounds has occurred; and (3) reproductive strategies in the genus range from oviparity to viviparity including all intermediates that could allow the gradual evolution of viviparity. Cladistic analysis of 18 allozyme loci found two most parsimonious trees that differ only in the branching of one species. According to this phylogeny estimate, Oreina species were originally associated with Asteraceae, with an inclusion of Apiaceae in the diet of one oligophagous species and an independent switch to Apiaceae in a derived clade. The original mode of defense appears to be the autogenous production of cardenolides as previously postulated; the additional sequestration of pyrrolizidine alkaloids could have either originated at the base of the genus or have arisen three times independently in all species that switched to plants containing these compounds. Viviparity apparently evolved twice in the genus, once without matrotrophy, through a retention of the eggs inside the female's oviducts, and once in combination with matrotrophy. We hypothesize that the combination of autogenous defense and a life history that involves mobile externally feeding larvae allowed these beetles to switch host plants more readily than has been reported for highly conservative systems.     

SYSTEMATIC STUDIES IN THE LEAF ANATOMY OF PALM GENUS SYAGRUS

A systematic survey of the leaf anatomy of 51 taxa in the palm genus Syagrus was made. Cross sections of the middle pinnae of each taxon were embedded, cut, stained, and mounted on slides. Criteria used to distinguish species were based mainly on differences in the laminar surface and hypodermis: frequency and location of various sized veins; frequency, shape, and location of nonvascular fibers; size and shape of midrib and main vascular bundle; and size and shape of expansion cell tissue. The included key to the species employs mostly these characteristics. Each taxon is listed under subgenera and sections in the order presented in a previous article, where gross morphology was used as the basis of classification. Relationships between species of each subgenus and section are discussed in terms of the original arrangement of each group and needed changes. It is significant that certain evolutionary sequences have become unfolded which were not apparent by use of morphological characters alone. Although all relationships have not been completely worked out, this survey has resulted in a revision of my original classification of the genus Syagrus and at the same time has also corroborated certain alignments of species previously based on gross morphology.