Topic
Ochrea
About: Ochrea is a research topic. Over the lifetime, 17 publications have been published within this topic receiving 111 citations.
Papers
TL;DR: It is concluded that the peculiarities of the heterophyllic leaf sequence in Muehlenbeckia are a property of the shoot system as a whole and may contribute to variations in leaf morphology.
Abstract: Flowering shoots of Muehlenbeckia platyclados Meisn. bear only reduced scale leaves which resemble the membranous sheath portion (ochrea) of leaves of other members of the Polygonaceae. Shoots propagated from cuttings bear enlarged foliage leaves with distinct lamina, petiole, and ochrea zones. The developmental basis for this heterophylly is explored in order to determine whether scale leaves resemble foliage leaves in their pattern of ontogeny or are developmentally unique. SEM and histological analyses have shown that scale leaves and foliage leaves are distinctive from inception. The scale leaf arises as a collarlike growth and extends over the shoot apex as a hooded sheath without evidence of blade initiation. By contrast, the first stage of foliage-leaf ontogeny is the differentiation of the distal lamina from the future leaf base. As the foliage-leaf ochrea encircles the stem axis, the lamina grows erect and projects from the abaxial surface of the sheath. Lamina reduction coupled with ochrea elaboration in intermediate leaf types indicate a homology between the entire scale leaf and foliage-leaf ochrea. Despite this homology, the production of the bladeless scale leaf does not involve a mere suppression of the foliage-leaf lamina. Erect growth of the saccate ochrea of the foliage leaf contrasts with the hooded expansion of the scale. Early histological differences, including contrasting rates of cell differentiation, also distinguish the two organs. This disparity in modes of growth and differentiation from inception results from separate, predetermined courses of ontogeny. Unlike other plants studied, leaf size and degree of leaf elaboration decrease with shoot meristem enlargement in Muehlenbeckia. Leaf packing does increase with shoot development and may contribute to variations in leaf morphology. It is concluded that the peculiarities of the heterophyllic leaf sequence in Muehlenbeckia are a property of the shoot system as a whole. IN RECENT YEARS, there has been a re-examination of the developmental and causal bases for the marked change in leaf form exhibited by the shoots of some plants (Cook, 1969; Critchfield, 1970; Feldman and Cutter, 1970a,b; Mauseth, 1977; Schmidt and Millington, 1968; for earlier references see Allsopp, 1965, 1967; and see references cited in remainder of text). In this regard the polygonaceous shrub, Muehlenbeckia platyclados Meisn. (vegetative tapeworm-centipede plant-ribbon bush), is of interest. While previous attention has been directed toward the morphogenesis of its unique flattened stems (Kaussmann, 1955; Troll, 1937), this species is also distinctive because of its heteroblastic leaf series. Shoots of seedlings and cuttings bear large, green, laminate-petiolate foliage leaves (Fig. 1), whereas I Received for publication 29 May 1978; revision accepted 31 August 1979. Research supported by National Science Foundation Grant DEB 74-02823 AOI. The authors wish to thank Dr. Dominick J. Paolillo, Jr. for his thorough reading of the manuscript as well as helpful comments on the plates. We are also grateful to Dr. M. V. Parthasarathy for the use of darkroom facilities. 2 Present address: Section of Botany, Genetics, and Development, Plant Science Bldg., Cornell University, Ithaca, N.Y. 14853. flowering shoots produce inconspicuous, nonphotosynthetic scale leaves (Fig. 4-6). The ontogenetic processes by which these and intermediate leaf types arise are compared and contrasted in this paper in order to determine the morphological relationship between them. Particular emphasis is placed on elucidating the developmental modifications which yield the scale leaf. The present investigation also serves as an evaluation of the relationship between shoot and leaf development in a species in which the more elaborate appendage type is generated early in the plant's development while the reduced type appears later. This condition is contrary to that described in previous investigations of heterophylly and is in need of detailed study. MATERIALS AND METHODs-Adult material of Muehlenbeckia was collected from a plant grown in the Botanical Garden of the University of California, Berkeley. The collector was Robert Dutton, but the original source of collection is unknown (Muehlenbeckia is endemic to the Solomon Islands). Juvenile material was obtained by propagation from stem cuttings of the adult plant. Adult and juvenile shoot tips were fixed in either CRAF III (Sass, 1958) or FAA (70%
27 citations
TL;DR: It was concluded that stipules are the principal photosynthetic organs in L. aphaca.
Abstract: Occurrence of stipules of different shapes, sizes and varying configurations, has been reported in species of many angiosperm families. However, the functions of stipules in the biology of plants that carry them remain to be understood. There is perception that stipules that have the green coloration of chlorophyll are photosynthetically active. Here, total photosynthesis in the stipules and leaves of Lathyrus aphaca was investigated, together with the nature of heteroblasty and relative morphology and anatomy of stipules and leaves in this species. At each of the hundreds of nodes in the extensively branched post-flowering stage plants of L. aphaca, more than 95 % of photosynthesis occurred in the foliaceous stipules. The leaves in the form of simple tendrils at the nodes accounted for <5 % of photosynthesis. The stipules of L. aphaca were about as effective in photosynthesis as the foliaceous stipules of af and AF pea (Pisum sativum) plants. The L. aphaca stipules possessed all the cells/tissues that characterized photosynthetic leaves, stomata in epidermis, palisade and spongy mesophyll parenchyma, and vascular bundles. The tendrilled leaves were devoid of palisade tissue. The embryonic nodes bore stipule pairs of small size and compound leaves comprising of a pair of leaflets. Several nodes, above the embryonic nodes, bore fully developed stipule pairs but vestigial leaves (tendrils). It was concluded that stipules are the principal photosynthetic organs in L. aphaca.
17 citations
TL;DR: The shoot apices of species from all subgenera were examined by light and scanning electron microscopy and the results interpreted in a phylogenetic context and two opposite cataphylls at the base of the new shoot were found.
10 citations
TL;DR: The structure of the inflorescences and stipules in Geissois sensu stricto supports the distinction between this group and the Australian species traditionally included in Ge ISS sensu lato.
Abstract: Geissois sensu stricto (ie excluding the Australian species of this genus) has 19 species restricted to islands in the south-west Pacific and is the sole group in Cunoniaceae in which the stipules are intrapetiolar (axillary) in the adult foliage In apical buds, paired opposite stipules are coherent round their margins and are either clearly intrapetiolar in relation to the most distal pair of developed leaves (Type I, most species), or they appear interpetiolar due to the abortion of the pair of leaves associated with them and the failure of the internode proximal to them to elongate (Type II, a few species) Stipules are often accrescent and the largest in the family occur in this group, reaching 10 cm long in some species The ornithophilous racemose inflorescences of members of this group normally consist of either axillary triads (G hirsuta only) or apparently simple, unbranched racemes which are ramiflorous or occasionally axillary However, bract scars on the axes proximal to the flowers show that both types of inflorescence module usually consist of two metamers The structure of the inflorescences and stipules in Geissois sensu stricto supports the distinction between this group and the Australian species traditionally included in Geissois sensu lato
7 citations
TL;DR: Coccoloba howardii appears to be closely related to C. subcordata, from which it differs primarily in the spiral arrangement of the short branches and leaf features such as the petiole inserted at the base of the ochrea, a membranous blade and alternate primary veins not grouped at the Base.
Abstract: Castaneda Noa I.: Coccoloba howardii (Polygonaceae), a new species from Cuba [Novitiae florae cubensis 38]. - Willdenowia 42: 95–98. June 2012. — Online ISSN 1868-6397; © 2012 BGBM Berlin-Dahlem. Stable URL: http://dx.doi.org/10.3372/wi.42.42112 Coccoloba howardii, a new species from the north-central region of Cuba, is described and illustrated. It appears to be closely related to C. subcordata, from which it differs primarily in the spiral arrangement of the short branches and leaf features such as the petiole inserted at the base of the ochrea, a membranous blade and alternate primary veins not grouped at the base.
6 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2016 | 1 |
| 2013 | 1 |
| 2012 | 4 |
| 2009 | 1 |
| 2008 | 1 |
| 2003 | 1 |