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gametophyte |
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PLANT |
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The main, ultimate, gamete-bearing stage in the haploid (n chromosomes) phase of a taxon's life cycle. Two morphologically and genetically distinct and alternate stages together constitute the complete life cycle in sexually reproducing taxa, the other phase (sporophytic) being diploid (2n chromosomes). Any taxon whose life cycle is confined to one or the other phase is limited to asexual means of reproduction, since sexual reproduction and consequent genetic recombination are impossible without alternation between haploid and diploid states via meiosis and fertilization. The term gametophytic applies to any part of the haploid phase, including all unicellular to multicellular entities belonging to it, whereas gametophyte is reserved for the principal and directly gamete-producing stage of that phase. In all vascular plant taxa the sporophyte is the dominant and most conspicuous phase of the life cycle. The gametophytes of "lower" vascular plants (ferns and "fern-allies") are physically independent of the sporophytes and, though inconspicuous, merit description in their own rights. Those of gymnosperms and angiosperms are minute and physically dependent upon (contained within) sporophytic structures and are not usually included in morphological descriptions. In the flowering plants at least, the haploid phase is (presumably evolutionarily) reduced to such a degree that the existence of gametophytes per se is debatable. |
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cormose |
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architecture |
plant |
Growing from corms. |
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calyx pl. calyces |
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STRUCTURE |
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Collectively, the sepals of a flower, whether distinct or connate; the outer or proximal envelope of a differentiated perianth, whether the other envelope (corolla) is also actually present or is deemed to be secondarily absent due to evolutionary reduction. |
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jacket cell |
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STRUCTURE |
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Any of the cells forming the portion of an antheridial wall between the basal cells and the cap cell(s). |
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perulate |
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architecture |
bud |
Having outer scales that enclose and protect the embryonic components, from which they differ significantly in texture, shape, size, relief and/or vestiture. See also naked. |
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vestiture |
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STRUCTURE / SUBSTANCE |
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See vesture. |
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epichilium |
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STRUCTURE |
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The distal portion of a labellum (lip) that has distinct proximal, distal, and sometimes also central parts; in Orchidaceae. See also hypochilium, mesochilium. |
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glome |
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nominative |
inflorescence |
A rounded cluster of sessile or subsessile flowers that are inserted very close together and oriented divergently, the whole more or less hemispheric and sessile or subsessile. |
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mucronulate |
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apex |
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Finely mucronate. See also apiculate. |
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resupinate |
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orientation |
lateral structure |
Inverted due to twisting distal to the point of insertion during development. |
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sympodial |
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architecture |
axes |
Branching laterally, each axis of each apparent order of branches comprising a series of laterally derived segments each of which functioned in turn as the distal leader, the apical meristem of each segment dominant until supplanted by that of the next. See also monopodial. |
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spinescent |
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architecture |
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Becoming spinose. |
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eusporangiate |
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reproduction |
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Having relatively large sporangia each of which develops from a group of initial cells that, by periclinal divisions, give rise to an outer layer of primary cells and an inner layer of sporogenous cells; in Psilotophyta, Lycopodiophyta, Equisetophyta, and some Polypodiophyta. |
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archegonium pl. archegonia |
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STRUCTURE |
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A female gametangium; a multicellular fertile organ of a mature gametophyte within which female gametes (eggs, ova) are produced and fertilized; having a broad, bulbous base and a narrower distal neck. Technically present but highly reduced and of no descriptive significance in Magnoliophyta. |
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gynoecium pl. gynoecia var. gynaecium |
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STRUCTURE |
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The pistil(s) of a single flower together with any ontogenetically equivalent or subordinate structures present, taken collectively; the total female (ovule-producing) structural complement of a single flower. It may include one to many pistils, each simple or compound. |
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ringed |
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relief |
bark |
Fissured, mainly horizontally, with at least some of the fissures individually encircling the stem more or less completely. |
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leaf-opposed |
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insertion |
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Nodal and directly opposite the leaf. |
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pliestesial |
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duration |
plant |
Perennial and monocarpic, living several to many years before reproducing sexually, dying promptly thereafter. |
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oblate |
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plane shape |
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Symmetrically elongate and broader than long perpendicular to the developmental or polar axis. |
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deciduous 2 |
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habit |
plant |
Perennial and having all leaves separating and falling away during a particular portion of the yearly cycle, especially the autumn or the dry season, between growing seasons. Semantically, this term is properly applied only to the entity that falls, not to the structure that it separates and falls from; in traditional usage, though, the term has been applied to trees and other perennial plants that shed all their leaves at some time during the yearly cycle. |
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circumscissile |
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dehiscence |
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Splitting transversely through the exterior wall about its entire circumference, the resulting upper cap-like portion falling away. |
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diaphragmed |
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architecture |
pith |
Uninterrupted by cavities but heterogeneous in texture at axis maturity, with sectors of spongy tissue separated by relatively thin transverse plates of denser tissue that occur at the nodes or are otherwise regularly spaced along the axis. |
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pachycaulous |
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architecture |
plant |
Having thick, more or less succulent stems. |
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seed |
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STRUCTURE |
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A mature or ripened ovule containing an embryonic sporophyte and a nutritive tissue (endosperm or perisperm) with stored food that sustains the initial growth of the embryo upon germination, except when such food reserve is stored instead in the cotyledon(s) of the embryo itself, these enclosed by one or two integuments (the testa), the whole serving as a propagule. A fertile seed (one containing a viable embryo) normally results from sexual fertilization of an egg by a sperm; however, fertile seeds are sometimes produced asexually by apomictic processes (e.g., parthenogenesis). |
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acrocaulous |
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insertion |
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At or very near the stem tip. |
