Word Finder - vegetative

definition

Of or relating to plants; especially to their growth.

definition

Of or relating to functions such as growth, nutrition and asexual reproduction rather than sexual reproduction.

definition

Physically inactive.

definition

Of a state of impaired brain function, where a person can respond to some stimuli but is incapable of voluntary acts.

The plants show great diversity in vegetative structure.

In this way we may distinguish, first, vegetative reproduction, the result of discontinuous growth of the tissues and cell-layers of the body as a whole, leading to (I) fission, (2) autotomy, or (3) vegetative budding; secondly, germinal reproduction, the result of the reproductive activity of the archaeocytes or germinal tissue.

A characteristic feature of the fungal vegetative plantbody (mycelium) is its formation from independent coenocytic tubes or cell-threads.

The formation of a massive body naturally involves the localization of the absorptive region, and the function of absorption (which in the simpler forms is carried out by the whole of the vegetative part of the mycelium penetrating a solid or immersed in a liquid substratum) is subserved by the outgrowth of the hyphae of the surface-layer of that region into rhizoids, which, like those of the Algae living on soil, resemble the root-hairs of the higher plants.

In order to effect this the individual chromosomes must become associated in some way, for there is no diminution in the actual amount of nuclear substance, and this leads to certain modifications in the division which are not seen in the vegetative nuclei.

Palaeontological evidence conclusively proves that the surface of the earth has been successively occupied by vegetative forms of increasing complexity, rising from the simplest algae to the most highly organized flowering plant.

There is often a marked alternation in the production of vegetative and flowering shoots respectively; and, sometimes, from various circumstances, the flowering shoots are not produced for several years in succession.

The nucleus in its vegetative stage shows a fine network throughout containing in the meshes the so-called nuclear-sap; attached to the network are the chromosomes, in the form of small irregular masses, which have a strong affinity for the " basic dyes."

These, having the full equipment of the vegetative order, will now develop the inherent power of proliferation to a greater or lesser extent.

In other lichens we should expect to find the ascogenous hyphae arising directly from the vegetative hyphae as in Humaria rutilans among the ordinary fungi, where the process is associated with the fusion of vegetative nuclei.

The difference between the various systems lies in the relative importance given to the reproductive characters on the one hand and the vegetative characters on the other.

Moreover, there is a generally recognised quasi-antagonism between the vegetative and reproductive processes, so that, other things being equal, anything that checks the one helps forward the other.

A check or arrest of growth in the vegetative organs seems to be a necessary preliminary to the development of the flower.

Owing, however, to the difference in their vegetative growth, they mature one after the other instead of simultaneously.

As with other plants, so in fungi the essential process of fertilization consists in the fusion of two nuclei, but owing to the absence of well-marked sexual organs from many fungi, a peculiar interest attaches to certain nuclear fusions in the vegetative cells or in young spores of many forms. Thus in Ustilagineae the chlamydospores, and in Uredineae the teleutospores, each contain two nuclei when young, which fuse as the spores mature.

Physiologically, any cell or group of cells separated off from a hypha or unicellular fungus, and capable of itself growing out - germinating - to reproduce the fungus, is a spore; but it is evident that so wide a definition does not exclude the ordinary vegetative cells of sprouting fungi, such as yeasts, or small sclerotium like cell-aggregates of forms like Coniothecium.

In addition to sporangia and the conidial spores referred to, some Mucorini show a peculiar mode of vegetative reproduction by means of gemmae or chlamydospores - i.e.

In some forms we find definite male and female sexual organs (Sphaerotheca, Pyronema, &c.), in others the antheridium is abortive or absent, but the ascogonium (oogonium) is still present and the female nuclei fuse in pairs (Lachnea stercorea, Humaria granulata, Ascobolus furfuraceus); while in other forms ascogonium and antheridium are both absent and fusion occurs between vegetative nuclei (Humaria rutilans, and probably the majority of other forms).

The ascocarps can be distinguished into two portions, a mass of sterile or vegetative hyphae forming the main mass of the fruit bod y, and surrounding the fertile ascogenous hyphae which bear at their ends the asci.

Reproduction is chiefly effected by the vegetative method.

In all the multicellular plants of this group which have been adequately investigated, vegetative multiplication by means of what are known as hormogonia has been found to occur.

Special provision for vegetative multiplication is not common among Chlorophyceae.

In Characeae no fewer than four methods of vegetative reproduction have been described, and the facility with which buds and branches are in these cases detached has been adduced as an evidence of affinity with Bryophyta, which, as a class, are distinguished by their ready resort to vegetative reproduction.

When a species resorts to both methods, it is generally found that the asexual method prevails in the early part of the vegetative period and the sexual towards the close of that period.

The proembryonic branches of Characeae, one of the means of vegetative reproduction already referred to, are so called because they repeat the characters of the proembryo.

Of the small family of the Tilopteridaceae our knowledge is as yet inadequate, but they probably present the only case of pronounced oogamy among Phaeosporeae.;.They are filamentous forms, exhibiting, however, a tendency to division in more than one plane, even in the vegetative parts.

Vegetative multiplication occurs only sparingly in Rhodophyceae.

It is possible, however, that the tetraspore formation should be regarded as comparable with the prolific vegetative reproduction of Bryophyta, and in favour of this view there is the fact that the tetraspores originate on the thallus in a different way from carpospores with which the spores of Bryophyta are in the first place to be compared; moreover, in certain Nemalionales the production of tetraspores does not occur, and the difficulty referred to does not arise in such cases.

While even in such cases it is obvious that interesting stages in the life of the plant may escape notice altogether, in the cases of those plants the reproduction of which is unknown, and which have been named and placed on the analogy of the vegetative parts alone, there is considerable danger that a plant may be named as a distinct species which is only a stage in the life of another distinct and perhaps already known species.

In the case of the freshwater algae, however, belonging to the Chlorophyceae and Cyanophyceae, although they required to be immersed during the vegetative period, the reproductive cells are often capable of resisting a considerable degree of desiccation, and in this condition are dispersed through great distances by various agencies.

Far more important is the vegetative, or "natural" increase, through the excess of births over deaths.

Panaetius had referred two faculties (those of speech and of reproduction) to animal impulse and to the vegetative " nature " (01,o-cs) respectively.

In these Vegetative cases no cilia have been observed, and there is a state.

An arthrospore, however, is not a true spore but merely an ordinary vegetative cell which separates and passes into a condition of rest, and such may occur in forms which form endospores, e.g.

Vegetative body unicellular; spheroidal, cylindrical or spirally twisted; isolated or connected in filamentous or other growth series.

Vegetative cells, cylindric but curved more or less spirally.

In the first place, the extremely small size and isolation of the vegetative cells place the protoplasmic contents in peculiarly favourable circumstances for action, and we may safely conclude that, weight for weight and molecule for molecule, the protoplasm of bacteria is brought into contact with the environment at far more points and over a far larger surface than is that of higher organisms, whether - as in plants - it is distributed in thin layers round the sap-vacuoles, or - as in animals - is bathed in fluids brought by special mechanisms to irrigate it.

To other monocotyledonous families the resemblances are merely of adaptive or vegetative characters.

Small tuberous shoots, comparable on a large scale with the bulbils of Lycopodium Selago, are occasionally produced in the axils of some of the persistent leaf-bases; these are characteristic of sickly plants, and serve as a means of vegetative reproduction.

The anatomical structure of the vegetative organs of recent cycads is of special interest as affording important evidence of relationship with extinct types, and with other groups of recent plants.

Sequoia sempervirens, the fertile branches bear leaves which are less spreading than those on the vegetative shoots.

What the vegetative increase has been since then (for there has been no immigration) is purely conjectural, as there are no available returns of births and deaths upon which an estimate can be based.

A highly specialized means of vegetative reproduction is seen in the tubers of Phylloglossum and the embryos of some Lycopods.

The sporangia are borne in groups (sori) on the under surface of the leaves; sometimes the fertile leaves differ more or less from the purely vegetative ones.

In some apogamous Ferns sporangia may occur on the prothallus and the vegetative organs of the sporophyte may also occur singly.

The development of the sporocarp shows that it corresponds to a pinna, although when mature it may appear to occupy a ventral position in relation to the vegetative portion of the leaf.

At the present day Gallego, which is simply Portuguese variously modified and with a development in some respects arrested, is much less important than Catalan, not only because the Spaniards who speak it (i,8oo,ooo) are fewer than the Catalans (3,500,000), but also because, its literary culture having been early abandoned in favor of Castilian, it fell into the vegetative condition of a provincial patois.

In Ulodendron the large circular, distichously arranged prints were supposed to have been formed by the pressure of the bases of sessile cones, though this interpretation of the scars is open to doubt, and it is now more probable that they bore deciduous vegetative branches; in the Halonial branches characteristic of the genus Lepidophloios the tubercles may perhaps mark the points of insertion of pedunculate strobili.

We will now describe some of the fructifications, which are grouped under generic names of their own; these genera, as having a more natural basis, tend to supersede the artificial groups founded on vegetative characters.

In many fern-like plants of this period the fronds were dimorphic, the fertile leaves or pinnae having a form quite different from that of the vegetative portions.