Growing point Sentence Examples
The body thus formed ment of is called the embryo, and this develops into the adult Primary plant, not by continued growth of all its parts as in an animal, but by localization of the regions of cell-division and growth, such a localized region being called a growing-point.
On germination of the seed the radicle first grows out, increasing in size as a whole, and soon adding to its tissues by cell division at its apical growing-point.
Further growth in length of the stem is thenceforward confined to the apical growing point situated between the cotyledons.
In other cases this growing-point becomes active at once, there being little or no elongation of the hypocotyl and tbe cotyledon or cotyledons remaining in the seed.
This is known as exogenous branch-formation In the root, on the other hand, the origin of branches is endogenous The cells of the pericycle, usually opposite a protoxylem strand divide tangentially and give rise to a new growing-point.Advertisement
This point of view was further developed in the following century by Caspar Friedrich Wolff (Theorici generationis, 1759), who first followed the development of the members at the growing-point of the stem.
These leaf-buds contain the rudiments of a shoot, and consist of leaves covering a growing point.
In Desmarestia and Arthrocladia, for example, it is found that the thallus ends in a tuft of such hairs, each of them growing by means of an intercalated growing point.
The " growing point " of the trunk is, in fact, situated in front of this region, and, when the full number of somites has been reached, the unsegmented part remaining forms the telson of the adult.
The prothallus and sexual organs may resemble those of the Polypodiaceae; in Aneimia and Mohria the prothallus, though flattened, is not bilaterally symmetrical, the growing point being on one side; a filamentous type of prothallus is known in Schizaea.Advertisement
Even the most delicate tissues, such as cambium and phloem, the endosperm of seeds, or the formative tissue of the growing-point, are frequently preserved cell for cell, both in calcareous and silicious material.
The development of the organ is already determined at its first appearance upon the growing-point; though, as already explained, the normal course of its ontogeny may be interfered with by some abnormal external or internal condition.
As in Gymnosperms, branching is monopodial; dichotomy or the forking of the growing point into two equivalent branches which replace the main stem, is absent both in the case able variety in form (see Leaf), but are generally small in comparison with the size of the plant; exceptions occur in some Monocotyledons, e.g.