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In botany, a cortex is an outer layer of a stem or root in a vascular plant, lying below the epidermis but outside of the vascular bundles. [1] The cortex is composed mostly of large thin-walled parenchyma cells of the ground tissue system and shows little to no structural differentiation. [ 2 ]
A stem is one of two main structural axes of a vascular plant, the other being the root. It supports leaves , flowers and fruits , transports water and dissolved substances between the roots and the shoots in the xylem and phloem , engages in photosynthesis, stores nutrients, and produces new living tissue. [ 1 ]
Researchers found a way to transform human skin cells into nerve cells using transdifferentiation, in which "cells are forced to adopt new identities". [74] During neurogenesis in the mammalian brain, progenitor and stem cells progress from proliferative divisions to differentiative divisions. This progression leads to the neurons and glia that ...
The meristem can be defined as the tissue or group of plant tissues that contain undifferentiated stem cells, which are capable of producing any type of cell tissue.Their maintenance and development, both in the vegetative meristem or the meristem of the inflorescence is controlled by genetic cell fate determination mechanisms.
The leaf and stem epidermis is covered with pores called stomata (sing; stoma), part of a stoma complex consisting of a pore surrounded on each side by chloroplast-containing guard cells, and two to four subsidiary cells that lack chloroplasts. The stomata complex regulates the exchange of gases and water vapor between the outside air and the ...
The metabolic functioning of sieve-tube members depends on a close association with the companion cells, a specialized form of parenchyma cell. All of the cellular functions of a sieve-tube element are carried out by the (much smaller) companion cell, a typical nucleate plant cell except the companion cell usually has a larger number of ...
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Magnolia grandiflora, a spiraled flower.. Depending on the family considered, the pieces of the flower can be arranged on the receptacle in two different ways. In the case of the spiral arrangement, the parts are inserted consecutively and at different levels, describing a spiral on the axis in the same way as the leaves are inserted on the stem.