Download The Saylor Foundation 1 Cell and Tissue Type Introduction The

Cell and Tissue Type Introduction
The plant body is organized into a root system and a shoot system. The root system is
usually underground and the shoot system is usually above ground. The shoot system
consists of stems with leaves, and in flowering plants, flowers, and fruits.
As you will learn in more detail later in the course in subunit 2.5.2, plant growth involves
three processes: cell division (mitosis), cell elongation, and cell differentiation. Plant
growth occurs only in specific areas called meristems. Meristematic growth may be of
two types: primary growth and secondary growth. Primary growth is an increase in the
length of the plant and occurs at the apical meristems located at the shoot tip and the
root tip. Cells of the shoot apical meristem divide, elongate, and differentiate to result in
the growth of the shoot system. Cells of the root apical meristem divide, elongate, and
differentiate to result in the growth of the root system. Secondary growth causes the
increase in girth of the plant and occurs predominantly in trees and shrubs. Secondary
growth is produced by lateral meristems (vascular cambium and cork cambium).
In the meristems, after the cells divide and elongate, they differentiate into specialized
cell types. These cells combine to form tissues, which in turn combine to form tissue
systems.
Plants are made up of three tissue systems: the ground tissue system, the vascular
tissue system, and the dermal tissue system. The ground tissue system consists of all
the tissues of the plant body other than the vascular tissues and the dermal tissues and
are involved in a variety of functions, including support, storage, and photosynthesis.
The vascular tissue system consists of tubular tissues that conduct material throughout
the body of the plant such as water, food (sugars) and dissolved minerals. The dermal
tissue system consists of tissues that form the plant’s protective covering.
In sections 1.1.2.1-1.1.2.4, we will take a closer look at the plant, its three tissue
systems, and the tissues and cells of each of the three tissue systems.
The Saylor Foundation 1