GROWTH AND DEVELOPMENT
Sexual reproduction involves the fusion of two sets of DNA to form a zygote. Development is the series of changes
in a zygote, which becomes an adult. The stage of multicelluar organism that develops from a zygote is called embryo. In
seed plants, the embryo is the part of the seed. The study of development of embyo is called embryology.
Growth is an increase in the amount of living material in an organism Growth is a fundamental characterstic of all
living organisms. The process of development is sa closely linked with growth that the phrase “ growth and development” is
commonly used to describe the processes which are normally thought of as growth. Development could be described as an
increase in complexity, and growth as the permanent and irreversible increase in size that occurs in an organism.
(a) Cell division: An increase in cell number as a result of mitosis and cell division.
(b) Cell enlargements: An irreversible increase in the cell size as a result of the uptake of water or the synthesis of living
material.
(c) Cell differentiation: It is the specialization of cells in its broad sense, growth also includes this phase of cell
development.
Growth in plants
The pattern of growth in plants is called open growth. A plant continues to grow throughout its life but the rate of
growth is not uniform throughout its life but rate of growth is not uniform throughout the pant body. Growth in plants is
confined to certain regions known as meristem. A meristem is a group of cells which retain the ability to divide by mitosis
producing daughter cells which grow and form the rest of the plants body. There are three types of meristem located at the
stem and roots these are:
(a) Apocal meristem.
(b) Intercalary meristem
(c) Lateral meristem.
(a) Apical Meristem:
The apical meristems are located at the root and shoot apex. These are responsible for primary growth, giving rise
to primary plant body.
(b) Intercalary Meristem
The intercalary meristem are located between regions of permanent tissue. E.g. at nides of many monocotyledons,
such as bases of grass leaves. Allow growth in length to occur in regions other than tips and play important role in the
production of leaves and flowers. Thes are of temporary nature.
(c) Lateral Meristem
These meristem are laterally situated in older parts of the dicot plants and gymnospems. E.g. cork cambium. These
are responsible for secondary growth. The lateral meristem may be determinate i.e. they grow to certain size and then stop
e.g. leaves, flowers and fruit or indeterminate i.e. they grow by meristem that continually replenish themselves, remaining
youthful e.g. vegetative root and stem.
Types of growth: there are two types of growth (a) primary growth (b) secondary growth.
Primary growth: It is caused by the apical meristem, as a result the plant elongates both in stem and root. Branches, leaves,
flowers are formed by apical meristem.
Secondary growth: It is caused by the lateral meristem as the plant increases in with both in stem and roots.
Phases of Growth in plants
Growth is not a simple process. During growth meristematic cells