Control and Co-ordination

Control and Co-ordination


 Tropic Movement in plants –

Tropic movements in plants refer to the directional growth responses of
plant organs to external stimuli, such as light, gravity, touch, and
temperature. These movements are important for plants to adapt to their
changing environment and optimize their growth and development.

The most well-known tropic movements in plants are phototropism,
geotropism, and thigmotropism. Phototropism is the growth response of
plant organs towards or away from light. Positive phototropism occurs when
plant organs grow towards a source of light, while negative phototropism
occurs when plant organs grow away from light. Geotropism is the growth
response of plant organs towards or away from gravity. Positive geotropism
occurs when roots grow towards gravity, while shoots grow against gravity.
Thigmotropism is the growth response of plant organs towards or away from
touch. For example, vines can wrap around a supporting structure as a result
of thigmotropism.

Tropic movements are regulated by plant hormones, such as auxins, which
are produced in response to external stimuli and transported to the site of
growth. These hormones control cell elongation and division, leading to
directional growth responses in plant organs.

Overall, tropic movements are essential for the survival and growth of
plants, allowing them to respond to their environment and optimize their use
of resources.

 Plant Hormones –

Plant hormones, also known as phytohormones or plant growth regulators,
are chemical compounds that regulate various physiological processes in
plants. These hormones are produced in different parts of the plant, such as
shoots, roots, leaves, and flowers, and are transported to different parts of
the plant through the vascular system.

, There are five main classes of plant hormones, each with their unique
characteristics and functions:

a.) Auxins: Auxins are the most well-known class of plant hormones, and
their primary function is to stimulate cell elongation in shoots and roots.
They also play a role in cell division, apical dominance, and tropic
movements.

b.) Gibberellins: Gibberellins stimulate cell elongation, seed germination,
and flowering in plants. They also play a role in stem elongation, fruit
development, and the regulation of gene expression.

c.) Cytokinins: Cytokinins are involved in cell division, shoot and root
development, and the prevention of senescence (aging) in plants. They also
interact with other hormones to regulate plant growth and development.

d.) Abscisic acid: Abscisic acid is a hormone that regulates various plant
responses to environmental stresses, such as drought, cold, and salinity. It
also plays a role in seed dormancy and maturation.

e.) Ethylene: Ethylene is a gaseous hormone that regulates various
processes in plants, such as fruit ripening, leaf abscission, and senescence. It
also plays a role in plant responses to environmental stresses, such as
flooding and pathogen attacks.

In general, plant hormones act at very low concentrations, and their effects
are often synergistic or antagonistic, depending on the concentration and the
specific physiological process involved. They are also regulated by various
factors, such as light, temperature, nutrients, and other hormones, to ensure
proper plant growth and development.

 Control and Co-ordination –
Control and coordination in animals refer to the physiological mechanisms that
enable animals to respond to internal and external stimuli and maintain
homeostasis. The nervous and endocrine systems are the two main systems
responsible for control and coordination in animals.