BIO6: Coordination

This unit talks about cooordination in animals

The harmonious functioning of interrelated organs and parts, applied especially to the process of the motor apparatus of the brain which provides for the co-working of particular groups of muscles for the performance of definite adaptive useful responses.

Coordination in plants

You see plants all around you. But, are they of the same size or height? Of course not! You see big trees, medium-sized shrubs, and even plant saplings.  This tells us that plants exhibit some growth changes as well as some movements. This coordination in plants is attributed to the presence of plant hormones. Unlike animals, plants do not have any muscular system or nervous system. But, they are still able to show movement and also coordination. These movements are always controlled and not haphazard. Let us learn more about coordination in plants.


What is coordination in plants?

Coordination is the ability to use different parts of the plant together, smoothly and efficiently. In plants, coordination is due to the result of a chemical system, wherein plant hormones or phytohormones have a major role.

Movement in plants

Plants exhibit two types of movements.

  1. Growth-dependent movements called the Tropic Movements. ( towards or away from a stimulus)
  2. Non-growth dependent movements called the Nastic Movements. ( independent of stimulus)

Tropic movements

These can be classified again into 5 types. They are:

  • Phototropism (light)
  • Geotropism (gravity)
  • Hydrotropism (water )
  • Chemotropism (chemicals)
  • Thigmotropism (touch)
  1. Phototropism– It is the movement of plants in response to light. The shoot system of a plant exhibits this characteristic. The shoot moves towards the light.
  2. Geotropism– It is the movement of a plant part towards the soil. This is a characteristic of the root system. The roots always move in the direction of the earth’s gravity.
  3. Hydrotropism– It is the movement of a plant towards the water. The stimulus here is water.
  4. Chemotropism– It is the movement of plants in response to a chemical stimulus. A classic example of this type of movement is the growth of the pollen tube towards the ovule, during fertilization, in a flower.
  5. Thigmotropism– It is a directional movement in plants in response to touch. For e.g. the plant tendrils climb around any support which they touch.

Nastic Movements

Nastic movements in plants are not directional movements. They are not dependent on stimulus and are growth independent. For example, the leaves of a touch me not plant (Mimosa pudica), fold up immediately when touched. These kinds of changes occur due to the changes in the amount of water in the leaves. Depending on the quantity, they either swell up or shrink.

Plant hormones or phytohormones

They are responsible for the control and coordination of plants. There are different types of hormones, which affect the growth of a plant. Phytohormones are chemical compounds which are released by stimulated cells. These hormones are diffused around the plant cells. They have a role to play in the cell division, cell enlargement, cell differentiation, fruit growth, falling of leaves, ripening of fruits, ageing of plants etc.

The different types of phytohormones are:

  1. Auxins
  2. Gibberellins
  3. Cytokinins
  4. Abscisic acid

Auxins– They help in the cell growth at the shoot tips. By elongating the cells, they help in the growth process.

Gibberellins – These hormones are responsible for the cell growth in the stem, seed germination, and flowering.

Cytokinins – They promote cell division in plants. They also promote the opening of the stomata and delay ageing in leaves.

Abscisic acid– This hormone inhibits the growth of the plant. And therefore, it promotes dormancy in seeds and buds. The detachment of fruits, flowers, and falling of leaves etc. are promoted by this hormone.

Coordination in animals

Animals are more complex than plants. They have many specialised organs that perform specialised functions for their control and coordination. This coordination in animals occurs due to the nervous coordination (Nervous System) and the chemical coordination (Endocrine System).  Both these systems act in a coordinated manner in animals, so as to regulate the various body activities. Let’s learn more about the hormones in animals.


Endocrine System

The endocrine system comprises of different endocrine glands and hormones. These endocrine glands in animals help in the chemical coordination. They secrete chemicals called hormones. They are special messengers that control many body functions, including hunger, body temperature, mood, growth and development, metabolism, reproductive processes etc.  The endocrine glands are ductless and hence are also called as ductless glands.

What are Hormones?

Hormones are chemicals secreted by the endocrine glands directly into the bloodstream. Through the blood, these hormones in animals reach their target organs to stimulate or inhibit specific physiological processes. The site of production of the hormones is different and the site of action is different. Even though there are different hormones in the bloodstream, each will act only on the specific target organ. There are around 20 major hormones in animals that are released by the endocrine glands into the blood, playing a major role in many of the physiological processes happening in the body.

Did you know that the hormone levels in the body can be influenced by several factors? Stress, infection, minerals in the blood etc. influence the hormone levels in animals.

Different Endocrine Glands

  • Hypothalamus
  • Pituitary gland
  • Thyroid gland
  • Parathyroid gland
  • Pineal gland
  • Adrenal gland
  • Pancreas
  • Testes
  • Ovaries


This gland forms an important link between the nervous system and the endocrine system, via the pituitary gland.

Some of the important functions are:

  • Helps in maintaining the body temperature, controls sleep, hunger, thirst, emotions and moods.
  • It also controls the release of 8 major hormones by the pituitary gland.
  • Controls the sexual behaviour and reproduction.
  • It controls the circadian rhythm of the body.

Pituitary Gland

The pituitary gland is very small in size but is called as the Master Gland, as many endocrine glands are controlled by the hormones secreted by it. It also stimulates other endocrine glands to produce hormones.  Some of the hormones released by this gland are growth hormone, thyroid stimulating hormone, MSH, LH, FSH etc.

Thyroid Gland

It is the largest endocrine gland that is shaped like a butterfly. It produces the thyroxine hormone, which controls the metabolic rate in the body. Apart from that, it also plays a role in the bone growth, development of the brain and nervous system in children. Iodine is important for the synthesis of thyroxine.

Parathyroid Gland

This gland releases parathormone which helps in regulating the calcium and phosphorus levels in the bone.

Pineal gland

This produces melatonin hormone that regulates the sleep patterns.

Adrenal gland

These glands are located on top of the kidneys and produce hormones such as adrenaline, cortisol, and aldosterone etc. These hormones control stress, help control blood sugar, burn protein and fat and also regulate blood pressure.


They secrete two important hormones – insulin and glucagon. Both work together to maintain the glucose levels in the blood.


These glands are present in males and produce testosterone hormone.


These glands are present in females. The hormones produced by ovaries are oestrogen and progesterone.

Plant hormones

Plant hormones are known as phytohormonesin botanical terms. They are chemicals just like animal hormones that help in the growth, development, and functioning of plants. Like animals, plants too are living organisms that function as a unit. They carry out vital biochemical reactions that are required to survive. These biochemical reactions require hormones also known as ‘plant growth substances’.

These hormones help in the formation of leaves, flowers, stems, fruit, etc. They also help in determining the sex of the flowers, the color of the fruits, and leaves. They help in formation of tissues, respiration, energy production, and even plant longevity and death. Just as hormones are necessary for an animal body to function without any glitches, they too help the green living beings to survive normally. In this article, we shall cover some information related to these secretions and their functions.

Echinacea purpurea
Phyllody on a purple coneflower (Echinacea purpurea), a plant development abnormality where leaf-like structures replace flower organs. It can be caused by hormonal imbalance, among other reasons.

What Are the Functions of Plant Hormones?

These hormones help in regulation of the plant body by responding to the various signals from the plant and environment. The hormones are regulated in different tissues during the different development stages. There are five major hormones which are auxin, cytokinin, gibberellin, abscisic acid, and ethylene. Each hormone differs in its effects.

The auxins, gibberellins, and cytokinins act as growth stimulators, whereas, abscisic acid and ethylene act as growth inhibitors. Plant hormones are simple in their structure as compared to those of animals or humans. There are no specific or specialized glands that produce these hormones. In fact, they are synthesized anywhere in the plant and act on any part as their target. Besides the hormones, there are many plant growth factors that affect the function and growth of plants.

List of Plant Hormones


This hormone is present in the seed embryo, young leaves, and apical buds’ meristem.

Lack of the plant hormone auxin can cause abnormal growth

Functions of Auxins

  • Stimulation of cell elongation, cell division in cambium, differentiation of phloem and xylem, root initiation on stem cuttings, lateral root development in tissue culture
  • Delaying leaf senescence
  • Suppression of lateral bud growth when supplied from apical buds
  • Inhibition or promotion of fruit and leaf abscission through ethylene stimulation
  • Fruit setting and growth induced through auxin in some plants
  • Auxin can delay fruit ripening
  • In Bromeliads, the auxin hormone promotes flowering
  • Stimulation of flower parts, femaleness of dioecious flowers, and production of high concentration of ethylene in flowering plants


They are synthesized in roots and then transported to other parts of the plant.

Functions of Cytokinins

  • Stimulation of cell division, growth of lateral buds, and apical dominance
  • Stimulation of shoot initiation and bud formation in tissue culture
  • Leaf cell enlargement that stimulates leaf expansion
  • Enhancement of stomatal opening in some plant species
  • Etioplasts converted into chloroplasts through stimulation of chlorophyll synthesis.


Ethylene is present in the tissues of ripening fruits, nodes of stems, senescent leaves, and flowers.

Functions of Ethylene

  • Leads to release of dormancy state
  • Stimulates shoot and root growth along with differentiation
  • Leaf and fruit abscission
  • Flower induction in Bromeliad
  • Stimulation of femaleness of dioecious flowers
  • Flower opening is stimulated
  • Flower and leaf senescence stimulation
  • Stimulation of Fruit ripening

Abscisic Acid

Abscisic acid is found mostly near leaves, stems, and unripe fruit.

Abscisic acid

Functions of Abscisic Acid

  • Stimulation of closing of stomata
  • Inhibition of shoot growth
  • Inducing seeds for synthesizing storage of proteins


Gibberellins are present in the meristems of apical buds and roots, young leaves, and embryo.

Functions of Gibberellins

  • Stimulates stem elongation
  • Leads to development of seedless fruits
  • Delays senescence in leaves and citrus fruits
  • Ends seed dormancy in plants that require light for induction of germination

ASSIGNMENT : Coordination Assignment MARKS : 20  DURATION : 24 hours


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