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These
are nitrogenous by products and poisonous. These are stored in different parts
of the plant. Some of the alkaloids are used in medicines. Common alkaloids,
the plant and the part in which they occur are give below……..
Tanninsare carbon compounds. These are stored in different parts of a plant of a plant
and are deep brown in colour. Tannins are used in tanning of leather and in
medicines e.g. cassia, acacia.
Plants
like Neem, Acacia secrete a sticky substance called gum when branches are cut.
The gums swell absorbing water and help in the healing of cut parts of a plant.
Economically, gums are valuable being used as adhesive and binding agents, in
the preparation of medicines, foods etc.
Latex
is the milky white substance by plants belonging to Euphorbiaceae,
Apocyanaceae. Asclepiadaceae and papvaraceae. Latex is stored in latex cells or
latex vessels. From the latex of Hevea braziliensis (rubber plant) rubber is
prepared.
Nitrogenous substances are also found in the
walls of pollen grains. These are protein substances and when they enter our
body, they cause allergy. Hence, they are called allergins. They cause skin
allergy(urticaria) asthma etc.
Aromatic oils and scents occur in the leaves
of lemon grass, ocimum, eucalyptus etc.
You
have learnt that a variety of end products are formed during metabolism and of
these nitrogenous wastes are important.
Plants
do not have any specific organ to excrete these wastes. As in animals, carbon
dioxide, water, ammonia and other nitrogenous wastes are also formed in plants.
In
the plants, carbon dioxide released during respiration is sent out through
stomata of leaves. Due to this, the heat in the plant body is reduced.
Even when leaves are absent, as in the
germinating seeds. Carbon dioxide formed during respiration is released into
the atmosphere. Plants have the capacity to utilize the by-products of one
metabolic activity as raw materials for another metabolic activity.
oxygen
released during photosynthesis is utilized for respiration. Carbon dioxide
released during respiration is utilized for photosynthesis. Plants can convert
nitrogen and ammonia into nitrates. However, several compounds are synthesized
by the plants for their own use, especially for defence.
As plants are sessile(do not have the capacity
to move), they cannot defend from the predators by running away.
Majority
of plants do not have organs for protection against the herbivores. Hence,
several plants prepare chemicals and store them in roots, leaves, seeds and
even in stem.
Most
of these chemicals are unpleasant to taste and hence herbivores usually do not
prefer to eat such plants. Some of the chemicals are toxic and may even kill
the animal that eats them.
Some of the plants secrete chemicals when injured.
These chemicals seal the wound and help
the plant to recover from the injury.
Though
plants produce these chemicals for their use, man has found other uses for
these chemicals and benefited immensely from these chemicals.
Some of the plants release attractants for other
Organisms which will help the plant in pollination, seed dispersal or even in
their nutrition.
For
example, plants having root nodules, secrete chemicals to attract rhizobia in
to the surroundings of the roots and form a symbiotic relationship with the
rhizobium. These compounds are called secondary metabolites.
The
biochemical substances produced in plants are of two types-primary metabolites
and secondary metabolites, Food materials like carbohydrates, fats and proteins
are the primary metabolites.
Alkaloids, Tannins, Resins, Gums, Latex etc.,
are some of the secondary metabolites in plants.
Excretion
is the elimination of wastes that are formed during the metabolism of various
substances in the body.
The
main substances excreted are nitrogenous substances like Ammonia, Urea and Uric
acid. Nitrogenous wastes are formed in the metabolism of amino acids and
nucleic acids.
Along
with these excess water, certain salts and organic substances are also excreted.
The main purpose of excretion is to maintain ionic balance in the body.
If
the metabolic wastes are not discharged from the body, they become toxic and
harm the body.
All the animals do not excrete the type of nitrogenous
wastes.
Some
animals, like crabs excrete ammonia, while frogs and man excrete urea, insects,
reptiles and birds excrete uric acid.
The
type of the product excreted may change during different stages of development
and availability of water.
Aquatic
animals prefer to excrete ammonia while animals like reptiles and birds, to
whom water is very scarce, excrete uric acid.
Connective
tissue helps in binding the other tissues and organs together and provides a
frame work and support to various organs in the body.
This
tissue also plays a major role in the transport of material from one tissue to
another.
It also helps in the body defense, body repair and in the storage of
fat.
There
are different types of connective tissues each performing a different function.
Areolartissue is one type of connective tissue which joins different tissues. It helps
in packing these tissues and thus help to keep the organs in pace.
These Cells called fibroblasts are the major
components in this type of connective tissue. These cells secrete fibrous
material which holds the other tissues in position. These cells also help in
repair of the tissues when they are injured.
Cartilage
is a type of connective tissue found in the joints of bones, tip of ribs, of
the nose, external ear and in trachea. Embryos of several vertebrates do not
have bone but have cartilage. The entire skeleton of fishes like sharks is made
of cartilage. Cartilage is hard but not as hard as bone.
Boneis another type of connective tissue. It is a major component of the skeletal
system of several vertebrates. Bone is
made calcium, phosphate and calcium carbonate.
These
salts are secreted by cells called osteocytes. These are present in the central
hollow portion of the bone called marrow.
Ligament
is yet another types of connective tissue that connects bones at the joints and
holds them in position. It is made us. These fibres are made of a protein
called collagen.
Tendon
is a type of connective tissue which is also made of fibres. The tendon joins
the muscles to the bone. It is also made of collagen.
Adipose
or fat tissue is a type of connective tissue which store fat. This tissue is
present beneath the skin, around the kidneys and in bone marrow. This tissue is
made of large numbers of cells called adipocytes or fat cells.
Cytoplasm
of these cells is filled with fat is used for the production of energy required
by the body during starvation. The layer of fat, especially, below the skin,
prevent heat loss from the body.
Blood
is called fluid connective tissue. It differs from other from types of
connective tissues. There are several different types of cells in blood each
one has a different function.
All
the cells in the blood float freely in the plasma. Extracellular space is filled
with a fluid called plasma. There are no fibres in blood. A normal adult humans
being has about 5 liters of blood. Chief component of blood is water.
Besides water, it also has several nutrients
such as glucose, amino acids, proteins, vitamins, and hormones etc. required
for the body and excretory products such as lactic acid, urea, salts etc.
plasma
also contain factors responsible for blood clotting. Cells present in blood are
called corpuscles and they are of three types- red blood cells, white blood
cells and blood platelets.
Red
blood cells, also known as erythrocytes, are red in color . In mammals, red
blood cells do not have mitochondria, nucleus, endoplasmic reticulum, lysosomes
and ribosomes.
In
fishes, amphibians and reptiles, they have a nucleus. These cells are concave
on both the sides.
They
have red colored protein called hemoglobin, which helps in the transport of
oxygen and carbon dioxide .One ml of human blood has about 500 crores of red
blood cells. In adults humans, red blood cells are formed in bone marrow and
live for 120 days I blood.
The
second type of cell present in blood are white blood cells. These cells do not
have hemoglobin, hence they are colorless. These cells are less in number.
There
are two kinds of white blood cells, they are granulocytes and a granulocytes.
There
are three types of granulocytes, neutrophils, basophils and eosinophils. These
three kinds of cells attack and destroy the micro organisms that enter the
blood . all these types of cells have granules in their cytoplasm. Hence they
are called granulocytes.
There
are two types of a granulocytes- they are lymphocytes and monocytes.
Lymphocytes secrete antibodies towards foreign material that enter into blood .
monocytes move like amoeba and along with granulocytes they attack the foreign
materials and engulf them. The foreign material are destroyed inside these
cells.
Blood
platelets are a separates group of cells which do not have a nucleus. They are
disk like bodies. Whenever a blood
vessel is injured, platelets accumulate at the site of injury and help in the
formation of a blood clot.
The
clot seals the wound in the blood vessel and prevent blood loss. Several
chemicals present in the blood required for clot formation.