Plant And Animal Hormone Flashcards
There are five major classes of plant hormones.
They are:
- Auxins
- Cytokinins
- Gibberellins
- Abscisic Acid (ABA)
- Ethylene
Among all these plant hormones ________ promote plant growth while __________ inhibit plant growth.
auxins, cytokinins and gibberellins
abscisic acid and ethylene
were the first plant hormones discovered.
Auxins (Gk. auxein = to grow)
The term auxin was introduced by
Kogl and Haagen- Smith (1931).
Auxins are produced at the tip of ______ from where they migrate to the zone of elongation
stems and roots
,who observed unilateral growth and curvature of canary grass (Phalaris canariensis) coleoptiles. He came to the conclusion that some ‘influence’ was transmitted from the tip of the coleoptile to the basal region
Charles Darwin (1880)
This ‘influence’ was later identified as Auxin by Went.
________ a Dutch biologist demonstrated the existence and effect of auxin in plants. He did a series of experiments in Avena coleoptiles
Frits Warmolt Went (1903-1990),
Types of Auxins: Auxins are classified into two types, namely
- Natural Auxins: Auxins produced by the plants are called natural auxins. Example: IAA (Indole-3- Acetic Acid)
- Synthetic Auxins: Artificially synthesized 15.1.2 C auxins that have properties like auxins are called as synthetic auxins. Example: 2,4D (2,4 Dichlorophenoxy Acetic Acid
______ promote the elongation of stems and coleoptiles which makes them to grow
Auxins
_______ induce root formation at low concentration and inhibit it at higher concentration.
Auxins
The auxins produced by the apical buds suppress growth of lateral buds. This is called
apical dominance
Seedless fruits without fertilization are induced by the external application of auxins. (___________) Examples: Watermelon, Grapes, Lime etc.
Parthenocarpy
Auxins prevent the formation of
abscission layer.உதிர்தல்
Phenyl Acetic Acid (PAA) and
Indole 3 Acetonitrile (IAN) are natural auxins.
Indole 3 Butyric Acid (IBA),
Indole-3- Propionic Acid, a-Naphthalene Acetic Acid (NAA),
2, 4, 5-T (2,4,5 Trichlorophenoxy Acetic Acid)
are some of the synthetic auxins
Cytokinin is found abundantly in liquid endosperm of .
coconut
Cytokinins (Cytos - cell; kinesis - division) are the plant hormones that __________or cytokinesis in plant cells
promote cell division
cytokinin was first isolated from ________
Herring fish sperm.
was the cytokinin isolated from Zea mays(makkacholam)
Zeatin
Morphogenesis
Both auxins and cytokinins are essential for the formation of new organs from the callus in tissue culture
Cytokinin induces cell division (cytokinesis) in the
presence of auxins.
Cytokinins promote the growth of ______ even in the presence of apical bud
lateral buds
Richmond Lang effect
Application of cytokinin delays the process of ageing in plants. This is called Richmond Lang effect.
Gibberellins are the most abundantly found plant hormones. _______ observed Bakanae disease or foolish seedling disease in rice crops
internodal elongation in rice was caused by fungus Gibberella fujikuroi. The active substance was identified as _______
Kurosawa (1926)
Gibberellic acid.
Application of gibberellins on plants stimulate extraordinary ________ e.g. Corn and Pea.
elongation of internode.
bolting
Treatment of rosette plants with gibberellin induces sudden shoot elongation followed by flowering. This is called bolting.
____ promote the production of male flowers in monoecious plants (Cucurbits).
Gibberellins
Gibberellins of potato tubers.
break dormancy
Gibberellins are efficient than auxins in inducing the formation of seedless fruit Parthenocarpic fruits (Development of fruits without fertilization) e.g. _____.
Tomato
Abscisic acid (ABA) is a growth inhibitor which regulates abscission and dormancy. of plants.
Abscisic acid increases tolerance of plants to various kinds of stress. So, it is also called as ________. It is found in the chloroplast
stress hormone
ABA promotes the process of ______(separation of leaves, flowers and fruits from the branch).
2.
abscission
During water stress and drought conditions ABA causes
stomatal closure.
ABA promotes senescence in leaves by causing loss of
chlorophyll
ABA induces _____ towards the approach of winter in trees like birch.
bud dormancy
ABA is a powerful inhibitor of ________ growth in tomato.
lateral bud
Ethylene is a _______plant hormone. It is a _______. It is mainly concerned with maturation and ripening of fruits. Maximum synthesis of ethylene occurs during ripening of fruits like apples, bananas and melons
gaseous
growth inhibitor
Physiological effects of ethylene
- Ethylene promotes the ripening of fruits. e.g. Tomato, Apple, Mango, Banana, etc.
- Ethylene inhibits the elongation of stem and root in dicots.
- Ethylene hastens the senescence of leaves and flowers.
- Ethylene 49 abscission stimulates formation of zone in leaves, flowers and fruits. This leads to premature shedding.
- Ethylene breaks the dormancy of buds, seeds and storage organs.
The branch of biology which deals with the study of the endocrine glands and its physiology is known as .
endocrinology
is of known as Father of Endocrinology.
Thomas Addison
English physiologists _______ introduced the term hormone in _____. They first discovered the hormone _______.
W.M Bayliss and E. H. Starling
1909
secretin
Exocrine glands have specific ducts to carry their secretions e.g.
salivary glands, mammary glands, sweat glands
Endocrine glands present in human and other vertebrates are
a. Pituitary gland
b. Thyroid gland
c. Parathyroid gland
d. Pancreas (Islets of Langerhans)
e. Adrenal gland (Adrenal cortex and Adrenal medulla)
f. Gonads(Testes and Ovary)
g. Thymus gland
The pituitary gland or _______ is a pea shaped compact mass of cells located at the base of the midbrain attached to the hypothalamus by a pituitary stalk.
hypophysis
They are the anterior lobe (_____) and the posterior lobe (______). The intermediate lobe is non-existent in humans.
adenohypophysis
neurohypophysis
The pituitary gland forms the major endocrine gland in most vertebrates. It regulates and controls other endocrine glands and so is called as the “”.
Master gland
Hormones secreted by the anterior lobe (Adenohypophysis) of pituitary
a. Growth Hormone
b. Thyroid stimulating Hormone
c. Adrenocorticotropic Hormone
d. Gonadotropic Hormone which comprises the Follicle Stimulating Hormone and Luteinizing Hormone
e. Prolactin