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Thursday, 15 October 2015

PLANT GROWTH AND DEVELOPMENT

PLANT GROWTH AND DEVELOPMENT
PLANT GROWTH AND DEVELOPMENT


Abscission : Shedding of plant organs like leaves, flowers and fruits etc. from the mature plant.
Apical dominance : Suppression of the growth of lateral buds in presence of apical bud.
Dormancy : A period of suspended activity and growth usually associated with low metabolic rate.
Photoperiodism : Response of plant to the relative length of day and night period to induce flowering.
Phytochrome : A pigment, which control the light dependent developmental process.
Phytohormone : Chemicals secreted by plants in minute quantities which influence the physiological activities.
Senescene : The last phase of growth when metabolic activities decrease.
Vernalisation : A method of promoting flowering by exposing the young plant to low temperature.
Growth : An irreversible permanent increase in size of an organ or its parts or even of an individual.
Abbreviations
IAA Indole acetic acid
NAA Naphthalene acetic acid
ABA Abscissic acid
IBA Indole-3 butyric acid
2.4D 2.4 dichlorophenoxy acetic acid
PGR Plant growth regulator
Measurement of growth : Plant growth can be measured by a variety of
parameters like increase in fresh weight, dry weight, length, area, volume and
cell number.
Phases of growth : The period of growth is generally divided into three
phases, namely, meristamatic, elongation and maturation.
(i) Meristematic zone : New cell produced by metotic division at root-tip
and shoot tip thereby show increase in size. Cells are rich in protoplasm and
nuclei.
(ii) Elongation zone : Zone of elongation lies just behind the meristematic
zone and concerned with enlargement of cells.
(iii) Maturation zone : The portion lies proximal to the phase of elongation.
The cells of this zone attain their maximum size in terms of wall thickning
and protoplasmic modification.
Growth rate : The increased growth per unit time is termed as growth rate.
The growth rate shows an increase that may be arithmetic or geometrical.
PLANT GROWTH AND DEVELOPMENT
Differentiation : A biochemical or morphological change in meristemic
cell (at root apex and shoot apex) to differentiate into permanent cell is called
differentiation.
Dedifferentiation : The phenomenon of regeneration of permanent tissue
to become meristematic is called dedifferentiation.Redifferentiation : Meristems/tissue are able to produces new cells that
once again lose the capacity to divide but mature to perform specific functions.
PHYTO HORMONE OR PLANT GROWTH-REGULATOR
Growth promoting hormones : These are involved in growth promoting
activities such as cell division, cell enlargement, flowering, fruiting and seed
formation. e.g., Auxin, gibberellins, cytokinins.
Growth inhibitor : Involved in growth inhibiting activities such as dormancy
and abscission. e.g., Abscisic acid and Ethylene
PLANT GROWTH AND DEVELOPMENT

QUESTIONS
Very Short Answer Questions (1 mark each)
1. Write the cause of 'Bakane' disease of rice.
2. Name the plant hormone which was first isolated from human urine.
3. Name the only gaseous plant hormone.
4. How does abscisic acid acts as stress hormone in drought condition ?
5. A farmer observed some broad-leaved weeds in a wheat crop farm. Which
plant hormone would you suggest remove them ?
6. Why do lateral buds start developing into branches when apical bud is removed ?
7. Flowering in certain plant occur only when they are exposed to low
temperature for a few weeks. Name this phenomenon.
8. Name the hormone released from over-ripe apples that affects all other apples
in a small wooden box.
Short Answer Questions-II (2 marks each)
9. How will you induce lateral branching in a plant which normally does not
produce them ? Give reason.
10. What induces ethylene formation in plants ? Give any two different action
of ethylene on plants.
11. What is meant by abscission ? Name the phytohormone involved in it.
12. What is meant by apical dominance ? Which hormone control it ?
13. Differentiate between photoperiodism and vernalisation.
Short Answer Questions-I (3 marks each)
14. What would be expected to happen if :
(a) GA3 is applied to rice seedling.
(b) a rotten fruit get mixed with unripe fruits.
(c) you forget to add cytokinin to the culture medium.
15. Which growth hormone is responsible for the following :
(a) induce rooting in a twig
(b) quick ripening of a fruit
(c) delay leaf senescence
(d) ‘bolt’ a rosette plant
(e) induce immediate stomatal closure in leaves (f) Induce growth in axil lary buds
16. Define differentiation, dedifferentiation and redifferentiation.
17. Where are auxins generally produced in a plant ? Name any one naturally
occuring plant auxin and any one synthetic auxin.
18. Define growth rate. Name two types of growth. Give the shape of curve for
these growth.
19. Mention various parameter taken into consideration for measuring the growth.
Long Answer Questions (5 marks each)
20. Inlist the five categories of phytohormone. Write atleast two uses of each.
ANSWERS
Very Short Answers (1 mark)
1. Gibberalla fujikuroi.
2. Auxin
3. Ethylene
4. ABA causes rapid closure of stomata, preventing loss of water by transpiration.
5. 2.4-D
6. Due to inhibit activity of Auxin lateral growth starts.
7. Vernalisation
8. Ethylene


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