Plant growth and development .... NCERT .... Revision p | JEE NEET MATERIALS

Plant growth and development ....

NCERT ....

Revision pointzzzzz...

A single maize root apical meristem can be give rise to more than 17500 new cells per hour

A wateremelon cell can increase its size upto 3,50,000 times

Arithmetic growth rate - Only one daughter cell continuous to divide while others differentiate and matures

Geometric growth rate - all the daughter cells produced will divide..Sigmoid growth curve is obtained

Absolute growth rate - Increase in growth per unit time

Relative growth rate - Increase in growth per unit time per unit initial parameter

Relative growth rate also called as Efficiency index

Differentiation - Conversion of meristamatic cell into structurally and functionally specialised Primary permanent tissue...eg: Formation of primary xylem

Dedifferentiation - Conversion of primary permanent tissue to Secondary meristems....eg: Formation of cork cambium

Redifferentiation - Formation of secondary permanent tissus from secondary meristems....eg: Formation of secondary xylem

Development in plants = Growth + differentiation

Eg of plasticity - Heterophylly in cotton, coriander, larkspur in which leaves of juvenile and mature stages are different......Heterophylly in buttercup in which leaves in terrestrial and aquatic habitat plants are different

Plants growth regulators can be any group of small chemical molecule They can be indole compounds eg: Indole 3 acetic acid (IAA).....Adenine derivatives eg: N6 furfuryl amino purine, kinetin.....carotenoids eg: abscisic acid....terpenes eg: gibberellic acid....Gases eg: ethylene

Plant growth promotors - Auxin, Cytokinin, Giberellic acid

Plant growth inhibitors - Abscisic acid

Ethylene has both properties

Auxin - Effects :

1. First isolated from human urine
2. IAA & IBA are natural auxins and NAA & 2,4 - D are synthetic auxins
3. Auxin initiate roots in stem cuttings
4. It promotes flowering in pineapples
5. Prevent abscission of young fruit and leaf...promotes abscission of old leaf & fruits
6. Promote apical dominance 7. 2,4-D act as herbicide in dicots

Gibberellins - Effects

1. Increase length of grape stalks
2. Causes fruits like apple to elongate and improve its shape
3. Delay senescence
4. GA3 promote malting in brewing industry
5. Increase length of stem in sugarcane and increase yield upto 20 tonnes per acre
6. Cause internodal elongation in beet, cabbage, and other rosette plants

Cytokinins - Effects

1. Promote cell division
2. Overcome apical dominance
3. Promote nutrient mobilisation

Ethylene - Effects

1. Promotes senescence and abscission
2. Promote ripening
3. Breaks seed and bud dormancy
4. Helps leaf & upper part of shoot to remain above water
5. Initiate flowering in pineapple

Abscissic acid - Effects

1. Inhibits seed germination
2. Also called stress hormone
3. Antagonist to GA