1. Phases of Growth
(Meristematic, Elongation, Maturation):Mnemonic: "MEM"
- M = Meristematic: Cells divide rapidly.
- E = Elongation: Cells increase in size.
- M = Maturation: Cells achieve their final form and function.
2. Differentiation, Dedifferentiation and Redifferentiation
Mnemonic: "Different Doors, Different Rooms"
- Different Doors = Differentiation: Cells specialize and assume new functions.
- Different = Dedifferentiation: Specialized cells revert to a more primitive, unspecialized state.
- Rooms = Redifferentiation: Cells become specialized once again after dedifferentiation.
3. Sequence of the Developmental Process in a Plant Cell
Mnemonic: "Dogs Eat Many Carrots"
- D = Division: Cell division occurs.
- E = Expansion (Elongation): Cells grow in size.
- M = Maturation: Cells differentiate and reach their final state.
- C = Cell Death: Cells undergo programmed cell death (senescence).
4. Types of Growth Regulators
(Auxins, Gibberellins, Cytokinins, Ethylene, Abscisic Acid):Mnemonic: "AGE CA"
- A = Auxins: Promote growth and fruit development.
- G = Gibberellins: Stimulate stem elongation and seed germination.
- E = Ethylene: Influences fruit ripening and flower opening.
- C = Cytokinins: Promote cell division and delay aging.
- A = Abscisic Acid: Induces seed dormancy and stress responses.
5. Functions of Growth Regulators
(a) Auxin - "Auxiliary Roots Foster Apical Parthenocarpy"
- Auxiliary: Promotes growth of lateral roots.
- Roots: Initiates rooting in stem cuttings.
- Foster: Inhibits growth of apical buds (apical dominance).
- Apical: Encourages apical bud removal effects, enhancing branch growth.
- Parthenocarpy: Induces parthenocarpy, particularly in tomatoes, leading to seedless fruits.
Apical dominance in plants : (a) A plant with apical bud intact (b) A plant with apical bud removed Note the growth of lateral buds into branches after decapitation.
- Great: Increases the size and modifies the shape of fruits.
- Grapes: Used commercially to lengthen grape stalks.
- Grow: Stimulates stem elongation and seed germination.
- Giant: Produces larger fruits and vegetables.
(c) Cytokinin - "Cells Clone, Leaves Last"
- Cells: Promotes cell division.
- Clone: Stimulates shoot regeneration in tissue culture.
- Leaves: Delays leaf senescence (aging).
(d) Ethylene - "Ethereal Effects: Ripening, Dropping"
- Ethereal: Affects various parts of plant growth and development being a gaseous hormone.
- Ripening: Promotes fruit ripening.
- Dropping: Stimulates flower and leaf drop.
(e) Abscisic Acid (ABA) - "Absolutely Blocks All"
- Absolutely: Acts as a major growth inhibitor.
- Blocks: Inhibits seed germination.
- All: Increases tolerance of plants to stress (drought, salt, cold).
