This category focuses on two major plant growth regulators: auxins, which control cell elongation and growth direction, and gibberellins, which promote stem elongation and seed germination. It includes explanations and practice questions to help understand their roles in plant development.
Parthenocarpy is the formation of seedless fruits without fertilization. Auxins and gibberellins, not abscisic acid, can induce parthenocarpy.
Ref: NCERT Class 11 Biology Chapter 13: Plant Growth and Development Plant Growth Regulators - Auxins and Gibberellins
Auxins, such as IAA and IBA, are used in tissue culture to promote root formation.
Ref: NCERT Class 11 Biology Chapter 13: Plant Growth and Development Plant Growth Regulators - Auxins and Gibberellins
Ethylene promotes rapid internode elongation in deepwater rice plants, enabling them to grow above the water level.
Ref: NCERT Class 11 Biology Chapter 13: Plant Growth and Development Plant Growth Regulators - Auxins and Gibberellins
Gibberellins promote bolting, which is the rapid elongation of the internodes just before flowering, particularly in rosette plants like cabbage and beet.
Ref: NCERT Class 11 Biology Chapter 13: Plant Growth and Development Plant Growth Regulators - Auxins and Gibberellins
Environmental heterophylly occurs when the shape of leaves changes in response to environmental conditions, such as in buttercup plants.
Ref: NCERT Class 11 Biology Chapter 13: Plant Growth and Development Plant Growth Regulators - Auxins and Gibberellins
Auxin is commonly used to induce parthenocarpy, which results in seedless fruit development.
Ref: NCERT Class 11 Biology Chapter 13: Plant Growth and Development Plant Growth Regulators - Auxins and Gibberellins
Parthenocarpy is the development of seedless fruits without fertilization. Auxins and gibberellins can induce parthenocarpy, not only cytokinins.
Ref: NCERT Class 11 Biology Chapter 13: Plant Growth and Development Plant Growth Regulators - Auxins and Gibberellins
Auxin promotes apical dominance; it does not inhibit it. Cytokinins help overcome apical dominance.
Ref: NCERT Class 11 Biology Chapter 13: Plant Growth and Development Plant Growth Regulators - Auxins and Gibberellins
Abscisic acid induces seed dormancy and inhibits germination. Ethylene promotes fruit ripening, and auxin suppresses lateral bud growth (apical dominance).
Ref: NCERT Class 11 Biology Chapter 13: Plant Growth and Development Plant Growth Regulators - Auxins and Gibberellins
2,4-D (2,4-dichlorophenoxyacetic acid) is a synthetic auxin, not a natural one. IAA (indole-3-acetic acid) is a natural auxin.
Ref: NCERT Class 11 Biology Chapter 13: Plant Growth and Development Plant Growth Regulators - Auxins and Gibberellins
E. Kurosawa discovered that gibberellins from the fungus *Gibberella fujikuroi* caused abnormal elongation in rice seedlings.
Ref: NCERT Class 11 Biology Chapter 13: Plant Growth and Development Plant Growth Regulators - Auxins and Gibberellins
Auxin produced at the apical bud suppresses the growth of lateral buds, resulting in apical dominance.
Ref: NCERT Class 11 Biology Chapter 13: Plant Growth and Development Plant Growth Regulators - Auxins and Gibberellins
