Biology · Plant Growth and Development · NEET
GA3 is one specific gibberellin (called gibberellic acid). There are more than 100 gibberellins named GA1, GA2, GA3 and so on, but GA3 is the most studied and most commonly used one. So when NCERT or NEET says 'gibberellin', they usually mean GA3. All gibberellins are acidic.
Sugarcane stores its sugar in the stem. Gibberellin makes the internodes (the parts of the stem between nodes) longer, so the stem grows longer. A longer stem stores more sugar, raising the yield by as much as 20 tonnes per acre. This is a direct NCERT line and a repeated NEET question.
Bolting is the sudden lengthening of the internodes (stem) just before flowering in rosette plants like cabbage and beet. Gibberellin promotes this internode elongation, so the short packed rosette stem shoots up tall. Note: bolting is stem elongation, not the flower itself.
Yes. Gibberellin is a growth promoter, so it breaks seed and bud dormancy and promotes germination. This is the opposite of abscisic acid (ABA), which induces dormancy. NEET often tests this contrast: GA3 is NOT an inhibitory substance, so it does not enforce dormancy.
Malting is the early step in making beer where barley seeds are made to germinate so that starch turns into sugar. GA3 speeds up this malting process because it makes the seed produce enzymes (like amylase) faster. So GA3 is matched with the 'brewing industry' in NEET matching questions.
Auxin mainly controls apical dominance, root initiation, tropic bending, and prevents early fruit/leaf drop. Gibberellin mainly elongates the whole plant axis (stem/internodes), causes bolting, speeds malting, and helps fruits like apple grow longer. Both are growth promoters, but auxin is about direction/dominance while gibberellin is about elongation.
Spraying sugarcane crop with which of the following plant growth regulators, increases the length of stem, thus, increasing the yield?
Spraying of which of the following phytohormone on juvenile conifers helps in hastening the maturity period, that leads to early seed production?
Match List-I (Growth Regulator) with List-II (Function/Effect): A. 2,4-D, B. GA3, C. Kinetin, D. ABA; I. Brewing industry, II. Stimulation of stomatal closure, III. Herbicide, IV. Nutrient mobilisation.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
GA3, also called gibberellic acid, is the most common and most studied gibberellin. There are over 100 gibberellins (GA1, GA2, GA3...), and all of them are acidic.
Elongate the stem/internodes and whole axis; cause bolting in rosette plants; increase sugarcane yield (up to 20 tonnes/acre); speed up malting in brewing; delay senescence and fruit-drop; make fruits like apple longer and better shaped; hasten maturity in juvenile conifers for early seed; and break seed and bud dormancy.
Gibberellins were first noticed from the fungus Gibberella fujikuroi, which caused the 'bakanae' or foolish seedling disease in rice, making the rice plants grow abnormally tall. The hormone was named after this fungus.
Gibberellin is a growth PROMOTER. It promotes growth and breaks dormancy, which is the opposite of abscisic acid (ABA), the inhibitor. NEET often tests that GA3 is NOT an inhibitory substance governing seed dormancy.
Bolting is only the sudden elongation of the internodes (stem) just before flowering, seen in rosette plants like cabbage and beet. It is a stem effect. It happens just before flowering but is not the flower itself.
