Q.11 ‘Hairy roots’ induced in vitro by the infection of Agrobacterium rhizogenes, are characterized by
- P. a high degree of lateral branching
- Q. genetic instability of culture
- R. an absence of geotropism
- S. poor biomass production
- (A) P and R only
- (B) P and Q only
- (C) Q and R only
- (D) R and S only
Hairy roots induced by Agrobacterium rhizogenes exhibit high lateral branching and lack geotropism, making them ideal for bioreactor production of plant metabolites. This SEO-optimized article answers the MCQ: ‘Hairy roots’ induced in vitro by the infection of Agrobacterium rhizogenes, are characterized by P. high lateral branching, Q. genetic instability, R. absence of geotropism, S. poor biomass—selecting (A) P and R only.
Correct Answer: Option (A) P and R Only
Hairy roots show P. high degree of lateral branching due to rol genes (rolA/B/C) overexpressing auxins/cytokinins, creating dense, bushy root systems for maximal surface area.
They display R. absence of geotropism (grow horizontally despite gravity) from aux1/rol gene disruption of polar auxin transport, enabling uniform bioreactor growth without sedimentation.
Explanation of All Statements
Classic hairy root phenotype from Ri plasmid T-DNA transformation:
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P. High lateral branching: True. Extensive plagiotropism yields 10x normal roots’ biomass in hormone-free media.
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Q. Genetic instability: False. Hairy roots maintain stable T-DNA integration across subcultures, unlike callus.
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R. Absence of geotropism: True. Agravitropic growth pattern is diagnostic for rhizogenes transformation.
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S. Poor biomass production: False. Rapid proliferation (doubling time 3-5 days) exceeds untransformed roots.
Statement Characteristic True/False Reason P High branching True Rol genes induce auxin excess Q Genetic instability False Stable transgenes long-term R No geotropism True Auxin transport disruption S Poor biomass False High growth rate hormone-free Biotechnology Applications
Hairy roots produce 1-10% dry weight secondary metabolites (paclitaxel, shikonin), linking to your fermentation kinetics expertise—scalable in airlift bioreactors without auxins, perfect for Rajasthan’s herbal biotech.
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