Root Cultures in Plant Tissue Culture: History, Protocol, Advantages & Applications

Root Cultures are a specialized and highly effective technique in plant tissue culture. While shoot and leaf cultures dominate mass multiplication, root cultures excel in producing valuable secondary metabolites and maintaining stable root systems in vitro.

Root Cultures Technique in Plant Tissue Culture

History of Root Cultures

The foundation of root culture was established by American plant physiologist Philip White in 1934. He successfully cultured excised tomato roots in a liquid medium for many years, demonstrating that roots could be grown indefinitely under controlled conditions. This work was a major milestone in the early development of plant tissue culture.

In the 1980s, scientists developed hairy root cultures by infecting plants with the bacterium Agrobacterium rhizogenes. This innovation created fast-growing, hormone-independent roots that revolutionized the production of pharmaceutical compounds.

Why Root Cultures Are Important

Even though many other explant types are available, root cultures remain essential because:

Roots are the primary site for synthesis of many bioactive compounds.
They offer high genetic stability.
Hairy root cultures provide an efficient “biofactory” system for commercial metabolite production.

Step-by-Step Protocol for Root Culture

1. Explant Selection Select healthy young root segments or root tips from disease-free plants.

2. Surface Sterilization Wash thoroughly → 70% ethanol (30–60 sec) → 0.1% HgCl₂ or sodium hypochlorite (5–10 min) → Rinse multiple times with sterile water.

3. Culture Initiation Inoculate on Murashige and Skoog (MS) medium.

Normal root culture: Add low auxin (0.5–1 mg/L IBA/NAA).
Hairy root culture: Use Agrobacterium rhizogenes transformation.

4. Incubation Maintain at 25±2°C, preferably in dark for normal roots.

5. Subculturing Transfer healthy root tips every 3–4 weeks to fresh medium.

6. Harvest or Regeneration Harvest for metabolite extraction or transfer to shoot induction medium for complete plant regeneration.

Advantages of Root Cultures

High production of secondary metabolites
Genetic stability (especially hairy roots)
Rapid biomass accumulation
Hormone independence in hairy roots
Suitable for bioreactor scaling

Common Plants Used in Root Cultures & Reasons

Catharanthus roseus → Anti-cancer alkaloids
Panax ginseng → Ginsenosides
Artemisia annua → Artemisinin (anti-malarial)
Hyoscyamus niger → Tropane alkaloids
Tomato → Model plant for physiological studies

These plants are chosen because their roots naturally produce high levels of valuable compounds that are difficult to obtain in large quantities from field cultivation.

FAQ – Frequently Asked Questions

Q1. Who first introduced root culture? Answer: Philip White in 1934.

Q2. What is the difference between normal root culture and hairy root culture? Answer: Hairy root cultures grow faster, are hormone-independent, and usually produce higher metabolite yields.

Q3. Can root cultures be used for mass plant propagation? Answer: Yes, but they are more commonly used for secondary metabolite production.

Q4. Are root cultures genetically stable? Answer: Generally yes, especially when avoiding prolonged callus phase.

MCQs with Answers (Exam Style)

Q1. Who successfully cultured isolated roots for the first time? A) Haberlandt B) Philip White C) Gautheret D) Skoog Answer: B

Q2. Hairy root cultures are induced by: A) Agrobacterium tumefaciens B) Agrobacterium rhizogenes C) Rhizobium D) E. coli Answer: B

Q3. Root cultures are mainly preferred for: A) Shoot multiplication B) Secondary metabolite production C) Virus elimination D) Haploid production Answer: B