Rhizogenesis - Growth of roots in in-vitro grown shoots
After adequate shoot growth, the next stage in plant tissue culture is growth of functional roots in the shoots or rhizogenesis. Clumps of growing shoots are collected from shoot growth medium and excised with sterile scalpel blades into individual shoots or in small group of shoots and aseptically transferred to another medium, which triggers root formation. There are two major triggers for shoot formation. The first is - reducing the concentration of cytokinins and increasing the concentration of auxins. The second trigger is lowering of mineral and organic nutrient content in the medium. So, in some cases, MS medium in half strength or one-fourth strength is used as root initiation medium.
The following table elucidates the plant growth promoters used by different authors for rhizogenesis from in-vitro grown adventitious shoots. The complete rhozogenesis process takes about 2 - 3 weeks. The preferred culture condition in terms of temperature, humidity, light intensity and photoperiod is sililar to that used in adventitious shoot growth stage.
Rhizogenesis in MS basal medium supplemented with 0.5 mg/L Indole Butyric Acid (IBA)
Noordin N, Peng CS, Ibrahim R, Ahmad Z, Salleh S, Osman MF, Bahari, N, Irwan N, Yahya NA , Ramli N (2015) Standard Operating Procedure (SOP) for Rapid and Efficient Production of Stevia Tissue Culture Seedlings, NTC 2015: Nuclear Technical Convention 2015; Bangi (Malaysia); 3-5 Nov 2015
Rooting quality and quantity under the effect of different hormonal condition
Ali Haji Mohammadi, Reza Zarghami, Ali Kashani, Hossein Heydari Sharifabad and Ghorban Nour Mohammadi, 2017. Effect of Different Hormonal Treatment on Stevia (rebaudiana Bertoni) Micro-propagation. Pakistan Journal of Biological Sciences, 20: 457-464.
Root induction in different IBA concentrations
Abdul Rashid, Nur Raifana. (2015). MICROPROPAGATION OF Stevia rebaudiana Bertoni THROUGH TEMPORARY IMMERSION BIOREACTOR SYSTEM..
Rooting of in-vitro plantlets in MS basal medium with NAA 4.0 mg/L
Khan, A., Jayanthi, M., Gantasala, N. P., Bhooshan, N., & Rao, U. (2016). A rapid and efficient protocol for in vitro multiplication of genetically uniform Stevia rebaudiana (Bertoni). Indian journal of experimental biology, 54(7), 477–481.