After shoot proliferation stage,transferred my tagetes (marigold) micro-shoots to different GA (0.5, 1.0 and 2.0 mg/l) supplemented mediums. For other crops, it is a regular practice in our lab so that the shoots became strong, healthy and more suitable for in vitro root induction. But here in the present study, I observed that elongation of shoots was maximum in MS medium devoid of hormones (control) as compared to GA enriched medium. Can anybody explain the reason behind this type of negative role of GA (shortening of shoots)? Has one observed the similar results in any other crops?
The level of GA may have been supra-optimal.
See:
Proceedings of the Indian Academy of Sciences - Section B
November 1978, Volume 87, Issue 11, pp 255–270
Effect of gibberellic acid on the growth of main shoot and axillary branches in Calendula officials :)
Thank you very much, sir. I have collected the paper and interestingly Tagetes is a close relative of Calendula (both are from Asteraceae and rich source of carotenoids). Maybe sura-optimal dose is the reason behind this.
Hi Ravindra,
In general, the amounts of plant hormones added to the culture media are very much higher than the endogenous quantities. In your case the effect is probably even more marked by the quantities of carotenoids. The plant no longer achieves a balance and the GAs have a negative effect on development.
Good luck in yours experiences,
David
Hi Ravindra, it is similar with my experience in tomato shoot culture. Addition of GA3 to elongation medium did not give positive effect. I think that endogenous level of phytohormone influence of explants response. If the plants naturally have high endogenous phytohormone including GA3, that addition exogenous can not give positive effect.
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