Abstract
This protocol establishes growth of Arabidopsis seedlings in a hydroponic medium that is suitable for the controlled addition or withdrawal of any number of nutrients, hormones or metabolites to the plants via the roots. In this case, the described protocol is used to assay sensitivity of shoot branching to exogenously supplied strigolactone, typically the artificial strigolactone GR24. Plants deficient in strigolactone synthesis or response will typically exhibit an increased number of axillary branches compared to wild type. Strigolactone synthesis mutants should respond to exogenous GR24 with reduced numbers and length of axillary shoots, while the phenotype of response mutants will not be rescued. We present here a more detailed protocol extended from that described in Waters et al. (2012).
Materials and Reagents
Equipment
Procedure
Expected Outcome
Recipes
Acknowledgments
We are grateful to Dr Brent Kaiser (University of Adelaide, Australia) for providing us with the hydroponics method outlined in this protocol. This protocol was further developed from Hoagland and Arnon (1941). The water culture method for growing plants without soil was adapted from miscellaneous publications including Gibeaut et al. (1997) and Tocquin et al. (2003). The work was funded by grants from the Australian Research Council (LP0776252 (RJ) and DP1096717 (MW)).
References
If you have any questions/comments about this protocol, you are highly recommended to post here. We will invite the authors of this protocol as well as some of its users to address your questions/comments. To make it easier for them to help you, you are encouraged to post your data including images for the troubleshooting.
No: for simplicity and ease of scaling, we did not use or try aeration. The boxes we use measure about 13 cm x 9 cm (LxW) and we add 160 ml of solution to each. That gives a decent surface area:volume ratio, or so it would seem. The solution, when changed every three days or so, either contains sufficient oxygen, or there is enough gas exchange through the other holes in the boxes. I have not formally compared growth rates with those of plants grown on soil or in other hydroponics systems, but they *seem* to grow pretty normally, flower, set seed etc. Probably aeration would help but it does complicate the set up. A maximum of six plants per pot is tolerable, though I prefer to use four to give them a bit more space. Depends in part on how valuable your media/compounds are.
I mean the concentration of the substrate.
The simple answer is no, we did not measure the concentration of GR24 during the study. It is possible to do so by HPLC to monitor degradation. From our tests, the half-life of GR24 at pH5.7 is about 3 days, but we have not explicitly measured its half-life in Hoaglands media.
We make each of the stock solutions ourselves in the lab. This is potentially expensive if you have to buy all the reagents, especially considering how little you need of some of the micronutrients. Some of the micronutrients can be substituted, e.g. ZnCl2 rather than ZnSO4, as it is the Zn2+ rather than the Cl- or SO4- that matters.
Thank you, Dr. Waters. I would also like to know where you purchased the rockwool used in your experiment, and what type of rockwool it is? Thank you.
Hi CharlesWe get our rock wool from these guys in Australia:http://www.growroom.com.au/shop/propagation/rockwool-wrapped-slab-75x900x150/The manufacturer is Grodan, and you may be able to find alocal distributor here:http://www.grodan.com/about+grodan/find+a+distributor
And more information on what rock wool actually is:http://www.grodan.com/about+grodan/stone+wool+substrate