More on Hydroponics

This post is intended to give a few more details on the hydroponics rigs that I constructed, and am currently testing with Greg O. I built these rigs in collaboration with John Gourlay (, who is a technician in the Botany Department workshop (room 1363; directly underneath the room that houses the growth chambers). John was able to create these rigs in less than a day after I described them to him, so if you’re thinking of starting a hydroponics project, you should consider having him do the work for you. He charges a small amount, and does the work very quickly. He’s also a very nice guy.

The rigs are based on a design that is pretty common in the world of hydroponics. The version described below is similar to one developed at Duke University by Jessica Selby and Kevin Wright (John Willis Lab). The idea is to suspend the roots of the plant in a nutrient solution, and provide oxygen to the roots via bubblers. As Greg says, the method requires development. However, it appears to work well for sunflowers (not so much for my plants). Anyway, here is the basic process of constructing the rigs.

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Hydroponics test run

Dylan and I have been working on getting hydroponic testing up and running. The basic set up is a large tub filled with dilute nutrient solution, with aeration provided by an air pump. Floating on top of the water is a large foam sheet with holes. In each hole we put a 2 ml tube packed with rock wool and perlite along with a seedling. Extending below the hole is a large bubble tea straw to make sure the roots don’t tangle together while growing.

Dylan with hydroponics

Dylan holding the foam board

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Seed size in H. exilis

Here is a curiosity I noticed while sorting seeds.

At one of my H. exilis sites (G136) there was a serpentine field beside a raised road. The field had a large population of tiny sunflowers, but there were also a few plants on the gravel embankment beside the road. These plants were much bigger, probably because the soil used in the embankment wasn’t serpentine. I collected seeds from both field and roadside plants.

The roadside seeds are much bigger than the serpentine seeds.

This has several possible explanations:

-Plasticity. The non-serpentine plants are much bigger, being bigger makes their seeds also larger.

-Selection. Bigger seeds are better on the disturbed habitat of the gravel embankment.

-Introgression. Gene flow from H. annuus could be coming in and only persisting on non-serpentine areas, bringing larger seed alleles.