In my post of two weeks ago, I reported on the experiment ruined thanks to the plate of seedlings falling over. While that one failed comically, the experiments over the following two weeks failed prosaically.

In the first one, when transferring seedlings onto a new plate for recording root growth, I laid a Kimwipe (tissue) over roots and kernels both. Previously, I had put the tissue over just the roots. Doing so is a little challenging and to minimize the chance of wrinkles in the tissue (which make measuring a bit of a chore), I thought just lay it over the whole thing. Sounds good in theory and there might indeed have been fewer wrinkles. But the roots were smothered, insofar as they grew in 16 h about as much as they typically would have grown in 2 h. Lack of oxygen I suppose. I don’t think the Kimwipe is toxic because roots have grown fine when they were covered without the shoot being covered.

Smothering was a problem for the experiment but I think it was also a problem for the set up. I had been placing a Kimwipe over kernels while they germinated on vertical agar plates. The Kimwipe hugs the agar above and below the kernels and keeps them from sliding down. And evidently also smothers the seedlings. This fit with the roots being shorter than expected at the time when I transfer them, shorter compared to their length when grown in jelly rolls. In the jelly roll, the shoots have complete access to air.

For experiment two, I wanted to stick with using agar plates rather than jelly rolls; first, because the roots would see red light during germination, as they would during the experiment; and second, because the transfer to start the experiment would involve agar to agar, rather than spongy paper to agar. But how to hold the kernels up and still allow the shoots to breathe? I decided to use a rectangle of brown towel, placed with its upper edge even with the top of the kernels and its bottom edge about 3 cm below. This would give a reasonable surface between agar and towel and I was hoping that the towel would be stiff enough to hold up the kernels. Because the assembly was open at the top edge, no problem about the shoot getting air.

When I set this up, I was happy to see that the kernels stayed up. The brown towel did not collapse. Alas, three days later, when I went to transfer seedlings to set up a new movie, I found that the roots took a hard left, or right, when they reached the place of contact between towel and agar. I had assumed that the roots would push right through. But nope, they went sideways, the easy way. The roots were nice and long, having plenty of oxygen. But their sideways orientation made them ill suited for transfer and subsequent growth measuring.

Well dang it. I could always go back to jelly rolls. But for the reasons given above I’d like to stick with agar. On the other hand, I want to keep the setup simple, so this might not be possible. I have one more idea. When I put the kernels on the agar, there is about 3 mm between their top surfaces and the top of the plastic Petri plate. I can take a paper towel, roll it into a cylinder, moisten it, and lay it over the row of kernels. If the roll is perhaps 4 to 5 mm wide, it should allow the plate top to push on the seeds, adding a pressure to hold them up. In this arrangement, the shoots will be free of covering above, as the roots below. I’ll try it!