A619 is going to be replaced by a Silver Queen. Last week, I set out a handful of A619 seed in a moist box right under the dim red LEDs. As explained last time the red light, compared to near darkness, will make the coleoptile grow faster and the A619 seed being fresh from last summer’s corn field should germinate well. I planned to watch and find out when would be the best time to experiment on the coleoptiles: they need to be long enough to cut up into 3 segments (a little more than 1 cm, all told) but not so long that the inner leaves have broken through, thus stopping that coleoptile’s growth forever.
To my dismay, the time never happened. Only about a quarter of the seeds in the box sent up a shoot at all. I realized that what I need for these experiments is not high total germination but mostly uniform germination. A619 is a maize inbred line, genetically well defined. I got the seed from my lab-neighbor, Madelaine Bartlett, who is a maize geneticist and had plenty of fresh A619 on hand, which she was confident would germinate fine. But the thing is, a geneticist who plants the seed in a field probably doesn’t care if the plants emerge separated by a few days. But for setting seed up for physiology, I need a bunch of uniform seedlings on the same day. Probably if I waited for some days, all of the seed in the box would, one by one, send up a shoot. That kind of time line just isn’t practical for physiology.
I suspect that back in the day when I was doing phototropism experiments on maize seedlings, the lab used a commercial hybrid, rather than a genetically defined inbred, like A619, for this very reason. Likewise, when I was in UK, starting out this line of experiments, I got seed of a hybrid from a breeder (by convenience not design) and that material germinated reasonably uniformly. Only now that it has aged, the yield of usable seedlings is getting less and less. That’s why I thought I would try fresh seed.
Not only was germination non-uniform, the coleoptiles were short. The leaves broke through the coleoptile before it was long enough for experimentation. Not sure why. There were just a few seedlings so perhaps had there been more, some of them would have been suitable. But it didn’t look promising. Benefitting from that famous vigor, hybrid seedlings, in addition to germinating more synchronously (being souped-up?), might grow longer coleoptiles.
Never to be daunted, or at least not this time, I drove down to Amherst Farmers’ Supply and bought a half-pound bag of Silver Queen, a popular variety of sweet corn around here. The kernels were translucent. I planted a bunch in the box and set them under the red LEDs. This week, the coleoptile vigil continues.
