The importance of light in top growth

[yoderjac]

In another thread (http://www.habitat-talk.com/index.p...uts-question-transfered-from-qdma-forum.5553/) I'm documenting my experience with Seguins and ACs. On of the things I want to try is etiolated grafting. It requires growing seedlings in the dark and then grafting them. This is usually done with chestnuts, but I figured I'd try it with ACs and seguins. I doubt it will work, but I like to experiment.

I've already learned something. The importance of light is producing top growth. Of 66 ACs started normally under lights, 52 have produced top growth. Of the 7 I'm starting in the dark 0 have top growth. They are not in total darkness. I just put them under the table holding my grow box where the other ACs are. I presume they will eventually produce top growth, but the lights have clearly had an impact on the other ACs. Other than the light the nuts were handled identically.

Thanks,

Jack

 

[Catscratch]

Interesting. I wonder what the significance is? I've seen acorn seeds turn green, which would indicate photosynthesis or at least a reaction to light of some sort. Of course until a plant has leaves they are reliant on the stored carbs in the nut for energy. If this is solely the case then you would expect a nut to send up top growth in either scenario (light or dark) as the energy source currently has nothing to do with light.

What about radiant heat? Are your nuts that are exposed to lights seeing higher surface temps than the one's under the bench? Are lights causing premature top growth before the roots are ready? Seeds will obviously grow in the dark as burying seed doesn't hurt as long as it isn't too deep.

 

[yoderjac]

I'm not sure what the significance is. I was surprised. Like you, I did not expect this effect. All of the nuts are covered by medium, not on top. It could be a statistical anomaly, but the numbers pretty convincing. I'm using fluorescent lights. Perhaps there is a degree or two difference at most between the surface temperature of the medium in the grow box verses out. Both are plenty warm enough for top growth. The top growth is not premature. It is consistent with all of the trees I've started indoors. Underdeveloped roots are not an issue with 18s. The root pruning probably drives more energy into the top growth as well as secondary and tertiary roots but the are all in 18s.

The nuts generally use gravity to determine down, but they use light to determine which way is up. The nut generally make a determination of "down" right before the radicle emerges. If you reorient a nut when you first see the radicle, the radical will keep growing in the previously determined down direction for a while and then reorient itself to the new "down" direction.

I wonder if light has the same effect. Perhaps even the small amount of light that penetrates the soil is enough. I don't know. I just thought this was an interesting finding. I don't claim to know why or that the information is actionable. I just found it interesting.

Thanks,

Jack

 

[yoderjac]

Well, most of the ACs under lights have emerged. They are anywhere between just poking their heads up to 3" tall with several leaves. Tonight, my first AC kept in the dart poked its head up slightly.

Thanks,

Jack