Next steps with this JBP

[bonsaisensation]

Ok. So I did a bit of reading in my Botany For Gardeners (Brian Capon) which was my introduction to plant hormones. I had in my head that auxin will accumulate in the top side of the branch. However it is in the lower part of a young stem that it accumulates causing the cells in the underside to elongate more and thereby the stem grows more upright. The same happens on the shady side of a stem causing the stem to grow towards the light. This is obviously more effective in a elongating stem as opposed to an established branch/trunk.

From further reading on the web the role of auxins on apical dominance seems to be relatively little understood but generally agreed that it is produced by the growing meristem (tip) and that will suppress lateral buds below it. Further away from the tip, lower concentrations allows lateral buds to develop and branching occurs. Different species produce different amounts of auxins and react differently to their presence and so some species are strongly apical dominant (pines are a good example), others not so and yet others exhibit very little (shrubs).

If i hadn't just spent good money on this pine I may have done some experimenting by wiring half the branches down and the others not to see if there is a difference. As it is I might remove a little more of the top, wire what I want to keep with a bit more to spare and repot in spring doing the half/half method recommended by Scott.

Hi dansai
I happened to visit a friend tonight and picked up his year 12 biology textbook and read the similar explanation about the presence of auxin on the underside of a branch that aids the elongation of the new growth. I suppose it explained why my Chinese elms would stretch couple of inches in new growth in the low light environment of the shopping centres within 24 hours
In any case, this discussion is to highlight the benefit of removing strong growth to promote advantageous back budding. So I only hope that it gives people more confidence in hard pruning.

Regards

[Jarad]

With all this talk about auxins.

Say you had your JBP under a shade cloth (or inside) and placed UV lights around the base of the tree facing up, would the auxins cause the tops of the branches to grow more than the bottoms and "naturally" make the branches grow downward?

Also, is it pines that don't like being bent below horizontal and would UV lights help?



I might need to invest in some UV lights and more JBP and have a play.

[dansai]

I'm not sure what causes the auxin to move to the shady side and wether its UV or some other factor, however it does move to the bottom of a stem, so wether that would counter act what your suggesting I also don't know.

I think too it would only be effective when stems are forming and once the wood has lignified it would be too late. Once a branch is more than a year old it is only putting wood around the original wood of the stem.

And pines are fine with branches below horizontal. In fact most are styled with branches below horizontal.

[Elmar]

I'm not sure what causes the auxin to move to the shady side and wether its UV or some other factor, however it does move to the bottom of a stem, so wether that would counter act what your suggesting I also don't know.

I think too it would only be effective when stems are forming and once the wood has lignified it would be too late. Once a branch is more than a year old it is only putting wood around the original wood of the stem.

From memory, you're spot-on. The light receptors are in young shoots only (the green wood) this allows the young seedlings to "go after" the sun to maximise their photosynthesis potential... once they're set, this ability moves on to the newer growth higher up the tree - as you can imagine, using these auxins costs energy and nutrients that the Seedlings don't want to keep expending if they don't have to! It gives them greater chance to grow and survive.

its in all species but some are more pronounced than others (ouch, that just hurt my memory banks...).

[dansai]

I have buds forming at the branch ends already. Only tiny and I'm sure they won't develop until next winter. Thing is, on most of the branches I was going for buds on the bare wood closer to the trunk as they are a bit leggy. Anyway, we will see how we go. Perhaps after some strong spring growth I may be lucky and get them further back.

Now that I think about it, I remember there is a section in Leongs book on getting them to back bud on older wood. Maybe I should do some