Organogenesis

Deebs

The Sentient Naturewalker
Staff member
Moderator
I am going to try to provide a very brief description of this from my current understanding.

The best way to describe this from my perspective is the formation of organs (leaves, roots, stems) from the callus. The callus, formed by the division of the explants cells (cytokinesis), is activated by the addition of plant growth regulators (auxins/cytokinens) in the culture medium.

There are 2 types:
Direct - explant is directly cultured to create a new plant without callus formation
Indirect - explant forms callus, then root/shoot formation

Plant Growth Regulators
Auxins
Cytokinins
Gibberellins

2 Stages of Organogenesis
Caulogenesis = Shoot Formation (A<C) PGR concentration
Rhizogenesis = Root Formation (A>C) PGR concentration
Cytokinesis (A=C)

@SCJedi - Hitting the key points? What am I missing? Thinking about Direct Organogenesis, can you provide an example of an explant directly creating a new plant without callus formation? Also let me know if you think this belongs in another section!

 

SCJedi

In Bloom
Nailed it. An example of direct organogenesis is placing a node into in vitro culture and getting it to grow roots. In this example roots are the target organ. No callus needed.

If you ever want callus use TDZ. Anything from 0.5-2.0 mmoles will knot tissue up pretty quickly. If callus is your target TDZ and leaf segments will get you there fast. The cellular edge of leaf typically remains or contain undifferentiated and will dedifferentiate easily.

The purpose of organogenesis is to take differentiated tissue, dedifferentiate it, and then differentiate it again. Using the leaf example above. It's a leaf, then is a cluster of undifferentiated cells (callus), then differentiate it into a new organ like shoots or roots.

One might ask aloud, "WTF? Why would you want to do this?". Lots of reasons. Callus is easy to split into pieces, it's easy to feed and slow down for storage, etc.
 

SCJedi

In Bloom
I never did answer the question about whether this is the correct section or not. Because organogenesis is a two-step process it really is initiation as well as multiplication. You could even take it a step further and call it rooting.
 

Deebs

The Sentient Naturewalker
Staff member
Moderator
Thanks man! TDZ..that's an herbicide right? It's also a growth regulator?

I was looking up different cytokinin, and was wondering about something.
I recalled something about different cultivars requiring different protocols (ratio of auxin/cytokinin).

Some of the main ones i see repeated a lot in literature...
Metatopolin, 2iP, 4-CPPU, Adenine, BA, Kinetin, N6-Benzoyladenine, Zeatin

I then started looking at different protocols in use, and noticed how some cannabis plants did well with one protocol, but not the other.
Tailoring protocols to the specific plant is the game!
Interesting stuff!
 
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