Leaf Anatomy

Presentation by our resident botanist Karl Horak.
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Transcript of Leaf Anatomy
Leaf Anatomy
for Bonsai
It’s all about photosynthesis
But what exactly is a leaf?
Evolutionarily, it’s a flattened stem
The key is to look for an axillary bud
What the hell is an axillary bud?
It’s a bud in an axil, of course.
Damn you, botanists… what the hell is an axil?
CO + H O + Light
Carbohydrates + O
CO in and O out,
but also H O out
The arrangement of leaves is controlled by auxins and other growth hormones
For bonsai, this is critical because…

That’s where the axillary buds are
and they control the appearance
of secondary branches

And e-vile botanists have
come up with all sorts of
terminology to describe
the results
All these variations are adaptations to deal with photosynthesis: conserve water, absorb light, exchange gases, protect from herbivores, resist disease, etc.
For bonsai, small leaves have the proper scale to
give the desired esthetic effect:
Juniper scales
Short-needled pines
Microphyllous leaves
Compound leaves w/small leaflets
Leaves amenable to size reduction
Lucky for us, leaves are very plastic.
Since they don’t have much to do with
reproduction, they can vary to suit changing
conditions (sun vs shade, wet vs dry, juvenile
vs maturity).

Phyllotaxy is the arrangement of leaves on the stem, usually in a spiral
Except for adventious buds, aka “breaking back”