1. Plant Organization:
Leaf development

2. Organization
Organization in plants is dependent upon programmed, controlled cell division, followed by growth, further cell division and ultimately, differentiation.
Programmed and controlled cell division occurs within the domain of the vegetative apex.
Leaves also follow a programmed development process

3. the apex
All the tissues within the apex differentiate rapidly. By about 150 µm, cells within the apical region are starting to differentiate. In the pine apex (above), you can see developing leaflets.
The Coleus apex to the right, shows rapidly developing leaflets beneath the apical dome.

4. internal organization
adaxial epidermis
palisade mesophyll
vascular bundles
spongy mesophyll
stomata

5. leaf development these form the epidermis and associated structures
marginal
two types of initials
submarginal
The diagrams which illustrate the development of the leaf were inspired by those that appear in ‘Plant Anatomy’ 2nd Ed. by Katherine Esau 1953: Library of Congress Catalogue card number: New York : John Wiley,  581.4 ESA    and especially Fig on page 455. The Leaf chapters are highly recommended as a basis for further study
these form mesophyll as well as the procambial and cambial tissue

6. how organized?
epidermal, mesophyll and vascular tissues are organized and develop in specific ways.
What is the control mechanism?

7. structural & functional tissue
dermal
non- vascular
vascular
dermal

8. two meristems
marginal
sub marginal

9. deriving procambium
marginal
sub marginal
procambium

10. Esau’s developmental outline
upper epidermis
palisade
parenchyma
bundle sheath
procambium
Vascular bundles MI SI
bundle sheath
The diagram above, illustrates (but not necessarily the strict sequence) the steps involved in a typical
mesomorphic dicotyledonous leaf.
The diagram can be modified to accommodate all leaf forms – including those in which the bundle sheath surrounds a mestome sheath
which may enclose the underlying vascular tissue entirely or partially. You are encouraged to read the following articles which deal with the ontogeny of the mestome sheath.
Dengler, N.G., Dengler, R. and Hattersley, P.W. (1985) Differing in ontogenetic origins of PCR ("Kranz") sheaths in leaf blades of C4 grasses (Poaceae). Amer. J. Bot. 72, (
Soros, C. and Dengler, N. (2001) Ontogenetic Derivation and Cell Differentiation in Photosynthetic Tissues of C3 and C4 Cyperaceae. American Journal of Botany 88 (6): Kawamitsu, Y., Hakoyama, S., Agata, W. and Takeda, T. (1985) Leaf interveinal distances corresponding to anatomical types in grasses. Plant Cell Physiol. 26,
middle spongy parenchyma
lower spongy parenchyma
lower epidermis
see
notes below

11. no middle spongy layer? upper epidermis palisade parenchyma
bundle sheath MI SI
procambium
vascular bundles
bundle sheath
lower spongy parenchyma
lower epidermis

12. add a mestome sheath upper epidermis palisade parenchyma bundle sheathSI
The mestome sheath is derived from the procambium, and forms the outermost layer of the vascular bundle.
The mestome sheath may become lignified at maturity, and will normally contain a high frequency of plasmodesmata at the outer bundle sheath, and to the inner vascular parenchyma cells.
Useful references:
Dengler, N.G., Dengler, R. and Hatterley, P.W. (1985) Differing in ontogenetic origins of PCR ("Kranz") sheaths in leaf blades of C4 grasses (Poaceae). Amer. J. Bot. 72,
Dengler, N. and Kang, J. (2001) Vascular patterning and leaf shape. Current Opinion in Plant Biology 4,
procambium
vascular bundles
mestome sheath
bundle sheath
lower spongy parenchyma
Notes
lower epidermis