DEVELOPMENT OF LEAF

Leaf is formed Exogenously while lateral roots are endogenous in origin.
Leaf Primordia is the earliest stage of development of leaf.
Leaf primordium generally begins as a slight bulge/Ridge on the flank of the SAM
In Dicots, the SAM is found between the two cotyledons and is the site of leaf initiation.
In the region of SAM there are ridges that broaden out to form emerging Leaf Primordia. These ridges are also called as Leaf Buttresses alternate in a genetically determined pattern called as Phyllotaxy.
During the formation of leaf primordia there is change in size and form of ridges that ultimately forms leaf.
The time between the formation of these successive primordia and during which these changes in form and size occurs is called Plastochron.
In Monocots shoots typically do not show tip growth or have a shoot apical meristem.
Instead, stem and leaf growth are driven by mitosis in a loose arrangement of meristematic cells that are scattered throughout a zone called an intercalary meristem.
Intercalary meristems are found between the nodes or at the base of leaves.

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