A shoot apical meristem is a dome-shaped mass of dividing cells at the shoot tip.
Axillary buds develop from meristematic cells left at the bases of leaf primordia.
Lateral shoots develop from axillary buds on the stem’s surface.
In most eudicots, the vascular tissue consists of vascular bundles that are arranged in a ring.
Shoot apical meristem
Organization of primary tissues in young stems
pith to cortex
Cross section of stem with vascular bundles forming
a ring (typical of eudicots)
Cross section of stem with scattered vascular bundles
(typical of monocots)
In most monocot stems, the vascular bundles are scattered throughout the ground tissue, rather than forming a ring.
Tissue Organization of Leaves
The epidermis in leaves is interrupted by stomata, which allow CO2 exchange between the air and the photosynthetic cells in a leaf.
Each stomatal pore is flanked by two guard cells, which regulate its opening and closing.
The ground tissue in a leaf, called mesophyll, is sandwiched between the upper and lower epidermis.
Below the palisade mesophyll in the upper part of the leaf is loosely arranged spongy mesophyll, where gas exchange occurs.
The vascular tissue of each leaf is continuous with the vascular tissue of the stem.
Veins are the leaf’s vascular bundles and function as the leaf’s skeleton.
Each vein in a leaf is enclosed by a protective bundle sheath.
(a) Cutaway drawing of leaf tissues