Summary

This chapter traced a flowering plant's internal structure from its dividing meristems through to its fully differentiated organs, and compared that structure between dicots and monocots at every level.

Meristems and permanent tissues. Apical, lateral and intercalary meristems -- distinguished by position -- produce the cells that differentiate into the permanent tissues: parenchyma, collenchyma and sclerenchyma (simple tissues, one cell type each) and xylem and phloem (complex tissues, each built of several cooperating cell types -- tracheids, vessels, fibres and parenchyma in xylem; sieve tube elements, companion cells, fibres and parenchyma in phloem).

Tissue systems. The epidermal system (epidermis, stomata, trichomes/root hairs), the ground system (cortex, pith, mesophyll) and the vascular system (xylem and phloem, arranged radially in roots or conjointly in stems and leaves) recur in every organ, though their detailed make-up differs from organ to organ.

Dicot vs monocot anatomy. A dicot root has few (diarch to hexarch) xylem bundles and a small or absent pith; a monocot root has many (polyarch) bundles and a large pith. A dicot stem arranges a limited number of open (cambium-bearing) bundles in a ring around a large pith, with a collenchymatous hypodermis; a monocot stem scatters numerous closed bundles through undifferentiated ground tissue, with a sclerenchymatous hypodermis. A dicot (dorsiventral) leaf differentiates its mesophyll into palisade and spongy layers and keeps most stomata on its lower surface; a monocot (isobilateral) leaf keeps its mesophyll uniform, spreads stomata on both surfaces, and adds water-conserving bulliform cells. …