🔬 Anatomy of Flowering Plants

1. Plant Tissues

A tissue is a group of cells having a common origin and usually performing a common function.

Cells with active cell division.

Apical Meristem: Occurs at tips of roots and shoots. Produces primary tissues.
Intercalary Meristem: Occurs between mature tissues (e.g., in grasses).
Lateral Meristem: Cylindrical meristems responsible for secondary growth (e.g., vascular cambium, cork cambium).

Cells that have lost the ability to divide.

Parenchyma: Thin-walled, living cells. Forms major bulk. Photosynthesis, storage.

Collenchyma: Living cells thickened at corners (pectin/cellulose). Provides mechanical support to growing parts.

Sclerenchyma: Dead, highly thickened lignified walls. Fibres and sclereids. Mechanical support.

Xylem: Conducts water/minerals from roots to stem/leaves. Elements: Tracheids, vessels, xylem fibres, xylem parenchyma.

Phloem: Transports food materials. Elements: Sieve tube elements, companion cells, phloem parenchyma, phloem fibres.

Epidermal: Epidermis, stomata, epidermal appendages (trichomes and hairs).
Ground: All tissues except epidermis and vascular bundles. Consists of cortex, pericycle, pith, and medullary rays.
Vascular: Complex tissues (xylem and phloem). Arranged in bundles. (Radial in roots, Conjoint in stems/leaves).

The increase in girth (thickness) of dicot stems and roots, driven by lateral meristems.

Vascular Cambium: Cuts off secondary xylem towards the inside (wood) and secondary phloem towards the outside.

Cork Cambium (Phellogen): Forms cork (phellem) on the outside and secondary cortex (phelloderm) on the inside.