Types of Plant Tissues

Types of Tissues

• Tissues are groups of cells with a common origin.
• Tissues are classified structurally into simple (one cell type) and complex (multiple cell types, like xylem and phloem).
• Tissues are also classified functionally into meristematic (dividing cells) and permanent (developed cells).
• Meristematic cells are living and have the ability to divide and form new cells.
• Permanent tissues are living or non-living, with specialized structure to perform specific functions.
• Apical meristem is the growing tip of the stem.

Plant Tissues (Diagrammed)

• Different meristems (ground, procambium, and protoderm) give rise to different permanent tissues (primary xylem, primary phloem, ground tissue, and epidermis).
• Secondary tissues (secondary xylem, secondary phloem, and periderm) develop from the vascular cambium.

Vascular Cambium

• The vascular cambium is a lateral meristem that makes secondary vascular tissues.
• It is formed of fusiform and ray initials.
• Fusiform initials are elongated and produce the axial system of secondary vascular tissues.
• Ray initials are isodiametric and form the parenchyma rays.
• The cambial zone is composed of axial and ray systems, with a single layer of cambial initials.
• Cambium cells divide either periclinally (producing new xylem or phloem cells) or anticlinally (increasing cambium diameter).
• Vascular cambium can be storied (stratified) or non-storied.

Ray Initials

• Ray initials divide periclinally, forming radial files of cells (parenchyma) towards the outside (secondary phloem) and inside (secondary xylem).
• Ray initials can also divide anticlinally in plants with biseriate or multiseriate rays.
• Vascular rays (ray parenchyma) are created from ray initials.