Primary and Secondary Growth in Roots and Stems

Primary Meristem

Initial growth tissue producing primary tissues.

Root Apical Meristem

Undifferentiated cells at root tip.

Procambium

Meristem producing vascular tissue.

Cortex

Tissue between epidermis and vascular tissue.

Epidermis

Outermost layer of cells in roots.

Root Hair

Extensions of epidermal cells for absorption.

Zone of Elongation

Region where root cells lengthen.

Zone of Cell Division

Area of active mitotic cell division.

Root Cap

Protective structure covering root tip.

Dermal Tissue

Tissue forming protective outer layer.

Ground Tissue

Tissue filling space between dermal and vascular.

Vascular Tissue

Tissue responsible for transport of nutrients.

Stele

Central vascular cylinder in roots.

Pericycle

Layer of cells outside vascular tissue.

Xylem

Vascular tissue transporting water and minerals.

Phloem

Vascular tissue transporting sugars and nutrients.

Endodermis

Innermost layer of cortex regulating water flow.

Leaf Primordia

Developing leaves from apical meristem.

Axillary Bud

Potential branch forming from meristematic cells.

Scierenchyma

Supportive tissue with thickened cell walls.

Vascular Bundle

Cluster of xylem and phloem in stems.

Epidermis

Outer layer derived from protoderm meristem.

Cortex

Ground tissue located inside the epidermis.

Vascular Bundles

Strands of xylem and phloem in stems.

Pith

Central ground tissue in dicot stems.

Rays of Ground Tissue

Connects cortex and pith in stems.

Collenchyma Cells

Supportive cells found beneath the epidermis.

Sclerenchyma Cells

Fibers providing additional support in stems.

Monocot Stem

Characterized by scattered vascular bundles.

Mesophyll Region

Tissue between upper and lower epidermis.

Palisade Layer

Columnar-shaped cells in the mesophyll.

Spongy Layer

Irregular cells with air spaces in mesophyll.

Stomata

Pores for gas exchange on leaf surfaces.

Guard Cells

Specialized cells regulating stomatal openings.

Waxy Cuticle

Layer preventing water loss from leaves.

Transpiration

Water loss from plants through stomata.

Vascular Cambium

Meristem producing secondary xylem and phloem.

Cork Cambium

Meristem forming protective outer covering.

Secondary Growth

Increase in stem girth from lateral meristems.

Xylem

Tissue transporting water and minerals upward.

Phloem

Tissue transporting sugars downward in plants.

Veins

Structures connecting xylem and phloem in leaves.

Vascular cambium

Meristematic tissue producing secondary xylem and phloem.

Secondary xylem

Wood tissue formed from vascular cambium growth.

Secondary phloem

Tissue for transporting nutrients in plants.

Cork cambium

Meristematic tissue producing cork cells externally.

Cork

Protective layer formed by dead cork cells.

Periderm

Outer protective tissue layer, includes cork.

Vascular rays

Radial structures for transporting nutrients and water.

Heartwood

Inner wood, older, non-functioning secondary xylem

Sapwood

Outer wood, secondary xylem still functioning in transport of water and minerals (xylem sap)

Annual growth rings

Layers indicating yearly growth patterns in trees.

Early wood

Larger diameter cells formed in spring growth.

Late wood

Thicker-walled cells formed in summer growth.

Bark

All tissues outside the vascular cambium.

Lenticels

Small openings in periderm for gas exchange.

Tracheids

Long, narrow cells for water conduction in xylem.

Vessel elements

Shorter cells facilitating efficient water transport.

Fibers

Supportive cells with thick lignified walls.

Cortex

Tissue between epidermis and vascular tissues.

Epidermis

Outer protective layer of plant stems.

Primary growth

Initial growth phase, lengthening stems and roots.

Secondary growth

Growth increasing stem and root thickness.

Pericycle

Layer of cells forming cork cambium in roots.