FBS 10 (LEC) 4

Shoot apical meristem (SAM)

Dome-shaped mass of dividing cells at the tip of the shoot.

Apical/terminal bud

Structure near the shoot tip that lengthens the shoot.

Axillary bud

Structure that may form a lateral branch or vegetative shoot.

Apical dominance

Phenomenon where the apical bud inhibits growth of axillary buds.

Break of apical dominance

Condition when axillary buds grow after removal of the terminal bud, making the plant bushy.

Leaf primordia

Leaf structures arising on the flanks of the apical meristem.

Axillary bud primordia

Groups of meristematic cells left at leaf primordia that later form axillary buds.

Protoderm

Primary meristem that gives rise to the epidermis.

Ground meristem

Primary meristem that gives rise to cortex and pith.

Procambium

Primary meristem that gives rise to primary xylem and primary phloem.

Epidermis

Outermost cell layer derived from protoderm, forming the protective covering.

Guard cells (stomata)

Openings in the epidermis that regulate gas exchange.

Trichomes

Epidermal outgrowths that may serve protective or absorptive functions.

Cuticle

Waxy outer layer secreted by epidermal cells to prevent water loss.

Cortex

Region of the stem just inside the epidermis, sometimes photosynthetic.

Pith

Central core of the stem, sometimes hollow, mostly used for storage.

Primary xylem

Vascular tissue that transports water and minerals.

Primary phloem

Vascular tissue that transports sugars and organic compounds.

Ring (cylindrical arrangement)

In dicots, vascular bundles are arranged in this pattern.

Scattered

In monocots, vascular bundles are arranged in this pattern.

Secondary xylem

Secondary tissue formed from vascular cambium, also called “wood.”

Periderm (bark)

Outer protective covering formed from cork cambium and secondary phloem, known as “bark.”

Rhizome

Modified stem that grows underground and stores nutrients.

Spine

Modified stem that appears as a sharp, pointed structure for defense.

Synergy of root and shoot systems

The interaction where the shoot system provides sugars while the root system supplies water and minerals.