Botany Chapter 6 Stems

Node

The area of a stem where a leaf attaches.

Internode

The region between nodes.

Blade

The broad, flat part of a leaf.

Petiole

The a stalk that attaches the leaf blade to the plant stem.

Axil

The angle between the petiole and the stem that contains a bud.

Deciduous

Trees that lose their leaves in autumn and grow new leaves in spring.

Leaf Scar

A mark left on a twig from where a leaf grew.

Bundle Scar

Tiny holes within a leaf scar caused by the xylem and phloem that was within the leaf that previously grew there.

Young Stem Development

Protoderm, procambium, and leaf primordia.

Protoderm

Becomes epidermis

Procambium

Becomes vascular cambium

Leaf primordia

Become leaves

Pith

Parenchyma tissue in the center of the stem. Used for food storage.

Cortex

Parenchyma tissue between the epidermis and endodermis. Also used for food storage.

Trace

A strand of xylem and phloem in a leaf or bud that branches off of the main cylinder of xylem and phloem.

Leaf Gap

A thumbnail shaped gap where a leaf trace occurs and which gets filled with parenchyma tissue.

Bud gap

A thumbnail shaped gap where a bud trace occurs and which gets filled with parenchyma tissue.

Vascular Cambium

A lateral meristem that produces the xylem and phloem, which increases the girth of the stem.

Cork Cambium

An outer layer of cambium that adds cork cells to the outer bark.

Cork Cells

Box-shaped cells loaded with suberin, which makes them waterproof.

Lenticel

Pocket of loosely arranged, suberin-impregnated parenchyma cells protruding through the periderm to allow gas exchange.

Stele

The central cylinder of a plant comprised of the xylem, phloem, and pith.

Cotyledon

A seed leaf in a germinating seed.

Monocot

A plant with a single seed leaf.

Dicot

A plant with two seed leaves.

Vascular Bundle

A patch of xylem and phloem within the stele.

Heartwood

Older, darker, dead wood at the center of a tree.

Springwood

Growth ring produced in spring by large vessel elements in xylem.

Summerwood

Growth ring produced in summer by smaller vessel elements in xylem.

Sapwood

The lighter, living, functioning wood close to the cambium in a tree.

Bark

The outer protective covering of a tree.

Vascular Ray

Rows of parenchyma cells in xylem or phloem that conduct fluids laterally.

Tyloses

Protrusions of adjacent parenchyma cells into conducting cells of xylem. Prevent conduction of water and enable accumulation of resins and gums that darken the heartwood

Laticifers

Specialized ducts that secrete latex that may help heal wounds in the tree.

Resin Canals

Tube-like canals in xylem that secrete resin.

Common in conifers.

Monocot stem arrangement

No vascular cambium or cork cambium.

Typical monocot vascular bundle arrangement

Two large xylem vessels, several smaller xylem vessels, and vascular bundle surrounded by sheath of sclerenchyma cells.

Rhizome

A horizontal, below-ground stem used for food storage.

Stolon

An above-ground horizontal stem with long internodes. Sometimes called a "runner."

Tuber

Swollen, fleshy, underground stem used for food storage.

Bulb

A large bud surrounded by numerous fleshy leaves, with a small stem at lower end.

Corm

Stem tissue with papery leaves that resembles and functions like a bulb.

Cladophyll

Flattened, leaf-like stem

Tendrils

Specialized stems that coil and grasp allowing a plant to grow and spread.

Wood Facts

50% of wood weight in a living tree is from water. Density = weight/unit volume. Durability = ability to withstand decay.

Knot

The base of a lost branch that has become covered with tissue over time.

Lumber

Solid wood used in construction.

Veneer

Thin sheet of desirable wood glued to cheaper lumber.

Pulp

Pulverized wood used for paper and other products.