Stem (Primary Growth) and Stele Types

Flashcards about stem primary growth and stele types.

Stem

The axial organ of the shoot with functions including support, conduction, photosynthesis, reproduction, and storage.

Nodes

Places on the stem where leaves are/were attached.

Internodes

The region between nodes on a stem.

Shoot Apical Meristem (SAM)

Found at the tip of the stem.

Axillary Buds

Found in the axils of the stem.

Phytomer

Repeating units produced by the apical meristem, consisting of a node and its attached leaf, an internode, and a bud.

Dermal, vascular, and ground tissue

The three tissue systems of the stem.

Primary phloem

The outer layers of the procambium become this.

Primary xylem

The inner layers of the procambium become this.

Stele

Core of the plant axis (root and stem) including vascular system, interfascicular regions, gaps, pith, and pericycle.

Protostele

Solid xylem center surrounded by phloem.

Siphonostele

Center composed of pith tissue, surrounded by xylem and phloem.

Haplostele

The xylem core is a solid cylinder surrounded by phloem.

Actinostele

The xylem has radiating arms or protuberances.

Plectostele

The xylem core is cylindrical but has masses of phloem interspersed within it.

Ectophloic Siphonostele

Central pith is surrounded by a cylinder of xylem, and phloem surrounds the xylem on the outside.

Amphiphloic Siphonostele

Central pith is enclosed by a cylinder of xylem with phloem surrounding the xylem on the inside and outside.

Eustele

A dissected ectophloic siphonostele.

Dictyostele

A dissected amphiphloic siphonostele.

Atactostele

Scattered vascular bundles with no central pith.

Collateral vascular bundle

Phloem is external to xylem.

Bicollateral vascular bundle

Has both external and internal phloem.

Amphivasal vascular bundle

Phloem surrounded by xylem.

Amphicribral vascular bundle

Xylem surrounded by phloem.

Dictyostele

Vascular strands interconnected such that several distinct bundles are observed in a stem cross-section, separated by leaf gaps.

Polycyclic Dictyostele

One stele occurs within another stele.

Solenostele

An amphiphloic siphonostele in which successive leaf gaps are few and considerably distant from one another.

Leaf gaps

Discontinuities in the vascular cylinder where leaf traces depart from the stele.

Leaf traces

Vascular bundles supplying leaves.

Intra-stelar Origin Theory

Cells in the center of the protostele did not mature into tracheids, leading to the formation of parenchymatous central pith.

Extra-stelar Origin Theory

Siphonostele evolved from the invasion of parenchymatous cells of the cortex into the stele.

Horsetail Stele

Collateral bundles arranged around a central air cavity (pith canal).