1 / 27

The Root: Structure and Development

The Root: Structure and Development. Chapter 24. Roots. Root - the descending axis of a plant, normally occurs below ground. Root Functions Anchorage. Absorption of water, minerals, inorganic ions. Storage. Conduction. Two types of root systems

winona
Download Presentation

The Root: Structure and Development

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Root: Structure and Development Chapter 24

  2. Roots • Root- the descending axis of a plant, normally occurs below ground. • Root Functions • Anchorage. • Absorption of water, minerals, inorganic ions. • Storage. • Conduction. • Two types of root systems • Taproot- a stout, tapering main root from which smaller lateral roots arise; deep; gymnosperms & dicots. • Fibrous- arise from stem similar to lateral roots; shallow; monocots.

  3. Root Penetration • Root depth and distance depend on soil: • Moisture • Temperature • Composition • FeederRoots- those involved in uptake of water and minerals, occur usually in the upper 1 meter of the soil.

  4. Rootcap- a thimblelike mass of parenchyma cells that covers the root and secretes mucigel.

  5. The epidermis in young roots absorbs water and minerals. • Root Hairs- tubular extensions of epidermis that facilitate absorption.

  6. Primary Development of the Root Tip • Region of cell division • ~1 mm in length. • Apical meristem. • Region of cell elongation • ~2 mm in length. • Cells elongate, functional xylem starts to develop and phloem is mature. • Region of maturation • ~2 mm-?? mm in length. • Root hairs are produced, functional xylem and phloem are present.

  7. Eudicot versus Monocot Roots • Eudicots • Vascular cylinder solid. • Cortical cells sometimes retained for life, but some shed due to secondary growth. • Monocots • Vascular cylinder in ring with pith. • Cortical cells retained for life, because they lack secondary growth.

  8. Cortex and Vascular Cylinder • Cortex- ground tissue (cells between the vascular cylinder and the epidermis) occupies the greatest area of the root. • Vascularcylinder- xylem, phloem, and pericycle. • Pericycle- 1 or more layers of nonvascular cells surrounding the vascular tissue of the root. • Intercellularspaces- empty spaces among cortical cells; essential for aeration of the root cells. • Epidermis- the outermost layer of cells (the root). • Exodermis- the outermost layer of the cortex, 1 or more cell layers in depth; casparian strip in walls. • Endodermis- the innermost layer of the cortex, lacks intercellular spaces; casparian strip in walls.

  9. Casparian Strip • CasparianStrip- a bandlike region of the primary cell wall containing suberin and lignin. Impermeable to water and ions, prevents water loss and attack by microorganisms.

  10. Lateral Roots Arise from the Pericycle

  11. Effects of Secondary Growth on the Primary Body of the Root • Secondary Growth in roots consists of: • 1) Secondary vascular tissues (secondary xylem and phloem) from vascular cambium. • 2) Periderm, mostly cork tissue from cork cambium.

  12. Root Modifications • AerialRoots- roots produced from above ground structures. • AirRoots- negatively gravitropic roots that aerate the root system. • FleshyRoots- specialized storage organs consisting of parenchyma and vascular tissue. Carrot, sweet potato, sugarbeet.

  13. FleshyRoot- an adaptation for food storage. Sugarbeet

  14. Sweet Potato

More Related