Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Introduction to Botany. Lecture 7

Alexey Shipunov

Minot State University

September 12th, 2011

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Outline

1 Questions and answers

2 Poikilo- and homoiohydricity (again)

3 Roots and root systemsRoot morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Outline

1 Questions and answers

2 Poikilo- and homoiohydricity (again)

3 Roots and root systemsRoot morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Outline

1 Questions and answers

2 Poikilo- and homoiohydricity (again)

3 Roots and root systemsRoot morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Previous final question: the answer

What is common between xylem and phloem?

VascularTransportCompoundPrimary and secondary

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Previous final question: the answer

What is common between xylem and phloem?

VascularTransportCompoundPrimary and secondary

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Poikilo- and homoiohydricity

Poikilohydric plants do not save water, they survive evencomplete desiccationHomoiohydric plants save water, they always have similarwater content and do not survive after desiccationCompare with poikilo- and homoiothermic animals (reptilesvs. mammals)

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Origins of poikilo- and homoiohydricityLife on the air and under the sun

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Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

More about plant classification

Mosses (Bryophyta)Ferns and allies (Pteridophyta)Seed plants (Spermatophyta)

Conifers (Pinopsida)Other classes of seed plantsAngiosperms (Magnoliopsida)

Monocots (Liliidae)Other subclasses of angiosperms (“dicots”)

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Root system and shoot system

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Definition and functions

Axial vegetative organ with a function of soil nutritionOther functions:

1 Anchor2 Synthesis3 Storage4 Communication

Features:1 No leaves2 Geotropic growth3 Locates in soil or water

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Types of roots

Primary root: originates from root of seedlingSecondary (lateral) roots: originate from primary rootsAdventitious roots: originate from stems

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Primary root

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Adventitious root

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Root systems

Tap root system: with well developed primary root (mostseed plants)Fibrous root system: without clearly visible primary root(monocots, ferns)

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Fibrous and tap root systems

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Root zones

Root capRoot meristemElongation zoneAbsorption zoneMaturation zone

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Structure of root tip

Initial cells (quiescent center)RAMPrimary meristemsRoot tip growing both forward (root cap) and backward(other root tissues), initial cells determine the direction ofgrowthIf root tip touch barrier, it starts to make rotatingmovements

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Root tip

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Development of tissues

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Origins of tissues

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Periphery of root

Rhizoderm (root epidermis): fast-degrading cellsCortex, which includes also:

Endoderm: 1-cell layer with specialized cell walls, locatedon the border with vascular cylinderAnd (sometimes) exoderm: similar to endoderm but locatedjust under rhizoderm

In some plants (i.e., orchids), cortex modified into velamen

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Root center: vascular cylinder

PericycleVascular tissues located in the centerNo central hollow, central parenchyma presents inmonocot roots

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Anatomy of root

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Pericycle

Long-lived parenchyma cells served as half-meristemInitiates development of lateral rootsContributes to vascular cambiumContributes to cork cambium

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Development of lateral roots

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Vascular bundle

Only one!Has radial (star-like) symmetryProtoxylem arranged in rays, multiple in monocots, 2-4 inother plants

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Radial structure of root vascular bundle in buttercup(Ranunculus sp.

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Root of monocot (Zea mays

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Secondary thickening

Vascular cambium is produced by both pericycle andresidual procambium (located between xylem and phloem)Cork cambium appears in cortex

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Root thickening

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Secondary root (Quercus sp.)

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Summary

Root is an axial vegetative organ with a function of soilnutritionRhizoderm and absorption zone are the mostphysiologically important parts of rootRoot differs from stem having rhizoderm, thick cortex,endoderm, long-lived pericycle and radially arrangedprimary vascular tissuesSecondary thickening make root more similar to stem

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Final question (1 point)

What are adventitious roots?

Shipunov BIOL 154.7

Questions and answersPoikilo- and homoiohydricity (again)

Roots and root systems

Root morphologyAnatomy and development of rootsDevelopment of root tissuesAnatomy of root

Final question (1 point)

What are adventitious roots?

Shipunov BIOL 154.7

Appendix For Further Reading

For Further Reading

J. E. Bidlack, Sh. H. Jansky.Stern’s introductory plant biology. 12th edition.McGraw-Hill, 2011.Chapter 5.

Th. L. Rost, M. G. Barbour, C. R. Stocking, T. M. Murphy.Plant Biology. 2nd edition.Thomson Brooks/Cole, 2006.Chapter 7.

Shipunov BIOL 154.7