Post on 13-Dec-2018
Introduction to Botany
Alexey Shipunov
Minot State University
Lecture 26
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Outline
1 Questions and answersQuiz
2 RootRoot morphologyAnatomy and development of rootsAnatomy and development of rootsOrigins of root tissuesWater transport in rootsDiversity of rootsDiversity of roots
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Outline
1 Questions and answersQuiz
2 RootRoot morphologyAnatomy and development of rootsAnatomy and development of rootsOrigins of root tissuesWater transport in rootsDiversity of rootsDiversity of roots
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Questions and answers Quiz
Questions and answersQuiz
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Questions and answers Quiz
Quizes
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Root Root morphology
RootRoot morphology
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Root Root morphology
Root system and shoot system
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Root Root morphology
Definition and functions
Axial vegetative organ with a function of soil nutritionOther functions:
A AnchorB SynthesisC StorageD Communication
Features:A No leavesB Geotropic growthC Locates in soil or water
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Root Root morphology
Types of roots
Primary root: originates from root of seedlingSecondary (lateral) roots: originate from primary rootsAdventitious roots: originate from stems
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Root Root morphology
Primary root
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Root Root morphology
Adventitious roots
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Root Root morphology
Root systems
Tap root system: with well developed primary root (most seedplants)Fibrous root system: without clearly visible primary root(monocots, ferns)
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Root Root morphology
Fibrous and tap root systems
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Root Anatomy and development of roots
RootAnatomy and development of roots
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Root Anatomy and development of roots
Root zones
Root capRoot meristemElongation zoneAbsorption zoneMaturation zone
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Root Anatomy and development of roots
Structure of root tip
Initial cells (quiescent center)RAMRoot tip growing both forward (root cap) and backward (other roottissues), initial cells determine the direction of growthIf root tip touch barrier, it starts to make rotating movements
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Root Anatomy and development of roots
Root tip
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Root Anatomy and development of roots
Periphery of root
Rhizodermis (rhizoderm, root epidermis): fast-degrading cellsCortex, which includes also:
Endodermis (endoderm): 1-cell layer with specialized cell walls,located on the border with vascular cylinderAnd (sometimes) exodermis (exoderm): similar to endoderm butlocated just under rhizodermis
In some plants (i.e., orchids), cortex modified into velamen
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Root Anatomy and development of roots
Root center: vascular cylinder
PericycleVascular tissues located in the centerNo central hollow, central parenchyma presents in monocot roots
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Root Anatomy and development of roots
RootAnatomy and development of roots
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Root Anatomy and development of roots
Anatomy of root
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Root Anatomy and development of roots
Pericycle
Long-lived parenchyma cells served as half-meristemInitiates development of lateral rootsContributes to vascular cambiumContributes to cork cambium
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Root Anatomy and development of roots
Development of lateral roots
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Root Anatomy and development of roots
Development of lateral roots (step by step)
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Root Anatomy and development of roots
Vascular bundle
Only one!Has radial (star-like) symmetryXylem arranged in rays, multiple in monocots, 2-4 in other plants
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Root Anatomy and development of roots
Radial structure of root vascular bundle in buttercup(Ranunculus sp.)
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Root Anatomy and development of roots
Root of monocot (Zea mays
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Root Origins of root tissues
RootOrigins of root tissues
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Root Origins of root tissues
Development of tissues
In essence, development of tissues in root is analogous to stem.
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Root Water transport in roots
RootWater transport in roots
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Root Water transport in roots
Rhizodermis and osmosis
The existence of root hairs dramatically increases the surface ofabsorptionEvery root hair cell increase the internal concentration of largemolecules, typically organic acidsProcess of concentration requires ATPAs a result, osmosis water flow starts from soil to root cells
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Root Water transport in roots
Endodermis and root pressure
From rhizodermis to endodermis, transport of water is bothsymplastic and apoplasticIn the endodermis cells, Caspari stripes stop apoplastic transportand therefore forced symplastic transportThis is a high-energetic process requires ATPAs a result, water will be pushed up from root: this is the rootpressure
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Root Water transport in roots
Apoplastic and symplastic transport in the root
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Root Water transport in roots
Casparian strips
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Root Water transport in roots
How Casparian strips are working
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Root Water transport in roots
Origin of root pressure
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Root Water transport in roots
Water flow in plants
Plants need water:
To supply photosynthesisTo cool via transpirationTo obtain required minerals
Water flows because of:
Root pressureCapillarity forceTranspiration “suction”
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Root Diversity of roots
RootDiversity of roots
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Root Diversity of roots
Modifications of roots
Adventive buds with root origin (many plants)Mycorrhizae: endotrophic (grasses, orchids) and ectotrophic(trees)Haustoria (parasites like Cuscuta—dodder plant)Root nodules (legumes, Fabaceae family)Contractile roots (Hyacinthus spp.—hyacynth, Taraxacumspp.—dandelion)Storage roots (Daucus carota—carrot, Armoraciaofficinalis—horseradish)Supportive roots (many tropical plants)Defensive, spiny roots (ivy)Photosynthetic roots (some orchids)
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Root Diversity of roots
RootDiversity of roots
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Root Diversity of roots
Endotrophic mycorrhizae in Corallorhiza orchid
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Root Diversity of roots
Ectotrophic mycorrhizae of trees
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Root Diversity of roots
Haustoria of Cuscuta (dodder)
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Root Diversity of roots
Nodulated roots of soybean (Glycine max)
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Root Diversity of roots
Contractile roots of Hyacinthus orientalis
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Root Diversity of roots
Supportive roots of mangrove plants
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Root Diversity of roots
Supportive roots of Pandanus sp.
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Root Diversity of roots
Defensive spiny roots of ivy (Hedera sp.)
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Root Diversity of roots
Photosynthetic aerial roots of orchids
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Root Diversity of roots
Table of modifications
Function Stem Leaf Root
Expansion ... Plantets Adventive buds
Storage ... Succulentleaves
Storage roots
Photosynthesis ... DEFAULT Some aerial roots
Defense ... Spines,scale
Root spines
Support DEFAULT Leaf ten-drils
Aerial and contractile roots
Interactions ... Traps,“stickytapes”,urns
Mycorrhizae, haustoria, nodu-lated roots
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Root Diversity of roots
Summary
Vascular tissues of root is a modified protostele or solenostele (inmonocots).Root hairs, Casparian strips, capillarity and transpiration worktogether to make water flow in plant.Root-related part of water flow is the root pressure.Roots have not less modifications than leaves.
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Root Diversity of roots
For Further Reading
A. Shipunov.Introduction to Botany [Electronic resource].Mode of access:http://ashipunov.info/shipunov/school/biol_154
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