~~ Roots ~~ BI 103: Plant-Animal A&P

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Ambrose Maxwell
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1 ~*~ Roots ~*~ BI 103: Plant-Animal A&P Outline: 1. Quiz #1 2. Leaves review 3. Lecture 4. Outside: roots? Plant Anatomy: Vegetative Organs Leaves: Photosynthesis Gas exchange Light absorption Stem: Support Transport Storage Roots: Anchorage Storage Transport Absorption Form = Function 1

Relevance of Roots Sources of food Carrots, sugar beets, turnips, horseradishes, cassava (tapioca), yams, sweet potatoes Spices Sassafras, sarsaparilla, licorice Dyes Drugs Aconite,

2 Relevance of Roots Sources of food Carrots, sugar beets, turnips, horseradishes, cassava (tapioca), yams, sweet potatoes Spices Sassafras, sarsaparilla, licorice Dyes Drugs Aconite, ipecac, Insecticide - Rotenone External Anatomy of a Root Root Cap -protects the apical meristem as the root pushes through the soil. Root Hairs - increase the surface area of the root. 2

43-13 root cap Functions of Roots Roots 1) Anchor the plant 2) Absorb & filter water 3)

3 Internal Anatomy root hair epidermis cortex endodermis of cortex pericycle xylem phloem vascular cylinder apical meristem Fig root cap Functions of Roots Roots 1) Anchor the plant 2) Absorb & filter water 3) Absorb minerals 4) Store surplus sugars 5) Transport water, minerals and sugars and hormones 6) Produce some hormones 7) Interact with soil fungi and bacteria 3

4 Organs: ROOT DICOT MONOCOT 1. Epidermal Epidermis Endodermis Root hairs 2. Meristematic Pericycle 3. Ground Parenchyma 4. Vascular Xylem Phloem Organ: Root 4

5 1. Epidermal Epidermis Endodermis Root hairs 2. Meristematic Pericycle 3. Ground Parenchyma 4. Vascular Xylem Phloem Organ: Root 1. Epidermal tissue in roots A. Epidermis Lacks waxy cuticle B. Root hairs Increase surface area for absorption C. Endodermis Contains casparian strip made of suberin Filters water 5

Dermal tissue in roots Obtaining nutrients Roots extract water and minerals from the soil. Only minerals dissolved in the soil water are available to the plant.

6 Dermal tissue in roots Obtaining nutrients Roots extract water and minerals from the soil. Only minerals dissolved in the soil water are available to the plant. Most minerals are moved into the cells of a plant via active transport. The plants receive oxygen and carbon (from CO2)via diffusion into the leaves, stem and roots. 6

Mineral and Water Uptake by Roots vascular cylinder cortex epidermis air soil particles pericycle endodermis xylem 5 4 water 3 plasmodesmata 2 1 root hair cell walls (a) Pathways of mineral and water

7 Mineral and Water Uptake by Roots vascular cylinder cortex epidermis air soil particles pericycle endodermis xylem 5 4 water 3 plasmodesmata 2 1 root hair cell walls (a) Pathways of mineral and water uptake endodermal cells Casparian strip Fig (b) Endodermal cells, showing the Casparian strip 1. Dermal Epidermis Endodermis Root hairs 2. Meristematic Pericycle 3. Ground Parenchyma 4. Vascular Xylem Phloem Organ: Root 7

mature Forms lateral (branch) roots and part of the vascular cambium Lateral root

8 2. Meristematic A. Pericycle - Outer boundary of vascular cylinder Continues to divide, even after mature Forms lateral (branch) roots and part of the vascular cambium Lateral root formation 1. Epidermal Epidermis Endodermis Root hairs 2. Meristematic Pericycle 3. Ground: Cortex Parenchyma 4. Vascular Xylem Phloem Organ: Root 8

9 3. Ground tissue A. Cortex--Region of ground tissue B. Made up of parenchyma cells between epidermis and vascular cylinder Functions: Mostly stores food In the form of starch 1. Epidermal Epidermis Endodermis Root hairs 2. Meristematic Pericycle 3. Ground: Cortex Parenchyma 4. Vascular Xylem Phloem Organ: Root 9

10 Root Types Tap Fibrous Adventitious - prop - butressed - aerial Taproots and Fibrous Roots Fig

11 Prop Roots Example: Corn - Prop roots support plants in high wind Buttress Roots Stability in shallow soil --Tropical Trees 11

Orchids - Velamen roots, with epidermis several

Contractile Roots Pull plant deeper into the

12 Orchids - Velamen roots, with epidermis several layers thick to reduce water loss Aerial Roots Ivies (English ivy, Virginia creeper) - Aerial roots aid plants in climbing Specialized roots Contractile Roots Pull plant deeper into the soil Example: Trillium ovatum (Family: Liliaceae) 12

13 Specialized roots: Haustoria Parasitic roots Cusucuta spp. Aka Dodder Specialized Roots Pneumatophores In plants with roots growing in water Spongy roots that extend above the water s surface Enhance gas exchange between atmosphere and subsurface roots Mangrove pneumatophores 13

14 Mycorrhizae: A Root Fungus Symbiosis Fig Endomycorrhizal fungi Internal fungal associations Also known as: vasicular-arbuscular 14

15 1. Endomycorrhizal fungi Internal fungal associations 2. Ectomycorrhizal fungi External fungal associations 15

16 2. Ectomycorrhizal fungi External fungal associations Root Nodules House Nitrogen-Fixing Bacteria nitrogen-fixing bacteria within cortex cells of nodules Fig nodule epidermis 16

17 For next week Read Chapter 44- Plant reproduction Homework 1 due! Bring to class Or me 17

Dynamic Plant. Functions of Primary Systems. History of Plants. Plants invaded the land around 400 mya.

Dynamic Plant. Functions of Primary Systems. History of Plants. Plants invaded the land around 400 mya. Dynamic Plant Roots & Water Acquisition Roots 1) Anchor the plant 2) Absorb water 3) Absorb minerals 4) Store surplus sugars 5) Transport water, minerals and sugars and hormones 6) Produce some hormones