Ch. 5 Roots Part 2 Flashcards
Cortex seen in roots
- Tissue just inside root epidermis
- Parenchyma cells
- Stores food
- Between epidermis and inner tissues
eventually suberized, not as thin anymore
Structures include endodermis, passage cells, vascular cylinder, and pericycle
Endodermis
single layer of cells surrounding the vascular tissue in roots and some stems; inner boundary or cortex
o Cells have casparian strips
Casparian strips
band of suberin around the radial and transverse walls of endodermal cell
Prevent water passing through cell walls
Forces to go through plasmodesmata, endodermal cells
Passage cells
o Endodermal cells
Suberin and lignin
o Thin-walled cell of endodermis
Vascular cylinder
o Tissues within endodermis
o Core of tissues, including xylem and phloem, that lies to the inside of the endodermis
o Primary xylem and primary phloem cells
Pericycle
o One cell wide usually
o Tissue sandwiched between the endodermis and phloem of the root
o Site of origin of lateral roots
o Outer boundary of vascular cylinder
o **cork cambium arises In pericycle
Describe specialized roots in potatoes and yam
o Potatoes and yam
Store carbohydrates and starch
Extra cambial cells develop in parts of xylem of branch roots
Produce large numbers of parenchyma cells
Provides food storage areas
Describe the specialized roots: water storage
Pumpkins (some)
- Arid region, little precipitation
- Water held in roots of plants when soil inadequate
Propagative roots
Have Adventitious buds: appearing in places other than stems
Produce aerial stems (suckers)
Apple, pear trees produce suckers
Pneumatophores
Black mangrove
* Spongy roots
* Extend above water surface, enchance gas exchange
Spongy root extedning above the surface of the water, produced by a plant growing in water
Pneumatophores facilitate ozygen absorption
Aerial roots
Non-parasitic plants attached to tree branches grow unconnected to the ground often have these
They extend into the air
Contractile roots
Roots of some bulb plants
Can pull plant depper into soil each year
Mycorrhizae
Greatly aid absorption of nitrogen
Symbiotic associations between roots of plant and fungi
Endotrophic: do invade host plant cells
Ectotrophic: do NOT invade plant cells
Root nodules
specialized tissues that surround beneficial bacteria
Symbiotic relationship with plants allows plants to utilized gaseous nitrogen
Plants cannot covert free nitrogen to usable form
Few species of bacteria produce enzymes that converts nitrogen nitrates and other nitrogenous substances readily absorbed by roots
Contain large numbers of nitrogen-fixing bacteria
Erosion
Example: excessive rain falls on developing soil
Flow of water through soil can lead to loss of important minerals
Loams
Best agricultural soils
Mixture of sand, clay, and organic matter
Best environment is drainage without erosion (so non-flooded plants that are still getting minerals from environment)
Name the types of water found in soil
Hygroscopic water, gravitational water, and capillary water
Hygroscopic water
- Physically bound to soil particles and unavailable to plants
- Acts this way, since it’s a polar molecule
Gravitational water
- Drains out of pore spaces after a rain
Capillary water
- Plant’s main dependent, after rain and drainage of gravitational water
- Water held against the force of gravity in soil pores
- Determined by structure and organic matter, by density and type of vegetation, and by the location of underground water tables
