Quiz 2: roots Flashcards
what are 3 functions of roots
- support/ anchorage
- water and mineral uptake
- storage of excess nutrients
what are primary roots
-roots that grow directly from the main root radicle that emerges from seeds
describe tap roots
what plant use this
single primary root is dominant provides main support for tree and anchors it firmly to ground *not all trees have one -gymnosperms and most dicots -then branching occurs
describe fibrous root system
what plants use this
network of similarly sized roots, - masses of fine feeding roots close to ground surface
-found in monocots
describe secondary (lateral) root system
emerges from primary root
-sometimes adventitious roots that emerge from stems and leaves
describe fibrous roots
a) characteristics (2)
b) pros
c) cons
a) shallow- 30cm-2 m of surface
- wide coverage area
b) - erosion control
c) lower tolerance for draught
- poor anchorage for large plants
role of lateral roots
- help anchor and support trunk—> may have wide spread (father than drip line)
define deeply descending roots “sinkers”
grow downward from lateral roots
describe tap roots
a) characteristics ( 2)
b) pros
c) cons
a) little branching off main root
- provides main support for tree and anchors it firmly to ground
* not all trees have one
b) good anchors
- nutrient storage
- better drought tolerance
c) none?
describe feeder roots
- major function is absorption of water and minerals
- located throughout entire canopy of tree
describe growth patterns of tree roots
> 50% roots grow beyond trip line
-can grow as deep and tree is tall and wide as tree is tall
describe secondary specialized root system
-adventitious roots- coming from outside , unusual place
what are 3 type of adventitious roots?
aerial: orchids, ivy
butressing: root flares for extra support
prop: corn –> extended stem for extra support
why do excess nutrients get stored in roots
- protection from predators- insects, larger herbivores
2. protection from climatic conditions –> seasonal dormancy
what is (arguably) primary purpose of root
water/ mineral uptake
where does mineral/ water uptake occur?
root hair, located just behind root tip
define root hair
extensions of epidermis
- where 95% uptake water and mineral takes place
- more surface area = greater potential uptake
define cortex
central core where vascular system is (xylen and phloem), between epi and endodermis
endodermis
encloses vascular tissue
pericycle
just inside endodermis
- area which branch roots start
xylem
- water conducting tissue
- located more centrally
phloem
- food conducting tissue
- located closer to exterior of cortex
epidermis
-outer layer of cells (skin)
zone of elongation
where cells expand in length
apical meristem
-region of actively dividing cells at root tips
root cap
-protection for delicate root tip
what are 2 mutualistic relationships a plant root may have
- hyphae of fungus
2. bacteria rhizobia
describe mycorrhizal fungus relationship with plants
- plant gets dissolved mineral ions released by fungus ( and increase water access)
- fungus gets carbs from plant
what is the most important nutrient for the biosphere
nitrogen
what is nitrogen mostly present as in earth atm.
79% N2 gas –> not usable for plants
how can plants uptake N?
- N fixation –> combined into ammonium (NH4) or nitrate (NO2)
- means N is limiting factor for growth
describe mycorrhizal bacteria mutualistic relationship
- with legumes, enter N fixing nodulation with bacteria rhizobia
- results in formation of root nodules
- provides major source of available N in biosphere
how does branch root form
- emerges from pericycle
- pushes aside endodermis, cortex and epidermis
describe formation of lateral root
- originates in pericycle ( outermost layer of vasuclar cylinder of root) and grows out through the cortex and epidermis
osmosis
movement of water from area of high to low concentration
capillary water
water held in tiny spaces between soil particles or between plant cells
turgid
swollen and firm due to internal water pressure
describe general movement of water and 2 different paths
- plant root epidermis –> cortex –> endodermis –> pericycle –> tracheary elements (xylem)
- apoplast = inbetween cells or symplast = through cells
describe process is which plant cells uptake water (2)
- roots hairs draw water into cells via osmosis
- when epidermal cells are turgid excess water is discharged bwteen cortex cells and works way into xyxlem –> works for short distances
- roots hairs draw water into cells via osmosis
- water is moved longer distances via transpiration
- water gets pulled up roots system b/c water exiting leaves
what are 3 needs of root system
what are they dependent on?
- water
- oxygen
- micronutrients
- soil structure and composition
describe soil structure of sand
- large particle size
- large spaces b/ween particles
- poor water holding capacity
describe soil structure of clay
- fine particles
- small spaces b/ween particles
- excellent water holding capacity
describe aeration
- allow circulation air to reach/ penetrate something
2. change liquid to gas ex carb drinks
describe compression
- compression of particle to make dense mass
what are 2 factors make up soil composition
1 . nutrient level: amount of micro and macro nutrients in soil –> slat levels affect water uptake
2. pH: percent hydrogen–> measure of relatively acidity or alkalinity , determines availability of nutrients
