physiology

Question 1

osmosis and turgor pressure

Answer 1

hypertonic inside, and lots of water present water will flow towards this direction. Cell will swell until it cant anymore, will pres against cell wall with osmotic pressure. This means cell has high turgor pressure (when high water is around)

If plants hypotonic, the water will flow out and the cell will collapse.

PASSIVE

Question 1

plasmolysis

Answer 1

contraction of the protoplast of a plant cell as a result of loss of water from the cell. PASSIVE

Question 2

imbibition

Answer 2

Coming into contact with water and swelling up.
the absorption of one substance by another, in particular the uptake of water by a plant or seed. PASSIVE

Question 3

active transport

Answer 3

water is passive in plant, others are not passive.
Occurs at cell membrane, either putting into tonoplast or pulling from environment. Req ATP and cellular transport channels

Driver is the proton pump by pumping H+ out of cell, up a gradient.

Potassium is needed in the cell, higher than sodium level in the plant. Potassium goes down charged gradient from + to - to get into cell.

Nitrate is - charged, so natural tendency is to leave the cell. Will bring in nitrate if H+ is attached.

Will take in sugars through a co-transport system, brings in sugar if attached to H+

Question 4

Living osmotically in unfavorable environments

Answer 4

Ex: black mangrove, saltbrush, salicornia

fill tissues with amino acids so that sodium wont pass inside osmotically, so still hypertonic to the saltwater around them.

salicornia (pickle weed): concentrate in one spot and then get rid of that spot of the plant

Question 5

water route in evapotranspiration

Answer 5

main route in which water moves through plant, water comes into roots via root hairs through cortex, goes through endodermis, gets into xylem tissue and goes up through xylem, root, stem, branch, vascular bundles in leaves and evaporates through stomata.

Question 6

what the water is used for

Answer 6

• kepps cells supplied
• raw material for photosynthesis
• capture CO2
• cooling plant

Question 7

how much water is involved in evapotranspiration

Answer 7

• a lot
• avg birch 50 gall x 4 a day
• olive tree about 50 gall a day, but can get by with about 5 gall a day
• every 1 kg of organic material, about 500 kg of water

Question 8

what process moves the water up through the plamt

Answer 8

• almost entirely a passive process
• 10x better than a “perfect pump”
• takes place mostly in dead cells (xylem)

Question 9

ideas about how trees sucking up water works

Answer 9

• capillary action (charged water will pull up), smaller tube you have, can pull up water a lot
• root pressure (pericycle transports water to xylem, cells which causes pressure and water to rise, like guttation)

both of these are only good for a few meters

• cohesion tension theoruy

Question 10

cohesion tension theory

Answer 10

• strong cohesion of water together, start at the top of a plant, water evaporates through stomata. get a meniscus in the corner of the cells, causes a (tension) pull of water out of the cell adjacent because air spaces not smooth.
• water film on spongy mesophyll shrinks
• meniscus draws water from mesophyll cells

(cohesion causes tension)
evaporation through leaf stomata

transpiration
- water potential of cell goes down, drops to lower of the cell next to it.
- water drawn from xylem in leaf vein
- water pulled up molecule by molecule through xylem

water passage into root:
- epidermic root hairs are water permeable, water passively enters into cell
- apoplastic (not entering cytoplasm), or symplastic route
- only symplastic at endodermis
- active transport of K+ in pericycle

Question 11

evidence supporting cohesion-tensio

Answer 11

• transpiration best at low humidity, open stomata
• negative pressure in xylem
• plant stems contract during transpiration
• captivation “pops” in xylem during transpiration

Question 12

problems with cohesion-tension

Answer 12

• water is not as cohesive as is needed
• requires extreme negative pressures in xylem
• captivation should cause irreversible embolism
• many trees function near cavitation limit (areas where not much water)2

Question 13

Alt model: compensating pressure

Answer 13

• living phloem and rays near xylem, which have positive pressure
• root pressure and evaporation work as in other model
• live cells provide static pressure to xylem
• after cavitation, water from live cells repair embolism

Question 14

supporting evidence for compensating pressure model

Answer 14

• flash freezing shows many embolized tracheids/vessels
• embolism highest in morning, repairs in afternoon
• sugars are in phloem, starches to sugars in rays
• micrographs

Question 15

regulation of the rate of transpiration

Answer 15

• relative humidity of the atmosphere
• temperature
• opening and closing of the stomata: presence of light… diurnal opening, CAM photosynthesis (nocturnal opening)
• bordered pits in vessels

Question 16

stomata

Answer 16

stomata:
- most plants during day, CAM at night
- presence of water

Question 17

anatoical features of leaves and stomata

Answer 17

stomata in crypts
- epidermal hairs

Question 18

bordered pits in vessels

Answer 18

• contain hydrogels
• hydrogels change flow rate based on ion content, shrinks bordered pits to promote water flow

Question 19

transport of solutes through phloem: pressure-flow hypothesis

Answer 19

• organic solute into sieve tubes by active transport
• water enters sieve tube by osmosis
• turgor pressyre drives bulk flow
• at sink, osmotic pressure low, water flows toward
• excess water enters xylem

Question 20

notes about pressure flow hypothesis

Answer 20

• solutes can flow different directions in different sieve tube elements
• does cytoplasm flow?
• does not explain movement of hormones

Question 21

main macronutrients

Answer 21

N, P , K Ca, Mg, S