transport in plants

Question 1

land plants

Answer 1

• acquire resources both above and below the ground
• algeal ancestors absorbed water, minerals and CO2 from the surrounding water
• evolution of xylem and phloem in land plants made possible long distance transport of water, minerals and products of photosynthesis
• adaptation= compromises b/w enhancing photosynthesis and minimizing water loss

Question 2

Transport

Answer 2

-The membrane potential (charge separation)
and the proton gradient can drive the
transport of solutes into the cell

-The membrane potential generated by
proton pumps contributes to the absorption
of K+ by root cells

Cotransport occurs when a transport protein couples the diffusion of one solute H+ with the active transport of another NO

A sucrose-H+ cotransporter couples
movement of sucrose against its
concentration gradient with movement of H+ down its electrochemical gradient

Question 3

osmosis

Answer 3

net absorption or loss of water by a cell

physcial pressure of the cell wall pushes back on expanding protplast

Question 4

water potential

Answer 4

pressure and solute concentration affect water potential

Question 5

solute potential

Answer 5

(ΨS) of a solution is proportional to the number of dissolved molecules

also called osmotic potential

Question 6

pressure potential

Answer 6

(Ψp) physcial pressure on a solution

Question 7

water movement

Answer 7

from higher to lower potential

a) addition of solutes reduces potential
b) physical pressure increases potential
c) negative pressure decreases potential

Question 8

major pathway of transport

Answer 8

water and minerals

1. out of the cell across a cell wall into another cell
2. sympplastic route: via continuum of cytosol
3. apoplastic: via cell walls and extracellular spaces

Question 9

bulk flow

Answer 9

movement of fluid transport driven by pressure

through xylem and phloem

Question 10

transport: roots to shoots

Answer 10

after soil solution enters root the surface area of cortical cell membrane enhances uptake of selected minerals

Question 11

transport into xylem

Answer 11

water can cross cortex via symplast or apoplast

waxy casoarian strip of endodermal wall blocks apoplastic transfer from cortex to vascular cylinder

Question 12

bulk flow in xylem

Answer 12

plants lose volume of water form transpiration( evaporation)

-water is replaced by bulk flow of water and minerals called xylem sap from steles of roots to the stems and leaves

Question 13

pushing xylem sap

Answer 13

• at night, transpiration is low so cells pump mineral ions into xylem of vascular cylinder lowering the water potential
• water flows in from root cortex generating root pressure
• positive pressure is relatively weak

Question 14

pulling xylem sap

Answer 14

water pulled by negative pressure
-transpiration produces negative pressure in the leaf, which exerts a pulling force on water in the xylem pulling water down into the leaf
-Water vapor in the airspaces of a leaf
diffuses down its water potential gradient
and exits the leaf via stomata

Question 15

cohesion and adhesion in ascent of xylem sap

Answer 15

• transportational pull on xylem sap is transmitted all the way from the leaves to root tips and even into the soil solution
• facilitated by cohesion of water molecules to each other and adhesion of water molecules to cell walls

Question 16

stomata

Answer 16

stomata open during the day and close at night

• opening is triggered by light, CO2, depletion and internal clock in guard cells
• changes in turgor pressure open and close stomata

Question 17

transport of sugars

Answer 17

photosynthesis transported through phloem

• phloem sap= aqueous solution high in sucrose
• form sugar source to sugar sink

Question 18

sugar source

Answer 18

in an organ that is a net producer of sugar, mater leaves

Question 19

sugar sink

Answer 19

net consumer of sugar, tuber or bulb

Question 20

transport of sugars 2

Answer 20

sugar loaded into sieve tube
depending on species, move by symplastic or both symplastic and apoplastic pathways

-transfer cells are modified companion cells that enhance solute movement between the apoplast and symplast

Question 21

bulk flow by positive pressure

Answer 21

angiosperm- sap moves through a sieve tube by bulk flow driven by positive pressure