water transport in plants

Question 1

what are xylem

Answer 1

hollow tubes that transport water. dead hollow cells form a continuous column

Question 2

whats transpiration

Answer 2

water evaporates out of stomata on leaves of plants. transpiration pull helps to transport materials in plant.

Question 3

whats the cohesion tension theory

Answer 3

explains the tension caused by water loss from the top (stomata) and water moving in at the bottom (root pressure)

lower water potential in mesophyll
water pulled up xylem
water molecules adhere/stick together by h bonds
forming a continuous water column
adhesion of water cells to walls of xylem

Question 4

what is transpiration increased by

Answer 4

light intensity- stomata open to allow co2 in for photosynthesis
temp- kinetic energy of water molecules increases, molecules move faster
air movement- removing the moist air surrounding the leaf lowering the water potential
air humidity - affects the water potential gradient

Question 5

what are potometers used for

Answer 5

measure water uptake. not truly transpiration rate water is lost in respiration used in photosyn and leaks in apparatus etc. potometers measure the distance the bubble has moved

Question 6

how to set up a potometer

Answer 6

must be airtight, cut shoot at a slant underwater. insert apparatus underwater
no air bubbles at the start or
note where bubble is a the start

Question 7

how do you calculate rate of transpiration with potometer

Answer 7

pie r squared x distance bubble moved

Question 8

whats the evidence for cohesion tension theory

Answer 8

tree trunks widest at night when least transpiration as theres less tension

Question 9

how do xerophytes reduce water loss by transpiration

Answer 9

thick cuticle
rolled up leaves - traps air becomes moist and reduces water potential gradient
hairy leaves - same reason as above
smaller sa to volume ratio of leaves- slower diffusion

the water potential gradient reduced by keeping water vapour close to the outside of the stomata

Question 10

whats translocation

Answer 10

how organic molecules and mineral ions are transported around the plant

Question 11

whats the phloem

Answer 11

the tissue that transports biological molecules in either direction. made of sieve tube elements arranged end to end. walls perforated to form sieve plates. companion cells often associated with sieve tube components.

Question 12

whats a source/sink

Answer 12

source= where sugars are made during photosyn
sink= where sugars are used/stored

Question 13

what is the mass flow hypothesis

Answer 13

sugars in the source actively transported into phloem by companion cells
lowers water potential of sieve cell/tube and water enters via osmosis
increase in pressure causes mass movement towards sink/root
sugars used and converted in root for respiration or storage

Question 14

what experiments used as evidence that translocation occurs in the phloem

Answer 14

ringer or tracer experiments

Question 15

what can be used to show that phloem carry sugar

Answer 15

phloem sap feeders. they feed without jaw muslces because there is a high hydrostatic pressure in phloem