Lecture 18: Phloem Transport

Question 1

non-circulatory vascular systems

Answer 1

xylem and phloem

Question 2

xylem travels in what direction for translocation

Answer 2

root-to-shoot

Question 3

phloem travels in what direction for translocation

Answer 3

source-to-sink

Question 4

source tissue

Answer 4

exporting plant tissues or organs that produce photosynthate mature and photosynthetically active leave

Question 5

sink tissue

Answer 5

non-photosynthetic developing organ or an organ that does not produce enough photosythate

Question 6

what end of the leaf is mature/source and immature/sink

Answer 6

leaf tip = mature
leaf base = immature

Question 7

K-deficient symptoms

Answer 7

substantial growth reduction
yellowing appears on the oldest leaves
brown necrotic lesions develop within yellow parts

Question 8

K is ______ in plants

Answer 8

mobile

Question 9

sieve tube

Answer 9

the functional units for long distance translocation of plant material

Question 10

sieve plate

Answer 10

a perforated wall between the sieve elements

Question 11

mature sieve elements contain:

Answer 11

1. structural phloem specific proteins (P-proteins)
2. endoplasmic reticulum
3. mitochondria
4. sieve element plastids

Question 12

mature sieve elements do not contain:

Answer 12

nucleus
vacuole
golgi bodies
chloroplast (at the shoot)

Question 13

what does P-proteins and callose do in phloem

Answer 13

protection mechanism in phloem that seals off damaged sieve elements by plugging pores and plant response

Question 14

is P-protein the short term or long term solution in plugging up sieve pores

Answer 14

short term

Question 15

is callose the short term or long term solution in plugging up sieve pores

Answer 15

long term

Question 16

sucrose moves through the ______ from the mesophyll cells to the phloem

Answer 16

plasmodesmata

Question 17

2 ways that sucrose is loaded into minor veins

Answer 17

1) symplasmic sucrose loading
2) apoplasmic sucrose loading

Question 18

can all sugar forms move through the phloem

Answer 18

nonreducing (less reactive) sugars can be transported via phloem
reducing sugars are not translocated through phloem

Question 19

what sugars are to reactive to go through phloem

Answer 19

glucose, mannose, and fructose

Question 20

sucrose

Answer 20

the most common form of sugar, translocated through the phloem

Question 21

types of sugar forms in phloem

Answer 21

sucrose, raffinose, stachyose, verbascose

Question 22

how is phloem sap exudate collected

Answer 22

severed aphid stylets

Question 23

what is being loaded/translocated through phloem

Answer 23

water
photosynthate (sugars)
proteins
RNA
Information superhighway

Question 24

Direction and rate of phloem translocation is controlled by ___________

Answer 24

local sink strength

Question 25

munch pressure flow hypothesis

Answer 25

tensional gradients pulls water up from roots in xylem. Water is pulled from xylem to phloem. Pressure gradient from source to sink (sink is lower pressure)