Topic 7.1: Structure of Plant Transport Tissues

Question 1

phloem

Answer 1

functions in transport of organic nutrients

Question 2

xylem

Answer 2

functions in transport of water and dissolved mineral ions

Question 3

endodermis

Answer 3

separates the cortex from the vascular tissue

Question 4

vascular tissue

Answer 4

xylem and phloem

Question 5

Casparian strip

Answer 5

a waxy barrier found in the cell walls of endodermal cells

Question 6

cortex

Answer 6

located between the epidermis and the vascular tissue

Question 7

root hairs

Answer 7

extensions to increase surface area for absorption of water and mineral ions

Question 8

epidermis in stem tissues

Answer 8

may be covered in a waxy cuticle

Question 9

waxy cuticle

Answer 9

inhibits water loss to the environment

Question 10

pith

Answer 10

located in the center of the stem

Question 11

vascular bundle in a stem tissue

Answer 11

xylem, cambium, phloem, fibers

[ x , c , p , f ]

Question 12

palisade mesophyll

Answer 12

column-shaped cells containing many chloroplasts, function = photosynthesis

Question 13

spongy mesophyll

Answer 13

loosely-packed cells separated by air spaces, function = photosynthesis

Question 14

How to remember the location of the phloem in leaf tissues?

Answer 14

phloem “below-em”

the phloem is on the bottom of the vascular bundle

Question 15

other name for vascular bundle

Answer 15

vein

Question 16

lower epidermis

Answer 16

contains pores called stomata that allow for gas exchange (CO2 in/O2 out) and transpiration (water vapor out)

Question 17

vessel elements

Answer 17

specialized cells found in xylem vessels

Question 18

features of vessel elements

Answer 18

elongated cylindrical cells arranged end-to-end, no end walls, dead at maturity (no cell contents), lignified cell walls, pits in side walls

Question 19

lignin

Answer 19

a hard material made by plant that is used to strengthen the cell walls of certain types of cells

Question 20

lumen

Answer 20

empty space containing no cytoplasm or other cell contents

Question 21

pits

Answer 21

unlignified gaps/lignin-free gaps in cell wall

Question 22

importance of a lack of cell contents in the xylem and the lack of end walls

Answer 22

creates an uninterrupted pathway for water flow

Question 23

importance of lignified cell walls

Answer 23

provides additional strength/structural support which prevents the inward collapse of the xylem walls

Question 24

why might the xylem walls “collapse” if lignified cell walls didn’t provide additional strength

Answer 24

due to tension (negative pressure/sunction)

Question 25

tension (negative pressure/suction)

Answer 25

transpiration creates tension in the xylem ---> tension "pulls" water upwards through the xylem ---> tension causes the walls of xylem to pull inwards

Question 26

importance of pits

Answer 26

allows water to move laterally in and out of xylem vessels because water cannot cross the lignified portions of the walls

Question 27

What are the two types of specialized cells found in phloem tissue that are involved in sucrose transport?

Answer 27

sieve elements and companion cells

Question 28

features of sieve elements

Answer 28

elongated cells that are joined end-to-end to form sieve tubes, cells are living but they lack a nucleus and ribosomes and contain very little cytoplasm, end walls of adjacent cells are perforated by large pores, forming a structure called a sieve plate

Question 29

importance of the sieve elements being living cells

Answer 29

living cells have CSM's and, therefore, can regulate the entry and exit of solutes

Question 30

importance of no nucleus and very little cytoplasm

Answer 30

allows the lumen to be mostly open/free thereby reducing resistance to sap flow

Question 31

peripheral cytoplasm

Answer 31

thin layer of cytoplasm found in the sieve elements

Question 32

importance of the large pores of sieve plates

Answer 32

allows sap to flow more easily between sieve elements while also providing some resistance which helps maintain the source to sink pressure gradient needed to "push" sap through the sieve tubes

Question 33

importance of sieve plates being sealed off rapidly with callose after being damaged

Answer 33

prevents excessive loss of sugars

Question 34

features of companion cells

Answer 34

a large number of mitochondria and ribosomes, and many plasmodesmata to connect their cytoplasm with the cytoplasm of associated sieve elements

Question 35

why is it important for companion cells to contain a large number of mitochondria

Answer 35

to produce the ATP needed for active transport of sucrose into companion cells

Question 36

why is it important for companion cells to contain numerous plasmodesmata

Answer 36

allows for quick diffusion of sucrose from companion cells into their associated sieve elements