Ch 29: Resource Acquisition, Nutrition, and Transport in Vascular Plants

Question 1

Define apoplast.

Answer 1

Everything external to the plasma membrane of a plant cell, including cell walls, intercellular spaces, and the space within dead structures such as xylem vessels and tracheids.

Question 2

Movement of water and minerals through the xylem,

movement of sugars through the phloem.

Answer 2

***

Question 3

Plants do use oxygen, but they make more than they need, so they have extra to emit back out into the environment

Answer 3

***

Question 4

The leaves are the site of sugar production, and then need to be transported around the plant to other parts. Sugars are carried to storage organs.

Answer 4

***

Question 5

Roots still take in ______, just as all eukaryotes do. And then still emit CO2, but the net production is of more O2.

Answer 5

oxygen

Question 6

Plants cells are connected by _______ (singular: plasmodesma) which allow materials to move from cell to cell.

Answer 6

plasmodesmata

Question 7

At maturity, xylem is just a cell wall, like a straw.

Answer 7

Apoplastic route

Question 8

The _________ consists of the entire mass of cytosol of all the living cells in a plant, as well as the plasmodesmata, the cytoplasmic channels that interconnect them.

Answer 8

symplast

Question 9

In the ________ route, water and solutes move out of one cell, across the cell wall, and into the neighboring cell, which may pass them to the next cell in the same way. The transmembrane route requires repeated crossings of plasma membranes as substances exit one cell and enter the next.

Answer 9

transmembrane

Question 10

The cell’s plasma membrane is selectively permeable.

Answer 10

ff

Question 11

The physical property that predicts the direction in which water will flow is called water potential, a quantity that includes the effects of solute concentration and physical pressure. If there is no barrier to the flow of free water, it moves from regions of higher water potential to regions of lower water potential.

Answer 11

Water moves from high water potential –> low water potential

Question 12

A water potential of 0 means there are no solutes present at all.

Answer 12

**Ch 5 has more info about water potential.

Question 13

Figure 5.10 Water molecules can pass through pores, but sugar molecules cannot.

Answer 13

Water moves from an area of higher to lower free water concentration (lower to higher solute concentration).

Question 14

Passive transport

Answer 14

d

Question 15

The movement of water molecules across biological membranes is too rapid to be explained by unaided diffusion. Transport proteins called ________ (see Figure 5.9) facilitate the transport of water molecules across plant cell plasma membranes. These channels, which can open and close, affect the rate at which water moves osmotically across the membrane.

Answer 15

aquaporins

Question 16

If a cell moves things against a concentration gradient, it has to use energy to do that (______ transport).

Answer 16

active

Question 17

When solute concentration in a solution increases, the water potential of the solution _________

Answer 17

decreases.

Question 18

Water and dissolved minerals located in the cell walls and intercellular spaces of the root cortex are in the __________ route of transport, and those in the ________ of cortex cells are in the symplastic route.

Answer 18

apoplastic
cytoplasm

Question 19

The _________ route requires plasmodesmata. The __________ route is obstructed by the Casparian strip, thereby forcing water and minerals to cross the plasma membranes of endodermal cells before gaining entrance into the vascular cylinder.

Answer 19

symplastic
apoplastic

Question 20

Solute potential is always negative.
Living cells have + turgor pressure. Dead cells have - pressure potential.

Answer 20

_

Question 21

Xylem transports water and minerals. At maturity, xylem cells are ____ and ______.

Answer 21

dead
hollow

Question 22

Vessel elements are found mostly in angiosperms.
Tracheids (think straws) are present in all vascular plants.

Answer 22

–

Question 23

Pressure potential inside xylem cells is negative.

Answer 23

Pressure potential in xylem changes with position in the plant. trunk xylem = -0.6 MPa

Question 24

Review hydrogen bonding – Concept 2.5 in text

Answer 24

hydrogen bonds between molecules of water (cohesion) is important

Question 25

Cohesion - water molecules have surface tension between them at air/water interfaces.

Answer 25

ii

Question 26

Adhesion - water molecules forming hydrogen bonds with other types of molecules.

Answer 26

adhesion - two different types of things sticking together
cohesion - two like things sticking together

Question 27

How does transpiration get started?

Answer 27

water evaporates out of the stomata of the leaf

Question 28

Cell walls aren’t solid. Microfibrils
More water from in between the microfibrils moves into the gas phase when water evaporates from the air spaces.
Surface tension increases when the gas spaces are full of evaporated molecules.

Answer 28

++

Question 29

The strong adhesion of water molecules (again by hydrogen bonds) to the __________ walls of xylem cells helps offset the downward force of gravity.

Answer 29

hydrophilic

Question 30

The plant expends no energy to lift xylem sap by bulk flow. Instead, the absorption of sunlight drives most of transpiration by causing water to ________ from the moist walls of mesophyll cells and by lowering the water potential in the air spaces within a leaf. Thus, the ascent of xylem sap, like the process of photosynthesis, is ultimately _____ powered.

Answer 30

evaporate
solar

p. 620

Question 31

How do materials get into the plant?

Materials can’t travel through the apoplastic route at the endodermis. There is a structure that prevents materials from traveling between cells, known as the Casparian strip.

Answer 31

materials that make it through the endodermis can enter the xylem.

Question 32

Phloem moves sugars.

Unlike xylem, phloem cells are living at maturity. Pressure potential in phloem cells is positive. 2 kinds of cells in phloem - sieve-tube element (only cytosol, no _______), the companion cell is packed with organelles. The companion cell supplies the sieve tube with what it needs.

Answer 32

organelles

Question 33

Translocation = transport of photosynthetic products (sugars). Photosynthesis happens in the _________

Answer 33

mesophyll

Question 34

Sugar travels from mesophyll to phloem using _____ ________ transport (not bulk flow).

Once it gets to the phloem, it moves by bulk flow.

Answer 34

short distance

Question 35

Phloem can carry sugars from a source cell (leaf) down to a sink cell (storage root).

Answer 35

This loading of sugar (most often sucrose), must be done by active transport bc the sugar is moving against a concentration gradient.

Question 36

Water potential is higher in the leaf than in the phloem, so water can move by osmosis/ passive transport.

Answer 36

The water at the leaf pushes material down the phloem into the sink. Increased water potential at the top, pushes materials down.

Question 37

Figure 29.22

3 - unloading of sugar into sink cell - happens by diffusion (down a concentration gradient)

Answer 37

The sink cell converts the sucrose to a polymer starch, to prevent the sucrose concentration from getting to high (which would stop diffusion).

Question 38

Down near the sink cells, water moves from the phloem back over to the xylem to be recycled, moved back up the plant.

Answer 38

Water recycling is passive - osmosis.