Plant Transport Key Terms

Question 1

define the term adhesion

Answer 1

The formation of hydrogen bonds between carbohydrates in the xylem vessel walls and water molecules. This contributes to the capillarity of water and transpiration pull.

Question 2

Adult haemoglobin

Answer 2

Haemoglobin in an adult has a lower affinity for oxygen than fetal haemoglobin. This enables the fetus to obtain oxygen from the mother’s blood.

Question 3

Aorta

Answer 3

The artery that takes oxygenated blood away from the heart to the body.

Question 4

Aphid

Answer 4

• A small insect that sucks sap through a mouthpart (known as a stylet) which is
  inserted into a sieve tube. The sap exuding from the stylet can provide evidence that sugars are carried in the phloem.

Question 5

Apoplast route

Answer 5

One of three pathways by which water and minerals move across the root.
Water moves through intercellular spaces between cellulose molecules in the cell wall.

Question 6

Capillarity

Answer 6

The tendency of water to move up the xylem, against gravity, due to adhesive forces that prevent the water column dropping back.

Question 7

Casparian strip

Question 8

Casparian strip

Answer 8

A waterproof strip surrounding the endodermal cells of the root that blocks
the apoplast pathway, forcing water through the symplast route.

Question 9

Cohesion-tension theory

Answer 9

The model that explains the movement of water from the soil to the leaves, in a continuous stream.

Question 10

Companion cells

Answer 10

The active cells of the phloem located adjacent to the sieve tube elements. They retain their nucleus and organelles, producing ATP for metabolic processes in both themselves and the sieve tube elements.

Question 11

Cytoplasmic strands

Answer 11

Small extensions of the cytoplasm between adjacent sieve tube elements and companion cells that allow communication and the exchange of materials.
They also hold the nucleus in place.

Question 12

Dicotyledonous plants

Answer 12

Plants that produce seeds that contain two cotyledons. They have two primary leaves.

Question 13

Endodermis

Answer 13

The innermost layer of the cortex of a dicotyledon root. It is impregnated with
suberin which forms the Casparian strip. Endodermal cells actively transport mineral ions into the xylem.

Question 14

Hydrophytes

Answer 14

Plants that are adapted to live and reproduce in very wet habitats,
e.g. water lilies.

Question 15

Mass flow theory

Answer 15

The main theory to explain translocation in the phloem. It suggests that sugars flow passively from the source (highest sugar concentration) to the sink (lowest sugar
concentration)

Question 16

Mesophytes

Answer 16

Terrestrial plants that are adapted to live in environments with average conditions and an adequate water supply. They have features that enable their survival at unfavourable times of the year

Question 17

Osmotic pressure

Answer 17

The movement of water into the blood by osmosis due to the tendency of plasma proteins to lower the water potential of the blood.

Question 18

Phloem

Answer 18

A living plant transport vessel responsible for the transfer of assimilates to all parts
of the plant. The phloem consists of sieve tube elements and companion cells.

Question 19

Potometer

Answer 19

An apparatus used to measure water uptake from a cut shoot

Question 20

Purkyne tissue

Answer 20

Specialised cardiac muscle fibres which make up the bundle of His and conduct the wave of excitation through the septum, from the AVN down to the apex of the ventricles.

Question 21

Root hair cells

Answer 21

Specialised cells responsible for the uptake of water and minerals from the
soil. They have long hair-like extensions known as root hairs, which are adapted as
exchange surfaces.

Question 22

Root pressure

Answer 22

The force that drives water into and up the xylem by osmosis due to the active transport of minerals into the xylem by endodermal cells.

Question 23

Sieve plates

Answer 23

The perforated end walls of sieve tube elements that allow plant assimilates
to flow between cells unimpeded.

Question 24

Sieve tube elements

Answer 24

The main cells of the phloem. They are elongated cells laid end-to-end with sieve plates between. They contain few organelles.

Question 25

Sinks (plants)

Answer 25

The regions of a plant that remove assimilates e.g. roots, meristem, fruits

Question 26

Sources (plants)

Answer 26

The regions of a plant that produce assimilates e.g. leaves, storage
organs.

Question 27

Suberin

Answer 27

A waterproof, waxy material that forms the Casparian strip in the endodermis.

Question 28

Translocation

Answer 28

The movement of organic compounds in the phloem, from sources to sinks.

Question 29

Symplast route

Answer 29

One of three pathways by which water and minerals move across the root.
Water enters the cytoplasm through the plasma membrane and moves between adjacent cells via plasmodesmata. Water diffuses down its water potential gradient by osmosis

Question 30

translocation

Answer 30

The movement of organic compounds in the phloem, from sources to sinks.

Question 31

transpiration

Answer 31

Water loss from plant leaves and shoots via diffusion and evaporation. The
rate of transpiration is affected by light, temperature, humidity and air movement.

Question 32

Transpiration stream

Answer 32

The flow of water from the roots to the leaves in plants, where it is
lost by evaporation to the environment

Question 33

Vacuolar route

Answer 33

One of three pathways by which water and minerals move across the root.
Water enters the cytoplasm through the plasma membrane and moves between vacuoles of adjacent cells. Water diffuses down its water potential gradient by osmosis.

Question 34

Vascular bundle

Answer 34

The vascular system in herbaceous dicotyledonous plants. It consists of
two transport vessels, the xylem and the phloem.

Question 35

Xerophytes

Answer 35

Plants that are adapted to live and reproduce in dry habitats where water
availability is low, e.g. cacti and marram grass.

Question 36

xylem

Answer 36

A non-living plant transport vessel responsible for the transfer of water and minerals from the roots to the shoots and leaves.