Plant Transport Key Terms Flashcards
define the term adhesion
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.
Adult haemoglobin
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.
Aorta
The artery that takes oxygenated blood away from the heart to the body.
Aphid
- 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.
Apoplast route
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.
Capillarity
The tendency of water to move up the xylem, against gravity, due to adhesive forces that prevent the water column dropping back.
Casparian strip
Casparian strip
A waterproof strip surrounding the endodermal cells of the root that blocks
the apoplast pathway, forcing water through the symplast route.
Cohesion-tension theory
The model that explains the movement of water from the soil to the leaves, in a continuous stream.
Companion cells
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.
Cytoplasmic strands
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.
Dicotyledonous plants
Plants that produce seeds that contain two cotyledons. They have two primary leaves.
Endodermis
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.
Hydrophytes
Plants that are adapted to live and reproduce in very wet habitats,
e.g. water lilies.
Mass flow theory
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)
Mesophytes
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
Osmotic pressure
The movement of water into the blood by osmosis due to the tendency of plasma proteins to lower the water potential of the blood.
Phloem
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.
Potometer
An apparatus used to measure water uptake from a cut shoot
Purkyne tissue
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.
Root hair cells
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.
Root pressure
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.
Sieve plates
The perforated end walls of sieve tube elements that allow plant assimilates
to flow between cells unimpeded.
Sieve tube elements
The main cells of the phloem. They are elongated cells laid end-to-end with sieve plates between. They contain few organelles.
Sinks (plants)
The regions of a plant that remove assimilates e.g. roots, meristem, fruits
Sources (plants)
The regions of a plant that produce assimilates e.g. leaves, storage
organs.
Suberin
A waterproof, waxy material that forms the Casparian strip in the endodermis.
Translocation
The movement of organic compounds in the phloem, from sources to sinks.
Symplast route
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
translocation
The movement of organic compounds in the phloem, from sources to sinks.
transpiration
Water loss from plant leaves and shoots via diffusion and evaporation. The
rate of transpiration is affected by light, temperature, humidity and air movement.
Transpiration stream
The flow of water from the roots to the leaves in plants, where it is
lost by evaporation to the environment
Vacuolar route
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.
Vascular bundle
The vascular system in herbaceous dicotyledonous plants. It consists of
two transport vessels, the xylem and the phloem.
Xerophytes
Plants that are adapted to live and reproduce in dry habitats where water
availability is low, e.g. cacti and marram grass.
xylem
A non-living plant transport vessel responsible for the transfer of water and minerals from the roots to the shoots and leaves.
