IB Biology HL Transport in Plants Flashcards

Flashcards about plant transport mechanisms, xylem and pholem adaptations, and translocation.

Transpiration

The evaporation of water vapor from plants, predominantly from the leaves, as a consequence of gas exchange.

Capillary action in plants

Water is able to naturally reach the leaves through the xylem due to cohesion and adhesion.

Stomata

Pores on the underside of leaves that are flanked by guard cells, which regulate gas exchange between the plant and the atmosphere.

Transpiration pull

The tension generated as water is drawn out of the xylem vessel due to negative pressure, allowing water to move up xylem in a continuous stream.

Root pressure

The pressure that accumulates within the root cells as water enters the roots due to osmosis.

Guttation

The appearance of water droplets on the pores/hydathodes on leaves of plants due to root pressure.

Xylem

Plant tissue made of dead cells that transports water passively from roots to shoots.

Tracheids

Long and thin cells with tapered ends in xylem that allow water to move between cells through pits.

Vessel elements

Xylem cells with thick walls of cellulose reinforced with lignin, forming continuous tubes for faster water flow.

Phloem

Living plant tissue that transports sap (sugars, amino acids, etc.) bidirectionally.

Sieve tube elements

Connected cells in phloem with sieve plates that allow movement of water and dissolved organic molecules.

Companion cells

Cells connected to sieve tube members by plasmodesmata, containing a nucleus and being mitochondria-rich to support sieve elements.

Source (in translocation)

Plant organ that is a net producer of sugar, either by photosynthesis or by hydrolysis of starch.

Sink (in translocation)

Plant organ that uses or stores sugars (e.g., roots, fruits, & seeds).

Translocation

The movement of organic molecules in plants through phloem tissue.

Phloem sap

The solution of organic molecules (sugars, amino acids, plant hormones, small RNA molecules) dissolved in water within phloem.

Apoplast route

The movement of sugar through the cell walls of companion cells, where a sucrose transport protein actively transports the sugar into the cell’s cytoplasm.

Symplastic route

The movement of sucrose between cells through connections called plasmodesmata, followed by conversion to an oligosaccharide.

Mass flow

The movement of pholem sap towards areas of lower pressure.

Plan diagrams

Drawings that show the distribution of tissue in an organism viewed under low magnification without showing individual cells.

Vascular bundle (in stems)

The xylem, phloem, and cambium in stems of dicots.

Cortex (in stems)

The water and nutrient transporter to the vascular bundles, responsible for food storage, and gas exchange.

Vascular bundle (in roots)

The xylem and pholem in roots of dicots.

Cortex (in roots)

The water and nutrient transporter to the vascular bundles, responsible for storage of starch.