Transport in plants

Which of the options describes movement of water through a plant?

A The Casparian strip forces water to enter the cytoplasm before it can enter the xylem.

B Water can move across the root by the apoplast pathway because of plasmodesmata between cells.

C Water is drawn up the xylem because of adhesion between water molecules.

D Water moves by osmosis from a low water potential to a high water potential.

Your answer

In 1933 two scientists published a study in which they investigated the movement of coloured dyes in the transpiration stream of the stems of sycamore trees growing in a wood.

They bored holes in the stems and poured dye solution into the borehole. Then they sealed the hole with impermeable tape.

Describe what is meant by the term transpiration stream.

Suggest why the scientists sealed the borehole with tape.

The scientists found that the dye moved both up and down the stems.

A student wanted to investigate this in the laboratory. They devised an experiment using water-soluble food dyes injected into the stems of sunflower plants growing in pots.

Suggest how they could observe the route taken by the dyes.

Plants are often watered with a solution containing minerals to help them grow.

While preparing a class practical a technician accidentally watered some sunflower plants with a mineral concentration that was 1000 times higher than normal.

Explain why the plants wilted, even though they were given a lot of water.

The teacher suggested that the same effect would be seen if the plants had been watered with a solution containing cyanide ions that inhibit ATP synthesis.

Explain whether the teacher was correct.

Explain why plants growing in high light intensity require more water than plants growing in shade, even when the temperatures are the same.

Water is transported across the root of a plant by more than one pathway.

Which of the following statements about water molecules moving via the symplast pathway is correct?

A Water molecules can move from cell to cell without crossing a membrane.

B Water molecules can pass through the Casparian strip.

C Water molecules must pass through the endodermis.

D Water molecules travel between cells down a water potential gradient.

Which of the following statements, A to D, describes the movement of water across plant roots?

A The Casparian strip blocks movement by the symplast pathway.

B The symplast pathway requires water to cross partially permeable membranes.

C Water moves from the soil to the root hair cells up a water potential gradient.

D Water moves through the leaves only by the symplast pathway and across the roots only by the apoplast pathway.

Your answer

Which of the following statements about water transport in plants is/are correct?

1 Transpiration happens as a consequence of the need for gas exchange. 2 There are cohesive forces between water molecules because they form hydrogen bonds with one another. 3 Water is drawn up the stem due to adhesive forces between water molecules.

A 1, 2 and 3

B only 1 and 2

C only 2 and 3

D only 1

Your answer