Question

Is the following statement true or false? Explain and support why you chose your answer.

“Water is actively transported in plants from their roots to their leaves and sugars move down plants from sites of photosynthesis into roots by gravity"

Answer 1

THE GIVEN STATEMENT IS FALSE.

The movement of water in the xylem is always upwards from (roots to leaves )and it is caused by suction of water due to the low pressure created by transpiration from leaves.

The movement of food (sugar) in the phloem can be upwards or downwards depending upon the need of the plant.

The movement of sugar(glucose) produced by the leaves as a product of photosynthesis in the phloem happens by translocation and this process of transport utilises energy .

Translocation is the process by which organic molecules move from the source to the sink cells through phloem by active transport.

The sugar (In the form of sucrose) is loaded by companion cells into the seive tubes in phloem tissue by using energy from ATP.

Water enters into the seive tubes containing sugar by the process of osmosis as the sugar creates concentration gradient, due to which the pressure in the phloem tissue rises. The high pressure in the phloem move the food to the parts of plant with less pressure( SINK/ storage cell) allowing the phloem to transport food according to the need of the plant.

Sugars are stored as starch in plants and release in simpler sugars as and when needed. sugar stored in root or stem tissue is transported by phloem to the buds which need high energy to grow.