STD VIII – TRANSPORT OF FOOD AND MINERALS IN PLANTS (Hybrid)

1. TRANSPORT IN PLANTS

Transport and Transpiration in Plants

The transport system in plants distributes water, food, and minerals to various parts of the plant. The transport system in flowering plants that have a very well developed system for transportation is known as vascular system. There are two vascular tissues namely, the xylem and the phloem, which help in the conduction of water, nutrients, and minerals throughout a plant’s body.

Xylem and phloem

Simple plants such as algae – simple diffusion across cell membrane.

Complex plants – conducting tissue comprising of xylem and phloem.

Energy needs low due to a) large number of dead cells b) no locomotion.

What is osmosis?

The movement of water from a region of higher concentration to a region of lower concentration across a semi-permeable membrane.

Ascent of sap, capillary action and transpiration

Ascent of sap:

Water enters a root hair → the cell content becomes dilute → cell next to the root hair cell will be more concentrated → Water enters by osmosis into this cell → Water, along with dissolved nutrients moves along from cell to cell and goes into the xylem.

Capillary action:

Capillary action is the movement of liquid through a narrow space like oil rising through the wick of a lamp. Since xylem cells are long and thin, water moves up by capillary action.

Transpiration

All leaves have small pores called stomata on the epidermis. Water is lost by evaporation from these stomata as water vapour by a process called transpiration. This creates a pull on the xylem cells and water rushes to fill the space left by evaporating water molecules. This forces the water to move up due to suctional pull or suction pressure.