NEET BIOLOGY

Detailed explanation-1: -Mass flow or bulk flow is the movement down a pressure gradient ( a pressure gradient in plants is observed due to variations in solute concentration) or temperature gradient of substances in bulk or in masses. Xylem and phloem in plants play a similar role as veins and arteries in animals.

Detailed explanation-2: -The photosynthetically active parts of a plant are referred to as the source. The areas of active growth and areas of storage are referred to as sinks.

Detailed explanation-3: -The best-supported theory to explain the movement of food through the phloem is called the pressure-flow hypothesis. It proposes that water containing food molecules flows under pressure through the phloem.

Detailed explanation-4: -Within the phloem, sugars migrate to regions of low osmotic concentration and low water pressure, called sinks, from areas of high osmotic concentration and high water pressure, known as sources.