Question

(a) What is respiration?
(b) Draw a labelled diagram of cross section of leaf.
(c) Explain the transportation of food and other substances in plants.

Answer 1

(a) The respiration refers to catabolic process of breakdown of reduced substrates. The respiration can be aerobic or anaerobic.

(c) Transportation of food requires living tissue. Sieve elements are the livingconducting cells of the phloem. They consist of sieve cell and sieve tube. They conduct carbohydrates (sucrose mainly), amino acids, hormones. The transportation of food in phloem is an active process achieved by utilizing energy from ATP which helps in creating osmotic pressure that transports food against the gradient from the area of high concentration to low concentration. Plants produce carbohydrates (sugars) in their leaves by photosynthesis, which is further conducted to different parts of the plant for proper functioning. For this reason, nutrients are translocated from sources (regions of excess carbohydrates, primarily mature leaves) to sinks (regions where the carbohydrate is needed). Some important sinks are roots, flowers, fruits, stems, and developing leaves.