Q.Which of the following exhibits the highest rate of respiration?

Among plant parts, tissues that are mobilising stored food reserves fastest to fuel active growth generally show the highest respiration rate.

• A germinating seed must rapidly break down its stored reserves (starch, fats or proteins) to power the growth of the embryo.
• This intense, ongoing mobilisation of substrate demands a correspondingly high, sustained rate of respiration. …

Respiration rate in a plant part broadly tracks how much metabolic work that tissue is doing at the time. Meristematic and actively growing regions — shoot apices, root tips, leaf buds — do respire at elevated rates because cell division and expansion both need a steady ATP supply.

A germinating seed, however, is not simply growing; it is converting its entire store of food reserves (carbohydrate, fat or protein, depending on the species) into the building blocks and energy needed to establish a new seedling, essentially all at once. This places a much larger, sustained demand on respiratory machinery than the incremental growth occurring at a single shoot apex, root tip or leaf bud. …

Method 1

1. Compare respiratory demand across the 4 listed plant parts: growing shoot apex, germinating seed, root tip, leaf bud.
2. Recognize germinating seeds mobilise their entire stored food reserve (starch/fat/protein) rapidly to fuel establishment of the seedling. …