Question

A plant mutant that shows normal gravitropic bending but does not store starch in its plastids would require a reevaluation of the role of _____________ in gravitropism.

(A) auxin

(B) calcium

(C) statoliths

(D) differential growth

Short answer

1. The option “auxin” isfalse.

2. The option “calcium” isfalse.

3. The option “statoliths” is true.

4. The option “differential growth” is false.

Step-by-step solution

Plastid

The membrane-bound cytoplasmic organelle found in the mesophyll plant cells and stored starch for producing energy is called plastid. Various functions performed by plastid are pigment or color storage, photosynthesis, and food manufacturing for plants.

Explanation of option ‘(A)’

The phytohormone formed in the plant bodies that help in fruit and plant growth is called auxin.

Thus, auxin helps in conveying gravity signals in plants in gravitropism.

Therefore, the given option is false.

Explanation of option ‘(B)’

The essential element taken by plants through their roots which acts as a structural cell wall component is calcium.

Thus, the three distinct roles performed by calcium in gravitropism are response, transduction, and perception.

Therefore, the given option is false.

Explanation of option ‘(C)’

The phenomenon in which the shoot of typical plants grow straight up and roots grow down in the direction of gravity is called gravitropism.

Thus, statoliths (a calcareous particle that allows plants to sense gravity) are starch-filled plastids that help plants orient them to gravity. They drive gravitropism, and if they are unable to store starch, then there is limited gravitropism.

Therefore, the given option is true.

Explanation of option ‘(D)’

The different rate at which distinct living structures like cells and organs grow in organisms like plants is called differential growth.

Thus, differential growth is responsible for the construction of the whole plant.

Therefore, the given option is false.