Question

Positive geotropic movement of root in a horizontally placed seedling is due to

• A. New cells that arise on the lower side of root
• B. Condensation of cells decrease on the lower side of root
• C. Auxins accumulate on the upperside of root, so cell elongation decreases in that area
• D. Auxins accumulate on the lower side of root, so cell elongation decreases towards lower side

Answer 1

The correct option is D Auxins accumulate on the lower side of root, so cell elongation decreases towards lower side

Cholodny-Went theory explains about the regulation of tropisms by auxins in plants. In a horizontally placed seedling auxins are accumulated on the lower surface of root. High auxin concentration decreases cell elongation and cells present at upper surface grows normally and root grows towards gravity. In the stem auxin increases growth in the region where they are more concentrated, in effect causing the stem to bend upwards against the pull of gravity, while in roots auxin would inhibit rather than stimulate growth in the area where it is concentrated, causing the root to bend downward.