Question

Which one theory is associated with phototropism and geotropism?
A. Skoog and Meer theory
B. Burg theory
C. Induced theory
D. Cholondy-Went theory

Answer 1

Tropism is a change towards a stimulus or away from it. It's called positive tropism when the motion is towards the stimulus, and it's called negative tropism when the motion is away from the stimulus. Phototropism is also the movement of a plant in reaction to sunlight. Similarly, geotropism helps plants to orient themselves correctly towards growth.

Complete answer:
Near a window, plant leaves can turn themselves toward the Sun. Geotropism is the response of a plant to the force of gravity. Plant roots respond positively to and grow down to geotropism, while the stem shows a negative gravity response and grows in the opposite direction upwards. This experiment was a combined study that converged from two similar proposals. The study of microgravity effects on the orientation of roots and stems of germinating seedlings was proposed in the first proposal. In order to determine the degree of illumination needed to generate the phototropic response, the second proposal proposed an experiment to determine the phototropic response under different light intensities. A basic and straightforward explanation of these phenomena is provided by the Cholodny-Went theory , which states that plant tropisms in roots and shoots are due to the unequal distribution of the growth regulator auxin in response to light or gravity.
There is more auxin on the lower side of the stems and roots than on the upper side, according to the Cholodny-Went theory. The higher concentration of auxin promotes development within the stem. Therefore, though roots grow more on the upper side, the stem grows more on the lower side , causing stems to bend upwards and roots to bend downwards. So, both phototropism and geotropism are correlated with the Cholodny-Went theory.

So, the correct option is "option D".

Note: Critics noted that the concentrations of auxin were never directly measured by Went and other early researchers, but instead relied on bioassays performed with agar blocks. In addition, the early studies focused on small sample sizes that were statistically inaccurate, and during tip removal, the researchers could have hurt the coleoptiles.