With which of the following process Cholodny-Went theory is concerned

The correct option is Phototropism.

Understanding the Cholodny-Went Theory:
The Cholodny-Went theory, proposed independently by Nikolai Cholodny and Frits Went in the late 1920s, is a classic botanical model that explains how plants bend in response to directional environmental stimuli, such as light (phototropism) and gravity (gravitropism).

How it works in Phototropism:
1. Perception of Light: When a plant coleoptile or stem is exposed to unidirectional light, the light stimulus is detected by photoreceptors (phototropins) located primarily at the growing tip.
2. Lateral Redistribution of Auxin: Instead of auxin being destroyed on the illuminated side, the Cholodny-Went theory proposed that the hormone auxin (indole-3-acetic acid) is actively transported laterally from the illuminated side to the shaded side of the tip.
3. Basipetal Transport: The accumulated auxin on the shaded side then moves downwards (basipetally) into the elongation zone.
4. Differential Growth: Higher concentrations of auxin promote greater cell elongation on the shaded side compared to the illuminated side. Consequently, the faster growth on the shaded side causes the stem to bend towards the light source, resulting in phototropism.

Therefore, the Cholodny-Went theory is directly concerned with the physiological mechanism underlying Phototropism.