Answer:
Tropism can be defined as a stimulant, with respect to it plant respond to it's external environment. Tropism includes light, water, touch and gravity. The phototropism refers to the movement of plant with respect to the light stimulus. Shoot or stem part of the plant shows positive phototropism because it grows and move in the direction of sunlight, whereas the root shows negative phototropism as it grows against the sunlight.
Yes, plants that live in the desert are expected to show more pronounced phototropism than the forest dwelling plants.This is because in a desert habitat the tree population is expected to be limited, and the plants are directly exposed to sun. The stem or shoot will be erect. But in forest dwelling plants the plants will be growing in shade of trees, will receive very low amount of sunlight. The shoots may not be erect, instead will be tilted. Hence, in desert plants the phototropism will be more prominent.