question_answer 58)

  Following are a few organisms (a) lichen                             (b) mosses                          (c) mango tree                  (d) cactus Which among the above can grow on stones; and also help in formation of soil? Write the mode of their action from making soil.

Answer:

  (a) Out of the above given organisms lichens can grow on rocks. During growth, they release certain substances that cause the rock surface 10 powders down and form a thin layer of soil. Lichens grow on the rock surface, extract minerals from them. This creates small crevices at places where a thin layer of soil builds up. Mosses grow over these crevices and cause deepening of the crevices and result in build sup of more soil inside them. Deeper crevices form cracks and cracks become wider and deeper when the roots of short lived herbs pass into them. With the passage of time, the roots of bigger plants, (e.g., peepal, banyan tree) pass into the cracks. Cracks gradually widen and cause slow fragmentation and eventually pulverization of rocks.