If all green plants in the world were distroyed which atmospheric gas will increase

 Trees are a crucial part of the carbon cycle, a global process in which carbon dioxide constantly circulates through the atmosphere into organism and back again. Carbon is the second most valuable element to life, you know, after water. Anyway, trees take carbon from the atmosphere through photosynthesis in order to make energy. This carbon is then either transferred into oxygen and released into the air by respiration or is stored inside the trees until they decompose into the soil. Therefore, the absence of trees would result in significantly HIGHER amounts of carbon dioxide in the air and LOWER amounts of oxygen! The filthy air would also be full of airborne particles andpollutants like carbon monoxide, sulfur dioxide and nitrogen dioxide and its temperature may increase by up to 12 F.

not always but somethings can be reproduced in a laboratory.