Question

if all the green plants are removed from the Earth life cannot be sustained comment

Answer 1

Carbon dioxide won't be converted to Oxygen. So after some time all oxygen will be used up and then no living objects other than green plants (if alive) will die.

Answer 2

If all the green plants are removed from the Earth life cannot be sustained because we wont get oxygen , air will get polluted ,there will be no rain which makes our water resources empty without which life cannot survive on earth, content of green house gases will increase which leads to global warming and ozone depletion and the earth will become very hot place , people my die because of the uv rays etc