Why is it difficult to grow anaerobes in vitro?

 Anaerobes are not able to have growth in the presence of much of oxygen environment as they do not have catalse .Catalse is the enzyme for clearance of oxygen.There are also anaerobes protects their own self from oxygen by production of an enzyme known as super oxide dismutase. Therefore, it is not easy task for creation an oxygen-absent environment for anaerobes in the vitro so they cannot be grown in vitro.

because the light is a great source of energy for the plants to survive. (i hope this )

answer: ice crystals in air

the water from the water body or another source of water gets evaporated as water vapor as an effect of heat on water. these water vapor rises in the upper layers of the earth atmosphere under high atmospheric pressure. the atmospheric pressure of these water molecules starts to decrease due to the effect of cold air. the invisible water vapor condenses into visible water droplets and ice crystals.these ice crystals and water droplets being less denser than the surrounding air floats on air as clouds.