# Why do green plants need sunlight to perform photosynthesis?

Aug 13, 2017

Is not the photosynthesis reaction strongly endothermic....?

#### Explanation:

When hydrocarbons combust the products are carbon dioxide and water. These are stable molecules that possess STRONG $C = O$ and ${H}_{2} O$ bonds.

Plants fix atmospheric carbon dioxide, and with water can use photosynthesis to make simple sugars.....

$6 C {O}_{2} \left(g\right) + 6 {H}_{2} O \left(l\right) + \Delta \rightarrow {C}_{6} {H}_{12} {O}_{6} \left(a q\right) + 6 {O}_{2} \left(g\right)$

As written, the reaction is highly endothermic; much energy has to be expended to break the $O - H$ and $C = O$ bonds. From where does the energy come? Does photosynthesis occur at night?