What will not occur if water isn't split during photosynthesis?

In photosynthesis, the splitting of water, a process known as photolysis, plays a crucial role in the production of oxygen and the generation of electrons, which are essential for the light-dependent reactions. When water is split, it releases oxygen as a byproduct and provides electrons that replace those lost by chlorophyll in the light reactions.

Chemiosmosis is the process through which ATP is synthesized as protons (H+ ions) move across the thylakoid membrane, creating a proton gradient. While this process does depend on the electron transport chain, which starts after photolysis occurs, it does not directly result from the splitting of water itself. Instead, chemiosmosis relies on the overall flow of electrons through the chain, which can continue as long as there are other electron donors available.

In contrast, if water is not split, oxygen production cannot occur, and there would also be no source of electrons for the light reactions, impacting the entire photosynthetic process. Ultimately, ATP synthesis as driven by chemiosmosis may still occur temporarily depending on other conditions, but it would not be sustainable without the continuous supply of electrons that would normally come from the water-splitting process.