What would happen if the electron transport system in the light-dependent reaction of photosynthesis was disabled for some reason?

Answer:

If the electron transport chain (ETC) were disabled, the plant would be unable to produce ATP and NADPH. Without these two energy-carrying molecules, the light-independent reactions (the Calvin cycle) could not take place, which means the plant would be unable to synthesize glucose. Ultimately, the plant would not be able to store energy or maintain its biological functions and would die.