Isolated chloroplasts were given electron donors and DCPIP (a Hill reagent that turns blue when reduced). Three conditions were tested: light + DCMU (PSII inhibitor), light alone, dark.
Which conclusion is best supported?
- A
DCPIP is reduced spontaneously without light.
- B
PSII is unnecessary for the reaction.
- C
DCMU stimulates electron transfer.
- Dcheck_circle
DCPIP reduction depends on light-driven electron flow originating at PSII.
Explanation
DCMU blocks electron transport at PSII; the failure to reduce DCPIP in DCMU-treated samples confirms that electrons flow from water -> PSII -> downstream acceptors only when PSII works and light is present.