That's not generally not how evolution works. Sure, a plant will do fine with the current efficiency of photosynthesis, but intuition would tell us that a plant

That's not generally not how evolution works. Sure, a plant will do fine with the current efficiency of photosynthesis, but intuition would tell us that a plant would do more fine if its leaves were more efficient. It would grow faster, have more or better seed and would generally outcompete other plants of its species. That the efficiency is not higher than this leads us to believe that either: - there are strong evolutionary imperatives to not raise the efficiency any further (ie: "there has been a need not to", rather than "there has not been a need to). This could be due to a lot of reasons; oxidative stress, a plant's 'desire' to have a large leaf surface, a tendency to dry out the soil too quickly, etc etc. - With the current 'design' of chlorophyl, it is not possible to increase efficiency further, and it's quite hard to get out of the local optimum.