Black plants, not green, could well be the rule in certain conditions.
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Given the scale of the cosmos and the consequent range of possible habitats, we must expect diversity beyond imagination. As plants are not bound to use chlorophyll, so the essentials of life are not bound to use carbon as a base; in its place, we may very well encounter silicon; we may also see life that processes phosphorus in lieu of nitrogen, or sulfur where we expect oxygen.
We have already found organisms conforming to some of these descriptions on our own world, so we can no longer plead a case for looking through a narrow lens. By this time next century, exobiology may well have entirely redefined “life as we know it.”