Evolutionary Biology of Plants

10 04 2007

The cactus has its bristling armament of spines that can radiate heat and defend its water-packed stem from herbivory (p 5)

Consider that the cactus spine would be an impossible adaptation unless the cactus stem or some other organ type carried on photosynthesis. The cactus spine is a highly modified leaf that functions in ways not otherwise normally entertained by green foliage leaves because the cactus stem is capable of assuming tasks of typical photosynthetic leaves (light interception, gas interchange, etc.). (p 6)

The Evolutionary Biology of Plants, Karl J. Niklas