The shoot system of a prickly pear cactus consists of broad paddle-like structures covered with clusters of spines. The spines are modified leaves, so the flat green paddles must be modified versions of what structure?

Consider the structure of the prickly pear cactus: The broad, flat, green paddles are involved in photosynthesis, which is a function typically associated with leaves, but in cacti, these structures are actually modified stems.

Recognize the adaptation in cacti: In many cacti, the stems have adapted to perform photosynthesis due to the modification of leaves into spines. This adaptation helps the plant survive in arid environments.