AP BIOLOGY

Detailed explanation-1: -Acacia trees (in the bean family) have spines made of modified leaf stipules. There are also plants whose entire leaves have been converted into spines, as is the case with cacti. All of these spines are dead at maturity, full of fibers, and no longer capable of photosynthesis.

Detailed explanation-2: -Landscape plants with true thorns include firethorn (Pyracantha), hawthorn and Japanese flowering quince. A sharp projection developed from a leaf, stipule or leaf part (rather than from a branch) is called a “spine”.

Detailed explanation-3: -Cactus plants have spines to keep predators away. It also helps cactus to withstand the harsh climate of desert.

Detailed explanation-4: -Prickles are comparable to hairs but can be quite coarse (for example, rose prickles). They are extensions of the cortex and epidermis. Technically speaking, many plants commonly thought of as having thorns or spines actually have prickles.