thorny question

[Allan Shanfield]

If thorns are often modified leaves with photosynthetic tissue, maybe it's
where ps and respiration occurs. Also, when thorns are modified epidermal
structures, often they are filled with chloroplasts; perhaps w/similar
functions. Wouldn't thorns in a dry climate lower the surface to area
ratio, modifying the boundary later - thus conferring a xerophytic
explanation.

Guesses from a non-physiological ecologist.

Allan Shanfield

Env. Hort.
UC Davis