The Thorns Of Life
In botanical morphology, thorns, spines, and prickles are hard structures with sharp, or at least pointed, ends. In spite of this common feature, they differ in their growth and development on the plant; they are modified versions of different plant organs, stems, stipules, leaf veins, or hairs. In nontechnical usage, the terms may be synonymous.
It has been proposed that thorny structures may first have evolved as a defense mechanism in plants growing in sandy environments that provided inadequate resources for fast regeneration of damage. However, the suggestion was unsupported by any argument to discount the likelihood that spiny defences might have been developed as means of defence in say, resource-rich environments where herbivory might have been more intense than in the hypothesized sandy environments.
Not all functions of spines or glochids are limited to defence from physical attack by herbivores and other animals. In some cases, spines have been shown to shade or insulate the plants that grow them (e.g. saguaro cactus spines shade the apical meristem in summer and in members of the Opuntioideae glochids insulate the apical meristem in winter).
April 6th, 2013
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