Line | Resin is a plant secretion that hardens when |
| exposed to air; fossilized resin is called amber. |
| Although Pliny in the first century recognized that |
| amber was produced from marrow discharged by |
(5) | trees, amber has been widely misunderstood to be |
| a semiprecious gem and has even been described |
| in mineralogy textbooks. Confusion also persists |
| surrounding the term resin, which was defined |
| before rigorous chemical analyses were available. |
(10) | Resin is often confused with gum, a substance |
| produced in plants in response to bacterial infections, |
| and with sap, an aqueous solution transported |
| through certain plant tissues. Resin differs from both |
| gum and sap in that scientists have not determined a |
(15) | physiological function for resin. |
| In the 1950s, entomologists posited that resin |
| may function to repel or attract insects. Fraenkel |
| conjectured that plants initially produced resin in |
| nonspecific chemical responses to insect attack |
(20) | and that, over time, plants evolved that produced |
| resin with specific repellent effects. But some insect |
| species, he noted, might overcome the repellent |
| effects, actually becoming attracted to the resin. |
| This might induce the insects to feed on those |
(25) | plants or aid them in securing a breeding site. |
| Later researchers suggested that resin mediates |
| the complex interdependence, or coevolution, of |
| plants and insects over time. Such ideas led to the |
| development of the specialized discipline of chemical |
(30) | ecology, which is concerned with the role of plant |
| chemicals in interactions with other organisms and |
| with the evolution and ecology of plant antiherbivore |
| chemistry (plants' chemical defenses against attack |
| by herbivores such as insects). |