Maize attacks herbivore, who's next?

Colourful maize
Maize plants can do much more than showing off their varied colours. When attacked, (Photo credit: Wikipedia)
If you were under the belief that plants are motionless beings, incapable of defending themselves, then its high time you start believing otherwise. On more than one occasion, have scientists found that plants are very much capable of protecting themselves and guaranteeing their survival when attacked.

The heading is not just an attempt to grab your attention, but a simple fact. A maize plant is actually capable of launching an 'in-direct' attack on a lepidopteran herbivore by releasing certain volatile compounds in the air that attract the lepidopteran's natural enemies.

Maize plants are usually attacked by larvae of lepidopteran insects such as moths and butterflies. The plant, too, has a patience threshold and allows the larvae to feed for a while. When the plant's foliage is excessively attacked, the plant increases expression of the tps10 gene that leads to high production of sesquiterpenes, such as beta-farnesene, alpha-bergamotene and seven others in fixed concentration. While the names of these compounds sound complex, their job is quite simple. These volatile compounds travel through the air and attract females of wasp species, Cotesia marginiventris. Female wasps use the lepidopteran larvae to lay their own eggs within them. The poor herbivores which were once attacking the maize plant are now themselves under attack from wasps, who will lay their eggs within them. The infested larvae have only the worst reserved for them since the wasp eggs incubate in the larval bodies and eat them from within after they hatch.

Cotesia marginiventris,  a wasp lays its eggs inside caterpillars Image credit: Phys.org
Cotesia marginiventris,  a wasp lays its eggs inside caterpillars
Image credit: Phys.org


Such a mechanism for defense has been reported in over 15 species of plants so far and is likely to be present in many more. So, next time you see someone unnecessarily chop down a tree, share this story with him!

Reference:

Schnee, C., Kollner, T., Held, M., Turlings, T., Gershenzon, J., & Degenhardt, J. (2006). The products of a single maize sesquiterpene synthase form a volatile defense signal that attracts natural enemies of maize herbivores Proceedings of the National Academy of Sciences, 103 (4), 1129-1134 DOI: 10.1073/pnas.0508027103


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