Phytoecysones, such as that found in Polypodium ferns growing on campus, play a role in plant defense against herbivory by insects via: a) Inhibiting digestibility b) Increasing production of trichomes c) Deterring insects from landing d) Causing premature moulting e) Attracting other organisms to defend the plant
The correct answer and explanation is:
The correct answer is: d) Causing premature moulting
Phytoecdysones are plant-derived compounds that mimic the action of insect ecdysone, a hormone involved in the regulation of moulting and development in arthropods. In plants such as those in the Polypodium genus, phytoecdysones are believed to play a role in deterring herbivory by insects. These compounds disrupt the insect’s normal growth cycle by causing premature moulting, a process where the insect sheds its exoskeleton in preparation for growth. When insects ingest plants containing phytoecdysones, the disruption of moulting may prevent the insect from developing properly, thereby affecting its survival and reproductive capacity.
This strategy of inducing premature moulting is an example of plant defense through hormonal interference. When an insect’s moulting process is disturbed, it can lead to death or an inability to feed and grow, making the plant less appealing as a food source. This defense mechanism is particularly effective in reducing the number of herbivores that are able to consume the plant.
Unlike physical barriers like trichomes, or chemical deterrents that act by making the plant unpalatable, phytoecdysones act by targeting the insect’s physiological processes, causing a direct disruption in their development. Such hormonal mimicry serves as an effective form of defense, especially when the insect population relies heavily on regular moulting to progress through its life stages.