Final answer:
Phytoalexins and phytoanticipins are compounds in plant defenses against microbes; phytoalexins are produced in response to attack while phytoanticipins exist in plants beforehand. Examples include resveratrol (a phytoalexin) and saponin (a phytoanticipin), both of which help modify plant-microbe interactions.
Step-by-step explanation:
The difference between a phytoalexin and a phytoanticipin lies primarily in their mode of production and action within plants as a response to microbial infection. Phytoalexins are antimicrobial substances that are synthesized de novo (newly formed) by plants in response to pathogen attack.
Examples of phytoalexins include resveratrol in grapevines and pisatin in peas. Their production is typically triggered by the interaction of pathogen-associated molecular patterns (PAMPs) with plant pattern-recognition receptors (PRRs), leading to a series of downstream defense responses.
In contrast, phytoanticipins are pre-existing compounds in plants that are constitutively present at low levels and may be toxic to pathogens or increase upon infection, but their presence is not induced by pathogens.
An example of a phytoanticipin is saponin, which is found in a variety of plant species.
Both phytoalexins and phytoanticipins contribute to the modification of plant-microbe interactions through creating a hostile environment for the microbes or directly inhibiting their growth and spread, thereby playing roles in the plant defense systems.