Question

How does a plant defend against herbivores?

a. Plant cells produce salicylic acid to warn the rest of the plant about the attack.
b. The hormone systemin is produced at the site of injury and signals the plant to produce proteinase inhibitors.
c. Plant cells at the site of attack are killed to starve the herbivore of nutrients.
d. The plant produces molecules that stimulate the herbivore's digestive enzymes.

Answer 1

Plants defend against herbivores by producing chemicals that can kill invaders, trigger defensive responses, attract predators, or cause the invaded tissue to rapidly die. Mechanical defenses such as thorns and spines also discourage herbivores. Additionally, plants produce hormones and toxins like salicylic acid and jasmonates to combat pathogens and deter further herbivory.

Step-by-step explanation:

Plants have developed a variety of strategies to defend against herbivory. One way plants defend themselves is by producing chemicals when under attack. These chemicals can serve multiple defensive functions: (1) they may kill the invader (phytoalexins), (2) trigger defensive responses in neighboring plants or attract predators of the herbivore, or (3) cause an 'hypersensitive response' where the invaded tissue rapidly dies to block the spread of infection, which can be particularly effective against biotrophic pathogens.

Plants can resort to mechanical defenses such as thorns and spines to discourage animals physically. When these first lines of defense are breached, plants may produce hormones and toxins, such as salicylic acid or jasmonates, to fight off pathogens and deter herbivores further by increasing toxic secondary metabolites or by attracting natural predators of herbivores.