Video Transcript
Plants that have wounds or damage
to their exterior may deposit gums. Why is this considered a defense
against pathogens? (A) The secretion of gums
encourages the development of structural defenses like thorns. (B) The secretion of gums can trap
pathogens and prevent them from entering the plant. (C) The secretion of gums can
initiate the hypersensitive response, which causes rapid cell death around the site
of infection. (D) This statement is incorrect
because gums only help defend the plant against herbivores, not pathogens.
We are being asked how a plant
depositing gums on an outside wound could be considered a defense against pathogens
or germs. To answer this, let’s review what
effect the deposition of gums has on the wounded bark of a tree. When a plant’s outer tissues are
damaged, gums and resins flow out of the plant. These are initially very thick
liquids. And as they flow out, they create a
covering over the entire damaged surface area. Then as they dry, they harden but
remain sticky.
Imagine a pathogen trying to enter
the plant’s tissues through the damaged area. Not only do the gums create a
physical blockage that would prevent a pathogen from being able to easily enter
through the wound, but they are also sticky. So any pathogens that attempt to
enter will likely get stuck to or within the gum and essentially be trapped
there. So gums provide defense both by
creating a physical blockage and by trapping pathogens within their stickiness.
Therefore, the correct answer must
be (B). The secretion of gums can trap
pathogens and prevent them from entering the plant.
