5. You are walking through the various sections of an arboretum garden. As you move through the section specializing in "desert plants," you notice that one of the trees has a gall forming in one area of the trunk near where it emerges from the soil. The plant has been infected by Rhizobium radiobacter. Would you expect this infection to trigger the tree’s "hypersensitive response"? a. Yes, because the hypersensitive response is the quickest way to limit the spread of Rhizobium throughout the plant. b. Yes, because the hypersensitive response is the last line of defense a plant can use against a pathogen. c. No, because Rhizbium radiobacter does not move through the plant. d. No, because Rhizobium radiobacter only infects a wounded area of the plant and those regions are already dead.

The correct answer is 'd' No, because Rhizbium radiobacter only infects wounded area of the plant and those regions are already dead.

Explanation:

Rhizobium is a genus of gram negative, soil bacteria that forms symbiotic relationship with certain plant, fixing nitrogen. However, soil borne plant pathogen, Agrobacterium tumefaciens, or rhizobium radiobacter, are tumor producing species that does not in anyway benefit the plant. The have a tendency to cause crown gall tumors by transfering T-DNA of its Ti plasmid intp a plant cell, where the T-DNA becomes integrated into the plant genome, Hence causing overproduction of plant growth hormones which ultimately results in tumor. A. tumefaciens does not elicit a typical Hypersensitivity response in a plant. As it enters only through wounds in the plant and these regions are already dead, hence no hypersensitivity response is produced by the plant.