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Study Questions

The study of which cellular process led to the discovery of cytokinin? What role did serendipity play in the discovery? Was the first discovered cytokinin a synthetic or naturally occurring hormone?
Name two plant diseases that are associated with cytokinin overproduction. In each case, what is the source of the excess cytokinin?
Compare the plant and microbial pathways of cytokinin biosynthesis. What are the naturally occurring cytokinins in plants?
Which enzyme catalyzes the first step in cytokinin biosynthesis? What is known about the gene(s) encoding this enzyme?
Cytokinins can act both locally and over long distances in the plant. Provide examples of both types of cytokinin action. In which tissue(s) does long distance transport occur?
Which enzyme is response for cytokinin degradation?
What is the nature of the cytokinin receptor? Compare and contrast the cytokinin receptor and signaling mechanism to bacterial two-component signaling systems. What role does phosphorylation play?
Which protein (or proteins) represents the “response regulator” in the cytokinin signaling pathway? What is their mechanism of action?
Diagram the main steps in the cellular pathway for cytokinin signaling. Which steps occur in the cytoplasm and which steps occur in the nucleus?
Discuss the roles of cytokinins in the following developmental phenomena: shoot growth, root growth, the cell cycle, tissue culture, apical dominance, leaf senescence, and vascular development. Cite experimental evidence whenever possible.
What are some potential applications of cytokinin manipulation to agriculture?