Chapter 6

Explain why plant senescence is regarded as the final stage of plant development.

Briefly describe the cellular differences between programmed plant senescence and stochastic plant senescence.

List the order of events in programmed senescence, occurring at the cellular level.

Programmed leaf senescence results in a decrease in sucrose concentration in phloem. Does this observation reflect a decrease in the synthesis of intracellular glucose and fructose because of the decline in photosynthesis? Explain.

Describe why the plant cell uses more energy during programmed senescence than during nonsenescent, normal cellular function.

The highly evolved genetic program for senescence in plants is evidenced by differences in the presenescent and senescent chlorophyll-degradation pathways. Explain.

Explain how the fatty acids found in normally functioning cellular membranes also play an important role in the degradation of membranes during leaf senescence.

The transition from programmed senescence to stochastic senescence can be characterized by the transition from source to sink metabolism. What is meant by the terms source and \(\sin k\) metabolism? What is the role of sink metabolism in the reproductive characteristics of the plant?

Discuss the differences between animal and plant mitotic cell senescence.

Explain how the lack of phototropism in an adult plant contributes to the initiation of leaf senescence.