28. Plants

At what point in photosynthesis is the electromagnetic energy of light first converted into chemical energy?

Why is the chlorophyll in chloroplasts less likely to produce fluorescence compared to extracted chlorophyll molecules?

What does it mean to say that a life cycle is gametophyte dominant versus sporophyte dominant?

Identify each of the following structures as haploid or diploid.

a. Sporophyte

b. Spore

c. Gametophyte

d. Zygote

The history of life has been punctuated by several mass extinctions. For example, the impact of a meteorite may have wiped out most of the dinosaurs and many forms of marine life at the end of the Cretaceous period. Fossils indicate that plants were less severely affected by this mass extinction. What adaptations may have enabled plants to withstand this disaster better than animals?

Draw a phylogenetic tree that represents our current understanding of evolutionary relationships between a moss, a gymnosperm, a lycophyte, and a fern. Use a charophyte alga as the outgroup. (See Figure 26.5 to review phylogenetic trees.) Label each branch point of the phylogeny with at least one derived character unique to the clade descended from the common ancestor represented by the branch point.

The evolution of cuticle presented plants with a challenge that threatened their ability to live on land. Describe this challenge, and explain why stomata represent a solution. Compare and contrast stomata with the pores found in liverworts.

Predict how the following conditions would affect the production of O₂, ATP, and NADPH and state whether noncyclic or cyclic electron flow would occur in each:

(3) blue and red photons hit a chloroplast, but a proton channel has been introduced into the thylakoid membrane, so it is fully permeable to protons.

An investigator exposes chloroplasts to 700-nm photons and observes low O₂ production, but high ATP production. Which of the following best explains this observation?

a. The electrons from water are directly transferred to NADP⁺, which is used to generate ATP.

b. Photosystem II is not splitting water, and the ATP is being produced by cycling electrons via photosystem I.

c. The O₂ is being converted to water as a terminal electron acceptor in the production of ATP.

d. Electron transport has stopped and ATP is being produced by the Calvin cycle.

What is a pollen grain?

a. sperm-producing gametophyte

b. egg-producing gametophyte

c. sperm-producing sporophyte

d. sperm