33. Plant Anatomy

You attached a birdfeeder to a tree 5 years ago at a position 6 feet above the ground. The tree has grown since at a rate of 1 foot per year. What is the current height of the birdfeeder?

On this cross section from a woody eudicot, label a growth ring, late wood, early wood, and a vessel element. Then draw an arrow in the pith-to-cork direction.

In the late 1950s, Herbert Taylor grew bean root-tip cells in a solution of radioactive thymidine (a precursor to one of the deoxyribonucleotides in DNA) and allowed them to undergo one round of DNA replication. He then transferred the cells to a solution without radioactive thymidine, allowed them to replicate again, and examined their chromosomes for the presence of radioactivity. His results are shown in the following figure, where red indicates a radioactive chromatid.

(b) What would the results of Taylor's experiment be if eukaryotes used a conservative mode of DNA replication?

In the late 1950s, Herbert Taylor grew bean root-tip cells in a solution of radioactive thymidine (a precursor to one of the deoxyribonucleotides in DNA) and allowed them to undergo one round of DNA replication. He then transferred the cells to a solution without radioactive thymidine, allowed them to replicate again, and examined their chromosomes for the presence of radioactivity. His results are shown in the following figure, where red indicates a radioactive chromatid.

(a) Draw labeled diagrams of double-stranded DNA molecules that explain the pattern of radioactivity observed in the sister chromatids after the first and second rounds of replication.

Place these tissues in order, starting at the center of a woody stem. (Hint: Review Figure 31.8A.).

a. Vascular cambium

b. Primary phloem

c. Epidermis

d. Primary xylem

Trees can be killed by girdling—the removal of bark and vascular cambium in a ring all the way around the tree. Explain why.

Plants experience a vast array of conditions that can alter their growth and development, including temperature and availability of water, nutrients, and light. They are also exposed to pollutants such as acid rain formed largely as a result of burning fossil fuels and volcanic eruptions. Acid rain can strip minerals and nutrients from the soil and eat away the outer waxy layer of tissue that protects a plant. Acid rain is still a major environmental problem in certain regions.

How does acid rain affect plant growth?

Develop a hypothesis on the likely effects of acid rain on primary growth in trees.

Based on your hypothesis, make some predictions about the impact of acid rain on the height of tree trunks.

Plants experience a vast array of conditions that can alter their growth and development, including temperature and availability of water, nutrients, and light. They are also exposed to pollutants such as acid rain formed largely as a result of burning fossil fuels and volcanic eruptions. Acid rain can strip minerals and nutrients from the soil, and eat away the outer waxy layer of tissue that protects a plant. Acid rain is still a major environmental problem in certain regions. How does acid rain affect plant growth? Researchers tested the effects of acid rain (pH 2.0) on seedlings of two different species, camphor tree (Cinnamomum camphora) and chinaberry tree (Melia azederach), using distilled water as a control. Results of the experiments are shown here. Note that acid rain caused a significant reduction of growth in chinaberry trees (*** means P < 0.001), but not in camphor trees. What was the approximate percentage of growth reduction observed in the chinaberry trees treated with acid rain?

Plants experience a vast array of conditions that can alter their growth and development, including temperature and availability of water, nutrients, and light. They are also exposed to pollutants such as acid rain formed largely as a result of burning fossil fuels and volcanic eruptions. Acid rain can strip minerals and nutrients from the soil, and eat away the outer waxy layer of tissue that protects a plant. Acid rain is still a major environmental problem in certain regions. How does acid rain affect plant growth? Which meristem was likely affected in the chinaberry tree?

Plants experience a vast array of conditions that can alter their growth and development, including temperature and availability of water, nutrients, and light. They are also exposed to pollutants such as acid rain formed largely as a result of burning fossil fuels and volcanic eruptions. Acid rain can strip minerals and nutrients from the soil, and eat away the outer waxy layer of tissue that protects a plant. Acid rain is still a major environmental problem in certain regions. How does acid rain affect plant growth? Give a plausible explanation for the differential effect of acid rain on height in camphor and chinaberry trees (i.e., what structural features might offer more protection from acid rain in one species versus another?).

Plants experience a vast array of conditions that can alter their growth and development, including temperature and availability of water, nutrients, and light. They are also exposed to pollutants such as acid rain formed largely as a result of burning fossil fuels and volcanic eruptions. Acid rain can strip minerals and nutrients from the soil and eat away the outer waxy layer of tissue that protects a plant. Acid rain is still a major environmental problem in certain regions. How does acid rain affect plant growth?

Based on the results presented here, predict the impact of acid rain on the vascular cambium in the two species.

How would that effect be apparent in the amount of wood produced in the tree trunks?

Plants experience a vast array of conditions that can alter their growth and development, including temperature and availability of water, nutrients, and light. They are also exposed to pollutants such as acid rain formed largely as a result of burning fossil fuels and volcanic eruptions. Acid rain can strip minerals and nutrients from the soil and eat away the outer waxy layer of tissue that protects a plant. Acid rain is still a major environmental problem in certain regions. How does acid rain affect plant growth?

Beyond primary and secondary growth, what other aspects of plant growth might be negatively affected when plants are exposed to environmental stress?