Question 1

All of the following contributed to the dust bowl in the American southwest during the 1930s except

Accepted Answer

While overgrazing, plowing of native grasses, planting of field crops, and lack of soil moisture all contributed to the dust bowl, clear-cutting of forest trees did not play a significant role in the region's environmental degradation.

Question 2

Several tomato plants are growing in a small garden plot. If soil water potential were to drop significantly on a hot summer afternoon, which of the following would most likely occur?

Accepted Answer

If soil water potential were to drop significantly, the plant would respond by reducing transpiration rates to conserve water. The stomatal apertures would decrease in response to this stress to limit water loss.

Question 3

According to the pressure flow hypothesis of phloem transport,

Accepted Answer

The answer of According to the pressure flow hypothesis of...

Question 4

All of the following are adaptations that help reduce water loss from a plant except

Accepted Answer

The answer of All of the following are adaptations that...

Question 5

Which of the following is of least concern to a researcher in a mineral nutrition experiment?

Accepted Answer

The ability of a laboratory balance to weigh very small quantities of chemicals is important for accurate measurements, but it is not the least concern compared to the other options. The purity of the chemicals and water used to make the nutrient solutions, as well as the chemical inertness of the container used to make and store the solutions, are critical for the success and accuracy of the experiment. The medium in which the test seedlings are grown is also important, but it is not necessarily the least concern compared to the other options.

Question 6

Ten tomato plants are germinated and maintained in a large tray with no drainage. After several weeks they all begin to wilt and die despite repeated watering and fertilization. The most likely cause of this die-off is

Accepted Answer

The lack of drainage in the tray means that water is not able to escape, leading to waterlogged soil. This can lead to anoxic conditions where there is not enough oxygen for the plant roots to survive. The buildup of toxic substances in the soil can also occur, but this is likely a secondary effect of the anoxia. Competition for resources and organic nutrient depletion are possible causes, but they are less likely to cause such a sudden and widespread die-off. No room left for root growth may be a factor, but it is unlikely to be the main cause of the problem.

Question 7

Most of the dry weight of a plant is the result of uptake of

Accepted Answer

The answer of Most of the dry weight of a...

Question 8

You are conducting an experiment on plant growth. You take a plant fresh from the soil that weighs 5 kg. Then you dry the plant overnight and determine the dry weight to be 1 kg. Of this dry weight, how much would you expect to be made up of organic molecules?

Accepted Answer

The answer of You are conducting an experiment on plant...

Question 9

A greenhouse experiment to test growth rates in tomato cultivars was conducted using sterile soil mix and watering with sterile solutions of water and fertilizer. Following germination, half of the plants in each group were transplanted into soil that was obtained from a nearby agricultural field (nonsterile), and the other half into sterile soil. After several weeks the plants that were transplanted into nonsterile soil exhibited a much higher growth rate compared to the plants transplanted into sterile soil. The most likely explanation for this result is

Accepted Answer

The most likely explanation for the higher growth rate in plants transplanted into nonsterile soil is that they were inoculated with mycorrhizae, which are beneficial fungi that form a symbiotic relationship with plant roots and help them absorb nutrients from the soil. The sterile soil and sterile watering solutions would have lacked these beneficial microorganisms, while the nonsterile soil would have had a natural population of mycorrhizae.

Question 10

Which one of the following statements about transport of nutrients in phloem is false?

Accepted Answer

While companion cells are involved in regulating the flow of phloem sap, they do not control the rate and direction of movement of phloem sap. These functions are primarily determined by the pressure gradient created by differences in osmotic concentration between the source and sink.

Question 11

Ignoring all other factors, what kind of day would result in the fastest delivery of water and minerals to the leaves of a tree?

Accepted Answer

On a warm, dry day, the rate of transpiration is higher due to increased evaporation of water from the leaves. This creates a greater pull on the water and minerals from the roots to the leaves, facilitating faster delivery.

Question 12

As a biologist, it is your job to look for plants that have evolved structures with a selective advantage in dry, hot conditions. Which of the following adaptations would be least likely to meet your objective?

Accepted Answer

Plants that do not produce abscisic acid and have a short, thick taproot would be least likely to have a selective advantage in dry, hot conditions. Abscisic acid helps plants to withstand drought by causing stomatal closure, reducing water loss. A short, thick taproot might not reach deeper water sources effectively.

Question 13

One is most likely to see guttation in small plants when the

Accepted Answer

Guttation occurs when root pressure exceeds transpiration pull, causing water droplets to be exuded from the tips or edges of leaves. This is most commonly seen in small plants that have not yet developed a well-established system for balancing water uptake and loss. High transpiration rates (option A) would increase the likelihood of wilting rather than guttation, as would hot, dry conditions (option C). Water potential in the stele of the root being high (option D) would not necessarily lead to guttation, and there is no evidence to suggest that mineral absorption by the roots (option E) is related to this phenomenon.

Question 14

Which cells in a root form a protective barrier to the vascular system where all materials must move through the symplast?

Accepted Answer

The endodermis forms a protective barrier to the vascular system in plant roots. This is accomplished through the presence of the Casparian strip, which blocks the movement of water and solutes through the apoplast, thereby directing them through the symplast. The cortex, epidermis, and exodermis are also involved in the root's protective functions, but they do not specifically regulate movement through the symplast. The pericycle is involved in lateral root development.

Question 15

In west Texas, cotton has become an important crop in the last several decades. However, in this hot, dry part of the country there is little rainfall, so farmers irrigate their cotton fields. They must also regularly fertilize the cotton fields because the soil is very sandy. Figure 29.1 shows the record of annual productivity (measured in kilograms of cotton per hectare of land) since 1960 in a west Texas cotton field. Use these data to answer the following questions.
  Figure 29.1
-Based on the information provided in Figure 29.1, what is the most likely cause of the decline in productivity?

Accepted Answer

The decline in productivity is most likely due to salination, as indicated by the increase in electrical conductivity of the soil (ECe) over time. Salination occurs when irrigation water contains dissolved salts that accumulate in the soil over time, leading to a more negative soil water potential and reduced plant growth. The other answer choices are not supported by the data provided.

Question 16

The water lost during transpiration is a side effect of the plant's exchange of gases. However, the plant derives some benefit from this water loss in the form of

Accepted Answer

Transpiration helps in evaporative cooling and aids in the transport of minerals from the soil to different parts of the plant.

Question 17

In west Texas, cotton has become an important crop in the last several decades. However, in this hot, dry part of the country there is little rainfall, so farmers irrigate their cotton fields. They must also regularly fertilize the cotton fields because the soil is very sandy. Figure 29.1 shows the record of annual productivity (measured in kilograms of cotton per hectare of land) since 1960 in a west Texas cotton field. Use these data to answer the following questions.
  Figure 29.1
-If you were the county agriculture agent, what would be the best advice you could give the farmer who owns the field under study in Figure 29.1?

Accepted Answer

The productivity of the cotton field has been declining since the 1990s, suggesting that the current practices of fertilization and irrigation may not be sustainable in the long term. As such, the best advice would be to switch to a variety of cotton that requires less water and can tolerate salinity, which would reduce the dependence on irrigation and minimize the impact of sandy soil on nutrient uptake. This would not only result in better yields but also be more environmentally sustainable.

Question 18

A young farmer purchases some land in a relatively arid area and is interested in earning a reasonable profit for many years. Which of the following strategies would best allow the farmer to achieve such a goal?

Accepted Answer

Selecting crops adapted to arid areas will be the best strategy for the farmer to earn a reasonable profit for many years in a relatively arid area. This will help the farmer to optimize the use of available water and reduce the need for extensive irrigation. The use of fertilizers and selling all parts of crop plants could also help increase profits, but selecting crops that can thrive in the arid conditions is the most important factor for the long-term success of the farm. Converting hillsides into fields might not be a feasible strategy in this case.

Question 19

If you were to prune the shoot tips of a plant, what would be the effect on the plant and the leaf area index?

Accepted Answer

Pruning the shoot tips of a plant encourages the growth of lateral branches, leading to a bushier plant. This increases the leaf area index because more leaves are produced as the plant becomes denser.

Question 20

Which of the following experimental procedures would most likely reduce transpiration while allowing the normal growth of a plant?

Accepted Answer

Increasing the level of carbon dioxide around the plant can reduce the need for the plant to open its stomata as frequently or as widely for gas exchange, which in turn can reduce water loss through transpiration, while still allowing for photosynthesis and normal growth.

Quiz 29: Resource Acquisition, Nutrition, and Transport in Vascular Plants