Key Concepts Quiz

This activity contains 12 questions.

	I was given a beautiful cactus plant a couple of months ago, and it recently died. I was told that it was overwatered. I know plants need water to survive and they take what they need from the soil, so how would adding too much water to the soil kill the cactus?   The plant only takes in as much water as it needs, so something else must have killed the cactus. The excess water must have diluted the minerals the plant needed to survive. The excess water must have blocked the diffused atmospheric oxygen needed for cellular respiration in the living root cells. Since water is H2O, there was too much oxygen available, causing the root cells to die.

	How do root hairs aid in water uptake in roots?   Root hairs increase the surface area of a root, thus increasing the root's absorptive capacity. Root hairs allow direct water passage to occur across the Casparian strip. Root hairs increase the number of cells found in a single root—the more cells, the more chemical processing that takes place. Root hairs are a direct connection to the xylem in the root.

	I tend to have an inquiring mind, and I want to know more about how water moves within the plant body. I take a common houseplant and cut the stem off about 1 inch from the soil surface. I notice water collecting at the cut as if some force is pushing it up through the roots and remaining stem. How could I best explain my findings?   There is excess water in the soil. There is a transpirational pull on the water, pulling it through the root system. The xylem cells in the remaining part of the plant act to siphon the water from the soil. Solutes in the xylem are producing a phenomenon called root pressure.

	Guard cells actively open and close the stomata of leaves. What delicate internal balance do these guard cells control with their actions?   water balance within the plant CO2 balance within the plant the balance between water uptake and gas exchange the internal balance of photosynthesis

	When considering the source-to-sink model of phloem transport, what structures can act as either a source or a sink?   stems and leaves roots buds tubers and bulbs flowers and fruits

	I have decided I want to grow tomatoes year-round using hydroponics methods. I have set up the appropriate mineral concentrations, solution circulation equipment, and aeration to maintain cellular respiration in the root system. Everything looks great for a couple of months, then the plants start to turn yellow, especially the tips of older leaves, and then die. What do you think is the likely cause of this problem?   There must be some kind of contaminant in the hydroponics solution. It is likely a nitrogen shortage, because you are not replenishing the hydroponics solution. There must be a problem in the aeration system that deprives the roots of needed oxygen. The plants must not be getting enough sunlight.

	I have decided to move to the tropics and start a banana plantation. After paying the loggers to clear-cut the land for my plantation, I plant my new crop of banana trees. The plants get off to a decent start, but soon growth halts and the plants wither and die. The tropics support some of the greatest plant diversity on the planet, so why are my banana trees dying?   The minerals that made the area "fertile" were locked up in the biomass that was removed by logging. The logging equipment used on the plantation was contaminated with the banana blight disease. I should have done my homework. I am not in an area that will support banana trees. Removing the trees changed the cation exchange capacity of the soil.

	As I walk through the local grocery store, I notice some beautiful tomatoes with a big "organically grown" sticker. I am quick to pay more for these tomatoes because they must be better for me. Is this a valid assumption?   Yes, the greater nutritional value is a valuable asset in any diet. Yes, there is added safety in the use of organic farming practices. No, most scientists agree that organically grown produce is actually less nutritious than produce grown by conventional means. No. There appears to be little difference in nutrition when comparing organic and conventional farming practices.

	In this modern age of science, which of the following shows the most promise in producing crops with a higher yield?   selective plant breeding choosing the best variety for a given area genetic engineering of crop plants adding more fertilizer to the soil

	I had the privilege of visiting Mt. St. Helens in the late 1990s. One of the things I noticed was that very few plants were growing in the blast zone due to the scarcity of certain essential elements. In fact, the few plants growing in the area were members of the plant group called legumes. What allows legumes to grow in this area?   They have a symbiotic association with nitrogen-fixing bacteria. The legumes obviously do not need the missing elements. The legumes were the first plants to grow in the area, and they have kept other plants from becoming established. Legumes produce substances that keep other plants from growing in the area.

	I own property with a barren hill that I decided to plant in pine trees. I notice that the trees are not doing very well; in fact, many are starting to die. I know that there are ample nutrients and water in the area. What is the likely culprit of the deaths in my tree plantation?   The mycorrhizal fungi are not present in the soil. The mycorrhizal fungi are blocking water uptake in the roots. The mycorrhizal fungi are using most of the available nutrients in the soil. The mycorrhizal fungi are blocking oxygen uptake in the roots.

	What conditions would produce plants that are parasitic or carnivorous?   The plants have lost the ability to photosynthesize. The plants are growing in an area missing one or more essential elements. The plants are taking advantage of the nutrients stored in other plants. The plants are supplementing nutrients to aid growth.

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