1). Phosphate uptake by roots involves
a). a PO4 channel in the endoderm of the root.
b). soil bacteria to make the phosphate bioaccessable.
c). symbiotic fungal hyphae to increase the effective surface area of the root.
d). root nodules fixing phosphate from the air.
2). In an attempt to create a nitrogen-fixing bioreactor, you set out to culture Rhizobium a). from the root nodules of pea plants. After months of work, you are still having trouble getting the Rhizobium to grow, let alone fix nitrogen. What might explain this failure?
a). Rhizobium only grows in association with plant root hairs.
b). Rhizobium from root nodules lacks a cell wall, so it will not grow in culture.
c). You accidentally put a fungicide in your growth medium that kills all of the Rhizobium.
d). Rhizobium from root nodules lacks chromosomal DNA, so it will not grow in culture.
3). You are performing an experiment to determine the nutrient requirements for a newly discovered plant and find that for some reason your plants die if you leave boron out of the growth medium but do fine with as low as 5 parts per million in solution. This suggests that boron is
a). an essential macronutrient.
b). a nonessential micronutrient.
c). an essential micronutrient.
d). a nonessential macronutrient.
4). You are setting up some planters to grow flowers in your apartment and discover that you bought sand rather than potting soil. You decide to go ahead and plant the flowers in the sand to save yourself a trip back to the store. Much to your dismay, all of your plants die! How can you explain this failure?
a). Sand does not pack tightly enough around the roots to hold the plants upright, so they fall over and die.
b). Sand does not hold enough water to sustain plant metabolism, so all of the plants die from dessication.
c). Sand does not contain enough nutrient material to sustain plant growth, so the plants die from starvation.
d). Sand is too abrasive and damages the roots as they grow through it, so the plants die.
5). If you discover a purely white plant growing on the forest floor, you can safely assume that it is a
a). mutant plant that uses a colorless pigment to carry out photosynthesis.
b). parasitic plant that acquires its macronutrients from other plants.
c). plant that only carries out the dark reactions of photosynthesis and therefore doesn't need green pigments.
d). plant that does not require macronutrients and therefore does not need photopigments.
6). Growing peas that are defective in flavonoid production would
a). prevent bioaccumulation of potassium in the roots.
b). prevent bioaccumulation of nitrogen in the roots.
c). prevent bioaccumulation of phosphorous in the roots.
d). prevent the production of flavor molecules in the seeds so that they would be unpalatable.
7). Feeding your Venus flytrap a common brand of all-purpose plant fertilizer would likely cause
a). it to die from nitrogen overload.
b). its traps to become large enough to capture small mammals.
c). no change, because these plants can only use nitrogen from insects.
d). its traps to fall off, because it would not need to acquire nitrogen from insects.
8). If you were asked how to clean up a trichloroethylene (TCE) spill without having to resort to burning or other chemical methods, how would you do it?
a). Plant poplar trees to phytoremediate the soil.
b). Plant bean plants to replace the TCE with fixed nitrogen.
c). Plant Brassica plants to phytoaccumulate the TCE.
d). Plant Indian pipe because it is not adversely affected by TCE in the soil.
Test Your Visual Understanding
1). If you found a grove of poplar trees like that shown in this image, what might you conclude about the area?
Answer: There are several reasons these poplar trees could be planted in this grove. They may have been planted as a windbreak (notice how they have grown with a bit of a tilt to the one side). However, having just read this chapter, you might hypothesize that they are being used for phytoremediation. Since the area around the trees appears to be barren, there may be toxins in the soil that are affecting the growth of other plants.
Apply Your Knowledge
1). Match each of the following nutrients with its appropriate function in plants, and discuss whether it is a macro- or micronutrient.
a). carbon ___ cell wall formation
b). nitrogen ___ nucleic acid formation
c). phosphorous ___ amino acid production
d). iron ___ nitrogen fixation
e). molybdenum ___ chlorophyll production
a). carbon a cell wall formation
b). nitrogen c nucleic acid formation
c). phosphorous b amino acid production
d). iron e nitrogen fixation
e). molybdenum d,e chlorophyll production
Carbon, nitrogen, and phosphorous are macronutrients that are need in large amounts for the production of carbohydrates, proteins, and nucleic acids. Iron and molybdenum are needed in much smaller amounts and are considered to be micronutrients. Molybdenum is used in nitrogen fixation. Iron is needed for several reasons, including the production of chlorophyll. Plants that are deficient in iron show chlorosis or a bleaching of leaf color.
2). If you were to eat one ton (1000 kg) of potatoes, approximately how much of the following minerals would you eat?
a). copper between .4 and 3 g
b). zinc between 1.5 and 10 g
c). potassium between 0.5 and 6 kg
d). iron between 2.5 and 30g
Answer: Here is how you solve the problems:
The macronutrient, potassium is constitutes 0.5 to 6 % of the dry weight. Let's assume that the potato is 90% water. The dry weight would be 10 % of 1000 kg or 100 kg. Next you calculate 0.5% of 100 which is 0.5 kg. You would do the same type of calculation for 6 %.
The micronutrient problems would also use the estimate of 100 kg dry weight. The conversion you need to use is that 1 ppm is the same as 1 mg per kg. So, 4 ppm of copper is the same as 4 mg/kg. Multiply this by 100 kg of dry weight potato and you have 400 mg of copper. Since there are 1000 mg in a gram, 400 mg X 1g/1000 mg = 0.4 g of copper in a ton of potato. The other micronutrient problems would be calculated in a similar manner.
3). Using what you know about phytoremediation, design a strategy to speculate for gold that would not require any digging or disruption of the soil.
Answer: Gold is a heavy metal. There are some hints that metal transporters exist that load metal in the soil into xylem and that it is later sequestered in vacuoles in leaves. You could start with plants known to hyperaccummulate heavy metals like lead and cadmium and see if they could also accumulate gold. All you would need to do then is to grow your plants, harvest them, dry them down, and isolate the gold. If this didn't work, you could search for plants that did take up gold and use those in your search for gold.