The length limit on Enotes responses prevents me from addressing all of these questions. Responding to your future questions will be easier if you cluster them by topic, such as plant anatomy, environmental effects, and lab experiments.
I chose a few of the high-point value questions to answer:
- Using plants to clean up toxic sites reduces the amount of labor or human involvement necessary in order to accomplish the task. This is likely to make it a cheaper option.
- Plants usually do not create toxic byproducts of their own; this will probably result in a simpler and "cleaner" solution that doesn't involve additional chemicals, combustion engines, human waste, etc, that might have been involved in a more complicated "hands-on" cleanup effort.
- The plants themselves may uptake the toxic residue, and it may then be distributed among the animals that eat those plants. While the site may be clean, the effect of the toxins persists.
- The plants may not be native to the location, raising the possibility that they will become invasive during or after the cleanup effort, displacing native species and altering the ecological composition.
43. Sunlight provides the main source of energy for the plant, but does not necessarily provide raw building materials for plant growth and repair. The energy in sunlight is utilized to excite electrons, whose energy is then captured in the form of glucose molecules synthesized from water and carbon dioxide. This is the photosynthetic process. Plants utilize a form of highly endosymbiotic cell structures called chloroplasts to perform photosynthesis, using a pigment called chlorophyll that gives plants their characteristic green color. Plants absorb different wavelengths of light based on the different ratios of chlorophyll and other pigments in their chloroplasts, each of which is sensitive to a different variety of electromagnetic wavelengths.
- Solution 1 produced the most robust results by far. The size and the deep green color, compared to the other two solutions, indicate successful synthesis of nutrients and production of chlorophyll. The plant had an abundance of nutrients available to it, which is the primary reason for its success.
- Solution 2 performed significantly worse than Solution 1 (nearly 33% size) but not quite as badly as solution 3. The small size and pale color indicates significant chlorosis, i.e. a lack of chlorophyll, indicating nutritional deficiency and poor chlorophyll production. This plant's results indicate that the presence of nitrogen is significantly more influential in the growth and health of the plant.
- Solution 3 produced the poorest results. The small size and pale color indicate chlorosis. The complete lack of nutrients likely resulted in the plant being incapable of synthesizing carbohydrates.