Answer to Question 1T
Answer to Question 2Plant use of nutrients is affected by soil features such as oxygen supply, water supply, and soil
temperature. Root distribution in the soil is another factor. Anything that interferes with photosynthesis
also reduces nutrient uptake. For instance, plants growing under low light make less sugar to send to
the roots and so take up fewer nutrients.
Because respiration uses oxygen, conditions that limit oxygen supply also limit nutrient
uptake. Poor drainage and soil compaction slow the movement of oxygen into the soil. These
conditions also limit the ability of plants to absorb nutrients.
Dry soils lower nutrient uptake because the lack of water impedes nutrient flow toward the
root hairs by mass flow and diffusion. Soil temperature also affects nutrient uptake. The rates of all
chemical reactions, including those in soil and plants, depend on temperature. Respiration rates go
down in cold soil, so the plant has less energy to take up nutrients, and root growth is slowed in cold
soil, limiting root interception of nutrients. Warmer soil temperature improves uptake up to around 85
degrees Fahrenheit, partially by speeding diffusion. Beyond that, uptake declines. Thus, both cold and
hot soil inhibit uptake.
An increase in the amount of nutrient ions in the soil improves absorption. Uptake is most
rapid, of course, where roots are numerous. Roots grow best where air, water, and nutrients are in good
supply. Drainage, compaction, and fertilization influence how well roots grow, as does soil or root
depth.
Organisms in the rhizosphere and their interactions with plant roots obviously influence
nutrient uptake. Soil-borne pathogens damage the ability of roots to take up nutrients.
reaction system of photosynthesis
pH scale
Time dependence of the rates of a chemical reaction
Soil Structures
Oxyanion reaction intermediate
The thymine dimer photolyase: Structures of FADH- and FADH+ and the likely reaction pathway