Question

Carbon makes up the bulk of the biological mass of living things. So when considering a seed and a full grown tree, we need to consider where did that mass come from. For a class experiment, three groups of students were given a dish with 1.5 grams of clover seeds. One-third of the class kept their seeds in the light with no water, another third kept their seeds in the light with water, and the final third kept their seeds in the dark with water. After two weeks, students brought back the dishes and we dried the contents to remove any weight gained by water. The image below shows the results. For each treatment, write an explanation of where did the biomass come from or where did it go? (Remember each dish started with 1.5 g of seeds) What process would result in the gaining or loss of carbon in each case. Students should explain that in increased biomass in #2 was the result of increased photosynthesis and the loss of biomass in #3 (and #1) is due to respiration that turns organic carbon into CO2 gas.

Answer 1

In case 1 seeds with light without water there is no reducing agent is present thus no oxidation reaction takes place hence oxygen can't liberate as well as carbohydrate can't formed.

In case 2 seeds with light and water -it's perfect condition for photosynthesis and biomass enhancement due to complete redox reaction and all metabolic reaction takes place.carbohydrate,oxygen and ATP evolved during this case.

In case 3 seeds with dark and water- biomass synthesis process is a endergonic process needs source of energy so here no light has given thus there is no formation of carbohydrate and hence no biomass increases.