Question

DRY MASS OF CORN SEEDLINGS GROWN UNDER DIFFERENT CONDITIONS
Initial Dry Mass of Dry Mass of10 Change in dry
Treatment Group Treatment 10 Plants (g) Plants After Mass of10 Plants
One Week () over One Week
I None 14.8
II Light 32.8 +18
III Dark 11.7 -3.1
Thirty corn seedlings of equal size were randomly assigned to one of three treatment groups. At the beginning of the experiment, the plants in group I were dried and the mass was determined. The plants in group II were maintained in light for a week. The plants in group III were maintained in the dark for a week. All conditions other than light, were the same for groups II and III. At the end of the week, the plants in groups II and III were dried and the mass was determined. The experimental results are provided in the table.
(a) To explain the increase in mass of the light-grown plants, identify ONE inorganic source of new plant mass and connect it to the cellular process underlying the increase in mass.
(b) To explain the decrease in mass of the dark-grown plants, identify the overall chemical reaction that is occurring in the plant cells and connect it to the cellular process underlying the decrease in mass.

Answer 1

Answer:

See the answer below

Explanation:

(a) One of the inorganic sources of new plant mass for the light-grown plants is the atmosphere. The carbon in the form of carbon dioxide in the atmosphere is sequestrated into the body of the light-grown plants through a process known as photosynthesis. During this process, the inorganic carbon dioxide becomes fixed into the body of the plant through a series of steps that include both light-dependent and light-independent. The overall equation of the process is as below:

$6CO_2 + 6H_2O + Light --> C_6H_1_2O_6 + 6O_2$

As more plant mass is being gained by photosynthesis, some of the gained mass is also being lost to energy generation through a process known as respiration. Respiration is like the complete opposite of photosynthesis but a gain in mass is still possible because the rate of photosynthesis is more than the rate of respiration in the light-grown plants.

(b) The chemical reaction that can be held responsible for the decrease in mass of the dark-grown plants is respiration. Some of the mass is lost to energy generation and this mass cannot be recouped by adequate photosynthesis due to light limitation. The energy is needed to metabolic processes that would keep the plants alive. The equation of respiration is as below:

$C_6H_1_2O_6 + 6O_2 --> 6CO_2 + 6H_2O + Energy$

Answer 2

Answer:

A) Inorganic source of cellular mass is CO2. Plants take up CO2 from the atmosphere. By the process of photosynthesis, plants prepare sugars . Sugar gets converted in to starch, cellulose and other carbohydrates which are stored in the cells of the plants. This increases the plant mass . Plant requires water,CO2, light chlorophyll.

Chlorophyll absorbs sun light and converts it in to chemical energy. Chemical energy is used by the plant to synthesize sugars. Because of the synthesis of the sugars ,starch etc , the mass of the plant increased. Plants need light for making sugars.

B. Decrease in the mass is due to cellular respiration. This group of plants are in dark. So they do not photosynthesis.

But they have to undergo respiration to get energy for the activities of the plant. So no photosynthesis is occurring, hence no sugar formation. But sugar present in the plant is consumed to release energy. That is why mass of the plants kept in dark is reducing.

Cellular respiration has 3 steps. 1. Glycolysis 2. Kreb's cycle. 3. Electron Transport Chain.

The cellar respiration provides energy to all living organisms.

$C6H12O6 + 6 O2 ---------> 6CO2 + 6H2O + energy (ATP)$

CO2 released is given out of the plant body. So this is reducing the plant mass.

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