Jan Ingenhousz (1730-1799), in his experiment with an aquatic plant, showed that in bright sunlight, small bubbles were formed around the green parts while in the dark, no such bubbles formed. He found out these bubbles to be of oxygen. He thus, confirmed that purification of air or formation of dephlogiston is carried out by green plants only in presence of sunlight. 

• Water in the plant is transported using a pressure flow mechanism. Translocation is the transport of nutrients and carbohydrates from source to sink, which is performed by the phloem. Pholem and xylem are present adjacent to each other in the vascular bundle of the plant. When the sugar ie sucrose is produced in the mesophyll of the leaves is produced it is transferred to the phloem to be transported. As the sugar concentration in the phloem increases water is diffused in the phloem from the xylem and this is what we call ascent of sap. When the water is diffused in the cells due the rigid wall the pressure in the cell increases. due to increase in the pressure at the source and low pressure at the sink the water along with the sugar is transported. As the sugar reaches the sink and leaves the cell water also moves out of the cell. Therefore the rate of photosynthesis is dependent on translocation rate. As the rate of translocation decreases the rate of photosynthesis also decreases.
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• Therefore, option A is correct. 
  

Sun derives the water cycle, heats up water in ocean and seas, and then water vapours evaporate to air. As the vapours move upward the cool temperature there causes it to condense into clouds and they fall as precipitate like rain, hailstone etc.

Phytochrome is a photoreceptor, a pigment that plants, and some bacteria and fungi, use to detect light. It is sensitive to light in the red and far-red region of the visible spectrum. Many flowering plants use it to regulate the time of flowering based on the length of day and night (photoperiodism) and to set circadian rhythms. It also regulates other responses including the germination of seeds, elongation of seedlings, the size, shape, and number of leaves, the synthesis of chlorophyll, and the straightening of the epicotyl or hypocotyl hook of dicot seedlings. 

Geotropism (also known as gravitropism) is a turning or growth movement by a plant or fungus in response to gravity. It is a general feature of all higher and many lower plants as well as other organisms. 

Accumulation of auxin as the apex of the plant, which is responsible for the phototropism movement so that plant cells are elongated.

To test that oxygen is evolved during photosynthesis few fresh Hydrilla plants in a glass beaker filled with water. A pinch of KHCO$ _{3}$ is added to it. It is kept in sunlight. After some time some bubbles (oxygen) escapes from the plant. This proves that oxygen is produced during the photosynthesis. It is evolved during the light reaction of the photosynthesis.

The plant kept in continuous light will live longer, because it will be able to produce oxygen required for its respiration by the process of photosynthesis.

The starch in the leaves is eliminated by keeping the plant in a dark place for 3 days. A leaf is selected and covered with a black strip on both sides. The plant is kept in sunlight for 4 hours. The experimental leaf is plucked and the strip is removed from it to perform the starch test. It is found that he leaf covered with black paper will turn brown and the part of the exposed leaf will turn blue-black. This result proves that starch is formed in the leaf where sunlight is available and is not formed in absence sunlight. Thus the correct answer is option  C.

Jan Ingenhousz (1730-1799), in his experiment with an aquatic plant, showed that in bright sunlight, small bubbles were formed around the green parts while in the dark, no such bubbles formed. He found out these bubbles to be of oxygen. He thus, confirmed that purification of air or formation of dephlogiston is carried out by green plants only in presence of sunlight. 

• Warburg discovered that a decrease in photosynthesis by increasing the oxygen concentration. Oxygen is the competitive inhibitor of the carbon dioxide fixation by RuBisCo, which initiates photosynthesis. Furthermore, oxygen stimulates photorespiration which reduces photosynthetic output. These two mechanisms working together are responsible for the Warburg effect. So, this option is incorrect.
• Arnon discovered the photosynthetic phosphorylation. So, this option is incorrect.
• Samuel Ruben discovered that oxygen, which is released during photosynthesis came from a water molecule. So, this option is incorrect.
• Emerson observed that when Chlorella cells are exposed to continuous light, the rate of photosynthesis was less as compared to those exposed to the intermittent light. 

If boiled water is used in the test tube, there will be no air bubbles. This is hydrilla cannot survive the high temperature of boiled water. 

Sunlight is essential for photosynthesis as the plant is kept in dark room for a week there is a lack of sunlight hence photosynthesis has not taken place.