Photosynthesis in Plants

Dry plant matter is composed of approximately 45% carbon by mass, as plants fix atmospheric carbon dioxide during photosynthesis.

Photosynthesis removes carbon dioxide from the atmosphere and releases oxygen as a byproduct, which is essential for the respiration of most living organisms.

During photosynthesis, plants capture carbon dioxide from the air and use the carbon atoms to build glucose molecules.

During photosynthesis, green plants convert light energy into chemical energy stored in the form of food.

The presence of pollutant adversely affect the plants. Reduction in chlorophyll is caused by toxic ions formed by the dissolution of SO$ _2$ in water inside leaf tissue, which preferentially incorporate into thylakoid membrane disturbs the photosystems. The oxides of sulphur transform into several poisonous substances which hamper the growth of the plants.

The increase in the concentration of the air pollutants results in an adverse effect on the plants and animal health. SO$ _2$ is considered as one of the pollutants which causes bleaching of the plants. The chlorophyll pigments in the leaves of the plants are destroyed in the presence of increased amounts of sulfuric acid which is formed by reacting with the water in plants. 

In nature, major source of liberation of oxygen is photosynthesis. Photodissociation liberates oxygen from water during the process of photosynthesis. Phytoplanktons are the most abundant photosynthesizers in nature.

Geotropism 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. Phototropism is the orientation of a plant or other organism in response to light, either toward the source of light (positive phototropism) or away from it (negative phototropism). Thermotropism or Thermotropic movement is the movement of a plant or part of a plant in response to a change in temperature. A common example is the curling of Rhododendron leaves in response to cold temperatures. Mimosa Pudica also show thermotropism by the collapsing of leaf petioles leading to the folding of leaflets, when temperature drops. 

• Phototropism is the growth of organisms in response to a stimulus. This causes the plant to have elongated cells on the farthest side from the light. Phototropism is one of the many plant tropisms or movements which respond to external stimuli. 
• Growth towards a light source is called positive phototropism, while growth away from light is called negative phototropism. Most plant shoots exhibit positive phototropism, and rearrange their chloroplasts in the leaves to maximize photosynthetic energy and promote growth.
  Hence, option A is correct.

The definition of photomorphogenesis is any change in form or function of an organism occurring in response to changes in the light environment. Photomorphogenesis is often defined as light-regulated plant development, but there are also changes in morphology and/or cell structure and function, which occur as transient acclimatizations to a changing environment, which are also light regulated.

The movement of chloroplasts in palisade cells in response to light is called as phototactic movement. Phototaxis is the movement of an organism in response to light; that is, the response to variation in light intensity and direction.

Etiolation is a process in flowering plants grown in partial or complete absence of light. It is characterized by long, weak stems, smaller, sparser leaves due to longer internodes and a pale yellow colour called as chlorosis.  It increases the likelihood that a plant will reach a light source, often from under leaf litter, or shade from competing plants. The growing tips are strongly attracted to light and will elongate towards it.

Plant in order to flower require a particular day length or light period called photoperiod and response of the plants to photoperiod in terms of flowering is called photoperiodism. Photoperiodism is the response to duration and timing of light and dark periods.

Photosynthesis is the process by which light energy from the sun is used to synthesise sugars from carbon dioxide, releasing oxygen as a waste product. In primitive days, cyanobacteria were only the primary producers because the redox structure of oceans favoured them to fix nitrogen and also they had the capacity to use water as the source of electrons in photosynthesis. They made the atmosphere oxygen rich and allowed the appearance of aerobic organisms. 

Phycocyanin Antioxidant. Phycocyanin is the main component in Linablue Spirulina Extract. It is a blue pigment that is important in the photosynthesis (food production) of cyanobacteria. It assists the function of chlorophyll, especially during low light conditions. So, the correct option is "C" (Phycocyanin).