Photosynthesis in Plants

The rate of photosynthesis would be maximum at the equator because the the rate of photosynthesis depends on the light intensity. Maximum intensity of light occurs at the equator, and gradually decreases with increasing distance from the equator to the south and north poles. So the correct answer is 'Equator'.

Transpiration is the process of loss of water, in vapour form, through stomata. The process depends on the turgidity of guard cell. An increase in turgidity of guard cells opens stomatal pore, whereas a decrease in turgidity of guard cells closes stomatal pore. The change in turgidity of guard cells is brought about by reversible influx and efflux of potassium ions.

Chlorophyll is the pigment responsible for photosynthesis. The light active in photosynthesis is a small part in the visible spectrum (400- 700 nm). The chlorophyll pigments mainly absorb blue and red light. Maximum absorption is in blue light but maximum photosynthesis occurs in red light.

Photosynthetically active radiation, often abbreviated PAR, designates the spectral range (wave band) of solar radiation from 400 to 700 nanometers that photosynthetic organisms are able to use in the process of photosynthesis. Sunlight comprises all effective lights PAR (photosynthetically active radiations) as required for photosynthesis. Thus, option A is correct.

• Around 50% of the total radiation from sunlight falls under photosynthetically active radiation and supports the process of photosynthesis. It constitutes the light of 400-700 nm wavelength which is absorbed by chlorophyll pigment. Out of which only 2 - 10% are captured by plants. Thus, the correct answer is option B.

Photosynthesis is the process by which light energy is converted to chemical energy. In plants, light is absorbed by pigments such as chlorophyll. Light hits these molecules and raises them to a higher energy. Light, however, occurs in a spectrum of wavelengths ranging from ultraviolet to visible light to infrared. The energy accompanying the absorption of light is dependent on the wavelength of the light. The amount of energy absorbed during the processes of photosynthesis depends on the wavelength of light absorbed. For processes requiring more energy, pigment molecules must be able to absorb the necessary wavelengths. 680 nm wavelength is absorbed maximum for photosynthesis because, 680 nm will be utilized by both the pigment systems.

Carotenoids are organic pigments that are found in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms, including some bacteria and some fungi. Carotenoids absorb light in the blue-green and violet region and reflect the longer yellow, red, and orange wavelengths. These pigments also dispose excess energy out of the cell. Thus, option A is correct and other options are incorrect.

Plants and other oxygenic photosynthetic organisms harvest light energy from the sun to fix carbon dioxide into the food and fiber required to sustain the biosphere. Since plants cannot move, they must cope with regular day-night cycles, seasonal cycles and neighbouring vegetation, all of which influence the intensity, direction and spectral quality of light impinging on their leaves. 

Higher plants utilize 1 to 2 % of sunlight for photosynthesis. Most crop plants store nearly 0.25% to 0.5% of the sunlight in the product. Examples are corn kernels, potato starch, etc. Photosynthesis increases linearly with light intensity at low intensity, but at higher intensity this is no longer the case.

Emerson defined red drop as decline in the quantum yield of photosynthesis  at wavelength beyond 680 nm. 

Photosynthetically Active Radiation (PAR) is the amount of light available for photosynthesis, which is light in the 400 to 700 nanometer wavelength range. PAR changes seasonally and varies depending on the latitude and time of day.

Photosynthesis occurs in small portion of spectrum, called as 'photosynthetically active radiation' or PAR (400-700 nm). Maximum absorption of light occurs in blue region (around 400 nm) followed by red light (around 700 nm). Maximum photosynthesis, however, occurs in red light. Least photosynthesis occurs in green light.

The photosynthesis process is essentially a light dependent synthetic process, which results in synthesis of sugars. A small part of the solar spectrum in the visible portion is used in the process of photosynthesis. This small portion of the solar spectrum is called photosynthetically active radiations or PAR. The wavelength of light active in PAR occur between 400 to 700 nm.

Blue light of the spectrum is absorbed more for the process of photosynthesis. Plants have two types of chlorophylls - a and b. Chloropphyll a is a specific form of chlorophyll used in oxygenic photosynthesis. It absorbs most energy from wavelengths of violet-blue and orange-red light. A yellow-green chlorophyll pigment which occurs only in plants and green algae. It functions as a light harvesting pigment that pass on the light excitation to chlorophyll a. It absorbs well at wavelength of 450-500 nm and 600-650 nm.

Chlorophyll absorbs red and violet-blue light, while transmitting and reflecting green light. Chlorophyll 'a' absorbs blue light with wavelengths of 430 nm and red light of 662 nm. 453 nm and 642 nm wavelengths are absorbed by chlorophyll 'b'.