Photosynthetic Activity

The light receiving photosynthetic pigments in the plant are at the thylakoid membrane in the chloroplasts. The most common pigment in his quantity and is present in all green plants and alga is ‘Chlorophyll a’. Other pigments are called secondary pigments and include ‘Chlorophyll b’ and carotenoids. To every photosynthetic pigment a typical absorption spectrum, meaning a different absorption ability of light in different wavelengths.

• Chlorophyll a – 420nm, 663nm
• Chlorophyll b – 453nm, 645nm
• Carotenoids – 420nm-480nm

The light receiving pigments array constructs a type of antenna that is used to transfer light energy to the reaction center (Chlorophyll a), which drives the light process in Photosynthesis. The quantitative ratio of different chlorophylls varies in different plants, organs at the same plant, different exterior conditions and different periods.

The absorption by the chlorophyll is mainly obvious in the red and blue-violet area, although absorption lines in other areas do exist. Chlorophylls a and b are separated by the wavelength at which maximum absorption occurs. The absorption lines of Chlorophyll a at both the blue and red ends of the spectrum are farther away than the absorption lines of Chlorophyll b. Chlorophyll quantities in a green leaf vary between 0.05%-0.2% of the fresh weight. The ratio between Chlorophyll a and Chlorophyll b is 2.5/1=a/b, although it is not permanent because Chlorophyll a is more easily destroyed, meaning the quantitative ratio varies under different conditions.

Types of Plants

Sun and shade plants differ by various leaf qualities due to the amounts of light reaching them. Shade plants allocate more resources to harvest light than CO2 fixation. This is why in shade plants the secondary pigments are produced in greater quantities – more Chlorophyll and less RuBisCO*.

* Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), is an enzyme that is used in the Calvin cycle to catalyze the first major step of carbon fixation, a process by which the atoms of atmospheric carbon dioxide are made available to organisms in the form of energy-rich molecules such as sucrose.

See Also:
Light & Plants Part I - The Basics
Artificial Light

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Light & Plants

Light is one of the most basic requirements for the existence of plants.
The energy source of plants is sugar. Instead of consuming it like almost any other life form, plants create their food in a process called Photosynthesis.
For this process to occur, the plant needs water, carbon dioxide (CO2) and sunlight which is the energy converted and stored in the sugar.

Types of Light

The white light contains various colors in it, just like demonstrated in a rainbow. Different colors of sunlight can be seen in different parts of the world and even different times of the day. Plants react differently to various colors of light, and actually use only some of them in Photosynthesis. The main colors of light used by plants are red and blue. High concentration of red light is manifested in yellow-orange light and with blue, white-bright blue light.

Light color is labeled as color temperature. The color temperature of a light source is determined by comparing its chromaticity with a theoretical, heated black-body radiator. The temperature (in Kelvin) at which the heated black-body radiator matches the color of the light source is that source’s color temperature.

See Also:
Light & Plants Part II - Hardcore Data
Artificial Light

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