Photosynthesis Photo receptors in Plants

Photosynthesis

photosynthesis chloroplast

Electromagnetic energy from the Sun Trigger a chemical reaction, as in photosynthesis Energy is dissipated as heat Fluorescence photosynthesis

3 uses for the Sun’s energy 1.Chemical changes for Photosynthesis Each quantum of light absorbed by a chlorophyll molecule gives an electron energy. Over 90% of the electromagnetic energy is used for photosynthesisEach

3 uses for the Sun’s energy 2.Heat Some of the electromagnetic wave energy is transferred as heat to the atmosphere

3 uses for the Sun’s energy 3.Fluorescence 3% -5% of the electromagnetic wave energy is fluoresced. Energy is re-emitted, but since some of the energy has been lost, the wavelength Increases, changing the emitted color to Red

Photosynthesis Human photoreceptors are rods and cones Plant photoreceptors are pigments such as chlorophyll – green shades carotene - red, orange, or yellow anthocyanins – dark red

Spinach Photosynthesis Spinach chromatograph Chlorophyl a Carotene Chlorophyl b

Spinach Photosynthesis Remember, green pigments are reflecting green light. They absorb other wavelengths such as blue/violet and red. Yellow pigments (carotene in spinach) reflects red and green wavelengths. It also absorbs in the blue range, although slightly different than chlorophyll.

Spinach Photosynthesis

Chlorophyll absorbs Blue wavelengths of light. Is blue light high or low energy? – (Remember the Electromagnetic Spectrum)

Photosynthesis So if absorbing more energy is better…should chlorophyll be black?

Photosynthesis Some scientists propose that black chlorophyll might absorb too much radiation and either overheat the plant or harm the plant by absorbing destructive UV and x-rays.

Photosynthesis Spinach has certain pigments as we’ve seen –Chlorophyll – Carotene Other plants have different pigments.

Photosynthesis of various tree types

Photosynthesis Chlorophyll is not a very stable compound; seasonal and weather conditions have to be just right for chlorophyll to remain viable. To maintain the amount of chlorophyll in their leaves, plants continuously make it. The synthesis of chlorophyll in plants requires sunlight and warm temperatures. Therefore, during summer chlorophyll is continuously broken down and regenerated in the leaves of trees.

Photosynthesis In the fall, chlorophyll breaks down. Other pigments In the leaves that are more durable continue to thrive and cause the colors to change.

Photosynthesis In the West, we have Aspen trees that show their carotene.

Calories in Spinach: 4 oz/100g = 25 calories On a clear day, the sun transmits about a kilowatt of power per square meter.

Chlorophyll is the molecule that traps this 'most elusive of all powers' - and is called a photoreceptor. It is found in the chloroplasts of green plants, and is what makes green plants, green. The basic structure of a chlorophyll molecule is a porphyrin ring, co-ordinated to a central atom. This is very similar in structure to the heme group found in hemoglobin, except that in heme the central atom is iron, whereas in chlorophyll it is magnesium.porphyrin ring Click for 3D structure file