Hloroplasty and others plastidy. Spectra of absorption and pigments

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Pigments represent the connections capable owing to the electronic structure to absorb radiation of certain length of a wave in a visible part of a spectrum. The schedule describing dependence of absorption from length of a wave, carries the name of a spectrum of absorption. The spectrum of absorption of the given connection can be unique, i.e. It can unequivocally characterise this connection, but even if it not so he nevertheless allows us to make at least some representation about structure of absorbing substance.

To investigate a spectrum of absorption of any connection, monochromatic light is required. It receive by means of a prism, difraktsionnoj a lattice or an optical filter. Then a light bunch pass through a solution of a studied pigment and compare the light energy which has passed through a solution to energy of a falling beam of light. Energy absorption depends on absorption factor (a pigment, from its concentration () and from length of an optical way (l). This dependence - it often name the law of Bera-Lamberta - it is possible to write down in a following kind:

Where I0 - energy of an incident light, and I - energy of light which has passed through a solution. For solutions usually use the decimal logarithm and instead of absorption factor (use factor ekstinktsii ().

We can write now

Where with - concentration in mol/l, I - an optical way to sm and e - factor moljarnoj ekstinktsii in l/mol/see Size lg-name absorption (or optical density (OD).

In spektrofotometre are carried out reception of a monochromatic light bunch, propuskanie it alternately through a solution of studied substance and through pure solvent, measurement / about and / and registration of the logarithm of their relation. The typical spectrum of absorption of a chlorophyll in organic solvent is presented on fig. 2.24. This pigment is painted in green colour because it absorbs in dark blue (400-450 nanometers) and red (600-700 nanometers) spectrum areas, but passes green and yellow beams.

In cages of the higher plants besides hloroplastov contain also other types plastid, deprived characteristic for hloroplastov lamelljarnoj structure and the photosynthetic device. Among these plastid distinguish colourless lejkoplasty and painted hromoplasty which colouring is defined by high concentration karotinoidnyh pigments. Similarly hloroplastam, these little bodies, apparently, are descended through any structures of type proplastid, present at parent cytoplasm. Lejkoplasty play to a cage a role of storehouses for spare nutrients, such, for example, as starch that is why, possibly, they have also the fermental device necessary for synthesis of these substances from smaller molecules-predecessors. Hromoplasty, most likely, promote pollination of plants and distribution of seeds as they give tsvetkam and to fruits their bright colouring involving animals. As a rule, hromoplasty in a cage do not develop, if in it are available hloroplasta. In some ripening fruits, for example in tomatoes, transition from green colouring to yellow, and then to the red reflects three consecutive stages of development: prevalence hloroplastov, a decrease hloroplastov and number growth hromoplastov, loaded karotinoidami. The reasons of this transition are not quite clear.