Effect of light stress on photosynthesis

Pavičić, Ivana (2015) Effect of light stress on photosynthesis. Bachelor's thesis, Faculty of Science > Department of Biology.

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Abstract

Plants produce their own energy and organic compounds through photosynthesis, converting light energy into chemical energy. Although photosynthesis requires sunlight, the changes of light intensity in nature - from low to high light, may have a negative effect on photosynthesis reactions. As a result, plants have developed different response mechanisms to changing light conditions - from leaves and chloroplasts movements to adjustments at the molecular level. Depending on the intensity and quality of light, plants develop chloroplasts specific for high light intensity or chloroplasts specific for low light conditions. Moreover, if the high portion of plastocyanin molecules are in reduced form, the transfer of electrons between photosystems II and I is disturbed, so the electrons can "escape" and react with oxygen to form singlet oxygen which can cause oxidative stress and damage photosynthetic apparatus. In such conditions, the increased amounts of carotenoid molecules act as antioxidants and protect the chlorophyll from photo-oxidation that occurs due to the increase of reactive forms of oxygen. In addition, the induction of xanthophyll cycle and synthesis of phenolic compounds, tannins, flavonoids and anthocyanins occurs. Reactive oxygen species may have the role of signalling molecules during the exposure of plants to light stress. Polypeptide D1 in PSII is the main target of photo-induced damage. It is rapidly degraded and replaced by a newly synthesized copy to allow the normal functioning of the PSII. It could be concluded that the plant, in order to successfully adapt to the environmental light conditions, must respond to a number of different signals from the environment. In this process a number of different mechanisms such as coordinated expression of the plastid genome and the nuclear genome are included.

Item Type: Thesis (Bachelor's thesis)
Supervisor: Vidaković-Cifrek, Željka
Date: 2015
Number of Pages: 18
Subjects: NATURAL SCIENCES > Biology
Divisions: Faculty of Science > Department of Biology
Depositing User: Silvana Šehić
Date Deposited: 14 Apr 2016 11:03
Last Modified: 14 Apr 2016 11:03
URI: http://digre.pmf.unizg.hr/id/eprint/4728

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