Indicators of senescence in tobacco leaves (Nicotiana tabacum L.)

Matan, Melita (2008) Indicators of senescence in tobacco leaves (Nicotiana tabacum L.). Diploma thesis, Faculty of Science > Department of Biology.

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Tobacco is often used as model plant because it is widely distributed and considered to be moderately tolerant plant species. The process of senescence is characterized by decline in photosynthesis and induction of oxidative stress. We have investigated the process of natural senescence in leaves old 14, 30, 120 and 270 days and process of artificial senescence induced by 10 mM hydrogen peroxide in leaves old 14 days. The efficiency of photosynthetic system (oxygen evolution and consumption, chlorophyll and carotenoid contents) structural changes in leaf cells, indicators of oxidative stress (contents of hydrogen peroxide, malondialdehyde and carbonyl groups as well as DNA damage) and activities of antioxidative enzymes were monitored. Chlorophylls and carotenoid contents declined while oxygen consumption increased as a result of both natural and artificially induced senescence. Number of chloroplasts decreased while that of plastoglobuls increased with senescence as evident by light microscopy. Ultrathin slices showed well developed thylakoids in all samples and increase of size and number of starch grains as well as plastoglobuls with senescence. Carbonyl and MDA contents increased with natural and artificial senescence while hydrogen peroxide showed increase and decrease with natural and artificial senescence, respectively. DNA damage evaluated by Comet test was not observed in senescent tobacco leaves. Superoxide dismutase activity increased while catalase and peroxidase activities decreased in senescent tobacco leaves. Senescence induced by hydrogen peroxide activities of all antioxidative enzymes increased. Presented results show the efficiency of antioxidative enzymes to fight oxidative stress and show the importance of hydrogen peroxide as a signal molecule.

Item Type: Thesis (Diploma thesis)
Keywords: senescence, Nicotiana tabacum L., oxidative stress, antioxidative enzymes, degradation of DNA, struktural changes
Supervisor: Pevalek-Kozlina, Branka
Date: 2008
Number of Pages: 57
Subjects: NATURAL SCIENCES > Biology
Divisions: Faculty of Science > Department of Biology
Depositing User: Silvana Šehić
Date Deposited: 15 Sep 2014 10:01
Last Modified: 15 Sep 2014 10:01

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