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Maharshi Dayanand University (2011)

Effect of drought stress on chloroplast biogenesis and photosynthesis

Dalal, Vijay Kumar

Titre : Effect of drought stress on chloroplast biogenesis and photosynthesis

Auteur : Dalal, Vijay Kumar

University : Maharshi Dayanand University

Grade : Doctor of Philosophy (PhD) 2011

Sommaire partiel
Plants are severely affected by various abiotic stresses due to their static nature. Abiotic stresses may be in the form of drought, salt, flooding, temperature, light or metal stress. Due to global warming many crops in various parts of the world are being subjected to drought stress and in the coming years this problem is going to become more severe. Plant growth and development is severely affected due to water stress. Photosynthesis is one of the most important factors determining the plant productivity under water limiting conditions. When plants germinate in the soil their seedlings remain in dark for a while. These seedlings do not synthesize chlorophyll and contain a special form of plastids called etioplasts. As seedlings come out of soil chlorophyll biosynthesis starts and etioplasts convert into chloroplasts. This process is called chloroplast biogenesis. Chloroplast biogenesis is a complex process and is regulated by light and other environmental factors like abiotic stress. Chloroplast biogenesis is intricately linked with photosynthesis, so the effect of drought stress on chloroplast biogenesis and photosynthesis was investigated. Because rice is a very important food crop in southern part of Asia including India, a drought-sensitive and high yielding cultivar of rice, Oryza sativa L cv Pusa Basmati 1, (PB1) was chosen for this study. Water stress was applied on six-day old etiolated seedlings by immersing their roots in 0 mM PEG 6000 or 30 mM PEG 6000 or 40 mM PEG 6000 or 50 mM PEG 6000 (half- strength Murashige & Skoog salt solution [vitamin and agar free] + 50 mM PEG 6000), 16 h prior to transfer to cool white fluorescent+incandescent light (100 µmol m-2 s
- 1 ), at 280C. Protein contents of rice seedling declined in response to increasing water stress. Chlorophyll (Chl) and carotenoids contents were also reduced to various extents due to water stress. There was a minor decrease at 30mM PEG 6000 mediated water stress. But there was an increased Chl and carotenoids reduction in the seedlings as the PEG concentration was increased. Chl a/ Chl b ratio decreased in water-stressed seedlings. 50mM PEG 6000 concentration was chosen for further analysing the effect of water stress on rice seedlings.

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