Photosynthetic changes that occur during aging of cypress (Cupressus sempervirens L.) needles |
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Authors: | N La Porta M Bertamini N Nedunchezhian K Muthuchelian |
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Institution: | (1) Istituto Agrario di San Michele all’ Adige, 38010 San Michele all’ Adige, Italy;(2) Center for Biodiversity and Forest Studies, School of Energy, Environment and Natural Resources, Madurai Kamaraj University, Madurai, 625 021, India |
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Abstract: | 2-years-old cypress needles (A2) were physiologically most active with regard to net photosynthetic (P
N) and electron transport rates. Variable to maximum fluorescence (Fv/Fm) ratios of dark-adapted needles were higher in A2 needles than in current year (A1) or senescent (A4) needles. Lower Fv/Fm values in these stages seemed to be caused not by photoinhibition but by a low photochemical capacity as suggested from the
chlorophyll (Chl) a/b ratios. In isolated thylakoids, lower rates of whole chain and photosystem 2 (PS2) activities were observed in A4 needles,
while higher rates were observed in A2 needles. A similar trend was noticed for contents of ribulose-1,5-bisphosphate carboxylase/oxygenase
(RuBPC) and total soluble proteins. The artificial exogenous electron donor Mn2+ failed to restore the loss of PS2 activity in 3-year-old (A3) and A4 needles, while diphenylcarbazide and NH2OH significantly restored the loss of PS2 activity. The marked loss of PS2 activity in A4 needles was primarily the result
of the loss of 33, 28–25, 23, and 17 kDa polypeptides. A marked loss of RuBPC activity in A4 needles is mainly due to the
loss of 15 (SSU) and 55 (LSU) kDa polypeptides. |
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Keywords: | chlorophyll fluorescence diphenylcarbazide donor side electron transport photosystems 1 and 2 polyacrylamide gel electrophoresis polypeptides ribulose-1 5-bisphosphate carboxylase/oxygenase |
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