Leaf Development in Lolium temulentum: Photosynthesis and Photosynthetic Proteins in Leaves Senescing under Different Irradiances |
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Authors: | Mae Tadahiko; Thomas Howard; Gay Alan P; Makino Amane; Hidema Jun |
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Institution: | 1Department of Agricultural Chemistry, Faculty of Agriculture, Tohoku University 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, 981 Japan
2AFRC Institute of Grassland and Environmental Research Plas Gogerddan, Aberystwyth, Dyfed SY23 3EB, United Kingdom |
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Abstract: | Changes in carbon fixation rate and the levels of photosyntheticproteins were measured in fourth leaves of Lolium temulentumgrown until full expansion at 360 µmol quanta m2s1 and subsequently at the same irradiance or shadedto 90 µmol m2 s1. Ribulose-1,5-bisphosphatecarboxylase/oxygenase (Rubisco), light-harvesting chlorophylla/b protein of photosystem II (LHCII), 65 kDa protein of photosystemI (PSI), cytochrome f (Cytf) and coupling factor 1 (CF1) declinedsteadily in amount throughout senescence in unshaded leaves.In shaded leaves, however, the decrease in LHCII and the 65kDa protein was delayed until later in senescence whereas theamount of Cyt f protein decreased rapidly following transferto shade and was lower than that of unshaded leaves at the earlyand middle stages of senescence. Decreases in the Rubisco andCF1 of shaded leaves occurred at slightly reduced rates comparedwith unshaded leaves. These results indicate that chloroplastproteins in fully-expanded leaves are controlled individually,in a direction appropriate to acclimate photosynthesis to agiven irradiance during senescence. (Received August 20, 1992; Accepted January 5, 1993) |
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