Photochemical activities and organization of photosynthetic apparatus of C3and C4plants grown under different light intensities

✍ Scribed by P. Sampath; G. Kulandaivelu

• Publisher: Springer
• Year: 1983
• Tongue: English
• Weight: 510 KB
• Volume: 4
• Category: Article
• ISSN: 0166-8595
• DOI: 10.1007/bf00041832

✦ Synopsis

Changes in the photochemical activities, influenced by variation in the growth light intensity, were followed in typical C3 (Phaseolus, lpomoea) and C, (Amaranthus, Sorghum) plants. Progressive decrease in the growth light intensity accelerated the O-P fluorescence induction in whole leaves. Such acceleration of the fluorescence kinetics was found to be not due to enhanced photosystem II activity but possibly a result of reduced rate of electron flow between the two photosystems. This is supported by 4 lines of evidence: (1) by the Hill activity determined in the presence of electron acceptors functioning before and after plastoquinone; (2) the photosynthetic unit size determined after flash excitation showing variations that were apparently too small to account for the changes observed fluorescence induction; (3)modification of the kinetics of secondrange lightqnduced absorbance changes at 520 nm; and (4) absence of significant changes in the ratio of PToJtotal chlorophyll ratio.

The PToo/Cytochrome f ratio, however, increased from the usual 1-1.5 to 3-4 in plants grown under 9% sunlight. Increase in the P,0o/Cytochrome f ratio was found to be due to a decrease in the cytochrome f/chlorophyll ratio, and this was due to perhaps to a simultaneous increase in chlorophyll and decrease in cytochrome content.