Photosynthetic activity and chloroplast membrane polypeptides in euploid cells of Ricinus [Euploidy]
1981
Timko, M.P. | Vasconcelos, A.C. (State Univ. New Brunswick, New Jersey (USA). Dept. of Botany)
The possible effects of altered nuclear complement size on the polypeptide composition and photochemical activity of chloroplasts in haploid, diploid, and tetraploid cells of Ricinus communis L. have been evaluated. The electron transport capacity in isolated chloroplasts decreases with the increase in nuclear genome size. Both Photosystem II (DCPIP reduction) and Photosystem I oxygen uptake (TMPD to methyl viologen) activities were lower in plastid preparations from tetraploid individuals than in diploid and haploid cell preparations. Photosynthetic O(,2)-evolution and CO(,2)-fixation rates in leaf tissue from euploid individuals were also found to decrease with the increase in size of the nuclear genome. Specific activity levels of RuBP-carboxylase were observed to increase with ploidy. Electrophoretic examination of the polypeptide composition of thylakoid membranes from haploid, diploid, and tetraploid cells revealed no difference in the relative proportions of the constituent polypeptides of these membranes. The regulation of chloroplast development and the basis for altered plastid function in the presence of altered nuclear genome size are discussed
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