Acquisition of Carbon in Elodea canadensis Michx

• Published in: Journal of plant physiology 1995, Vol.145 (1), p.50-56
• Main Authors: Krabel, Doris, Eschrich, Walter, V. Gamalei, Yuri, Fromm, Jörg, Ziegler, Hubert
• Format: Article
• Language: English
• Subjects: Aquatic plants; bicarbonate photosynthesis; Biological and medical sciences; Elodea canadensis; Freshwater; Fundamental and applied biological sciences. Psychology; Metabolism; microautoradiography; pH polarity; Photosynthesis, respiration. Anabolism, catabolism; Plant physiology and development; scanning electron microscopy; thin layer chromatography
• ISSN: 0176-1617; 1618-1328
• DOI: 10.1016/S0176-1617(11)81845-6

Mature shoots of Elodea canadensis Michx., grown in artificial pond water, were exposed to 14CO 2 orsubmersed in solution containing H 14CO 3 − for 30 min under PAR. The macroautoradiographs indicated that bicarbonate was used for photosynthesis, while gaseous 14CO 2 was not incorporated. Accordingly, gas exchange measurements showed no reduction of CO 2-content in the cuvette. Microautoradiographs indicated that 14C was taken up by penetrating the epidermis of the stem and that of the lower side of the leaves. In the symplast, label was accumulated in the chloroplasts of both epidermal layers and in the plastid envelope of the chloroplasts of cortex cells. In the stem no label occurred inside the central cylinder. Among sieve tubes, only those of the leaf traces were labeled. Thin layer chromatograms of extracts of labeled plants were autoradiographed. The main spots were identified by co-chromatography as malic acid, glucose, asparagine, proline and hexose phosphates, while sucrose appeared only slightly labeled. By SEM, strands of stretched cells with inflated ends were observed and named ≪canal cells≫. In the light microscope, canal cells were found among cells of the lower leaf epidermis. Upon illumination with PAR they increasingly were filled with gas, but in the dark no gas collected in the canal cells. They probably are used for collecting and transferring photosynthetically produced oxygen. Accordingly, acquisition of carbon and release of oxygen seem to follow different pathways in Elodea canadensis.