Light piping driven photosynthesis in the soil: Low-light adapted active photosynthetic apparatus in the under-soil hypocotyl segments of bean (Phaseolus vulgaris).
Photosynthetic activity was identified in the under-soil hypocotyl part of 14-day-old soil-grown bean plants (Phaseolus vulgaris L. cv. Magnum) cultivated in pots under natural light-dark cycles. Electron microscopic, proteomic and fluorescence kinetic and imaging methods were used to study the photosynthetic apparatus and its activity. Under-soil shoots at 0-2cm soil depth featured chloroplasts with low grana and starch grains and with pigment-protein compositions similar to those of the above-soil green shoot parts. However, the relative amounts of photosystem II (PSII) supercomplexes were higher; in addition a PIP-type aquaporin protein was identified in the under-soil thylakoids. Chlorophyll-a fluorescence induction measurements showed that the above- and under-soil hypocotyl segments had similar photochemical yields at low (10-55μmolphotonsm(-2)s(-1)) light intensities. However, at higher photon flux densities the electron transport rate decreased in the under-soil shoot parts due to inactivation of the PSII reaction centers. These properties show the development of a low-light adapted photosynthetic apparatus driven by light piping of the above-soil shoot. The results of this paper demonstrate that the classic model assigning source and sink functions to above- and under-soil tissues is to be refined, and a low-light adapted photosynthetic apparatus in under-soil bean hypocotyls is capable of contributing to its own carbon supply.
Department of Plant Anatomy, Institute of Biology, Eötvös Loránd University, Pázmány P. s. 1/c, Budapest H-1117, Hungary.
Andrea
A
Kakuszi
Department of Plant Physiology and Molecular Plant Biology, Institute of Biology, Eötvös Loránd University, Pázmány P. s. 1/c, Budapest H-1117, Hungary.
Éva
É
Sárvári
Department of Plant Physiology and Molecular Plant Biology, Institute of Biology, Eötvös Loránd University, Pázmány P. s. 1/c, Budapest H-1117, Hungary.
Ádám
Á
Solti
Department of Plant Biology, Institute of Biology, University of Pécs, Ifjúság u. 6., Pécs H-7624, Hungary.
Gyula
G
Czégény
Department of Plant Biology, Institute of Biology, University of Pécs, Ifjúság u. 6., Pécs H-7624, Hungary.
Éva
É
Hideg
Institute of Biochemistry, Biological Research Centre of the Hungarian Academy of Sciences, Temesvári krt. 62., Szeged H-6726, Hungary.
Éva
É
Hunyadi-Gulyás
Department of Plant Anatomy, Institute of Biology, Eötvös Loránd University, Pázmány P. s. 1/c, Budapest H-1117, Hungary.
Károly
K
Bóka
Department of Plant Anatomy, Institute of Biology, Eötvös Loránd University, Pázmány P. s. 1/c, Budapest H-1117, Hungary. Electronic address: bela.boddi@ttk.elte.hu.
Béla
B
Böddi
D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism; D018546:Hypocotyl / Q000737:chemistry / Q000378:metabolism; D008027:Light; D013058:Mass Spectrometry; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D027805:Phaseolus / Q000254:growth & development / Q000378:metabolism*; D010788:Photosynthesis / Q000528:radiation effects*; D045332:Photosystem II Protein Complex / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D018087:Plastids / Q000378:metabolism; D020543:Proteome / Q000032:analysis; D040901:Proteomics; D012987:Soil / Q000737:chemistry; D020524:Thylakoids / Q000378:metabolism
D045332:Photosystem II Protein Complex; D020543:Proteome; D012987:Soil; D002734:Chlorophyll
Aquaporin; Chlorophyll fluorescence; Chlorophyll-protein complex; Greening; Light piping