1989. On the aggregational states of protochlorophyllide and its protein complexes in wheat etioplasts. -Physiol. Plant. 76: 135-143.The inner membranes from wheat {Triticum aestivum L. cv. Walde) etioplasts were separated into membrane fractions representative of prolamellar bodies and prothylakoids by differential and gradient centrifugations. The isolated fractions were characterized by absorption-, low-temperature fluorescence-, and circular dichroism (CD) spectroscopy, by high performancy liquid chromatography and by sodium dodecyl sulphate polyacrylamide gel electrophoresis. The prolamellar body fraction was enriched in NADPH-protochlorophyllide oxidoreductase (E.C. 1.6.99.1), and in protochlorophylhde showing an absorption maximum at 650 nm and a fluorescence emission maximum at 657 nm. Esterified protochlorophyllide was mainly found in the prothylakoid fraction. The carotenoid content was qualitatively the same in the two fractions. On a protein basis the carotenoid content was about three times higher in the prolamellar body fraction than in the prothylakoid fraction. The CD spectra of the membrane fractions showed a CD couplet with a positive band at 655 nm, a zero crossing at 643-644 nm and a negative band at 623-636 nm. These results differ from earlier CD measurements on protochlorophyllide holochrome preparations. The results support the interpretation that protochlorophyllide is present as large aggregates in combination with NADPH and NADPH-protochlorophyllide oxidoreductase in the prolamellar bodies.

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Possible mechanisms behind the light-induced wilting of dark-germinated pea (Pisum sativum L.) epicotyls were studied. Illumination with photosynthetically active radiation caused a fast turgor loss and wilting in the middle segments of the epicotyls accompanied by accumulation of water in the intercellular cavities. During this process, room temperature fluorescence emission spectra showed gradual bleaching of porphyrin-type pigments, which was lessened by incubating the epicotyls with excess ascorbate before illumination. Detection of singlet oxygen and lipid peroxidation products in the illuminated epicotyls suggested the occurrence of porphyrin-photosenzitized membrane damage as a cause of disordered water status and sequential wilting.