Etioplasts with protochlorophyll and protochlorophyllide forms in the under-soil epicotyl segments of pea (Pisum sativum) seedlings grown under natural light conditions.

To study if etiolation symptoms exist in plants grown under natural illumination conditions, under-soil epicotyl segments of light-grown pea (Pisum sativum) plants were examined and compared to those of hydroponically dark-grown plants. Light-, fluorescence- and electron microscopy, 77 K fluorescence spectroscopy, pigment extraction and pigment content determination methods were used. Etioplasts with prolamellar bodies and/or prothylakoids, protochlorophyll (Pchl) and protochlorophyllide (Pchlide) forms (including the flash-photoactive 655 nm emitting form) were found in the (pro)chlorenchyma of epicotyl segments under 3 cm soil depth; their spectral properties were similar to those of hydroponically grown seedlings.

Reactive oxygen species from type-I photosensitized reactions contribute to the light-induced wilting of dark-grown pea (Pisum sativum) epicotyls.

Type-II, singlet oxygen-mediated photosensitized damage has already been shown to occur in epicotyls of dark-germinated pea (Pisum sativum L.) seedlings upon illumination, resulting in fast turgor loss and wilting. In this study we show evidence that the palette of reactive oxygen species (ROS) is more complex.

Etiolation symptoms in sunflower (Helianthus annuus) cotyledons partially covered by the pericarp of the achene.

Background And Aims: Etiolation symptoms and the greening process are usually studied on dark-germinated seedlings and this raises the question--can these results be generalized for plants growing under field conditions? This work examines various aspects of the plastid differentiation under the covering of the achene wall, which often remains attached to the cotyledons of sunflower (Helianthus annuus) seedlings grown under light.

Methods: Cotyledons of 7- to 10-d-old sunflower seedlings grown in the dark and on light were examined. The partially covered cotyledons were sectioned into light-exposed, covered and transition zones.