No abstract

Protochlorophyllide (Pchlide) and protochlorophyll (Pchl) were found in epicotyls of 14-day-old dark-germinated seedlings and in 100-day-old dark-grown stems of red oak (Quercus rubra L.). Fluorescence spectroscopy measurements of epicotyls at 77 K showed that the majority of Pchlide and Pchl is present as a shorter wavelength-emitting monomer with a fluorescence emission maximum at 629-631 nm. A small amount of a monomeric form emitting at 635-636 nm was also present. Minor amounts of Pchlide were aggregated into larger complexes with fluorescence emission maxima at 640, 644-646 and 652-654 nm, as seen in etiolated leaves. Flash illumination transformed the 652-654-nm-emitting form to chlorophyllide, but not those forms with emission maxima at 629-631, 635-636 and 644-646 nm. These shorter wavelength-emitting forms were transformed to chlorophyllide by continuous illumination, but the process took several hours. Epicotyls and young stems were light sensitive, with exposure to full daylight causing strong pigment bleaching and tissue destruction. Complete greening took place only at low irradiances. Light sensitivity was greater at 4 degrees C than at room temperature. We conclude that the monomeric arrangement of the pigments accounted for the light and temperature sensitivity of the greening process in epicotyls and stems.

The last steps of chlorophyll (Chl) biosynthesis were studied at different light intensities and temperatures in dark-germinated ginkgo (Ginkgo biloba L.) seedlings. Pigment contents and 77 K fluorescence emission spectra were measured and the plastid ultrastructure was analysed. All dark-grown organs contained protochlorophyllide (Pchlide) forms with similar spectral properties to those of dark-grown angiosperm seedlings, but the ratios of these forms to each other were different. The short-wavelength, monomeric Pchlide forms were always dominating. Etioplasts with small prolamellar bodies (PLBs) and few prothylakoids (PTs) differentiated in the dark-grown stems. Upon illumination with high light intensities (800 micromol m(-2) s(-1) photon flux density, PFD), photo-oxidation and bleaching occurred in the stems and the presence of (1)O(2) was detected. When Chl accumulated in plants illuminated with 15 micromol m(-2) s(-1) PFD it was significantly slower at 10 degrees C than at 20 degrees C. At room temperature, the transformation of etioplasts into young chloroplasts was observed at low light, while it was delayed at 10 degrees C. Grana did not appear in the plastids even after 48 h of greening at 20 degrees C. Reaccumulation of Pchlide forms and re-formation of PLBs occurred when etiolated samples were illuminated with 200 micromol m(-2) s(-1) PFD at room temperature for 24 h and were then re-etiolated for 5 days. The Pchlide forms appeared during re-etiolation had similar spectral properties to those of etiolated seedlings. These results show that ginkgo seedlings are very sensitive to temperature and light conditions during their greening, a fact that should be considered for ginkgo cultivation.

It is unclear whether light affects the structure and activity of exogenous secretory tissues like glandular hairs. Therefore, transmission electron microscopy was first used to study plastid differentiation in glandular hairs and leaves of light-grown rosemary (Rosmarinus officinalis "Arp") plants kept for 2 weeks under ambient light conditions. During our detailed analyses, among others, we found leucoplasts with tubuloreticular membrane structures resembling prolamellar bodies in stalk cell plastids of peltate glandular hairs. To study the effect of darkness on plastid differentiation, we then dark-forced adult, light-grown rosemary plants for 2 weeks and observed occasionally the development of new shoots with elongated internodes and pale leaves on them. Absorption and fluorescence spectroscopic analyses of the chlorophyllous pigment contents, the native arrangement of the pigment-protein complexes and photosynthetic activity confirmed that the first and second pairs of leaf primordia of darkforced shoots were partially etiolated (contained low amounts of protochlorophyll/ide and residual chlorophylls, had etio-chloroplasts with prolamellar bodies and low grana, and impaired photosynthesis). Darkness did not influence plastid structure in fifth leaves or secretory tissues (except for head cells of peltate glandular hairs in which rarely tubuloreticular membranes appeared). The mesophyll cells of cotyledons of 2week-old dark-germinated rosemary seedlings contained etioplasts with highly regular prolamellar bodies similar to those in mesophyll etio-chloroplasts of leaves and clearly differing from tubuloreticular membranes of secretory cells. Analyses of the essential oil composition obtained after solid phase microextraction and gas chromatography-mass spectroscopy showed that in addition to light, the age of the studied organ (i.e., first leaf primordia and leaf tip vs. fifth, fully developed green leaves) and the type of the organ