Wheat Etioplasts Research Articles

Light-induced EPR signal I and signal II in wheat etioplasts greened under intermittent light without or with subsequent continuous light

The behaviour of light-induced electron paramagnetic resonance (EPR) Signal I and Signal II in wheat plastids lacking O 2 evolving capacity due to development under intermittent light (IL plastids) is compared with that of plastids whose water-splitting system has been photoactivated by a brief subsequent continuous light (ICL plastids). EPR spectra in the absence or presence of DCMU as well as the observations of rise kinetics over a long time course clearly reveal that in ICL plastids Signal I (identified with P 700 +) is the result of competing processes that oxidize P 700 on the one hand and reduce it on the other. In IL plastids the high Signal I level indicates a high steady-state concentration of oxidized P 700 due to the absence of normal electron flow from Photosystem II (PS II). The three kinetic components (dark, slow-decaying and fast-decaying) of Signal II are observed both in IL and ICL plastids. Signal II is not chemically induced as Signal I by ferricyanide. Protease eliminates Signal II but leaves Signal I intact. Only the fast Signal II is abolished by DCMU and electron donors to PS II. It is assumed to reflect the oxidation state of a component functioning on the PS II oxidizing side.

Light-mediated Oxygen Uptake Measured in Wheat Etioplasts

An in vitro O(2) assay was used to measure early response of wheat (Triticum aestivum L.) etioplasts to light. A transient photoinducible O(2) uptake occurred when dark-grown etioplasts were initially exposed to light. The rate of inducible O(2) consumption was dependent on both the intensity of light and the quantity of organelle protein present. Higher light intensities resulted in greater O(2) utilization per minute, and a greater quantity of organelle protein in the sample resulted in an increased rate of O(2) uptake under the same light intensity conditions. Experiments with various plant tissues as well as with mitochondrial respiratory inhibitors indicated that etioplasts are the organelles responsible for the photoinduced O(2) uptake phenomenon. A preliminary action spectrum study revealed that wavelengths 640 to 680 nm resulted in maximum O(2) uptake. This indicated the presence of an etioplast red light receptor pigment which induces O(2) uptake in etioplasts.

Chlorophyll, carotenoid, and lipid content in Triticum sativum L. plastid envelopes, prolamellar bodies, stroma lamellae, and grana

The pigment and lipid content, expressed on a protein basis, is compared in wheat etioplast and chloroplast membrane fractions. Chloroplast envelopes contain less carotenoid and 1/3 more lipid than etioplast envelopes. The minute amount of chlorophyll and carotenoid found in chloroplast envelopes could be due to thylakoid contamination. Prolamellar bodies and grana have nearly the same amount of total lipid and total carotenoid per mg of protein although their respective compositions differ. On a protein basis, the lipid, chlorophyll, and carotenoid contents are lower (2.3, 10, and 20 times, respectively) in stroma lamellae than in grana membranes, but the latter contains a higher proportion of β-carotene, chlorophyll a, and sulfolipid.

Mn content changes in wheat etioplast membranes during greening under intermittent or continuous light

Study of Mn content changes in wheat etioplasts during greening under intermittent or continuous light reveal an heterogeneity in the development of the chloroplast Mn pool. Under intermittent light plastids contain only the Tris extraction-resistant Mn pool. Such plastids are known to have no O 2 evolution capacity. The formation of the tightly bound Mn pool appears not to be a light-requiring process. But under intermittent light followed by 15 min continuous light plastids contain, like the control chloroplasts, two distinct Mn pools, the Tris extraction-resistant and the Tris-extracted pools. Such plastids are known to be capable of evolving O 2 in the presence of Hill reagents. The formation of the loosely bound Mn pool is a light-requiring process. Under continuous light, only the loosely bound Mn pool increases rapidly in the early stages of greening. These results suggest that protein complexes capable of Mn binding pre-exist in etioplasts and Mn atoms are light-inserted into the membrane complexes a as chlorophylls are synthesized.

Pre-existence of chloroplast lamellar proteins in wheat etioplasts. Functional and protein changes during greening under continuous or intermittent light

FEBS LettersVolume 31, Issue 3 p. 308-312 Full-length articleFree Access Pre-existence of chloroplast lamellar proteins in wheat etioplasts. Functional and protein changes during greening under continuous or intermittent light R. Remy, R. Remy Laboratoire de Physiologie Cellulaire Végétale Associé au C.N.R.S. Faculté des Sciences, 91405 Orsay FranceSearch for more papers by this author R. Remy, R. Remy Laboratoire de Physiologie Cellulaire Végétale Associé au C.N.R.S. Faculté des Sciences, 91405 Orsay FranceSearch for more papers by this author First published: May 01, 1973 https://doi.org/10.1016/0014-5793(73)80128-0Citations: 26AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume31, Issue3May 01, 1973Pages 308-312 ReferencesRelatedInformation