1. The unequivocal chemical composition of sporopollenin is unknown. Ir was often hypothesized that sporopollenin represents a derivative of carotenoids and/or carotenoid esters. Proceeding from this working hypothesis the influence of inhibitors of carotenoid biosynthesis (DPA, nicotine, Sandoz) on the sporopollenin accumulation was studied in order to test whether an intact carotenoid metabolism is involved. 2. Drastic changes in carotenoid spectra as well as in carotenoid patterns in pollen extracts were used as a “marker” for the uptake and transport of the inhibitors into the anther loculus, the site of sporopollenin biosynthesis. Of the three inhibitors of carotenoid metabolism, DPA, nicotine and Sandoz, only Sandoz appeared to influence carotenoid metabolism in the anthers. 3. After application of Sandoz the sporopollenin accumulation in anthers and pollen was only slightly affected. The amount of sporopollenin after treatment is similar to, or possibly even marginally higher than the control, if dry weight is chosen as reference. If the amount is expressed with respect to one pollen grain, the content is very slightly decreased in the case of pollen from treated plants. Therefore, it is concluded that severe interference in carotenoid biosynthesis does not result in a subsequent drastic inhibition of sporopollenin biosynthesis. 4. A significant increase of PAL activity under the influence of Sandoz indicates that effects upon phenylpropanoid metabolism are possible.

The appearance and development of photosynthetic activity, and the accumulation of chlorophylls, carotenoids and quinones, was investigated in etiolated barley shoots (Hordeum vulgare L. cv. Villa) during greening in flash light, periodic light‐dark cycles, and continuous white light. Greening and the development of photosynthetic activity was delayed in flash and periodic light compared to continuous white light. Photosystem II activity occurred after 6 light‐dark cycles and increased continuously during greening. After 3 h greening in continuous white light, photosystem II activity appeared with a very high rate and decreased to that of a green leaf after 50 h greening. Parallel to the development of photosynthetic activity, light stimulated the biosynthesis of prenyllipids. Moreover, chlorophylls and those carotenoids and quinones that are contained in etioplasts in relatively small amounts, were particularly enhanced in their biosynthesis. Chlorophyll a was synthesized without a lag phase during greening in flash light, whereas a 2 h lag phase occurred in continuous white light. In all three modes of illumination the formation of chlorophyll a exceeded that of chlorophyll b. After 4 flashes and 2 light‐dark cycles, chlorophyll b could be detected with a very high initial a/b ratio. Higher chlorophyll a/b ratios were reached after 200 flashes (a/b=10.9) and 50 light‐dark cycles (a/b=6.6) than after 50 h continuous white light (a/b=3.3). The formation of carotenes, lutein, violaxanthin and neoxanthin was also enhanced by light. This was also confirmed for plast‐ouinone‐9. ş‐tocopherol,α‐tocoquinone and phylloquinone. A comparison of the carotenoid and quinone composition of the differentiating thylakoid membrane before and after onset of photosynthesis, reveals that the photosynthetic membrane is already equipped with photosynthetic pigments and quinones before the appearance of photosystem II activity. It is concluded that during development of the photo‐synthetic apparatus the thylakoid membrane with its structural and functional constituents is formed first. In a second and slower process the water splitting enzyme system and enzymes of the Calvin cycle are activated.

Tracer kinetic studies of chloroplast pigments of Chlorella pyrenoidosa were carried out in a special steady-state apparatus which allowed the simultaneous recording of oxygen evolution, CO2-fixation and (14)CO2-incorporation. A special cylindrical vessel which permits labeling experiments with larger algae suspensions (800 ml) is described.-1. After 2 h of (14)CO2-photosynthesis (fixation rate 100-160 μmol CO2/μmol chlorophyllxh) 3.3% of the total (14)C-uptake (5.66 mCi) was found in the Chlorella lipid fraction. Total and specific radioactivity were higher in total carotenoids than in the chlorophylls. Chlorophyll a gave a higher labeling degree (2.4%) than chlorophyll b (1.3%).-2. Among the carotenoids α-and β-carotene were labeled after 2 h (14)CO2 exposure with the same specific radioactivity and with a particular high labeling degree of c. 19%. The xanthophylls exhibit lower labeling degree (violaxanthin 5.1%, zeaxanthin 1.9%, lutein 1.4%, antheraxanthin 1.3%, and neoxanthin 0.7%).-3. During the 4 h (12)CO2-exposure period, which followed the 2 h (14)CO2-incorporation time, the specific and total radioactivity of the α-and β-carotene pools decrease with a concomitant increase in the α-ionone-(lutein) and β-ionone xanthophylls (violaxanthin, zeaxanthin, antheraxanthin). The possibility, that the decrease of (14)C label in the carotenes may in part be due to a photo-oxidative degradation, is discussed.-4. Calculation of biological half-life-times from the (14)C-incorporation kinetics during the first hour of the experiment, when the pigment concentration is almost unchanged, results in times from 30 to 60 min. Half lives are shorter in the precursor pools such as chlorophyll a (30 min), α-carotene (40 min) and β-carotene (50 min) and violaxanthin (60 min) respectively.

Abstract— Depending on the light intensity that they received during growth, radish seedlings altered not only the pigment and quinone composition of the thylakoid membrane but also the chloroplast ultrastructure. In strong light, sun chloroplasts of radish were very similar to those from sun leaves of beech trees, while those developed under under dim light possessed a typical shade chloroplast. Radish shade chloroplasts contained a higher chlorophyll content and a higher concentration of xanthophylls resulting in a lower xanthophyll to carotene ratio as compared to sun chloroplasts. Chloroplasts from radish grown in strong light showed a much higher activity in their terpenoid metabolism than plastids from shade plants. Chlorophylls and carotenoids which are involved in the absorption of light and the transfer of energy during photosynthesis were labeled by [3H]‐mevalonate to a much higher degree in plastids from sun leaves as compared to plastids from shade leaves. This shows that in strong light where pigments are continuously broken down and resynthesized in order to maintain photosynthesis, chlorophylls and carotenoids exhibit a much higher turnover rate than the pigments of shade plants.

The prenylquinone composition of two species of mosses (Polytrichum formosum Hedw., Sphagnum acutifoiium Ehrh.) and two species of liver mosses (Lumdaria cruciata (L.) Dum., Peilia epiphylla (L.) Cord.) was determined and compared with the chlorophyll content and the photosynthetic activity of the intact moss and liver moss tissues. 1. Green moss and liver moss tissues possess in principle the same prenylquinone composition as higher plants with plastoquinone-9, n-tocopherol, (t-tocoquinone and the phylloquinone K, as main components. On a chlorophyll basis the lipoquinone levels are lower than in higher plants. Differences among the individual mosses as well as within one species only occur in the quantitative levels of the chloroplast prenylquinones, but there are no differences between musci and liver mosses. 2. There are differences in the maximal fiuorescence of liver mosses and mosses. The variable fluorescence in tum, which is a measure of in vivo photosynthetic activity, is very similar for all examined species of mosses and liver mosses (values from 0.7 to 1.0) but somewhat lower than in leaf pieces of higher plants. DCMU blocks the variable fluorescence and the concomitant oxygen evolution in all mosses and liver mosses. 3. From the lower prenylquinone levels and the low values for the variable fiuorescence it is concluded that mosses and liver mosses exhibit on a chlorophyll basis fewer reaction centres and electron transport chains than chloroplasts of higher plants.