The photosynthetic CO2-fixation rates, chlorophyll content, chloroplast ultrastructure and other leaf characteristics (e.g. variable fluorescence, stomata density, soluble carbohydrate content) were studied in a comparative way in sun and shade leaves of beech (Fagus sylvatica) and in high-light and low-light seedlings. 1. Sun leaves of the beech possess a smaller leaf area, higher dry weight, lower water content, higher stomata density, higher chlorophyll a/b ratios and are thicker than the shade leaves. Sun leaves on the average contain more chlorophyll in a leaf area unit; the shade leaf exhibits more chlorophyll on a dry weight basis. Sun leaves show higher rates for dark respiration and a higher light saturation of photosynthetic CO2-fixation. Above 2000 lux they are more efficient in photosynthetic quantum conversion than the shade leaves. 2. The development of HL-radish plants proceeds much faster than that of LL-plants. The cotyledons of HL-plants show a higher dry weight, lower water content, a higher ratio of chlorophyll a/b and a higher gross photosynthesis rate than the cotyledons of the LL-plants, which possess a higher chlorophyll content per dry weight basis. The large area of the HL-cotyledon on the one hand, as well as the higher stomata density and the higher respiration rate in the LL-cotyledon on the other hand, are not in agreement with the characteristics of sun and shade leaves respectively. 3. The development, growth and wilting of wheat leaves and the appearance of the following leaves (leaf succession) is much faster at high quanta fluence rates than in weak light. The chlorophyll content is higher in the HL-leaf per unit leaf area and in the LL-leaf per g dry weight. There are no differences in the stomata density and leaf area between the HL- and LL-leaf. There are fewer differences between HL- and LL-leaves than in beech or radish leaves. 4. The chloroplast ultrastructure of shade-type chloroplasts (shade leaves, LL-leaves) is not only characterized by a much higher number of thylakoids per granum and a higher stacking degree of thylakoids, but also by broader grana than in sun-type chloroplasts (sun leaves, HL-leaves). The chloroplasts of sun leaves and of HL-leaves exhibit large starch grains. 5. Shade leaves and LL-leaves exhibit a higher maximum chlorophyll fluorescence and it takes more time for the fluorescence to decline to the steady state than in sun and HL-leaves. The variable fluorescence VF (ratio of fluorescence decrease to steady state fluorescence) is always higher in the sun and HL-leaf of the same physiological stage (maximum chlorophyll content of the leaf) than in the shade and LL-leaf. The fluorescence emission spectra of sun and HL-leaves show a higher proportion of chlorophyli fluorescence in the second emission maximum F2 than shade and LL-leaves. 6. The level of soluble carbohydrates (reducing sugars) is significantly higher in sun and HL-leaves than in shade and LL-leaves and even reflects changes in the amounts of the daily incident light. 7. Some but not all...

Adaptation of Chloroplasts, Chlorophyll Fluorescence, Chlorophyll a-Proteins, Chloroplast Ultrastructure, High-Light ChloroplastsIn saturating light radish seedlings grown in high-light growth conditions (90 W • n r 2) possess a much higher photosynthetic capacity on a chlorophyll and leaf area basis than the low-light grown plants (10 W • m-2). The higher C 0 2-fixation rate o f HL-plants is due to the presence of HL-chloroplasts which possess a different ultrastructure and also different levels o f the individual chlorophyll-carotenoid-proteins than the LL-chloroplasts of LL-seedlings. 1. Ultrastructure: The high-light adapted chloroplasts are characterized by fewer photo synthetic membranes per chloroplast section, by low grana stacks (only few thylakoids per granum), a lower stacking degree o f thylakoids, a higher proportion o f non-appressed mem branes (stroma thylakoids + end grana membranes) and a high starch content. The LL-chloro plasts possess no starch, their grana stacks are higher (up to 17 thylakoids per granum) and also significantly broader than that o f HL-chloroplasts. 2. Chlorophyll-proteins: The photosynthetic apparatus o f HL-chloroplasts contains a larger proportion of chlorophyll a-proteins of photosystem I (CPIa + CPI) and of photosystem II (CPa, the presumable reaction center o f PS II) than the LL-chloroplasts which possess a higher propor tion of light-harvesting chlorophyll a/fc-proteins (LHCP,, LHCP2, LHCP3, LHCPy). The higher levels of LHCPs in LL-plants are associated with a higher ground fluorescence fo and maximum fluorescence fp of the in vivo chlorophyll. Chlorophyll and carotenoid ratios: The chloroplasts o f HL-plants possess a higher proportion of chlorophyll a and /2-carotene (higher values for the ratios chlorophyll a /b and lower values for a/c and x /c ) which reflect the increased level o f the chlorophyll a//?-carotene-proteins CPIa, CPI and CPa. The higher level o f light-harvesting chlorophyll a/6-xanthophyll-proteins (LHCPs) in LL-plants is also indicated by an increased content o f xanthophylls and chlorophyllb as seen from lower a /b and higher x /c and a /c ratios. 4. The results indicate that plants possess the capacity for an ontogenetic adaptation o f their photosynthetic apparatus to the incident light intensity. The HL-chloroplasts o f HL-plants which contain less antenna chlorophyll, are adapted for a more efficient photosynthetic quantum conversion at light saturation than the LL-chloroplasts with high grana stacks. The correlation between higher levels o f light-harvesting chlorophyll ö/6-proteins (LHCPs) and a higher stacking degree of thylakoids, and the involvement o f LHCPs in stacking is discussed. Abbreviations: a/b, ratio chlorophyll a/b', a /c, weight ratio chlorophyll a to /^-carotene, CPI and CPIa, the two P700 containing chlorophyll a /?-carotene-proteins o f photosys tem I; CPa, chlorophyll a /?-carotene-protein o f photosys tem II, c/x, ratio /?-carotene/xanthophylls; fo, ground fluo rescence of the in vivo chlorophyll fluorescence; fp, maxi ...

The level of 7 chlorophyll‐carotenoid‐proteins was determined in chloroplasts from radish seedlings (Raphanus sativus L. var. Saxa Treib) grown in high‐light (HL; 90 W m−2 and low‐light (LL; 10 W m−2) growth conditions with and without application of the photosystem 2 herbicide bentazon (10−4M) and compared with the degree of thylakoid stacking. The photosynthetic apparatus of HL‐chloroplasts contains higher proportions of the photosystem 1 chlorophyll a‐proteins CPI and CPIa than LL‐chloroplasts or chloroplasts from bentazon‐treated plants. In LL‐chloroplasts and in chloroplasts from bentazon‐treated plants a higher proportion of light‐harvesting chlorophyll a/b‐proteins (LHCP1, LHCP2, LHCP3, LHCPy) is found. Bentazon treatment changes the proportion of LHCPs to about the same levels under both HL and LL‐growth conditions. The amounts of free chlorophyll found in bentazon chloroplasts (27–29%) is higher than in the HL or LL‐controls (16–18%). The increase in degree of thylakoid stacking (% proportion of appressed membranes per total chloroplasts membranes) of LL‐chloroplasts as compared to HL‐chloroplasts of 7 to 9% (3rd to 5th day of illumination) is paralleled by a similar increase in the LHCPs of 5% and 8% (3rd and 5th day). The importance of light harvesting chlorophyll a/b‐proteins as a prerequisite for thylakoid stacking is discussed.

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There are specific differences between red and blue light greening of etiolated seedlings of Hordeum uulgare L. Blue light results in a different prenyl lipid composition of chloroplast as compared to red light of equal quanta density. This is documented by a much higher prenylquinone content, higher chlorophyll a / b ratios, and lower values for the ratio xanthophylls to carotenes (-tic). The photosynthetic activity of "blue light" chloroplasts (Hill reaction) is higher than that of "red light" chloroplasts. These differences in prenylquinone composition and Hill-activity are associated with a different ultrastructure of chloroplasts. "Red light" chloroplasts exhibit a much higher grana content than "blue light" chloroplasts. The difference in thylakoid composition, photosynthetic activity and chloroplast structure found between blue and red light greening are similar to those found between sun and shade leaves and those between plants grown under high and low light intensities.