Adaptation of Barley Thylakoid Membranes to Changing Light Intensity

Barley seedlings (Hordeum vulgare L. cv. Boone) were grown at 20°C with a 16h/8h light/dark cycle of either high (H) intensity (550 μmole m(-2) s(-1)) or low (L) intensity (55 μmole m(-2) s(-1)) white light. Plants were transferred from high to low (H → L) or low to high (L → H) light intensity at various times from 4 to 8 d after leaf emergence from the soil. Primary leaves were harvested at the beginning of the photoperiod and a 3 cm apical segment removed for analysis. H control plants had greater chlorophyll (Chl) per leaf area and higher Chl a/b ratios than L controls. Analysis of Chl-protein complexes revealed that H and L plants had the same percentage of total Chl (62-65%) associated with Photosystem II (PS II), but that the organization of Chl within PS II was different. H plants contained lower levels of light-harvesting complex (LHC-II) and higher levels of the PS II complex CPa compared with L plants. Leaf Chl content and Chl organization within PS II were sensitive to changes in light intensity. In H → L plants, leaf Chl content decreased, Chl a/b ratio decreased, and a redistribution of Chl from CPa to LHC-II occurred during acclimation to low light. Acclimation of L → H plants to high light involved an increase in leaf Chl content, an increase in Chl a/b ratio, and a decrease in LHC-II. In contrast, the level of photosystem I related Chl-protein complexes (CP1 + CP1a) was similar in all light treatments. The light acclimation process occurred slowly over a period of 6 to 8 d in H → L and L → H plants.

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Acclimation of barley to changes in light intensity: photosynthetic electron transport activity and components

Torre

Burkey

1990

Photosynth Res

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Barley seedlings (Hordeum vulgare L. Boone) were grown at 20°C with 16 h/8 h light/dark cycle of either high (H) intensity (500 μmole m(-2) s(-1)) or low (L) intensity (55 μmole m(-2) s(-1)) white light. Plants were transferred from high to low (H → L) and low to high (L → H) light intensity at various times from 4 to 8 d after leaf emergence from the soil. Primary leaves were harvested at the beginning of the photoperiod. Thylakoid membranes were isolated from 3 cm apical segments and assayed for photosynthetic electron transport, Photosystem II (PS II) atrazine-binding sites (QB), cytochrome f(Cytf) and the P-700 reaction center of Photosystem I (PS I). Whole chain, PS I and PS II electron transport activities were higher in H than in L controls. QB and Cytf were elevated in H plants compared with L plants. The acclimation of H → L plants to low light occurred slowly over a period of 7 days and resulted in decreased whole chain and PS II electron transport with variable effects on PS I activity. The decrease in electron transport of H → L plants was associated with a decrease in both QB and Cytf. In L → H plants, acclimation to high light occurred slowly over a period of 7 days with increased whole chain, PS I and PS II activities. The increase in L → H electron transport was associated with increased levels of QB and Cytf. In contrast to the light intensity effects on QB levels, the P-700 content was similar in both control and transferred plants. Therefore, PS II/PS I ratios were dependent on light environment.

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Adaptation of Barley Thylakoid Membranes to Changing Light Intensity

Cited by 3 publications

References 8 publications

Factors that affect the carotenoid composition of higher plants and algae

Factors that affect the carotenoid composition of higher plants and algae

Acclimation of barley to changes in light intensity: chlorophyll organization

Acclimation of barley to changes in light intensity: photosynthetic electron transport activity and components

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