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

Abstract

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.

Response of Soybean Photosynthesis and Chloroplast Membrane Function to Canopy Development and Mutual Shading

“…The steady state levels of specific thylakoid membrane-proteins are known to change in response to irradiance manipulations under growth chamber conditions. Experiments with barley ( 14), lettuce ( 13), mustard (33), pea (9,16,24), soybean (Table I), spinach (10), and tomato ( 12) have shown that levels of CF and Cyt fare dependent on growth irradiance. In results reported here, both coupling factor and Cyt f levels were affected by canopy shading under field conditions.…”

“…The concentration of P-700 was determined from the reversible light-induced P-700 A697, change using an extinction coefficient of 64 mm-' cm-' (19). Details have been published elsewhere (14).…”

“…Thus, light environment plays a critical role during leaf expansion in determining the photosynthetic properties of the mature leaf. More recently, controlled environment studies with a number of species have shown that fully expanded leaves retain the capacity to 'fine-tune' photosynthesis in response to changes in growth irradiance (8,12,14,15,33). This study was conducted to determine whether light acclimation is a significant factor under field conditions in leaves that become shaded during canopy development.…”

Inducible Repression of Nuclear-Encoded Subunits of the Cytochrome b6f Complex in Tobacco Reveals an Extraordinarily Long Lifetime of the Complex

“…The cyt-bf contents increase with actinic light intensity in higher plants, but the amplitudes of the changes are dependent on the species. For example, Alocasia macrorrhiza (Chow et al, 1988), barley (Hordeum vulgare; De la Torre and Burkey, 1990), and spinach (Spinacia oleracea; Chow and Hope, 1987) all retain relatively high cyt-bf contents in low light, and therefore the cyt-bf content increases less than 2-fold with light intensity. In pea (Pisum sativum; Evans, 1987) and tobacco (Petersen et al, 2011), more pronounced changes in cyt-bf contents with light intensity closely correlate with linear electron flux capacity.…”

Novel Light-Regulated Chloroplast Thylakoid Membrane Protein

“…The irradiance and spectral quality of light surrounding an individual leaf controls the capacity ofthat leafto conduct photosynthesis (1)(2)(3)10) and associated processes such as chloroplast electron transport (3,6,9,10) and photophosphorylation (4,7,10). Light regulates these photosynthetic activities by controlling the levels of specific chloroplast proteins associated with each function.…”