Effects of natural shade on soybean thylakoid membrane composition

Abstract

The effect of natural shade on chloroplast thylakoid membrane activity and composition was examined for soybean (Glycine Max. cv. Young) grown under field conditions. Plots with high (10 plants m(-1) row) or low (1 plant m(-1) row) plant density were established. Expanding leaves were tagged at 50, 58 and 65 days after planting (DAP). At 92 DAP, tagged leaves were used as reference points to characterize canopy light environments and isolate thylakoid membranes. Light environments ranged from a photosynthetic photon flux density (PPFD) of 87% of full sun to a PPFD of 10% of full sun. The decline in PPFD was accompanied by an increase in the far-red/red (735 nm/645 nm) ratio from 0.9 to approximately six. The major effects of shade on chloroplast thylakoid membranes were a reduction in chloroplast coupling factor and a shift in light-harvesting capacity from Photosystem I to Photosystem II. Photosynthetic electron transport capacity was not affected by differences in PPFD, but was 20 to 30% higher in the 1 plant m(-1) row treatment. The plant density effect on electron transport was associated with differences in plastocyanin concentration, suggesting that plastocyanin is a limiting factor in soybean. Shade did not have a significant effect on the concentration of Photosystem II, Cyt b6f, or Photosystem I complexes.

Photosynthetic complex stoichiometry dynamics in higher plants: environmental acclimation and photosynthetic flux control

“…A strong increase in plastocyanin content with the light intensity was observed in barley ( Hordeum vulgare , Burkey, 1993) and in soybean (Burkey and Wells, 1996). Because cytochrome b 6 f complex and PSII contents increased less strongly, plastocyanin displayed the best correlation with linear electron flux capacity.…”

“…The cytochrome b 6 f complex is mainly quantified via difference absorbance signals of cytochrome f alone (according to Whitmarsh and Ort, 1984; method applied by: Leong and Anderson, 1984; Chow and Anderson, 1987; Chow and Hope, 1987; Evans, 1987; Chow et al, 1988; Burkey and Wells, 1996; Hikosaka, 1996) or of both cytochromes f and b 6 (Kirchhoff et al, 2002; Schöttler et al, 2004; Petersen et al, 2011). …”

“…Plastocyanin quantification is either done immunologically (Burkey, 1993, 1994; Burkey and Wells, 1996) or via difference absorbance measurements at multiple wavelengths in the far-red range between 800 and 950 nm wavelength, to separate the plastocyanin difference absorbance changes from signals arising from P 700 absorption (Kirchhoff et al, 2004; Schöttler et al, 2004, 2007a, b; Petersen et al, 2011). …”

“…Changes in the composition of the electron transport chain during the adjustment to increasing light intensities have been analyzed in a variety of species such as Alocasia macrorrhiza (Chow et al, 1988), Arabidopsis thaliana (Bailey et al, 2001), barley ( Hordeum vulgare , Burkey, 1993), pea ( Pisum sativum ; Leong and Anderson, 1984; Chow and Anderson, 1987; Evans, 1987), soybean ( Glycine max ; Burkey and Wells, 1996), spinach ( Spinacea oleracea ; Chow and Hope, 1987), tobacco ( Nicotiana tabacum , Petersen et al, 2011), and morning glory ( Ipomoea tricolor ; Hikosaka, 1996). All plant species displayed similar changes in the composition of their photosynthetic apparatus (summarized in Table 1 ).…”

Changes in the photosynthetic characteristics and photosystem stoichiometries in wild-type and Chl b-deficient mutant rice seedlings under various irradiances

“…The levels of the PSII reaction centre complex were also affected by the irradiance, while those of the PSI reaction centre complex remained unchanged (Leong and Anderson 1984, Lee and Whitmarsh 1989, De la Torre and Burkey 1990, Burkey and Wells 1996. As a result, the PSII/PSI ratio represented an imbalance between the two photosystems.…”