Blue radiation stimulates photosynthetic induction in Fagus sylvatica L.

Abstract

This study was designed to test the hypothesis that the spectral composition of incident radiation, as defined by the relative proportions of blue (B; λ max = 455 nm) and red (R; λ max = 625 nm) photons, can affect photosynthetic induction, since B photons stimulate stomatal opening and are more effectively absorbed by leaves than R photons. Different stages of photosynthetic induction, primarily determined by the photo-modulation of Rubisco activity and stomata opening, were investigated in dark-adapted leaves of Fagus sylvatica transferred to saturating irradiance [800µmol(photon) m -2 s -1 ] at B/R ratios of 1/3, 1/1, or 3/1.In agreement with our hypothesis, photosynthesis was induced faster by irradiance with a high B/R ratio (3/1); as demontrated by a higher IS 60 (induction state 60 s after leaf illumination) and lower T 90 (the time period required to reach 90 % of maximum steady-state photosynthesis). However, there were no differences in induction between leaves receiving equal (1/1) and low (1/3) B/R ratios. Electron transport was highly sensitive to radiation quality, exhibiting faster induction kinetics with increasing B/R ratio. Such stimulation of carbon-assimilatory processes corresponds with faster activation of Rubisco and lower non-photochemical quenching (NPQ) as the proportion of B photons is increased. In contrast, the kinetics of stomatal opening was independent of the spectral composition of incoming radiation. Since slightly higher absorption efficiency of high B/R radiation does not fully explain the changes in induction kinetics, the other possible mechanisms contributing to the stimulation of electron transport and Rubisco activity are discussed.Additional keywords: blue/red ratio, electron transport, non-photochemical quenching, radiation quality, Rubisco activation, transient limitations of photosynthesis.

Carbon dioxide exchange and canopy conductance of two coniferous forests under various sky conditions

“…This suggests that the overall effect of light conditions on photosynthesis might be mediated through a stomatal response rather than any direct effect on light on the photosynthetic machinery. This is an important conclusion as others (Portis et al 2008) have suggested that blue light can activate Rubisco and enhance electron transport in the thylakoid membranes (Košvancová-Zitová et al 2009b). …”

“…An additional hypothesis relates to the blue light component of the in-canopy light climate. Stomata are known to be especially responsive to light between 430 and 470 nm (Raschke 1975;Morison and Jarvis 1983;Karlsson 1986;Briggs and Christie 2002), and there are also reports of a direct blue light effect on the induction kinetics of photosynthesis (Košvancová-Zitová et al 2009b), and on the electron transport through thylakoid membranes (Portis et al 2008;Košvancová et al 2009a). Blue light enrichment inside coniferous canopies has been observed under cloudy skies (Urban et al 2007), and so it is not unreasonable to suppose that part of the enhancement of photosynthesis under cloudy and overcast Communicated by Nina Buchmann. conditions is caused by blue light enrichment.…”

Impact of clear and cloudy sky conditions on the vertical distribution of photosynthetic CO2 uptake within a spruce canopy

“… Although there are reports of a stimulating effect of blue light on the hydraulic conductance of leaf blades (Sellin et al. 2011) and on the activation of photosynthetic processes (Kosvancova‐Zitova et al. 2009), blue light enrichment in diffuse conditions did not cause a substantial stimulation of photosynthesis through its effect on stomatal conductance (Fig.…”

Red/blue light ratio strongly affects steady‐state photosynthesis, but hardly affects photosynthetic induction in tomato (Solanum lycopersicum)

“…Blue light often stimulates stomatal opening when combined with red light (Zeiger and Field 1982, Wang et al 2008, Zait et al 2017, and adding blue to dynamically changing red light intensities may ameliorate stomatal limitation on carbon gain. To date, however, only few studies have explored blue light effects on photosynthetic induction (Košvancová-Zitová et al 2009, Zhang et al 2011, Kaiser et al 2017, and available findings are contradictory. Interestingly, the stimulating effect of blue light on stomatal opening seems to be highly sensitive to the growth environment.…”