Inhibition of Photosystem I and Photosystem II in Wheat Seedlings with their Root–shoot Transition Zones Exposed to Red Light

Abstract

The present study was conducted to observe the role of the root-shoot transition zone in the development of PS I and PS II in red light. The development of PS II and PS I was severely inhibited when root-shoot transition zones of wheat seedlings were exposed to red light (670 nm) of intensity 500 micromol m(-2) s(-1). Chlorophyll biosynthesis was also inhibited in these seedlings. Most of the PS I and PS II proteins (D1, LHCPII, CP47, OEC33) and their transcript levels were severely inhibited but cyt b6f complex proteins were only partially inhibited. Protein and transcript levels of Rubisco large subunit and protochlorophyllide (Pchlide) biosynthesis were also severely inhibited in these seedlings. When incubated in the dark with or without the precursor of chlorophyll biosynthesis ALA, these plants accumulated most of the Pchlide, as non-phototransformable Pchlide, suggesting low activity of NADPH:protochlorophyllide oxidoreductase (EC 1.6.99.1) in these plants. These effects were not observed when the seedlings were grown in red light with their root-shoot transition zones covered. These results suggest that the root-shoot transition zone plays an important role in the overall greening process involving transcription and translation of photosynthetic genes.

Light-hormone interaction in the red-light-induced suppression of photomorphogenesis in rice seedlings

“…1). Most of the enzymatic activities, involved in Chl biosynthesis and greening process, are impaired in seedlings grown in red light having their shoot bottom exposed (Sood et al 2005;Sood et al 2004). Suppression of photomorphogenesis by red light (400 μmol photons m −2 s −1 ) is a red-HIR response of PhyA (Roy et al 2013).…”

“…In previous studies, we have shown rice and wheat seedling grown with their shoot bottom exposed to constant red light or when given in the form of light-dark cycles do not accumulate chlorophyll (Chl) (Gupta et al 2010;Roy et al 2013;Sood et al 2005;Sood et al 2004;Tripathy and Brown 1995). Red light perceived by the shoot bottom downregulates the protein and gene expression of the enzymes involved in the biosynthesis of tetrapyrroles (Sood et al 2005;Sood et al 2004;Tripathy and Brown 1995).…”

“…Red light perceived by the shoot bottom downregulates the protein and gene expression of the enzymes involved in the biosynthesis of tetrapyrroles (Sood et al 2005;Sood et al 2004;Tripathy and Brown 1995). This red-light-induced suppression of photomorphogenesis is a red high-irradiance response (red HIR) of PhyA (Roy et al 2013).…”

Protochlorophyllide reduction - what is new in 2005?

“…Table 3. Comparison of the spectral heterogeneity of the non-photoactive and photoactive protochlorophyllide pools observed in etiolated bean leaves , during greening (Amirjani and Sundqvist 2004), and in red-radiation-grown wheat (Sood et al 2004 Sood et al (2004) studied the effect of irradiation of the root-shoot transition zone on the accumulation of Pchlide in leaves in red-radiation-grown wheat (500 µmol m -2 s -1 , wavelength = 670±26 nm). The leaves from plants with an irradiated root-shoot transition zone differed from those which zone was not irradiated, by the absence of the spectral bands corresponding to photosystems in fluorescence spectra.…”

Effects of the red:far-red light ratio on photosynthetic characteristics of greenhouse cut Chrysanthemum - Short communication

“…We found that the chlorophyll fl uorescence parameters of the chrysanthemum leaves were not linearly correlated with the R:FR ratios. Th e eff ects of R:FR ratios on the fl uorescence parameters may be related to the balance between PSI and PSII (Sood et al 2004).…”