Abstract
We examined the effects of light quality on growth characteristics and porphyrin biosynthesis of rice seedlings grown under different wavelengths from light emitting diodes (LEDs). After 10 days of exposure to various wavelengths of LEDs, leaf area and shoot biomass were greater in seedlings grown under white and blue LEDs than those of green and red LEDs. Both green and red LED treatments drastically decreased levels of protoporphyrin IX (Proto IX) and Mg-porphyrins compared to those of white LED, while levels of Mg-Proto IX monomethyl ester and protochlorophyllide under blue LED were decreased by 21% and 49%, respectively. Transcript levels of PPO1 were greatly upregulated in seedlings grown under red LED compared to white LED, whereas transcript levels of HO2 and CHLD were upregulated under blue LED. Overall, most porphyrin biosynthetic genes in the Fe-porphyrin branch remained almost constant or upregulated, while most genes in the Mg-porphyrin branch were downregulated. Expression levels of nuclear-encoded photosynthetic genes Lhcb and RbcS noticeably decreased after exposure to blue and red LEDs, compared to white LED. Our study suggests that specific wavelengths of LED greatly influence characteristics of growth in plants partly through altering the metabolic regulation of the porphyrin biosynthetic pathway, and possibly contribute to affect retrograde signaling.
Highlights
Tetrapyrroles play an essential role in photosynthesis, cellular respiration, catalytic activities of enzymes, and signal transduction [1,2]
Levels of porphyrin metabolites and photosynthetic pigments as well as growth properties were greatly influenced by different wavelengths of light emitting diodes (LEDs)
The greater leaf width and dry biomass in rice seedlings grown under blue LED and broad spectrum-white LED may be related to the fact that porphyrin compounds absorb blue wavelength intensely
Summary
Tetrapyrroles play an essential role in photosynthesis, cellular respiration, catalytic activities of enzymes, and signal transduction [1,2]. Acclimatory responses of plants to light quantity and light spectral distribution often involve changes in the relative amounts of pigment-binding protein complexes, such as light-harvesting chlorophyll proteins (Lhcs), accompanied by corresponding changes in chlorophyll content in chloroplasts [6,7]. In this study,, wwe eexxamined the effect of llight quality on the regulation of plant growth and morphology in rice seedlings grown under different wavelengths of light. S of various LED light, the shoot height of rice seedlings treated with white LED or red LED was taller than that of blue LED, green LED or dark condition (FToalblolew1i)n. MInooruprhostluodgyy, alenadf ggrroowwtthhaonfdrischeosoetebdiloimngassswere contrwoellreedgbreyattlhyeplriogmhtoqteudabliytywohfitLeEaDnds.blue light, demonstrating that morphology and growth of rice seedlings were controlled by the light quality of LEDs. 2.2. Effects of Different Wavelengths of LEDs on the Levels of Photosynthetic Pigments and Porphyrin Metabolites 2.2. Twoetarel RpNurAifisewdefrreopmurpilfaiendtsfraonmd prelavnetrsseantrdarnesvcerribseedtr.aTnhscerirbeesdu.ltTahnet rceDsuNlAtasntwceDrNe uAssewd earse tuemsepdlaastetsemfoprlqatReTs-fPoCr RqRuTs-iPnCgRAuctsiinngasAactnininatsearnnailncteornntarol lc.onTthroel.wThhietewLhEitDe L(cEoDnt(rcooln) twroals) wusaesdusfoerd nfoorrmnoarlimzaatliiozant,iowni,thwtihthetehxeperxepssrieosnsiolenvleelvoefl tohfethseamsapmleplseetsetot t1o.1E. rErrorrorbabrasrsininddiciacateteSSEEMMffrroommtthhrreeee iinnddeeppeennddeenntteexxppeerriimmeennttss((nn== 33));;eeaacchheexxppeerriimmeenntthhaasstthhrreeeebbiioollooggiiccaallrreepplliiccaatteess..MMeeaannssddeennootteeddbbyy tthheessaammeelleetttteerrddiiddnnoottddiiffffeerrssigignnifiifcicaanntltylyaattpp
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