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Plants have evolved a suite of photoreceptors to perceive information from the surrounding light conditions. The aim of this study was to examine photomorphogenic effects of light quality on the growth of Scots pine (Pinus sylvestris L.) seedlings representing southern (60 °N) and northern (68 °N) origins in Finland. We measured the growth characteristics and the expression of light-responsive genes from seedlings grown under two LED light spectra: (1) Retarder (blue and red wavelengths in ratio 0.7) inducing compact growth, and (2) Booster (moderate in blue, green and far-red wavelengths, and high intensity of red light) promoting shoot elongation. The results show that root elongation, biomass, and branching were reduced under Retarder spectrum in the seedlings representing both origins, while inhibition in seed germination and shoot elongation was mainly detected in the seedlings of northern origin. The expression of ZTL and HY5 was related to Scots pine growth under both light spectra. Moreover, the expression of PHYN correlated with growth when exposed to Retarder, whereas CRY2 expression was associated with growth under Booster. Our data indicates that blue light and the deficiency of far-red light limit the growth of Scots pine seedlings and that northern populations are more sensitive to blue light than southern populations. Furthermore, the data analyses suggest that ZTL and HY5 broadly participate in the light-mediated growth regulation of Scots pine, whereas PHYN responses to direct sunlight and the role of CRY2 is in shade avoidance. Altogether, our study extends the knowledge of light quality and differential gene expression affecting the early growth of Scots pines representing different latitudinal origins. [ABSTRACT FROM AUTHOR]

Based on available literature, ecology and economy of light emitting diode (LED) lights in plant foods production were assessed and compared to high pressure sodium (HPS) and compact fluorescent light (CFL) lamps. The assessment summarises that LEDs are superior compared to other lamp types. LEDs are ideal in luminous efficiency, life span and electricity usage. Mercury, carbon dioxide and heat emissions are also lowest in comparison to HPS and CFL lamps. This indicates that LEDs are indeed economic and eco-friendly lighting devices. The present review indicates also that LEDs have many practical benefits compared to other lamp types. In addition, they are applicable in many purposes in plant foods production. The main focus of the review is the targeted use of LEDs in order to enrich phytochemicals in plants. This is an expedient to massive improvement in production efficiency, since it diminishes the number of plants per phytochemical unit. Consequently, any other production costs (e.g. growing space, water, nutrient and transport) may be reduced markedly. Finally, 24 research articles published between 2013 and 2017 were reviewed for targeted use of LEDs in the specific, i.e. blue range (400-500 nm) of spectrum. The articles indicate that blue light is efficient in enhancing the accumulation of health beneficial phytochemicals in various species. The finding is important for global food production. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Two-and 3-year-old Scots pine (Pinus sylvestris L.) seedlings were grown in plexiglass chambers and control plots at two study sites in northern Finland. The chambers were made of either orange or transparent plexiglass. The former removed the blue wavelengths (400–500nm) of incoming sunlight, while the latter was transparent to all visible wavelengths. The removal of blue reduces the total amount of incoming light. This may theoretically enhance etiolation responses (i.e. increased stem elongation and reduced leaf development) in the seedlings grown under blue light depletion. Artificial removal of blue light did increase elongation of the main stem, although only at the sub-arctic latitude (69°N) of the experiment, not at the mid-boreal (64°N) latitude. However, elongation of the lateral branches, needle area and the weight of the new stem and needles were also increased in the seedlings grown in orange chambers at the sub-arctic latitude. Therefore, the increased elongation of the main stem of the seedlings grown under blue light depletion cannot be attributed to etiolation alone. [Copyright &y& Elsevier]

Species-specific differences in synthesis of flavonoids and phenolic acids were studied under lengthening periods of enhanced blue light in a greenhouse experiment in Northern Finland in the autumn of 2012. The aim was to compare red- and blue- weighted light spectra in relation to biosynthesis of the compounds. The species studied were red leaf lettuce and basil. There were five treatments for these inter-lighting LED manipulations using traditional high pressure sodium lamps as background light sources. Two treatments were exposed for the entire experimental period with (1) red- and (2) blue- weighted light for 48 days. The other three treatments were initiated with red- weighted light, but after each subsequent 12 day sub-period, one red-weighted treatment was switched to blue, resulting in the following treatments: 48, 36, 24, 12 and 0 days under enhanced blue light. Flavonoid and phenolic acid biosynthesis in plants were found to be species dependent. The most abundant compound in red leaf lettuce was cichoric acid (a dicaffeoyltartaric acid) while rosmaric acid (an ester of caffeic acid and 3,4-dihydroxyphenyllactic acid) dominated in basil. Other compounds detected also varied between the species. Red leaf lettuce was much more responsive to supplemental blue light. Based on these results, it is suggested that both blue and red light may be needed to regulate the accumulation of phenolics in basil. Some of the compounds detected accumulated continuously as a function of the spent time under supplemental blue light in red leaf lettuce, but not in basil. [ABSTRACT FROM AUTHOR]