In Vitro Multiplication and Rooting of Plum Rootstock 'Saint Julien' (Prunus domestica subsp. insititia) under Fluorescent Light and Different LED Spectra.

In recent years, light emitting diodes (LEDs), due to their low energy consumption, low heat emission and specific wavelength irradiation, have become an alternative to fluorescent lamps (FLs) in plant tissue culture. The aim of this study was to investigate the effects of various LED light sources on the in vitro growth and rooting of plum rootstock Saint Julien (Prunus domestica subsp. insititia). The test plantlets were cultivated under a Philips GreenPower LEDs research module illumination system with four spectral regions: white (W), red (R), blue (B) and mixed (W:R:B:far-red = 1:1:1:1). The control plantlets were cultivated under fluorescent lamps (FL) and the photosynthetic photon flux density (PPFD) of all treatments was set at 87 ± 7.5 µmol m-2 s-1. The effect of light source on the selected physiological, biochemical and growth parameters of plantlets was monitored. Additionally, microscopic observations of leaf anatomy, leaf morphometric parameters and stomata characteristics were carried out. The results showed that the multiplication index (MI) varied from 8.3 (B) to 16.3 (R). The MI of plantlets grown under mixed light (WBR) was 9, lower compared to the control (FL) and white light (W), being 12.7 and 10.7, respectively. In addition, a mixed light (WBR) favored plantlets' stem growth and biomass accumulation at the multiplication stage. Considering these three indicators, we could conclude that under the mixed light, the microplants were of better quality and therefore mixed light (WBR) was more suitable during the multiplication phase. A reduction in both net photosynthesis rate and stomatal conductance in the leaves of plants grown under B were observed. The quantum yield (Yield = FV/FM), which represents the potential photochemical activity of PS II, ranged from 0.805 to 0.831 and corresponded to the typical photochemical activity (0.750-0.830) in the leaves of unstressed healthy plants. The red light had a beneficial effect on the rooting of plum plants; the rooting was over 98%, significantly higher than for the control (FL, 68%) and the mixed light (WBR, 19%). In conclusion, the mixed light (WBR) turned out to be the best choice during the multiplication phase and the red LED light was more suitable during the rooting stage.

Effects of Light Spectral Quality on Photosynthetic Activity, Biomass Production, and Carbon Isotope Fractionation in Lettuce, Lactuca sativa L., Plants.

The optimization of plant-specific LED lighting protocols for indoor plant growing systems needs both basic and applied research. Experiments with lettuce, Lactuca sativa L., plants using artificial lighting based on narrow-band LEDs were carried out in a controlled environment. We investigated plant responses to the exclusion of certain spectral ranges of light in the region of photosynthetically active radiation (PAR); in comparison, the responses to quasimonochromatic radiation in the red and blue regions were studied separately. The data on plant phenotyping, photosynthetic activity determination, and PAM fluorometry, indicating plant functional activity and stress responses to anomalous light environments, are presented. The study on carbon isotopic composition of photoassimilates in the diel cycle made it possible to characterize the balance of carboxylation and photorespiration processes in the leaves, using a previously developed oscillatory model of photosynthesis. Thus, the share of plant photorespiration (related to plant biomass enrichment with 13C) increased in response to red-light action, while blue light accelerated carboxylation (related to 12C enrichment). Blue light also reduced water use efficiency. These data are supported by the observations from the light environments missing distinct PAR spectrum regions. The fact that light of different wavelengths affects the isotopic composition of total carbon allowed us to elucidate the nature of its action on the organization of plant metabolism.

Effects of Light Spectral Quality on the Micropropagated Raspberry Plants during Ex Vitro Adaptation.

This work focuses on developing light environments for the effective regulation of morphogenesis and ex vitro conditions adaptation in micropropagated raspberry plants on the basis of photomorphogenetic control of physiological processes using light-emitting diodes (LEDs). In experiments with cloned plants growing ex vitro in stressful conditions during acclimation, the effects of optical radiation of various spectral combinations from different photosynthetically active radiation (PAR) spectral regions were studied. The data on the plant development and state of the photosynthetic apparatus, features of photosynthetic gas exchange and transpiration, accumulation of photosynthetic pigments, light curves of photosynthesis, and data on growth processes in light modes using combined quasimonochromatic radiation (either mixture of red, green, and blue light or red, far-red, and blue light) with various ratio of the distinct spectral regions were obtained. Photosynthetic apparatus functional activity under different light conditions was studied with chlorophyll fluorescence determination, and plant stress responses to growing under artificial spectral light conditions were characterized. The experiments were accompanied by detailed plant phenotyping at the structural and functional levels. Plant acclimation and photosynthetic improvements in response to added far-red and green light wavelengths to the main red-blue spectrum have been elucidated.

Environmental Influences on the Growing Season Duration and Ripening of Diverse Miscanthus Germplasm Grown in Six Countries.

The development of models to predict yield potential and quality of a Miscanthus crop must consider climatic limitations and the duration of growing season. As a biomass crop, yield and quality are impacted by the timing of plant developmental transitions such as flowering and senescence. Growth models are available for the commercially grown clone Miscanthus x giganteus (Mxg), but breeding programs have been working to expand the germplasm available, including development of interspecies hybrids. The aim of this study was to assess the performance of diverse germplasm beyond the range of environments considered suitable for a Miscanthus crop to be grown. To achieve this, six field sites were planted as part of the EU OPTIMISC project in 2012 in a longitudinal gradient from West to East: Wales-Aberystwyth, Netherlands-Wageningen, Stuttgart-Germany, Ukraine-Potash, Turkey-Adana, and Russia-Moscow. Each field trial contained three replicated plots of the same 15 Miscanthus germplasm types. Through the 2014 growing season, phenotypic traits were measured to determine the timing of developmental stages key to ripening; the tradeoff between growth (yield) and quality (biomass ash and moisture content). The hottest site (Adana) showed an accelerated growing season, with emergence, flowering and senescence occurring before the other sites. However, the highest yields were produced at Potash, where emergence was delayed by frost and the growing season was shortest. Flowering triggers varied with species and only in Mxg was strongly linked to accumulated thermal time. Our results show that a prolonged growing season is not essential to achieve high yields if climatic conditions are favorable and in regions where the growing season is bordered by frost, delaying harvest can improve quality of the harvested biomass.

Extending Miscanthus Cultivation with Novel Germplasm at Six Contrasting Sites.

Miscanthus is a genus of perennial rhizomatous grasses with C4 photosynthesis which is indigenous in a wide geographic range of Asian climates. The sterile clone, Miscanthus × giganteus (M. × giganteus), is a naturally occurring interspecific hybrid that has been used commercially in Europe for biomass production for over a decade. Although, M. × giganteus has many outstanding performance characteristics including high yields and low nutrient offtakes, commercial expansion is limited by cloning rates, slow establishment to a mature yield, frost, and drought resistance. In this paper, we evaluate the performance of 13 novel germplasm types alongside M. × giganteus and horticultural "Goliath" in trials in six sites (in Germany, Russia, The Netherlands, Turkey, UK, and Ukraine). Mean annual yields across all the sites and genotypes increased from 2.3 ± 0.2 t dry matter ha-1 following the first year of growth, to 7.3 ± 0.3, 9.5 ± 0.3, and 10.5 ± 0.2 t dry matter ha-1 following the second, third, and fourth years, respectively. The highest average annual yields across locations and four growth seasons were observed for M. × giganteus (9.9 ± 0.7 t dry matter ha-1) and interspecies hybrid OPM-6 (9.4 ± 0.6 t dry matter ha-1). The best of the new hybrid genotypes yielded similarly to M. × giganteus at most of the locations. Significant effects of the year of growth, location, species, genotype, and interplay between these factors have been observed demonstrating strong genotype × environment interactions. The highest yields were recorded in Ukraine. Time needed for the crop establishment varied depending on climate: in colder climates such as Russia the crop has not achieved its peak yield by the fourth year, whereas in the hot climate of Turkey and under irrigation the yields were already high in the first growing season. We have identified several alternatives to M. × giganteus which have provided stable yields across wide climatic ranges, mostly interspecies hybrids, and also Miscanthus genotypes providing high biomass yields at specific geographic locations. Seed-propagated interspecific and intraspecific hybrids, with high stable yields and cheaper reliable scalable establishment remain a key strategic objective for breeders.

Site-Specific Management of Miscanthus Genotypes for Combustion and Anaerobic Digestion: A Comparison of Energy Yields.

In Europe, the perennial C4 grass miscanthus is currently mainly cultivated for energy generation via combustion. In recent years, anaerobic digestion has been identified as a promising alternative utilization pathway. Anaerobic digestion produces a higher-value intermediate (biogas), which can be upgraded to biomethane, stored in the existing natural gas infrastructure and further utilized as a transport fuel or in combined heat and power plants. However, the upgrading of the solid biomass into gaseous fuel leads to conversion-related energy losses, the level of which depends on the cultivation parameters genotype, location, and harvest date. Thus, site-specific crop management needs to be adapted to the intended utilization pathway. The objectives of this paper are to quantify (i) the impact of genotype, location and harvest date on energy yields of anaerobic digestion and combustion and (ii) the conversion losses of upgrading solid biomass into biogas. For this purpose, five miscanthus genotypes (OPM 3, 6, 9, 11, 14), three cultivation locations (Adana, Moscow, Stuttgart), and up to six harvest dates (August-March) were assessed. Anaerobic digestion yielded, on average, 35% less energy than combustion. Genotype, location, and harvest date all had significant impacts on the energy yield. For both, this is determined by dry matter yield and ash content and additionally by substrate-specific methane yield for anaerobic digestion and moisture content for combustion. Averaged over all locations and genotypes, an early harvest in August led to 25% and a late harvest to 45% conversion losses. However, each utilization option has its own optimal harvest date, determined by biomass yield, biomass quality, and cutting tolerance. By applying an autumn green harvest for anaerobic digestion and a delayed harvest for combustion, the conversion-related energy loss was reduced to an average of 18%. This clearly shows that the delayed harvest required to maintain biomass quality for combustion is accompanied by high energy losses through yield reduction over winter. The pre-winter harvest applied in the biogas utilization pathway avoids these yield losses and largely compensates for the conversion-related energy losses of anaerobic digestion.

Progress on Optimizing Miscanthus Biomass Production for the European Bioeconomy: Results of the EU FP7 Project OPTIMISC.

This paper describes the complete findings of the EU-funded research project OPTIMISC, which investigated methods to optimize the production and use of miscanthus biomass. Miscanthus bioenergy and bioproduct chains were investigated by trialing 15 diverse germplasm types in a range of climatic and soil environments across central Europe, Ukraine, Russia, and China. The abiotic stress tolerances of a wider panel of 100 germplasm types to drought, salinity, and low temperatures were measured in the laboratory and a field trial in Belgium. A small selection of germplasm types was evaluated for performance in grasslands on marginal sites in Germany and the UK. The growth traits underlying biomass yield and quality were measured to improve regional estimates of feedstock availability. Several potential high-value bioproducts were identified. The combined results provide recommendations to policymakers, growers and industry. The major technical advances in miscanthus production achieved by OPTIMISC include: (1) demonstration that novel hybrids can out-yield the standard commercially grown genotype Miscanthus x giganteus; (2) characterization of the interactions of physiological growth responses with environmental variation within and between sites; (3) quantification of biomass-quality-relevant traits; (4) abiotic stress tolerances of miscanthus genotypes; (5) selections suitable for production on marginal land; (6) field establishment methods for seeds using plugs; (7) evaluation of harvesting methods; and (8) quantification of energy used in densification (pellet) technologies with a range of hybrids with differences in stem wall properties. End-user needs were addressed by demonstrating the potential of optimizing miscanthus biomass composition for the production of ethanol and biogas as well as for combustion. The costs and life-cycle assessment of seven miscanthus-based value chains, including small- and large-scale heat and power, ethanol, biogas, and insulation material production, revealed GHG-emission- and fossil-energy-saving potentials of up to 30.6 t CO2eq C ha-1y-1 and 429 GJ ha-1y-1, respectively. Transport distance was identified as an important cost factor. Negative carbon mitigation costs of -78€ t-1 CO2eq C were recorded for local biomass use. The OPTIMISC results demonstrate the potential of miscanthus as a crop for marginal sites and provide information and technologies for the commercial implementation of miscanthus-based value chains.