Sustainable development in the building sector requires the integration of energy efficiency and renewable energy utilization in buildings. In recent years, the concept of net zero energy buildings (NZEBs) has become a potential plausible solution to improve efficiency and reduce energy consumption in buildings. To achieve an NZEB goal, building systems and design strategies must be integrated and optimized based on local climatic conditions. This paper provides a comprehensive review of NZEBs and their current development in hot and humid regions. Through investigating 34 NZEB cases around the world, this study summarized NZEB key design strategies, technology choices and energy performance. The study found that passive design and technologies such as daylighting and natural ventilation are often adopted for NZEBs in hot and humid climates, together with other energy efficient and renewable energy technologies. Most NZEB cases demonstrated site annual energy consumption intensity less than 100 kW-hours (kWh) per square meter of floor space, and some buildings even achieved “net-positive energy” (that is, they generate more energy locally than they consume). However, the analysis also shows that not all NZEBs are energy efficient buildings, and buildings with ample renewable energy adoption can still achieve NZEB status even with high energy use intensity. This paper provides in-depth case-study-driven analysis to evaluate NZEB energy performance and summarize best practices for high performance NZEBs. This review provides critical technical information as well as policy recommendations for net zero energy building development in hot and humid climates.

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A review of net zero energy buildings in hot and humid climates: Experience learned from 34 case study buildings

Light quantity (intensity and photoperiod) and quality (spectral composition) affect plant growth and physiology and interact with other environmental parameters and cultivation factors in determining the plant behaviour. More than providing the energy for photosynthesis, light also dictates specific signals which regulate plant development, shaping and metabolism, in the complex phenomenon of photomorphogenesis, driven by light colours. These are perceived even at very low intensity by five classes of specific photoreceptors, which have been characterized in their biochemical features and physiological roles. Knowledge about plant photomorphogenesis increased dramatically during the last years, also thanks the diffusion of light-emitting diodes (LEDs), which offer several advantages compared to the conventional light sources, such as the possibility to tailor the light spectrum and to regulate the light intensity, depending on the specific requirements of the different crops and development stages. This knowledge could be profitably applied in greenhouse horticulture to improve production schedules and crop yield and quality. This article presents a brief overview on the effects of light spectrum of artificial lighting on plant growth and photomorphogenesis in vegetable and ornamental crops, and on the state of the art of the research on LEDs in greenhouse horticulture. Particularly, we analysed these effects by approaching, when possible, each single-light waveband, as most of the review works available in the literature considers the influence of combined spectra.

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Light-Quality Manipulation to Control Plant Growth and Photomorphogenesis in Greenhouse Horticulture: The State of the Art and the Opportunities of Modern LED Systems

The primary issues regarding the lack of protocol reproducibility among laboratories are environmental factors. Light (quantity and particularly quality), is one of those main factors, and studies seldom present the spectral quality of the light sources used. With the advent of light-emitting diode (LED) technology, impressive progress has been made in environmental controls and morphogenetic responses, as directed by the light used in the culture shelves. A wide array of LED lights with different spectra are currently available and light is important in large-scale propagation, especially liquid bioreactor systems. LED technology continues to evolve rapidly and has created additional possibilities. This laboratory has dedicated extensive efforts to implement photoautotrophic propagation, and light is a key component of the system. This review presents relevant topics on the influence of light in various plant tissue culture-based techniques.

Light quality in plant tissue culture: does it matter?

Carotenoids are isoprenoids widely distributed in foods that have been always part of the diet of humans. Unlike the other so-called food bioactives, some carotenoids can be converted into retinoids exhibiting vitamin A activity, which is essential for humans. Furthermore, they are much more versatile as they are relevant in foods not only as sources of vitamin A, but also as natural pigments, antioxidants, and health-promoting compounds. Lately, they are also attracting interest in the context of nutricosmetics, as they have been shown to provide cosmetic benefits when ingested in appropriate amounts. In this work, resulting from the collaborative work of participants of the COST Action European network to advance carotenoid research and applications in agro-food and health (EUROCAROTEN, www.eurocaroten.eu, https://www.cost.eu/actions/CA15136/#tabs|Name:overview) research on carotenoids in foods and feeds is thoroughly reviewed covering aspects such as analysis, carotenoid food sources, carotenoid databases, effect of processing and storage conditions, new trends in carotenoid extraction, daily intakes, use as human, and feed additives are addressed. Furthermore, classical and recent patents regarding the obtaining and formulation of carotenoids for several purposes are pinpointed and briefly discussed. Lastly, emerging research lines as well as research needs are highlighted.

A comprehensive review on carotenoids in foods and feeds: status quo, applications, patents, and research needs

This review presents recent developments in plant photobiology and lighting systems for horticultural crops, as well as potential applications for cannabis (Cannabis sativa and C. indica) plant production. The legal and commercial production of the cannabis plant is a relatively new, rapidly growing, and highly profitable industry in Europe and North America. However, more knowledge transfer from plant studies and horticultural communities to commercial cannabis plant growers is needed. Plant photosynthesis and photomorphogenesis are influenced by light wavelength, intensity, and photoperiod via plant photoreceptors that sense light and control plant growth. Further, light properties play a critical role in plant vegetative growth and reproductive (flowering) developmental stages, as well as in biomass, secondary metabolite synthesis, and accumulation. Advantages and disadvantages of widespread greenhouse lighting systems that use high pressure sodium lamps or light emitting diode (LED) lighting are known. Some artificial plant lighting practices will require improvements for cannabis production. By manipulating LED light spectra and stimulating specific plant photoreceptors, it may be possible to minimize operation costs while maximizing cannabis biomass and cannabinoid yield, including tetrahydrocannabinol (or Δ9-tetrahydrocannabinol) and cannabidiol for medicinal and recreational purposes. The basics of plant photobiology (photosynthesis and photomorphogenesis) and electrical lighting systems are discussed, with an emphasis on how the light spectrum and lighting strategies could influence cannabis production and secondary compound accumulation.

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An Update on Plant Photobiology and Implications for Cannabis Production

Current status and recent achievements in the field of horticulture with the use of light-emitting diodes (LEDs)

Regulation of the growth, development and quality of plants by the control of light quality has attracted extensive attention worldwide. The aim of this study was to present the effects of continuous LED spectrum for indoor plant pre-cultivation and to investigate the morphological and physiological responses of a common broadleaved tree species in Mediterranean environment, Quercus ithaburensis var. macrolepis at seedling developmental stage. Thus, the seedlings were pre-cultivated for 28 days, under five different LED light qualities: 1) Fluorescent (FL) as control light 2) L20AP67 (high in green and moderate in far-red), 3) AP673L (high in green and red), 4) G2 (highest in red and far-red), AP67 (high in blue, red and far-red) and 5) NS1 (highest in blue and green and lowest in far-red) LEDs. Further examination was held at the nursery for one year, on several seedling quality traits. Indeed, AP67 and AP673L triggered higher leaf formation, while L20AP67 positively affected seedling shoot development. NS1 and AP67 LED pre-cultivated seedlings showed significantly higher root fibrosity than those of FL light. Furthermore, NS1 and AP673L LEDs induced four-fold increase on seedling root dry weight than FL light. Hence, evaluating the seedling nursery performance attributes, most of those photomorphogenetic responses previously obtained were still detectable. Even more so, LED pre-cultivated seedlings showed higher survival and faster growth indicating better adaptation even under natural light conditions, a fact further reinforced by the significantly higher Dickson’s Quality Index acquired. In conclusion, the goal of each nursery management program is the production of high quality seedlings with those desirable traits which in turn satisfy the specific needs for a particular reforestation site. Thus, the enhanced oak seedling quality traits formed under continuous LEDs spectrum especially of NS1 and AP673L pre-cultivation may potentially fulfill this goal.

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Continuous Spectrum LEDs Promote Seedling Quality Traits and Performance of Quercus ithaburensis var. macrolepis

The effects of four different continuous spectrum LED light qualities on the growth characteristics of Pinus sylvestris L. (PS) and Abies borisii-regis Mattf. (AB) seedlings were studied. The seedlings were exposed for 35 days inside growth chambers to G2 (high in red and far-red), AP67 (high in blue and far-red), AP67-ARCH (high in green), and NS2 (high in blue including a small percentage in the UV area) LEDs, as well as fluorescent light (FL) as Control. Each species showed a unique light-adapted response. G2 treatment stimulated needle formation of PS seedlings, while AB seedlings were unaffected. Hypocotyl elongation was promoted by FL; however, LEDs resulted in compact plants with greater root development, especially under the AP67-ARCH and AP67 spectra for PS and AB, respectively. In PS, AP67-ARCH and G2 significantly increased dry weight, while AB was affected significantly by AP67 and NS2. Furthermore, root growth potential of both species was better after LED pre-cultivation than the FL....

Effects of continuous spectrum LEDs used in indoor cultivation of two coniferous species Pinus sylvestris L. and Abies borisii-regis Mattf

Light intensity required by forest species has been widely studied, leading to their classification in heliophilous, sciaphilous and intermediate species. Conversely, few studies are available on light quality requirements. Artificial lights for plant growth have been designed mainly for agricultural crops that are all heliophilous, with high percentages of blue and red wavelengths in order to increase the photosynthetic activity. These light sources may be considered adaptable to heliophilous forest species; in order to test this hypothesis, a presumed heliophilous species, Platanus orientalis, was cultivated under different LED and fluorescent light sources, commercially available, in a controlled growth chamber. Some seedlings showed a progressive yellowing or reddening of leaves, leading to the hypothesis of a light stress. Therefore, the real light conditions in which natural regeneration occurs were analysed. The Natural Reserve of Pantalica (Sicily), was chosen as study area. Light spectra were collected along Anapo river, in July, from 10 a.m. to 2 p.m., in correspondence of different points with and without natural regeneration. Seedlings resulted to grow in slight shadow, frequently interrupted by short sunflecks. The spectra associated to shadow and sunflecks resulted to be different, both in terms of quality and quantity. Therefore, it seems that Platanus orientalis is not properly heliophilous, as reported in literature; this fact may explain why, as some sciaphilous species, it lacks of a complete xantophyll cycle, showing only leaf hairs as a protection against light excess. The results of this research show that the analysis of light requirements for each species is essential to define the best light conditions, in terms of quality and quantity, for artificial propagation.

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Sonia Smirnakou

Papers

Current status and recent achievements in the field of horticulture with the use of light-emitting diodes (LEDs)

Continuous Spectrum LEDs Promote Seedling Quality Traits and Performance of Quercus ithaburensis var. macrolepis

Effects of continuous spectrum LEDs used in indoor cultivation of two coniferous species Pinus sylvestris L. and Abies borisii-regis Mattf

Artificial propagation of Oriental Plane through leds