In recent years, consumption of herb products has increased in daily diets, contributing to the prevention of cardiovascular diseases, chronic diseases, and certain types of cancer owing to high concentrations of phytonutrients such as essential oils and phenolic compounds. To meet the increasing demand for high quality herbs, controlled environment agriculture is an alternative and a supplement to field production. Light is one of the most important environmental factors influencing herb quality including phytonutrient content, in addition to effects on growth and development. The recent development and adoption of light-emitting diodes provides opportunities for targeted regulation of growth and phytonutrient accumulation by herbs to optimize productivity and quality under controlled environments. For most herb species, red light supplemented with blue light significantly increased plant yield. However, plant yield decreased when the blue light proportion (BP) reached a threshold, which varied among species. Research has also shown that red, blue, and ultraviolet (UV) light enhanced the concentration of essential oils and phenolic compounds in various herbs and improved antioxidant capacities of herbs compared with white light or sunlight, yet these improvement effects varied among species, compounds, and light treatments. In addition to red and blue light, other light spectra within the photosynthetically active region—such as cyan, green, yellow, orange, and far-red light—are absorbed by photosynthetic pigments and utilized in leaves. However, only a few selected ranges of light spectra have been investigated, and the effects of light quality (spectrum distribution of light sources) on herb production are not fully understood. This paper reviews how light quality affected the growth and phytonutrient accumulation of both culinary and medicinal herbs under controlled environments, and discusses future research opportunities to produce high quantity and quality herbs.

Consumption of basil ( Ocimum basilicum ) has been increasing worldwide in recent years because of its unique aromatic flavor and relatively high concentration of phenolics. To achieve a stable and reliable supply of basil, more growers are turning to indoor controlled-environment production with artificial lighting due to its high environmental controllability and sustainability. However, electricity cost for lighting is a major limiting factor to the commercial application of indoor vertical farming, and little information is available on the minimum light requirement to produce uniform and high-quality sweet basil. To determine the optimal daily light integral (DLI) for sweet basil production in indoor vertical farming, this study investigated the effects of five DLIs, namely, 9.3, 11.5, 12.9, 16.5, and 17.8 mol·m ⁻² ·d ⁻¹ on basil growth and quality. ‘Improved Genovese Compact’ sweet basil was treated with five DLIs provided by white fluorescent lamps (FLs) for 21 d after germination, and gas exchange rate, growth, yield, and nutritional quality of basil plants were measured to evaluate the effects of the different DLIs on basil growth and quality. Results indicated that basil plants grown under higher DLIs of 12.9, 16.5, or 17.8 mol·m ⁻² ·d ⁻¹ had higher net photosynthesis, transpiration, and stomatal conductance ( g _S ), compared with those under lower DLIs of 9.3 and 11.5 mol·m ⁻² ·d ⁻¹ . High DLIs resulted in lower chlorophyll (Chl) a+b concentration per leaf fresh weight (FW), higher Chl a/b ratios, and larger and thicker leaves of basil plants. The shoot FW under DLIs of 12.9, 16.5, and 17.8 mol·m ⁻² ·d ⁻¹ was 54.2%, 78.6%, and 77.9%, respectively, higher than that at a DLI of 9.3 mol·m ⁻² ·d ⁻¹ . In addition, higher DLIs led to higher soluble sugar percent and dry matter percent than lower DLIs. The amounts of total anthocyanin, phenolics, and flavonoids per plant of sweet basil were also positively correlated to DLIs, and antioxidant capacity at a DLI of 17.8 mol·m ⁻² ·d ⁻¹ was 73% higher than that at a DLI of 9.3 mol·m ⁻² ·d ⁻¹ . Combining the results of growth, yield, and nutritional quality of sweet basil, we suggest a DLI of 12.9 mol·m ⁻² ·d ⁻¹ for sweet basil commercial production in indoor vertical farming to minimize the energy cost while maintaining a high yield and nutritional quality.

Phenolic compounds in basil (Ocimum basilicum) plants grown under a controlled environment are reduced due to the absence of ultraviolet (UV) radiation and low photosynthetic photon flux density (PPFD). To characterize the optimal UV-B radiation dose and PPFD for enhancing the synthesis of phenolic compounds in basil plants without yield reduction, green and purple basil plants grown at two PPFDs, 160 and 224 μmol·m⁻²·s⁻¹, were treated with five UV-B radiation doses including control, 1 h·d⁻¹ for 2 days, 2 h·d⁻¹ for 2 days, 1 h·d⁻¹ for 5 days, and 2 h·d⁻¹ for 5 days. Supplemental UV-B radiation suppressed plant growth and resulted in reduced plant yield, while high PPFD increased plant yield. Shoot fresh weight in green and purple basil plants was 12%–51% and 6%–44% lower, respectively, after UV-B treatments compared to control. Concentrations of anthocyanin, phenolics, and flavonoids in green basil leaves increased under all UV-B treatments by 9%–18%, 28%–126%, and 80%–169%, respectively, and the increase was greater under low PPFD compared to high PPFD. In purple basil plants, concentrations of phenolics and flavonoids increased after 2 h·d⁻¹ UV-B treatments. Among all treatments, 1 h·d⁻¹ for 2 days UV-B radiation under PPFD of 224 μmol·m⁻²·s⁻¹ was the optimal condition for green basil production under a controlled environment.

Water shortages and poor water quality are critical issues in many areas of the world. With rapid increases in population and shortage of water supplies in urban areas, use of alternative water sources such as municipal reclaimed water and other sources of non-potable waters for irrigating landscapes is inevitable. A potential concern is the elevated salt levels in these alternative waters. This article briefly summarizes general information regarding alternative water sources and general responses of landscape plants to salinity stress. Methodology of screening and evaluating salt tolerance of landscape plants are discussed. Recent research results on salt tolerance of landscape plants and their physiological responses to salinity stress are reviewed. Like agricultural crops, a wide range of salt tolerance among landscape plants has been found. In addition to plant species, dominant salt type, substrate, irrigation method and management, and environmental conditions also affect plant responses to salinity stress. A number of mechanisms of salinity tolerance have been observed among landscape species, including restriction of ion uptake, selective ion uptake, and tolerance to high internal concentrations of sodium and/or chloride.

The increasing population, its requirements for food, and the environmental impact of the excessive use of inputs make crop production a pressing challenge. Integrated nutrient management (INM) has emerged as a critical solution by maximizing nutrient availability and utilization for crops and vegetables. This review paper highlights the potential benefits of INM for various vegetables and field crops and explores the conceptual strategies, components, and principles underlying this approach. Studies have shown that a wide range of vegetables and field crops benefit from INM, in terms of increased yield and improvements in yield attributes, nutrient contents and uptake, growth parameters, and various physiological and biochemical characteristics. This paper discusses biostimulants, their categories, and their impact on plant propagation, growth, photosynthesis, seed germination, fruit set, and quality. Additionally, this review explores modern sustainable soilless production techniques such as hydroponics, aeroponics, and aquaponics. These cultivation methods highlight the advancements of controlled-environment agriculture (CEA) and its contribution to nutrient management, food security and minimizing the environmental footprint. The review concludes by proposing methods and fostering discussions on INM’s future development, while acknowledging the challenges associated with its adoption. Finally, this review emphasizes the substantial evidence supporting INM as a novel and ecologically sound strategy for achieving sustainable agricultural production worldwide.

Green light penetrates deeper into the plant canopy because of its high transmittance and reflectance, and may potentially increase light interception and whole-canopy photosynthesis, whereas red and blue light is absorbed primarily by upper leaves. Moreover, green light induces shade avoidance responses and regulates secondary metabolism in plants. In this study, we investigated the effects of substituting partial red and/or blue light with green light on plant growth and development in basil ( Ocimum basilicum ) ‘Improved Genovese Compact’ (green) and ‘Red Rubin’ (purple) plants. There were four treatments: one combined red and blue (R&B) light treatment, R ₇₆ B ₂₄ [the proportion of red (R) and blue (B) light was 76% and 24%, respectively]; and three green (G) light treatments—R ₄₄ B ₂₄ G ₃₂ , R ₇₄ B ₁₆ G ₁₀ , and R ₄₂ B ₁₃ G ₄₅ —with green light proportions of 32%, 10%, and 45%, respectively. The experiment was conducted in a growth room and the photosynthetic photon flux density ( PPFD ) of all treatments was set at 220 μmol·m ⁻² ·s ⁻¹ with a 16-h photoperiod. Plants were subirrigated as needed using a nutrient solution with an electrical conductivity (EC) of 2.0 dS·m ⁻¹ and a pH of 6.0. The net photosynthetic rate (P _n ) in lower leaves was unaffected by green light treatments in green basil plants, whereas in purple basil plants it increased by 59% and 45% under treatments R ₄₄ B ₂₄ G ₃₂ and R ₇₄ B ₁₆ G ₁₀ , respectively, compared with the combined R&B light. In green basil plants, treatments R ₄₄ B ₂₄ G ₃₂ and R ₄₂ B ₁₃ G ₄₅ induced stem elongation, but green light treatments showed no effects on petiole elongation, leaf expansion, leaf thickness, or plant yield. In purple basil plants, treatments R ₄₄ B ₂₄ G ₃₂ and R ₄₂ B ₁₃ G ₄₅ induced stem elongation and decreased leaf thickness and plant yield, but only the R ₄₂ B ₁₃ G ₄₅ treatment induced petiole elongation, and green light treatments showed no effects on leaf expansion. Concentrations of anthocyanin, phenolics, and flavonoids, and antioxidant capacity in green basil leaves showed no differences between treatments R ₇₆ B ₂₄ and R ₄₄ B ₂₄ G ₃₂ , but decreased under treatments R ₇₄ B ₁₆ G ₁₀ and R ₄₂ B ₁₃ G ₄₅ . Concentrations of phenolics and flavonoids, and antioxidant capacity in purple basil leaves showed no differences between treatments R ₇₆ B ₂₄ and R ₇₄ B ₁₆ G ₁₀ , but decreased under treatments R ₄₄ B ₂₄ G ₃₂ and R ₄₂ B ₁₃ G ₄₅ . Combining plant yield, nutritional values, and the working environment for growers, a white light with low green light proportion (≈10%) is recommended for basil production in a controlled environment.