Abstract
Vegetables and herbs play a central role in the human diet due to their low fat and calory content and essential antioxidant, phytochemicals, and fiber. It is well known that the manipulation of light wavelengths illuminating the crops can enhance their growth rate and nutrient contents. To date, it has not been easy to generalize the effects of LED illumination because of the differences in the plant species investigated, the measured traits, the way wavelengths have been manipulated, and the plants’ growing environments. In order to address this gap, we undertook a quantitative review of LED manipulation in relation to plant traits, focusing on vegetables and herbs. Here, we use standardized measurements of biomass, antioxidant, and other quantitative characteristics together with the whole range of the photosynthetic photon flux density (PPFD). Overall, our review revealed support for the claims that the red and blue LED illumination is more reliable and efficient than full spectrum illumination and increases the plant’s biomass and nutritional value by enhancing the photosynthetic activity, antioxidant properties, phenolic, and flavonoids contents. Although LED illumination provides an efficient way to improve yield and modify plant properties, this study also highlights the broad range of responses among species, varieties traits, and the age of plant material.
Highlights
Light is crucial for plant development and protection, as it provides the required energy for the photosynthesis process [1] and critical sensory signals that enable plants to adapt to external stimuli [2]
Since light-emitting diodes (LED) illumination provides Photosynthetically active radiation (PAR) that the plant uses for photosynthesis, PAR plays a significant role in morphogenesis [4,5]
The use of LED illumination sources for increasing the growth rate of greenhousegrown vegetables and herbs is on the rise worldwide
Summary
Light is crucial for plant development and protection, as it provides the required energy for the photosynthesis process [1] and critical sensory signals that enable plants to adapt to external stimuli [2]. The use of LEDs for greenhouse illumination has significantly improved plant quality, especially in geographic regions with reduced sunlight during winter seasons [6] This boost plant productivity due to the high efficiency of variable-power LEDs that can emit wavelengths over a broad spectrum. It enables the optimization of the illumination spectrum for specific plants, maximizing the yield and nutritional quality of the vegetables and herbs. In addition to the combination of optimal wavelengths of light across the PAR range, responses of vegetables and herbs may differ according to the time at which the plant was grown and which specific traits have been measured (e.g., wet or dry mass, phenolics or growth rate). This paper reviews the literature to identify the most critical aspects of LED lighting installation and explicitly organizes the comparative analysis of plant traits such as growth rate, morphology, and nutritional contents
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