Improving quality parameters of spinach by adjusting light spectra under moderate water deprivation conditions

Spinach (Spinacia oleracea L.) is a highly valuable leafy vegetable, abundant in vitamins, minerals, and antioxidants, offering various health benefits such as enhancing cardiovascular health, reducing inflammation, and aiding digestion. Consequently, it is crucial to effectively cultivate and maintain spinach's quality. Light plays a pivotal role in the growth and development of plants, including spinach, where different light qualities can influence its morpho-physiological traits and overall quality. To explore this, an experiment was conducted, using three distinct LED lighting sets for spinach cultivation. Light 1 emphasized blue light, Light 2 served as the standard white light control, and Light 3 focused more on red light with occasional brief UV-C flashes. Additionally, mild water deprivation was induced using 2.5% polyethylene glycol (PEG). The results revealed that using a high red-to-blue light ratio with intermittent UV-C radiation significantly reduced various growth parameters of spinach, such as root length, shoot length, root volume, fresh and dry root and shoot weight, as well as total and relative chlorophyll contents, when compared to the control group. Furthermore, water deprivation had a negative impact on spinach's growth, affecting shoot and root length, and fresh and dry weight in all light qualities, proving to be fatal under Light 3 conditions. Therefore, it is essential to carefully select appropriate light qualities throughout the plant's life cycle to enhance the quality of spinach, especially when mild water deprivation is involved. Opting for a higher blue-to-red light ratio was found to be somewhat beneficial in improving the overall quality of spinach.