Synergistic effect between green light and nitrogen concentration on nitrate primary metabolism in lettuce (Lactuca sativa L.)

In spite of various studies exploring nitrate metabolism impacts by nitrogen supply and spectral composition, there is a lack of research on nitrate metabolism synergistic with green light and nitrogen supply in hydroponically cultivated vegetables. Plants rely on nitrate as a fundamental source of nitrogen for development, productivity, and overall quality. It is common for previous studies to focus on nitrogen supply levels without considering spectral composition. According to recent research, the green light plays a more complex role in plant physiology. Among other processes, it regulates leaf anatomical structures, growth orientation, stomatal conductance, and photosynthesis. This research highlights the importance of green light in the process of plant growth and implies the existence of interactions between green light and nitrate metabolism that are not yet fully comprehended. Certainly, it evaluates diverse aspects of plant responses. This comprises the assessment of growth and developmental patterns, the measurement of nitrate concentrations, the analysis of protein content, and the examination of enzyme activities associated with nitrate metabolism. Furthermore, the study delves into the transcription levels of key genes crucial for nitrogen metabolism in two lettuce varieties, youmaicai and rapid . The aforementioned analyses are carried out under diverse circumstances, wherein the proportions of green light within the spectrum are manipulated (ranging from 10 % to 30 % at 480-560 nm) and the nitrogen supply levels in the nutrient solution are altered (ranging from 2.5 mmol/L to 18.5 mmol/L). The aim is to gain a thorough comprehension of the interplay between these factors and their impact on the physiological processes and nitrogen utilization in the examined plant varieties. A two -factor three -level crossover experiment was set up, and the youmaicai and rapid were transplanted for 35 days. The findings revealed that both green light and nitrogen regulate nitrogen assimilation, protein synthesis, and biomass accumulation in leafy lettuce. However, the accumulation of nitrate in the shoot exhibit a significant correlation only in rapid. Nitrogen availability and the proportion of green light have a synergistic effect on nitrate reductase (NR) and glutamine synthetase/glutamine synthetase (GS/GOGAT) cycles. As nitrogen supply increases, glutamate dehydrogenase (GDH) activity declines. Moreover, when the green light proportion is 30 % and the nitrogen supply is 10.5 mmol/L, the biomass and protein content reach their highest levels, and the GS/GOGAT cycle activity is the strongest. It provides a fundamental scientific framework for understanding how green light proportions in cultivation spectrum and nitrogen supply affect nitrate metabolism in plants, thereby increasing hydroponic leafy vegetables' yields.