# Effects of Climate Conditions before Harvest Date on Edamame Metabolome
## 3 Discussion
Similar to Pro, Lys and Tyr were also found to be correlated with the sunshine duration and average temperature. The fluctuation of the levels of amino acids, including Lys and Tyr, in plants treated with abiotic stresses has been reported in metabolomic studies [41; 42]. Lys-derived alkaloids and Tyr-derived flavonoids are known to be biosynthesized in leguminous plants in response to various stresses [43; 44]. Similar to Pro, their role in the stress response is not clear, but since these amino acids serve as raw materials for various secondary metabolites,they may be biosynthesized as part of edamame's response to stress caused by sunlight and temperature. The amounts of organic acids and nucleotides showed a negative correlation with the accumulated sunshine duration and average temperature in the few days before harvest (Figures 5 and 7). Sugar and citric acid amounts were reduced in tanned mandarin fruits [45]. In this study, the observed decrease in these metabolites correlates with higher sunlight exposure and a larger temperature difference. In soybean leaves, the amounts of citric acid and malic acid decreased significantly under high-temperature conditions [46]. In addition, in tomato fruits, citric acid and malic acid increased and decreased, respectively, at high temperatures; however, these showed different responses to nitrogen fertilization [47]. In grapes, the amount ratio of tartaric acid and malic acid changed depending on the temperature conditions [48]. Although these studies involved different plant types and parts, a close relationship between the changes in the organic acid amount and sugars was reported. On the other hand, there are several reports that the amount of nucleotides in plants changes in response to phosphate or oxygen deficiency [49; 50; 51; 52]. In addition, the glycolytic system, which involves many reactions with nucleotides such as ATP, responds to nutrient deficiency, osmotic stress, drought, and cold [53]. Furthermore, some nucleotide compounds, such as cAMP or ppGpp, are thought to act as signal response factors in plants [54; 55; 56], and the dynamics of these signal factors may change in response to changes in climate conditions. Further studies are needed to investigate whether the nucleotides that fluctuated in this study could serve as biomarkers for differences in climate conditions before the harvest date. In this study, we clarified the effects of sunlight duration and the average temperature on edamame components by comparing the meteorological conditions in the days before harvest and the edamame metabolome over a 6-year period. The amount of edamame components varied greatly depending on the harvest date, including the amino acids that have an important effect on edamame flavor. Although more detailed research is required, edamame harvested after a series of sunny and hot days may have a better flavor. These effects are expected to differ not only depending on the type and variety of agricultural products but also on fertilization and the original soil composition. To produce high-quality agricultural products, it may be necessary to use climate conditions before the harvest date as an indicator.