Figure 4

Gene co-expression networks of nitrogen metabolism, circadian rhythms, and hormone signal transduction pathways in the root system of walnut seedlings under nitrogen starvation (a) and excess (b). ○ represents genes related to circadian rhythms, △ represents genes related to nitrogen metabolism, and □ represents genes related to plant hormone signal transduction. The colour gradient of connections, from green to red, indicates a Pearson correlation coefficient from −1 to 1; a darker colour and a thicker connection indicate a higher correlation. The colour gradient of dots, from blue to red, indicates a log₂(fold change) from negative to positive, and a darker colour indicates a greater absolute value of log₂(fold change).