Fig. 6.

Nitrate in co-provision with ammonium promotes growth in both spinach, which shows a boost at pH 8, and pea, which is unaffected by pH levels. (A) The phenotype of hydroponically cultivated spinach and pea plants, with white vertical lines indicating a scale of 5 cm. (B) The connection between biomass of the shoot and root, the proportion of ammonium to nitrate, and pH levels. As the proportion of ammonium to nitrate in the nutrient solution increases, biomass decreases. The trend is quantified by R² and is represented by the dashed lines. Statistical significance is shown in bold, with a significance level of P≤0.05. Asterisks indicate significant differences in pH as determined by Student t-test. *0.05>P>0.01, **0.01>P>0.001. Spinach and pea plants were grown for 3 weeks and 2 weeks, respectively, and were exposed to varying proportions of ammonium and nitrate, ranging from sole nitrate to sole ammonium continuously. The total nitrogen level was 5 mM for spinach and 10 mM for pea plants.