FIGURE 5.

¹³C and ¹⁵N uptake rates in ATP equivalents of excised poplar roots in dependency on temperature and on acid phosphatase inhibition by MoO₄^2-. Roots were excised from poplar plants cultivated with 0.25 mM P_i. (A) Excised poplar roots were incubated with 0.169 mM ATP (14 atom% ATP-¹³C₁₀¹⁵N₅) at 15°C (n = 9) or at 24°C (n = 9) either solely or together with the acid phosphatase inhibitor MoO₄^2- (0.5 mM). Data from experiments performed in June/July are presented as box plots with individual data left to the box plots. In order to be able to compare ¹³C and ¹⁵N uptake rates, both were calculated as ATP equivalents, i.e., five ¹⁵N correspond to 1 ATP while 10 ¹³C are equivalent to one ATP. Significant differences were analyzed with the non-parametric Kruskal–Wallis test because normal distribution of the data was not given. Nevertheless, significant differences were not found at p < 0.05. (B) Correlation between ¹³C and ¹⁵N uptake rates as ATP equivalents of all individual incubation chambers, i.e., all samples and treatments. Correlation characteristics are given in Table 1.