作物の養分吸収に関する動的研究(第9報) : 大麦幼植物による加里・燐酸・アンモニアの吸収に及ぼす 2,4-Dinitrophenol の影響について

抄録

In the previous reports it was shown that the nutrients uptake by plant roots was largely dependent on their metabolic activity, and that in view of the linkage in the metabolic cycle its degree decreased in the order K_2O, P_2O_5>SiO_2,Br, SO_3>NH_4,MnO>MgO, CaO; K_2O and P_2O_5 linking most directly in the cycle. In this report the uptake of K_2O, P_2O_5 and NH_4-N by barley seedlings as influenced by 2,4-Dinitrophenol (DNP) was studied. DNP is well qualified as one of the agents which break up the link between substantial and energetical metabolisms by inhibiting oxidative phosphorylation. Barley seedlings were grown by customary water culture technique and treated with DNP or NaN_3. The uptake of K_2O, P_2O_5,NH_4-N was calculated from the residual nutrients in the culture solution and the oxygen uptake by WARBURG'S manometric technique. The relationships between the oxygen uptake of the roots of barley seedlings and concentration of inhibitors were shown in Table 1 and Fig. 1. It is evident that 10^<-4> Mol. DNP increased the oxygen uptake by barley roots as contrasted to the remarkable depression through NaN_3. Moreover, this effect normally continued during the expected measurement and treatment, indicating that this normality of the inhibitor is suitable for the aforementioned purpose within the experimental conditions (cf. Fig. 2 & 3). The uptake of NH_4-N, P_2O_5 and K_2O by barley seedlings as influenced by l0^<-4> Mol DNP and 10^<-2> Mol NaN_3 were shown in Table 2 and Fig. 4. In either case P_2O_5 excreted out, whereas K_2O excreted out by NaN_3 but its uptake ceased by DNP. The uptake of NH_4-N was appreciably depressed by NaN_3 but very slightly by DNP. The result was discussed on the basis of the characteristic different behaviors of the pertinent inhibitors. Assume that P_2O_5 accumulation is primarily and directly linked with the formation of energy rich phosphate through oxidative phosphorylation, there is no wonder that DNP and NaN_3 decidedly and equally inhibited P_2O_5 uptake. The excretion of phosphate may be due to the superior counter reaction from organic phosphate to inorganic phosphate. K_2O uptake most probably proceeds through the combination of K at the specific sites of certain acceptor by the expense of energy derived from energy rich phosphate bonding such as ATP. NaN_3 inhibits not only this process but also most likely the formation of this acceptor, whereas DNP seems to be almost indifferent from the latter substantial process, resulting in a different inhibition by the two inhibitors. The first step of NH_4-N uptake is believed to be the combination of NH_4^+ with certain Keto-acid, and the next step the formation of amide as a result of condensation of the formed amino-acid with NH_4^+. Only the latter process repuires energy from the energy rich phosphate bonding such as ATP. Therefore, NaN_3 most probably inhibits both processes and DNP the latter only, resulting in a different inhibition as shown in the Table. Moreover, the slight inhibition in general of NH_4-N as compared to P_2O_5 would be attributed to the slower counter reration in the uptake of N as compared to P.