Fat Synthesis and Its Regulation in PlantsⅦ.The Ac...
To elucidate the relationship between the accumulation of organic compounds and the respiratory pathways is of great significance.This work was conducted to investigate the relation of fat and protein synthesis to the HMP and EMP-TCA pathways respectively，using the seeds of soybean of various developmental ages as experimental material on account of its ability to accumulate both fat and protein extensively.In order to appreciate the different respiratory pathways the experiment with respiratory inhibitor and the enzyme study on the HMP and EMP pathways were performed.The results are summarized in Table 6 and Figure 3，from which the following conclusions may be drawn：
（1）During the development of soybean seeds the amount of soluble substances including inorganic phosphorus，acidsoluble organic phosphorus，soluble nitrogen，amino acids and sugars progressively increases，followed by the intensification in the activity of the synthesis of organic compounds and extensive accumulation of storage compounds（protein，oil，starch and phytin）.Analyzing the products of seeds at different stages of development showed that the fat synthesis predominates within 20—30 days after flowering，more than half of fat content of ripe seeds being accumulated within this period，while the protein synthesis proceeds mainly within 30—40 days after flowering，52.4%of total protein content of ripe seeds being accumulated within these ten days.
（2）In parallel with the course of the synthesis and accumulation of organic compounds in seeds the respiratory intensity per seed rises rapidly，especially from 10 to 15 days after flowering，with a respiratory peak near 30 days.It is believed that the respiration of seeds provides the necessary materials and energy for the synthesis of organic compounds.The sensitivity of respiration to iodoacetamide of soybean seeds at different developmental ages is different from each other.The respiratory fraction（EMP）inhibited by iodoacetamide（0.01 mol/L）rises progressively from 11 to 32 days after flowering，but declines after 32 days.The residual respiration（HMP）varies in the same way，but more sharply.The tendency of the activities of enzymes of two pathways is in good agreement with that of respiratory experiment.
（3）The effects of methylene blue and dinitrophenol（DNP）on the respiration of seeds at different stages of the development were compared.Methylene blue shows different degrees of stimulatory effect on respiration of seeds at various stages，but mainly in the later period.DNP stimulates respiration of seeds only in early and later period，particularly in the latter case.In period of respiratory peak，the effect of methylene blue is relatively small and no effect of DNP has been observed.(https://www.daowen.com)
On the basis of the results obtained，it seems most reasonable to assume that the synthesis and conversion of organic compounds by seeds closely coincide with the changes in the respiratory pathways.It is interesting to show that not only the conclusion on the relation of fat synthesis to the HMP pathway presented in our previous papers has further been justified and confirmed，but also the dependence of protein synthesis on the EMP-TCA pathway has also been demonstrated.The respiratory peak and regulatory factors in respiration were also discussed in this paper.
[1]Y.S.Zhu，C.Tan and C.N.Shih（Institute of Plant Physiology，Academia Sinica）
