Pyridine Nucleotide Content in the Higher Plant. Effect of Age of Tissue

Abstract

Both levels of DPN and TPN components were determined to be a rate-limiting factor for the metabolism of various plant tissues. Changes in amount of pyridine nucleotides (PN) in the cotyledons and the hypocotyl of Vigna sesquipedalis in the germination stage, difference in PN level between the storage organ (cotyledons of endosperm) and the growing part of 9 kinds of germinating seeds, PN contents in several portions of the Vigna root in every stage of germination, and difference in PN pattern between old and young tobacco leaves were observed. The parallelism between changes in pattern of PN and of metabolism accompanying aging is comprehensively discussed. Generally, a characteristic of youthfulness is defined as the maintenance of a high TPNH/TPN ratio and a high TPN+TPNH level. In all germinating seeds checked, the TPN+TPNH/DPN+DPNH quotient is low in the storage organ and high in the growing part. The striking difference in metabolic pattern between the storage organ and the growing part is considered to be due to the difference in the PN pattern. TPN isocitric dehydrogenase was purified some 70-fold from clear extract of Vigna cotyledons and used for the TPN or TPNH assay by coupling with TPNH diaphorase.