Nicotinamide Adenine Dinucleotide in Potato Tuber Slices in Relation to Respiratory Changes with Age.

The respiration of slices of a variety of bulky storage tissues rises gra(lually three to fourfold within a (lay of cutting (7, 8, 9, 10). The respiration rate of freslh tissue cani be sharply raise(d ith 2,4 dinitrophenol, however, as (lemionstrate(I in chlicory and potato slices. Both the age-inducedI an(d DNPinducedl respiration incremzents are inhibite(d by imalonate. It has been sh]own that whereas malate restores the respiration of imialoniate inhibite(d aged chicorv slices to the normal level, malate is virtually without effect upon the respiration rate of 2,4 dinitrophenol-treatecl, malonate-inhibited fresh tissue (9). The foregoing observation suggeste(d that the respirlationi of fresh storage organ slices may be lim1itedl by the levels of en(logenous nucleotidles. particularlv NAD. However NAD concentrations w-ere not ascertainable bv the milethodis use(d in the foregoing stu(l. In the present studlv NAD levels of fresh andl aged lpotato slices were (letermined an(I the effect of NAD on the oxi(lation of organic acids by Illitochondria isolatecl from1 freshi and age(l tissue wvas stu(lie(l.