Respiratory Activity of the Mitochondrial Fractions Isolated from Healthy Potato Tubers and from Tuber Tissue Incubated after Cutting or Infection with Ceratocystis fimbriata.

'Ihe respiratory activity of miany plait tissues is consi(deral)v increased after infectionl wN-ith iicroorganiisn;.s. Initially an uncoup)ling of the respiration from the oxidative p)hosphorylation w-as thouight to he responsible for this effect. Since theni ample evidenlce has been acctimtilate(I %Nhich suiggests that a metabolic activation lea(linlg to ain accelerate(d ttilizationi of high energy phosl)hate ind(utce(d the increase of the O.) uptake after infectioni ( 1. 11). 'I'he respiratory inlcrease occurring, in l)otato tul)er tissuie after infectioni wvith various fuingi (2, 12) or after wounding (4,7.8) has also beeln cxl)lailie(l on the basis of the conitiniue(d coupling letween oxidative andl p)hosl)horYlative l)rocesses. However, all evidence has been of a imiore or less iindirect natulre, sinice it w7as gathered froml exl)erinlents with unllcouplillg agenits all(n froml resuilts iin(licaLimani inicrease of the svynthetic activity inl the tissuies. Bolinner aln(d \'oss (3) xvere the first wNho (lescribe(d respiratory coIntrol by ADP inl isolated p)lant militochond(iria. \\Viskichi and( 13Boniel(13 ) isolate(l mitocholn(dria fromi l)otato tuber tissile inl which the rate of 0., uptake wN-as accelerated 1b a(ldition of ADP)l buit decrease(d againi wheni the A\1)P had 1)een colisuime(l. In both investigations the oxygen electro(le metho(d (5) wN-as used for the study of imitochoindrial activity. However, the mitochonidria isolated b)y \Viskich aind Bonner as wsell as those (lescrilbe(l 1w Hackett et ail. (4) showed l)ellonllelila which suggested that the l)articles imiight have beeni (laillaged (luritng isolation. The l)resellt paper deals with experiments wvitli mitochon(dria isolate(d by a soimewhat changed method resulting in particulate suspensions ini which the mitochonidria seeml to be ini a better condlitioni thani those previously (lescribed ( Verleur. 1965. Plant Physiol. Iii )ress).