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Balance between Cyanide‐Sensitive and ‐Insensitive Respiration in Wheat Root Mitochondria, as Influenced by Salt Concentration in the Plant Growth Medium
Author(s) -
MØLLER I. MAX
Publication year - 1978
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1978.tb02540.x
Subject(s) - salicylhydroxamic acid , mitochondrion , respiration , electron transport chain , alternative oxidase , cyanide , biochemistry , cellular respiration , chemistry , biophysics , biology , enzyme , botany , inorganic chemistry
Mitochondria were isolated from 7‐day‐old wheat roots ( Triticum vulgare Vill. cv. Svenno Spring Wheat) grown in either a full‐strength culture medium (100%) or in the same medium diluted 100 times (1%). Outer membrane integrity was assayed using the cytochrome c reduction assay. This indicated about 20% damage. Using an oxygen electrode the respiration of the mitochondria was measured with either malate or succinate as the substrate (both 40 m M ). KCN (3 m M ) and salicylhydroxamic acid (SHAM, 1 m M ) were used as inhibitors. The properties of the isolated mitochondria (STATE 3 rate, ADP/O ratio, and KCN‐sensitivity) depend upon the ionic concentration of the growth medium of the roots. In the mitochondria isolated from roots grown in the 1% medium (1% mitochondria) there is a synergistic effect of KCN and SHAM. This means that electrons can be shifted from one pathway to the other when only one of the inhibitors is added. This flexibility between the electron pathways is almost nil in the mitochondria isolated from roots grown in the 100% medium (100% mitochondria). The maximal capacity of the alternative electron pathway (= rate in the presence of KCN) is higher in 1% (40 nmol O 2 min −1 (mg protein) −1 ) than in 100% mitochondria (20 nmol O 2 min −1 (mg protein) −1 . In 100% mitochondria the alternative pathway seems to be operating at maximal capacity in the absence of KCN with both substrates and in both STATES 3 and 4. In 1% mitochondria the alternative pathway functions at >50% of its capacity in the absence of KCN.