Effects of three diphenylether herbicides [2,4-dichlorophenyl-p-nitrophenyl ether (nitrofen); 2,4,6-trichlorophenyl-4′-nitrophenyl ether (hereinafter referred to as MC-1478); and 2,4′-dinitro-4-trifluoromethyl-diphenylether (hereinafter referred to as C-6989)] were measured on phosphorylation and electron transport in spinach(Spinacia oleraceaL.) chloroplasts, and mung bean(Phaseolus aureusL., var. Jumbo) and white potato tuber(Solarium tuberosumL.) mitochondria. All of the diphenylethers acted primarily as inhibitors of chloroplast noncyclic electron transport, and the coupled photophosphorylation. The compounds ranked in the following decreasing order of inhibitory effectiveness: MC-1478 ≥ C-6989 >> nitrofen. A site of action close to light reaction II was suggested. At high molar concentrations, marginal interference with cyclic electron transport or phosphorylation was obtained. In mitochondria, MC-1478 and nitrofen acted primarily as electron transport inhibitors with malate, NADH, and succinate as substrates. MC-1478 was a slightly stronger inhibitor than nitrofen. Only slight stimulation of ADP-limited oxygen uptake was obtained during the oxidation of NADH and succinate; whereas, strong inhibition of oxygen uptake was obtained with malate. C-6989 also weakly stimulated ADP-limited oxygen uptake with NADH and succinate but differed from the two chlorinated diphenylethers in that electron transport was not inhibited when ADP was present in excess. Interference with ATP generation could be one of the mechanisms through which the phytotoxicity of diphenylether herbicides is expressed.

Fruit pH, inflection point pH, % acid content at inflection point pH, and % acid content at pH 8.1 were unpredictable based on days from full bloom and were not useful as maturity indices for 3 red strains of ‘Delicious’ or ‘Law Rome’ apple (Malus domestica Borkh.). Soluble solids content of the red strains of ‘Delicious’ could not be predicted consistently. Soluble solids/% acid (SS/A) at pH 8.1 values were the most predictable for all red strains of ‘Delicious’ with apparent optimum fruit quality within the 40 to 50 range index. None of these parameters were reliable for ‘Law Rome’ fruits.

Fruit pH, inflection pH, soluble solids, % acid content at the inflection point pH and % acid content at pH 8.1 were found not to be correlated with days from full bloom in North Carolina ‘Golden Delicious’ apple fruits (Malus domestica Borkh.). The ratio of soluble solids to % acid content at pH 8.1 was highly correlated with days from full bloom.