Abstract. Mitochondria isolated from 2 strains of cotton plant hypocotyls (Gossypium hirsutum L. var. Rex smootlh leaf and Rex glandless) were examined for their oxidative phosphorylation activities. Bovine serum albumin at a relatively high concentration was essential in the extraction medium for the isolation of oxidatively active mitochondria from both strains of cotton. Phosphorylation was obtained only with Rex glandless cotton mitochondria. This activity was low in comparison to the mitochondria isolated from soybeans (Glycine max L. var. Lee). The endogenous gossypol content was found to be much higher in the Rex smooth leaf tissue than in the Rex glandless tissue. In turn, comparable gossypol differences were found associated with their respective mitochondrial fractions. Exogenous gossypol uncoupled succinate oxidation with active mitochondria isolated from soybeans. Gossypol as a possible uncoupler is discussed and compared to carbonyl cyanide, m-chlorophenvl hydrazone and 2,4-dinitrophenol.Metabolically active mitochondria have been isolated and studied in a xvide variety of plant tissues (7), but verv little xvork has been reported on cotton mitochonclria. Throneherry (13) reported that an extract fromii cotton tissue inactivatedc mitochondria prepared fromii sovbean seedlin,gs. He showed that the inclusion of bovine serum albumin (BSA) in the extractioni medium facilitated the isolation of active mitochondria from cotton hypocotyls. Later, Throneberry (14) found that the phosphorylation mechanism was probably more sensitive to endogenous inhibitors than were the oxidative enzymnes. Plants of the genus Gossvpium, of which cotton is a member, normally containi several pigments unique to the plant kingdom. Some of the pigments are enclosed in glands that are distribuited throughout the above ground part of some strains of cotton. An important component of the glands is gossypol (1.1 ', 6,6',7,7'-hexah. droxy-3,3' -dimethvl-15,5' -diisopropvl-2,2' -binaphthyl-8,8'-dialdehyde), a polyphenolic. toxic, velloNv compound (2). MAvers and Throneherrv (9) reported that gossylpol affected mitochondria prepared from sweet potato and beef heart tissuies. Gossypol was showvn to inhibit oxidative phosphorylation at concentrations which had no effect on oxidation. This prompted the investigation of a glandless strain of cotton. relatively free of gossypol. Rex glan(dless, hereafter referred to as glanded and glandless, respectively) and soybeans (Glycine mlax L. var. Lee) were used as the experimental material. The seeds were surface sterilized with 0.5 % (w/v) sodium hvpochlorite. After rinsing thoroughly, the seeds wvere germinated in paper towels, moistened w\ith n0.1 mAi CaCI.., at '0O in the dark. Five-dav old hypocotyls were harvested, cut into 3 to 5 cm segments, and chilled at 0 .A slight modification of the Bonner and Sikes procedure (1) was used for mitochondria isolation.The hypocotyl segments were disrupted in a WaringBlendor at a reduced speed using a volume of extraction medium equal to the weiglht of ...

Effects of the inhibitors DNP (2,4-dinitrophenol) and oligomycin, and the substituted dinitroaniline herbicides, trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline], and oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide) on mitochondrial tractions isolated from soybean (Glycine maxL. ‘Lee’) hypocotyls were examined. Oryzalin and nitralin uncoupled succinate oxidation at the ADP-limited state 4, as did DNP. Trifluralin caused no effect on the second state 4, but inhibited oxidative phosphorylation in a manner similar to the effect of the energy-transfer inhibitor oligomycin. Studies of the interaction of these inhibitors indicate that the sites of action for these herbicides may be different.

Studies were conducted on the effects of fluometuron [1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea] on autotrophic growth (no sugar), heterotrophic growth (with sugar), and oxygen evolution and uptake and on the effects of MSMA (monosodium methanearsonate) on autotrophic growth and oxygen evolution and uptake by the unicellular green algaChlorella pyrenoidosaEmerson strain (University of Texas). Two methods of analysis (probit and kinetic) were used to characterize the dosage-response ofChlorellato these herbicides. All measurements ofChlorellaresponse to fluometuron were satisfactorily characterized by probit analysis, but only autotrophic cell number was adequately characterized by kinetic analysis. The fluometuron concentrations giving 50% inhibition on the probit plot were as follows: autotrophic cell number, 2.4 × 10−6M; chlorophyll at 400 nm, 3.3 × 10−6M; heterotrophic cell number, 2.4 × 10−6M; oxygen evolution, 20 × 10−6M. The response of the alga to MSMA was stimulatory instead of inhibitory. Since this stimulation did not consistently range between 10 and 90% of the control, it was not possible to characterize the MSMA dosage-Chlorellaresponse using either type of analysis.