Roger J. Romani

Salicylic acid: A new inhibitor of ethylene biosynthesis.

Salicylic acid and acetylsalicylic acid at concentrations of 10−6M to 10−4M effectively inhibit ethylene production by pear cell suspension cultures. Results suggest these acids act by blocking the conversion of 1-aminocyclopropane-1-carboxylic acid to ethylene.

Salicylic acid inhibition of ethylene production by apple discs and other plant tissues

Ethylene production by apple discs is effectively inhibited by salicylic acid. Inhibition is pH dependent, being greatest from pH 3.5–4.5 and minimal at pH 6.5 and above. With 100 μM salicylic acid maximal inhibition, approximately 90%, is achieved in 3 h with an apparent Ki of 40 μM. At somewhat higher concentrations salicylic acid also inhibits the conversion of 1-aminocyclo-propane-1-carboxylic acid to ethylene by pear discs and mung bean hypocotyls. Salicylic acid interferes with action of the putative ethylene-forming enzyme and in this respect is somewhat more effective than cobalt ion. The inhibitory effects of salicylic acid and cobalt ion are not additive. Implications for the limits and locus of salicylic acid inhibition are discussed.

Anaerobic irradiation of alcohol dehydrogenase, aldolase and ribonuclease☆

Abstract Alcohol dehydrogenase, aldolase, and ribonuclease have been irradiated under anaerobic conditions, and the inactivation rates, sulfhydryl losses, effect of sulfhydryl reductants, and ionic yields are reported. On the basis of these experiments it would appear that anaerobic irradiation inactivation of enzymes results from a nonspecific protein denaturation. Complete enzymic inactivation is closely associated with the formation of characteristic irradiation odors.

Radiation physiology of fruit—Respiration during and immediately following kilorad doses of ionizing radiation

Abstract Several variables were incorporated in experiments designed to study the respiration of fruit undergoing irradiation. These included fruit type, fruit maturity, atmospheric composition before and during irradiation, and absorbed dose. Radiation induced an immediate rise in respiration rate which continued to increase with prolonged exposure. The respiration response was not linear with dose, however, suggesting a transition zone in the tissue tolerance for radiation. With increasing physiological age the respiratory response both during and immediately following exposure was markedly reduced and may also reflect radiation tolerance. Anaerobic pre-treatment and irradiation did not appreciably change the post-irradiation respiratory pattern suggesting the prevalence of direct radiation damage. It was further shown that the immediate respiratory response to ionizing radiation was not mediated by radiation products external to the fruit. Radiobiological and metabolic implications of the data are discussed.

Quantitative changes in tRNA during ethylene induced ripening (ageing) of tomato fruits

Abstract Iso-accepting forms of t RNA met , t RNA leu , t RNA lys , and t RNA tyr were isolated from combined walls and septa of tomato fruits at 5 consecutive stages of ethylene induced ripening. Changes in the relative amount of some t RNA leu and t RNA lys were discerned 10hr after exposure to ethylene. Individual patterns of change for each of several iso-acceptor t RNAs were evident throughout the ripening sequence. Maximal changes were: t RNA lys , −66.3%; t RNA leu , −24.8%; and t RNA met , +26.7%.

RADIOBIOLOGICAL PARAMETERS IN THE IRRADIATION OF FRUITS AND VEGETABLES.

Publisher Summary This chapter attempts to discuss radiation mechanisms and current trends in radiation and radiobiological research as they relate to the irradiation of foods, especially fresh fruits and vegetables. Time becomes a vital parameter in analyzing radiation mechanisms and in interpreting radiation effects: time for completion of the radiochemical event, time for development of the biochemical lesion and its manifestation, and time for radiation repair or for eventual cell death. Equally vital parameters are the quantitative, energetic, and spatial aspects of radiation events, all of which bear upon the ultimate fate of the irradiated specimen. The chapter discusses these aspects of radiation mechanisms and reviews units and dosimetry, the essential tools of any radiation research. Chemical, biochemical, and metabolic events observed in irradiated fruits and vegetables have been viewed from a radiobiological context. The chapter is also presents a discussion on irradiation facilities. The characteristics of each particular radiation source have been discussed, with specific reference to outputs, advantages, and disadvantages, characteristics of radiation, and others. The chapter outlines some of the features most essential to a research irradiator.

Mitochondrial resistance to massive irradiation in vivo: III. Suppression and recovery of respiratory control☆☆☆

Abstract Mitochondria capable of respiratory control have been isolated from pear and apple tissues. Respiratory control, as an index of mitochondrial integrity, was then used to assess dose-dependent radiation damage and postirradiation recovery in vivo . Dose thresholds for suppression of respiratory control lie between 250 and 500 Krad. Recovery of respiratory control will occur 48 hours after doses of 500 and 750 Krad. There is no recovery in a similar period following a dose of 1000 Krad. Such marked radioresistance on the part of fruit mitochondria is in concert with other responses of this tissue to ionizing radiation. Cytological implications are discussed with reference to the established radiosensitivity of animal mitochondria.

Survival of plant mitochondria in vitro: Form and function after 4 days at 25 °C

Abstract The energy-dependent maintenance of morphological and functional integrity by avocado mitochondria during incubation for 4 days at 25 °C is confirmed by (1) sustained levels of oxidation, phosphorylation, and respiratory control; (2) membrane intactness as evidenced by three diagnostic enzymes: succinate:cytochrome c, NADH:cytochrome c, and α-ketoglutarate:K3Fe(CN)6 oxidoreductase; and (3) the retention of physical properties as shown by rate-zonal centrifugation and electron microscopy. Some changes do occur in the mitochondrial population during the 4 days. These include an increase in density and the conversion of some organelles to dumbbell shapes. Bacterial growth, though difficult to control, does not appear to be directly responsible for the eventual loss of energy-linked functions.

MITOCHONDRIAL RESISTANCE TO MASSIVE IRRADIATION IN VIVO. V. REPAIR AND THE REPAIR OVERSHOOT.

Abstract An immediate mitochondrial response to injury is apparent when megarad doses of ionizing radiation are absorbed by quiescent fruit cells. Mitochondrial oxidative activity, ADP O , and respiratory control were used as indices of radiation injury and repair. The time-course of recovery and the response to split radiation doses reveal an overcompensation of the initial injury. This is interpreted to result from an overshoot either in repair processes or in de novo synthesis of mitochondria.

Mitochondrial resistance to massive irradiation in vivo—I: Structural stability as evidenced by electron microscopy, membrane functions, and fatty acid composition☆☆☆

Abstract Mitochondria were isolated from fruit (cherries and pears) which had absorbed from 250 to 1000 krad of ionizing radiation. A lack of obvious structural damage or changes in several membrane characteristics suggest a marked radioresistance of the mitochondria.