PubMed Health⌕ Search

Biomedical subjects

G E Hobson

Publications and source records attributed to G E Hobson.

13 recordsLinked to original sources
PubMed1987

Effect of silver ions on ethylene biosynthesis by tomato fruit tissue.

Mature-green tomato fruit (Lycopersicon esculentum Mill.) were treated asymmetrically with 2 millimolar silver thiosulfate (STS) through a cut portion of the peduncle while still attached to the plant. One-half of the fruit received silver and remained green while the other half ripened normally and was silver-free (less than 0.01 parts per billion). Harvested mature-green fruit were also treated with STS through the cut pedicel. Green tissue from silver-treated fruit had levels of 1-aminocyclopropane-1-carboxylic acid (ACC, the immediate ethylene precursor) slightly less or similar to that of turning or red-ripe tissue from the same fruit, and similar to that of mature-green tissue from control fruit. Ethylene production was higher in green tissue from silver-treated fruit than from either red tissue from the same fruit, or mature-green tissue from control fruit. By inhibiting ACC synthesis with aminoethoxyvinyl glycine, and by applying ACC +/- silver to excised disks of pericarp tissue from control or silver-treated tomatoes, we showed that short-term silver treatment did not affect the biological conversion of ACC to ethylene, while long-term treatment stimulated both the conversion of ACC to ethylene and the synthesis of ACC.

Journal Article↗
PubMed1983

Release of protein from normal and mutant tomato cell walls.

The nitrogen content of cell wall preparations from normal tomato (cv Ailsa Craig) fruit remained constant during ripening, whereas salt-soluble protein increased throughout this process. Tomato polygalacturonase released about twice as much protein from the preparations as salts did, with a maximum at the orange stage of development. Polygalacturonase-solubilized protein from the tomato mutant ;ripening inhibitor' (rin) was less, and that from the mutant ;Never ripe' (Nr) cell walls was more than that from normal wall preparations. Release of protein by fungal cellulase was limited, but was increased by the addition of polygalacturonase from the same source. Salt-solubilized protein contained a range of enzymic activities but these were distributed between fewer multimolecular forms than is the case for whole cell preparations. The results suggest that metabolically active protein, removable by strong salt solutions, cellulase, or polygalacturonase, remains attached to the cell walls of tomato fruit until late in ripening. The unusual amounts of protein attached to the cell walls of mutant fruit appear to be a reflection of the absence of some or all of the isoenzymes of polygalacturonase that are associated with normal ripening.

Journal Article↗
PubMed1981

The constituents of tomato fruit--the influence of environment, nutrition, and genotype.

It is proposed to describe briefly the rise in popularity of the tomato during the 20th century to become the world's fourth most significant fruit, making an important contribution to human nutrition. The grading standards for fruit used in various major tomato-producing countries will be outlined. A major part of the review will be devoted to describing changes in composition during the maturation, ripening, preservation, and storage of good quality tomatoes especially as regards carbohydrates, organic and amino acids, proteins, steroids, pigments, minerals, and the lipids, volatiles, and other minor constituents. A range within which composition should normally fall will be given. Additionally, the effects on composition of environment, cultivar, nutrition, and physiological disorders inter alia will be described. How new growing methods and genetic manipulation could influence the tomato of the future will also be considered.

Acids↗
PubMed1967

Metabolic processes in cytoplasmic particles of the avocado fruit. IX. The oxidation of pyruvate and malate during the climacteric cycle.

Mitochondria isolated from preclimacteric avocado fruit oxidize pyruvate at a much lower rate than those separated from climacteric fruit. The external addition of thiamine pyrophosphate (TPP) increased the rate of pyruvate oxidation in both cases. The study of the influence of TPP on the rate of oxidation of malate by mitochondria obtained from both preclimacteric and climacteric fruit indicated that the effect of this cofactor could be understood by assuming that malate was converted to pyruvate. TPP stimulation of malate oxidation was prevented by arsenite, an inhibitor of keto acid oxidation. The addition of glutamate increased the rate of malate oxidation through the transamination of oxaloacetate. This suggests that the rate of oxidation of malate is highly dependent upon mechanisms which remove oxaloacetate efficiently. Incubation of mitochondria from preclimacteric fruit with malate-U-(14)C resulted in the labeling of oxaloacetate and the accumulation of labeled pyruvate. Addition of TPP to this system induced the rapid formation of citrate. This conversion was completely inhibited by arsenite. The results indicate that the ability to carry out the oxidative decarboxylation of alpha-ketoacids improves as the ripening process progresses. The idea was advanced that TPP available to the mitochondria plays an important controlling role.

Carbon Isotopes↗