Miklos Faust

Non-destructive detection of watercore in apple with nuclear magnetic resonance imaging

Abstract A nuclear magnetic resonance (NMR) imaging method in radiology is used to obtain images of watercore and its distribution in ‘Red Delicious’ apples ( Malus domestica Borkh.). The uneven distribution of mobile water and its NMR relaxation times, spin-lattice ( T 1 and spin-spin ( T 2 , produce signals that are used to reconstruct cross-sectional images. From the variation of signal intensity in the images, detailed internal structures of apple fruit, including petal bundle, endocarp, outer limit of carpel, dorsel bundle of carpel, cortex of receptacle, pith of receptacle and seeds, can be discerned. Both the normal and watercored tissues can also be clearly differentiated on the images. Based on NMR images, watercore occurred primarily in the area ±20 mm from the center of the fruit of an affected apple, and the area most affected was between 5 and 10 mm from the center, toward the stem end.

Changes in the activities of catalase, peroxidase, and polyphenol oxidase in apple buds during bud break induced by thidiazuron

The breaking of dormancy in apple buds (Malus domestica Borkh cv. York Imperial) by thidiazuron (N-phenyl-N′-1,2,3,-thidiazol-5-ylurea) was investigated in relation to catalase, peroxidase, and polyphenol oxidase activities and their isoenzyme patterns. The activity and number of isoenzymic components of catalase increased progressively during bud break, then decreased after buds started to grow. Peroxidase activity was highest during dormancy and declined during bud swell, increased at bud break, and decreased after bud expansion. Several isoperoxidases were observed in gel electrophoresis. Similar patterns were found at different growth stages of apple buds except for one peroxidase isoenzyme, P3, which disappeared 12 days after thidiazuron treatment. There was an inverse relationship between the activities of polyphenol oxidase and peroxidase during the development of apple buds. Apple buds have a very similar polyphenol oxidase isoenzyme pattern throughout bud development. However, the appearance and disappearance of minor isoenzymes were also observed. Phloridzin, rutin, p-coumaric, epicatechin, naringin, chlorogenic acid, and catechol were found in apple buds. Among them, phloridzin, rutin, and p-coumaric were the dominant phenolic compounds. Dormant buds contained a high amount of phenolic substances which decreased after bud break (4 days after thidiazuron treatment) then increased until the start of bud expansion. Phenolic compounds are found to be potent modifiers of catalase, peroxidase, and polyphenol oxidase activity, as both inhibitors and stimulators in apple buds.

Changes in water status in peach buds on induction, development and release from dormancy

Abstract Peach shoots collected prior to onset of chilling in early November from mid Georgia, were exposed to short days or cold temperature to induce dormancy. A gradual increase in bound water under both conditions was found in comparison to control left under warm long days condition. To release dormancy, buds were exposed to 0 or 4°C, temperature that break dormancy, and to a 6–24°C, diurnally cycled treatment that prevents chilling accumulation, and is inefficient in breaking dormancy. Chilling temperatures (0 and 4°C) induced somewhat freer water after 39 days than the 6–24°C treatment. The proportion of free water increased until 55 days. When shoots were transferred to forcing conditions, a further rapid increase in free water was noted especially with shoots that were exposed to chilling previously. The conversion of bound to free water on exposure to forcing conditions was also verified with orchard-chilled peach buds. Buds on branches that were not exposed to effective chilling were also showing the appearance of free water after exposure to high temperatures for a long duration. Evaluating these data raises the possibility that bound water in buds of temperate fruit trees is correlated with the level of cold resistance rather than with the level of endo-dormancy. This may explain the much higher levels of freer water during dormancy in the less cold-resistant peach than in the more cold-resistant apple.

Metabolic changes associated with bud break induced by thidiazuron

Bud break in apple (Golden Delicious,Malus domestica Borkh) was induced by thidiazuron (N-phenyl-N′-1,2,3-thidiazol-5-ylurea). In control and thidiazuron-treated shoots, higher amounts of soluble carbohydrates (sorbitol, fructose, glucose, sucrose) and galacturonic acid were found in the phloem, but higher amounts of starch and cell wall polysaccharides, including cellulose and xylose, were found in the xylem. A decrease in soluble carbohydrates and starch in both phloem and xylem was associated with induction of bud break by thidiazuron. However, little change in cell wall polysaccharides was found. Total carbohydrates were higher in the upper than in the lower portion of shoots. The breaking of dormancy by thidiazuron was also associated with an increase in organic acid content and respiration in buds. KCN inhibited bud respiration during all stages of development. Organic acid content was inversely related to carbohydrate content in developing buds. Axes contained more carbohydrates and organic acids than did scales.

Nitroguanidines induce bud break and change sterol content in apple

Bud break in apple (Malus domestica Borkh cv. Golden Delicious) was induced by 1-(3,5-dichlorophenyl)-3-nitroguanidine or 1-(α-ethylbenzyl)-3-nitroguanidine. The optimum dose was 1000 μM. An increase in bud fresh weight, dry weight, and length was more prominent in buds treated with 1-(α-ethylbenzyl)-3-nitroguanidine than in those treated with 1-(3,5-dichlorophenyl)-3-nitroguanidine. The sterol compositional changes during bud break induced by 1-(3,5-dichlorophenyl)-3-nitroguanidine were similar to those induced by 1-(α-ethylbenzyl)-3-nitroguanidine. β-Sitosterol and sitosteryl ester were the predominant sterols. The amounts of these sterols increased immediately after dormancy was broken and then declined. A decrease in the percentage of the sitosterol and sitosteryl ester was accompanied by an increase in campesterol and stigmasterol at the beginning of rapid growth. A decrease in the ratio of free sterols to phospholipids and an increase in the ratio of campesterol + stigmasterol to sitosterol upon breaking dormancy occurred in apple buds induced by 1-(3,5,-dichlorophenyl)-3-nitroguanidine or 1-(α-ethylbenzyl)-3-nitroguanidine. 1-(m-Methoxybenzyl)-3-nitroguanidine did not affect breaking of apple bud dormancy and also had no effect on changes in sterol content. The sterols in apple buds were confirmed by gas chromatography-mass spectrometry.

Effect of paclobutrazol on cell wall polysaccharide composition of the apple tree

Abstract The effect of paclobutrazol, a gibberellin biosynthesis inhibitor, on cell wall carbohydrate composition of apple shoots was determined. Inhibition of apple shoot extension corresponded to a change in wall composition. Paclobutrazol did not inhibit shoot growth during the first year (1983) after the treatment. There was also no significant difference in cell wall carbohydrate composition between control and paclobutrazol treated shoots. In the second year (1984), however, paclobutrazol altered the composition of cell wall polysaccharides and inhibited shoot extension. Paclobutrazol treatment increased rhamnose, arabinose and galacturonic acid but decreased cellulose. The ratio of xylem to phloem was also reduced by paclobutrazol treatment.

The relationship of internode length to carbohydrate content in genetic dwarf apple trees

Abstract The relationship of internode length to carbohydrate content in 10-year-old hybrid seedlings of ‘Goldspur Delicious’ × ‘Redspur Delicious’ apple ( Malus domestica Borkh.) throughout the growing season was examined. Short-internode shoots contained high galacturonic acid but were low in soluble carbohydrates, starch and cell wall polysaccharides (xylose and cellulose). Dry matter percentage of phloem, xylem and leaf tissue was higher in long-internode trees compared to short-internode trees. Short-internode trees exhibited shorter shoot and higher phloem to xylem ratio compared to long-internode trees. Phloem contained higher amounts of soluble carbohydrates and galacturonic acid; whereas, xylem contained a higher amount of starch and cell wall polysaccharides of both cellulose and xylose. The non-cellulosic neutral sugar (rhamnose, arabinose, xylose, mannose, glucose, galactose) and cellulose levels in long-internode shoots were generally higher compared to short-internode shoots, especially in xylem tissue.