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Abstract
Fruit and leaf explants of ‘Pineapple’ orange were aged for 2 to 36 hr after excision and prior to treatment with ethylene or 2,4-dichlorophenoxyacetic acid (2,4-D). Abscission of fruit explants, aged for various durations, was accelerated by ethylene applied as early as 2 hr after excision but was delayed by 2,4-D administered within 26 hr after excision. Leaf explants did not exhibit an abscission response to ethylene up to 20 hr following excision, but they became responsive at 28 hr. The growth substance, 2,4-D, was effective in delaying abscission of leaf explants aged for 44 hr. Ethylene, 2-chloroethylphosphonic acid (Ethrel), and cycloheximide failed to accelerate abscission in young ‘Valencia’ orange fruit (3.1 to 3.8 cm diam.) while they greatly accelerated abscission in mature fruit. Citrus leaf, but not mature fruit explants, exhibit the 2-stage abscission phenomenon in response to auxin and ethylene. Results suggest the possibility of differential abscission promotion in mature vs immature ‘Valencia’ orange fruits.
Abstract
Changes in susceptibility to chilling injury of grapefruit (Citrus paradisi MacF.) were found to vary directly with the growth activity of the trees. Exogenous growth regulators were applied to test the hypothesis that they may be involved in seasonal variations in susceptibility to chilling injury. Benzyladenine, gibberellic acid and 2,4-dichlorophenoxyacetic acid applied postharvest and benzyladenine and 2,4-D applied preharvest significantly altered susceptibility to chilling injury although the direction and extent of the changes were neither consistent nor predictable.
Abstract
Free phenolic constituents increase more than 2-fold in injured peel of oranges (Citrus sinensis Osbeck) cv. Valencia after 48 hr at 30°C and 96 to 98% relative humidity (rh). Concomitantly, conjugated phenolic compounds decrease to near depletion as a heavily lignified layer forms on injured cells. At 5°C all wound healing processes slow down. Infection of injured tissue by Penicillium digitatum Sacc. at 27°C inhibits lignin synthesis and the disappearance of conjugated phenolic compounds, but does not interfere with the usual increase in free phenolics. Mycelium of P. digitatum contributes little to the level of phenolic compounds of decayed fruit tissue. Extracts of free phenolic substances from healed tissue d) not exhibit fungistatic activity on P. digitatum spores, Lignin formation provides a mechanical barrier which retards or inhibits penetration of injured tissue by P. digitatum.
Abstract
Healing of minor injuries to ‘Valencia’ orange (Citrus sinensis (L) osbeck) occurs rapidly at 30°C and 96-98% relative humidity. It is manifested by a marked increase in the activity of phenylalanine ammonia-lyase (PAL) and deposition of lignin. PAL activity is confined mainly to injured flavedo while uninjured peel and albedo tissues exhibit very little activity. Inoculation of injured flavedo, immediately after injury, with P. digitatum sacc. disrupts the increase in PAL activity. When acetone powder from decayed peel was mixed with that of healed injured fruit and enzyme preparation was made from the mixture, there was no apparent reduction in phenylalanine ammonia-lyase activity, except that cuased by dilution. The synthesis of both PAL and lignin in mature fruit is strongly inhibited by cycloheximide, but not by actinomycin D.
Abstract
Activated charcoal or Polyclar AT removed sodium o-phenylphenate (SOPP) from laboratory-prepared Solutions and citrus packinghouse effluents. Activated charcoal at 0.25 g/100 ml of 100 ppm SOPP removed 99.6% SOPP, while Polyclar AT at 10 g/100 ml of 100 ppm SOPP removed 95% of the phenolic fungicide. Efficiency of SOPP removal declined when the amount of added Polyclar was reduced below 10% or the concentration of SOPP in treated Solutions exceeded 100 ppm.
Abstract
Fruit of ‘Valencia’ orange (Citrus sinensis Osbeck) and ‘Murcott’ tangerine (Citrus reticulata Blanco) were subjected to cold treatment at 1.1°C for 17 days as prescribed for the disinfestation of citrus of the Caribbean fruit fly (Anastrepha suspensa (Loew) in the plant protection and quarantine treatment manual. Fruit quality was evaluated during subsequent storage at 4.4°C for one week followed by 2 weeks at 21.1°. Fruit under cold treatment did not develop any physiological disorders. Fruit color and general appearance remained unaffected. Loss due to decay was 2.3% for ‘Murcott’ tangerine and 7.2% for ‘Valencia’ orange. Moisture loss for both varieties was about 5%. Fruit quality, including flavor, was found to be acceptable in ‘Murcott’ during subsequent storage. Yet the quality of ‘Valencia’ remained acceptable for one week only at 4.4°. Cartons used for packing fruit and stored at 1.1° absorbed more moisture when transferred to 21.1° than the cartons at 4.4° or 21.1° because of moisture condensation on fruit.
Abstract
The uptake, translocation, and metabolism of 14C-gibberellic acid (14C-GA3) was studied in 3-year-old container-grown ‘Marsh’ grapefruit trees (Citrus paradisi Macf.). A total of 1.65 × 105 disintegrations per min (dpm) in 200 μl of solution was applied evenly over the entire fruit surface, or, on both surfaces of 3 to 5 subtending leaves of a fruit. Absorption of 14C-GA3 by leaves and peel began within 1 hr of application and continued for 8 hr. Translocation of labeled material from leaves to peel and the reverse began 4 to 8 hr after application and continued for 4 weeks. No labeled material was recovered from juice or seeds. Labeled material persisted in albedo, flavedo, and leaves for 8 weeks with the highest accumulations in the peel. Separation of 14C-GA3 metabolites from the 95% EtOH extract by reversed-phase HPLC produced 2 14C-labeled peaks. Analysis of these 2 peaks by β-D-glucosidase hydrolysis, n-butanol partitioning, and cochromatography with 14C-GA3 standards suggested that the major component was 14C-GA3 and the other a polar metabolite.
Abstract
Taste panels compared the flavor and texture of lowbush blueberry fruits (Vaccinium angustifolium Ait.) with combinations of blueberries and foreign edible berries, commonly called chokepears [fruit of purple chokeberry, Pyrus floribunda Lindle (syn. Aronia prunifolia (Marsh.) Rehder) and black chokeberry, P.. melanocarpa (Michx) Willd. (syn. Aronia melanocarpa Willd.)], in 14 sensory tests. Combinations which were rated as undesirable were: raw, 20 to 10% chokepears; sauce, 14 to 9%; muffins, 67 to 17%. Per cents of chokepears which were undetected were: muffins and tarts, 14 and 12% and pies, 4 and 2%. Masked by the batter and pastry in muffins and tarts, relatively large percentages of chokepears were acceptable to the panelists.