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  • Author or Editor: M. J. Bukovac x
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Abstract

Physiological parameters of abscission at the zone between the pedicel and fruit of the sour (Prunus cerasus L. ‘Montmorency’) and sweet (Prunus avium L. ‘Windsor’) cherry were investigated using fruit explants. 3-Indoleacetic acid, 2-(chloroethyl)phosphonic acid (ethephon), gibberellin A3, and abscisic acid hastened abscission (during Stage III) in sour cherry, while only ethephon enhanced abscission in the sweet cherry. Cycloheximide blocked abscission in both sour and sweet cherry and negated the effect of ethephon. Explants prepared from fruits during various stages of development exhibited a differential response to ethylene. Abscission in the sour cherry was enhanced by increasing temperature and was greater in dark than in light, while both high CO2 and low O2 levels delayed abscission.

Open Access

Abstract

(2-Chloroethyl)phosphonic acid (ethephon) significantly reduced the fruit removal force (FRF) at the lower abscission zone of ‘Montmorency’ sour (Prunus cerasus L.) and ‘Windsor’ sweet (Prunus avium L.) cherry fruit near maturity. No qualitative differences were detected in abscission layer development as a result of ethephon treatment. The primary effect was an acceleration of fruit separation following a pattern similar to that observed in the control. Separation in both treated and control sour cherry fruit was preceded by a loss of pectin and polysaccharides and a loss of cellulose orientation in the walls of cells comprising the abscission layer. Although separation in treated sweet cherry fruit was more extensive than in the control at maturity, it was still localized as in nontreated fruit and was not preceded or accompanied by a change in pectin, cellulose, or polysaccharides in the abscission layer. No effect of ethephon was observed on the upper abscission zone for either species through fruit maturity. Ethephon caused a dramatic increase in ethylene evolution from cherry fruit.

Open Access
Authors: and

Abstract

Fruit deformation, characterized by excessive enlargement, together with early coloring and premature softening of the ventral side, was observed in peach when 2-(m-chlorophenoxy)-propionamide (CPA) was applied for fruit thinning. The early maturing cvs., Garnet Beauty, and Sunhaven, were affected to a greater extent than ‘Redhaven’, ‘Richhaven’ and ‘Redskin’. The incidence of fruit deformation in ‘Redhaven’ was related to size of fruit at time of CPA treatment, a high incidence being observed when fruit were greater than 20 mm in length at time of treatment. Malformation was attributed to increased cell size in the mesocarp tissue at the suture region.

Open Access

Abstract

Abscission of maturing sweet cherry fruit (Prunus avium L. cv. Windsor) occurred at 2 different abscission zones, depending on the stage of fruit development. Immature fruit abscised at the upper zone between the pedicel and peduncle; mature fruit abscised at the lower zone between the fruit and receptacle. Separation in the abscission layer began directly above the stony pericarp and resulted in the formation of a cavity. Later separation occurred at the fruit : pedicel indentation and extended through the abscission layer toward the vascular bundles. Abscission involved the fracturing of cell walls as well as wall separation. There was no evidence of change in pectins, cellulose or other polysaccharides in the cell walls of the abscission layer prior to or during fruit separation. No starch accumulation in the abscission zone or lignification of tissue adjacent to the abscission layer was observed through fruit maturity.

Open Access
Authors: and

Abstract

S-Ethyl dipropylthiocarbamate (EPTC, 2.24 kg/ha) altered wax composition on developing leaves of cabbage [Brassica oleracea L. (Capitata group) cv. Market Prize], but did not affect cutin composition. The alkane, ketone and secondary alcohol content of the epicuticular wax was reduced and ester content increased. C29 constituents (alkane, ketone, aldehyde and sec-alcohol) accounted for 72.5% (34.1 μg/cm2) and 40.2% (7.2 μg/cm2) of the epicuticular wax on control and EPTC-treated leaves respectively. Homlog composition within a chemical group was not changed. Chemical composition was similar for abaxial and adaxial leaf surfaces, and the EPTC-induced change in chemical composition was similar for both surfaces. In contrast with epicuticular wax, cuticular wax contained higher percentages of fatty acids and primary alcohols, and lower percentages of alkanes, and ketones. All constituents except the unidentified polar materials and fatty acids were lower in cuticular wax extracted from EPTC-treated than non-treated plants. The main component of the cutin fraction from both control and EPTC-treated plants was identified as dihydroxyhexadecanoic acid. Cutin acids were not quantitatively changed by the EPTC treatment.

Open Access

Abstract

Effects of the surfactants Pace, Regulaid and Tween 20 were determined on foliar penetration of NAA and on NAA-induced ethylene production by cowpea [Vigna unguiculata (L.) Walp. subsp. unguiculata cv. Dixielee]. All three surfactants decreased surface tension of NAA solutions, causing a marked increase in wetting and in droplet : leaf interface area. The greatest increase in NAA penetration was obtained with Regulaid followed by Pace and Tween 20. The surfactant effect was most pronounced during the droplet drying phase, but penetration continued to take place from the deposit after drying. The mode of action of surfactants in enhancing NAA penetration is complex. Regulaid-enhanced penetration closely paralleled the increase in interface area, but similar relationships were not found for Pace or Tween 20, particularly at concentrations above the critical micelle concentration. Surfactant-enhanced NAA penetration caused an increase in NAA-induced ethylene production. There was a strong correlation (r = 0.82) between NAA penetration and ethylene production for doses of 0.5 to 2.5 μg/disk. Above 2.5 μg/disk, ethylene production increased at a decreasing rate. The potential for using auxin-induced ethylene production as an index for quantifying auxin penetration is discussed. Chemical names used: l-naphthaleneacetic acid (NAA), polyoxyethylene polypropoxypropanol dihydroxypropane (Regulaid), polyoxyethylene (20) sorbitan monolaurate (Tween 20), surfactant blend in paraffin base petroleum oil (Pace).

Open Access

Abstract

Mechanical injury to the seed of immature sour cherry (Prunus cerasus L., cv. Montmorency) fruit caused an immediate and marked increase in ethylene evolution followed by abscission of the fruit at the peduncle: pedicel zone. Ethylene evolution was induced when the seed, but not the pericarp, was injured. The magnitude of ethylene evolution was related to stage of fruit development at time of injury, and was most pronounced when the nucellus was the dominant tissue in the seed. Ethephon (500 and 1000 ppm) also caused immature fruits to abscise and abscission was preceded by embryo abortion. The site of ethephon-induced fruit separation differed depending on stage of fruit development at time of treatment. Fruit separation occurred at the peduncle:pedicel abscission zone when immature fruits were treated, and at the pedicel fruit zone when mature fruits were treated. The role of ethylene in the abscission of immature sour cherry fruit is discussed.

Open Access

Abstract

Peroxidase activity was demonstrated in the abscission zone and adjacent tissues of sour cherry fruit (Prunus cerasus L., cv. Montmorency) from Stage I of fruit growth to maturity. Activity was markedly greater in the receptacle and abscission zone, than in the fruit tissues. A difference was observed histochemically in the peroxidase of the abscission layer from that of the adjacent tissues. Moreover, peroxidase activity in the abscission zone increased to a maximum at a stage of development coinciding with the initiation of the separation phase. This increase in activity was accompanied by an increase in 2 of the major isoenzymes and the appearance of a third. The relationship between changes in peroxidase and abscission in fruit explants was less clear. Ethylene and ethephon had no significant effect on total peroxidase activity; however, ethylene appeared to increase the activity of a basic isoenzyme. Cycloheximide treatment decreased total and isoenzyme activity. Lowering the endogenous ethylene level did not reduce total activity, although the activity of a basic isoenzyme was decreased.

Open Access

Abstract

Factors influencing the foliar penetration of naphthaleneacetamide (NAAm) were established by following penetration from a glass vial into pear leaf discs (Pyrus communis L. cv. Bartlett). Penetration through the upper surface was linear for 96 hr, whereas, through the lower surface there was rapid penetration for 48 hr followed by a reduced rate. Uptake of NAAm was proportional to the concentration applied. Penetration was not influenced by pH of treatment solutions ranging from 3.0 to 7.0. Increasing temperature from 5–35°C caused a marked increase in penetration with Q10 values ranging between 1.59 to 5.46. Increasing light intensity resulted in increased penetration through the lower surface up to about 300 ft-c, but had no effect on NAAm penetration through the upper surface. Penetration was greater through the upper than lower surface in expanding leaves, but the reverse was true when leaves were fully expanded. Tween 20 and Triton B-1956 (0.1%) increased NAAm penetration through the lower surface, but to a lesser degree than X-77 (0.1%). No surfactant studied enhanced penetration through the upper surface. Penetration from microdroplets was similar to that from solutions in glass cylinders until the droplets dried. Droplet drying resulted in an immediate increase in penetration.

Open Access

Abstract

Abscisic acid (ABA) was isolated from sour cherry (Prunus cerasus L. cv. Montmorency) fruit and identified by thin-layer and gas-liquid chromatography and combined gas chromatography-mass spectrometry. Inhibitor levels in the seed paralleled those in the pericarp and were, in general, directly related to growth rate of the fruit, higher levels being found during the initial rapid growth (Stage I) than during the retarded growth phase (Stage II). The level of the inhibitor increased in Stage III, then decreased in the final stages of maturity. The possible role of endogenous ABA in cherry fruit development is discussed.

Open Access