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Open access

Haim Nerson, Ron Cohen, Menahem Edelstein, and Yosef Burger

Abstract

The effects of paclobutrazol (cultar, PP333) on yield and fruit quality of muskmelon (Cucumis melo L. var. reticulatus Naud. cv. Galia) were examined in a series of field experiments, in the spring at Newe Ya’ar (northern Israel) and in autumn at Biq’at HaYarden (lower Jordan Valley, eastern Israel). In the spring experiments, paclobutrazol applied at 2 and 4 mg·liter−1 as a drench to the media-mix of muskmelon transplants increased total fruit yield 15% to 20% at various plant populations and in combination with ethephon and/or chlorflurenol, but tended to decrease the early yield. Yield increase was due to an increase in fruit weight rather than number. Paclobutrazol, in general, tended to improve marketable yield, yield concentration, and netting index. In the autumn experiment, paclobutrazol was applied at 250 mg·liter−1 as a spray from flowering through fruit maturation and compared with benzyladenine (BA), and N, P, and K fertilization. Paclobutrazol reduced early leaf-yellowing symptoms, but was not as effective as BA. Paclobutrazol in the autumn experiment did not affect yield or yield components, but soluble solids content was significantly increased and keeping-quality was unaffected. Chemical names used: β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-l ethanol (paclobutrazol); (2-chloroethyl)phosphonic acid (ethephon); (methyl-2-chloro-9-hydroxyfluorene-(9)-carboxylate) (chlorflurenol); benzyladenine (BA).

Open access

Avinoam Golomb and Eliezer E. Goldschmidt

Abstract

Two alternate-bearing ‘Wilking’ mandarin (Citrus reticulata Blanco) trees, an “on” and an “off” tree, were uprooted and dissected into 11 organ types during the time of fruit maturation (February). Total or water-soluble N, P, K, Ca, and Mg (nitrate for soluble N) content were determined for each organ. Calcium was separated further into water-soluble, exchangeable, insoluble, and oxalate fractions. Leaves and twigs of on trees had reduced N, P, and particularly K levels. Organs of on trees, including minor roots and fruit, contained increased nitrate levels. Leaves, twigs, and minor roots of on trees accumulated Ca, mainly as Ca oxalate. The amounts of N, P, and K present in the fruit represented 32.2%, 43.7%, and 57.8%, respectively, of the total for an on tree. Fruit were very low in Ca, containing only 6% of the tree total. A 15-month follow-up of seasonal fluctuations in minerals of on and off ‘Wilking’ trees showed that the mineral composition of leaves and twigs was rapidly changed by the presence or absence of fruit. Defruiting in July prevented mineral depletion and permitted reasonable flower-bud differentiation on subsequent year. Leaf disks of on trees had low initial nitrate–reductase activity but responded weakly to nitrate induction. Leaves of overloaded on trees appear to suffer from a metabolic disorder involving relatively high nitrate levels, Ca accumulation, and loss of the nitrate–reductase induction response.

Open access

Anita Nina Miller, Beth Allyn Krizek, and Christopher S. Walsh

Abstract

The rate of ethylene evolution of peach fruit (Prunus persica L. Batsch) and ACC content of peach pericarp/mesocarp and seeds was determined during development. Ethylene measurements of whole fruit began 18 days after anthesis (DAA), and ACC quantification was started 32 DAA. ACC levels and ethylene evolution followed similar patterns during stages I and II of fruit growth. At 39 DAA, there was an increase in ethylene evolution and extractable ACC concentration of both pericarp and seeds; however, variability was high at this time. Ethylene evolved by nondeveloping fruit of the “second wave” and “June drop” increased after senescence of the ovule was observed. By 49 DAA, ethylene production and ACC concentration reached a minimum that lasted until a 10-fold increase in ethylene evolution was detected in late stage III. This 10-fold increase in ethylene occurred in four different peach cultivars sampled at “firm-ripe” stage. Seeds excised at 67 DAA, which were incubated for 6 hr in ambient O2 conditions, evolved 400 nl·g−1·hr−1 ethylene and ACC concentration averaged 54 nmol·g−1 fresh weight. It is suggested that in split-pit fruits, ethylene generated by the seeds may accelerate fruit maturation and ripening. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).

Open access

T. J. Facteau

Abstract

Foliar applications of gibberellic acid (GA3) to mature ‘Lambert’ sweet cherry trees (Prunus avium L.) about 21 days before harvest increased fruit weight (fresh and dry), soluble solids (SS), alcohol-insoluble substances (AIS) (both concentration and per fruit), ash weight, and fruit firmness at harvest. Application of GA3 did not affect concentrations of ethylene diamine-tetraacetic acid (EDTA) or pectinase-soluble pectins and fruit Ca. GA3-treated fruit had lower concentrations of water-soluble pectins and reduced surface pitting. Fruits sampled at 3–7 day intervals (starting about 21 days before harvest) from control and GA3-treated trees showed that as an average response over a 29-day sampling period GA3 increased fruit weight, firmness, AIS concentration, AIS per fruit, pectinase-soluble pectins, and decreased water-soluble pectins. Neither total, residual, or soluble fruit Ca were affected by treatment with GA3. Fruit Ca levels remained constant, on a per fruit basis, during the last 3 weeks of fruit maturation but Ca concentration, expressed as fresh or dry weight, decreased as a result of increased fresh and dry weight. Higher Ca levels were not associated with firmer fruit (comparing GA3 and nontreated fruit), but were correlated positively with firmness in nontreated fruit.

Open access

G. Nir, I. Klein, S. Lavee, G. Spieler, and U. Barak

Abstract

The effect of evaporative cooling on budbreak and yield of Vitis vinifera L. (‘Perlette’ and ‘Thompson Seedless’) vines grown in the southern Jordan Valley in Israel was investigated. Overhead microsprinklers were operated from 0600 to 1800 hr daily during the autumn and winter months, either alone or in combination with cyanamide sprays after pruning. Evaporative cooling decreased the temperature of buds exposed to direct sunlight from 30° to 16°C and that of shaded buds from 25° to 13°. Evaporative cooling induced an early uniform budbreak. However, when evaporative cooling was combined with cyanamide spray, its effect was evident only during the initial phase of bud emergence. In 1985 cyanamide spray and evaporative cooling alone increased yield of ‘Perlette’ by 6% and 6% to 24%, respectively, and by 17% to 46% when both treatments were combined. In 1986 prolonged evaporative cooling increased the yield of ‘Perlette’ by 25% but, in combination with cyanamide, by only 11.6% over the unwetted cyanamide-treated control. In both years, evaporative cooling with or without cyanamide advanced fruit maturation.

Open access

Sylvia M. Blankenship and C.R. Unrath

Abstract

Internal ethylene levels, fruit firmness, soluble solids content, and starch–iodine reaction in ‘Delicious’ and ‘Golden Delicious’ apples (Malus domestica Borkh.) were measured weekly for 6 to 8 weeks during fruit maturation for 3 years. Internal ethylene level did not consistently correlate with minimum maturity as judged by agricultural inspection or optimum maturity as judged by a taste panel in either cultivar. Internal ethylene levels ranged from 0 to 26 μl·liter−1 in ‘Delicious’ and 0 to 41 μl·liter−1 in ‘Golden Delicious’ on taste panel harvest dates. Decreases in fruit firmness and increases in starch conversion and soluble solids content were observed prior to any increase in internal ethylene in both ‘Delicious’ and ‘Golden Delicious’. Thus, internal ethylene concentration is not a reliable index of maturity for harvest determination for immediate sale on the fresh market. The combination of fruit firmness decrease, soluble solids increase, and conversion of starch seem to be more closely tied to perception of maturity by both the agricultural inspectors and taste panel.

Open access

Shohei Yamaki and Kazuko Ishikawa

Abstract

Activities and roles of 4 sorbitol enzymes, sorbitol-6-P dehydrogenase, NAD+-dependent sorbitol dehydrogenase, NADP+-dependent sorbitol dehydrogenase and sorbitol oxidase, and acid invertase in apple (Malus domestica Borkh. ‘Jonnagold’) leaves and fruit were studied. Almost all of the soluble carbohydrates in leaves are present as sorbitol throughout the season. Sorbitol-6-P dehydrogenase had the highest activity among the enzymes, being high in young leaves and decreasing with age; whereas NAD+- and NADP+-dependent sorbitol dehydrogenases and sorbitol oxidase activities were barely detectable. Sorbitol was translocated from leaves to fruits where it was readily metabolized to other sugars, so the sorbitol concentration did not increase. NAD+-dependent sorbitol dehydrogenase that converts sorbitol to fructose had the highest activity of the 4 enzymes in developing fruits. Its activity rose in June, decreased in midseason, and increased again with fruit maturation. The fluctuation in enzyme activity corresponded to changes in fructose concentration. Sorbitol oxidase activity, which was about one-fifth that of NAD+-dependent sorbitol dehydrogenase, increased proportionately as fruits enlarged. Acid invertase activity was distinctly higher than sorbitol enzyme activities in both leaves and fruit, but its roles in sugar translocation and metabolism were not clearly established. The levels of sorbitol in stems and peduncles remained relatively constant during the season indicating that little metabolism occurred in the phloem during transit.

Open access

R. E. Bir, W. J. Bramlage, and J. R. Havis

Abstract

Richared Delicious’ apple (Malus pumila, Mill.) fruit tissues exhibited 2 distinct freezing points (exotherms) during freezing. Exotherm 1 occurred at −1.5° to −2.2°C and Exotherm 2 occurred between −4.2° and −7.7°C. The inception temperature of Exotherm 2 varied considerably both within a fruit and among different fruits. During fruit maturation from August to October, no significant change in freezing pattern occurred, although soluble solids increased 55% during the period tested. Inception of Exotherm 1 caused no distinct change in physical properties of cortex tissue. Inception of Exotherm 2 was associated with significant softening and increased ion leakage from the tissue. Just beyond termination of Exotherm 2, the tissue lost its capacity to exhibit multiple exotherms on thawing and refreezing, and underwent massive changes in firmness, ion leakage, and respiration; it was concluded that freezing to this point was lethal to the tissue. The concept that tissue injury is related to specific points on the freezing curve of apples is presented.

Open access

Evangelos M. Sfakiotakis and D. R. Dilley

Abstract

Ethylene and other olefinic compounds cause apples and other climacteric fruits to ripen. Propylene, which fruits do not produce, was employed to determine, 1) the stage of maturity apples must attain to autocatalytically produce ethylene, and 2) the effect of O2 tension on autocatalysis. ‘Red Delicious’ apples harvested at developmental stages representing 52, 58, 65, and 75% of maturity were gassed with propylene at concentrations of 0, 10, 50, 100, 500, and 1000 ppm for 1 week at 20°C. Propylene induced ethylene synthesis at all stages of maturity. Its ability to stimulate ethylene production, however, increased progressively with fruit maturation, although rate of production following treatment with 500 ppm propylene was constant. A shorter lag time to the onset of autocatalytic production was observed in more mature fruits which reflects a natural increase in sensitivity. Propylene administered at 6.5% O2 or less did not induce ethylene production, but an anaerobic atmosphere was necessary to completely inhibit ethylene synthesis in fruits once autocatalysis began.

Open access

P. Spiegel-Roy, M. Evenari, and D. Mazig

Abstract

Soil moisture use, shoot growth, fruit size, and yield of apricot (Prunus armeniaca) trees (cv. Hatif de Colomer) were measured under flood water-spreading conditions in the desert. Root distribution was estimated from interpretation of soil moisture data. A highly significant correlation was found between pooled values of past and current seasons' water depletion values and current season's yield. Relative maximum water depletion (on a daily use basis) occurred during fruit maturation. Maximum trunk growth occurred in spring. In some seasons a second, small peak occurred in the autumn.

Shoot growth usually terminated by the beginning of June, and maximum trunk rate growth was usually (except in 1967) attained shortly thereafter.

Trees survived the extremely dry 1968 season (no flood, and only 80 mm of rain), with partial recovery in shoot growth and yield and full recovery in trunk growth during the subsequent year.

Moisture depletion under the trees, per 1000 m2, during the active period of the trees (March to end of September) was only 26 mm in 1968, about 100 mm in 1966, 106 mm in 1967 and 146 mm in 1969. Yields per tree (26 trees per 1000 m2) ranged from 1.4 kg (in 1970) to 27.4 kg (in 1967).

The central cylinder around the tree (2 meters in diam) accounted for the highest relative use of water in comparison with other annuli extending around the tree.