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  • Author or Editor: Michael W. Smith x
  • Journal of the American Society for Horticultural Science x
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Abstract

Nitrogen and K were applied to 26-year-old ‘Western’ pecan [Carya illinoensis (Wangenh.) C. Koch] trees at 0, 56, 112, or 224 kg ha−1, and 0, 93, or 186 kg ha−1, respectively, for 6 consecutive years (1978–1983). There was a positive relationship between N rate and leaf N concentration and shoot growth. The number of new shoots per 1-year-old shoot was increased by N application. Yield was greater using 56, 112, or 224 kg N ha−1 than no N. Nitrogen rate was negatively related to leaf K concentration and curvilinearly related to leaf Mn concentration, but did not affect leaf Ca or Mg. Leaf P and Zn concentrations were reduced during some years by N application. Potassium application increased leaf K concentration in 1980, 1982, and 1983, but did not affect leaf K concentration in other years. Surface applied K moved to the 30–45 cm depth by 1980 and to the 45–60 cm depth by 1982. Potassium rate was positively related to leaf Mn concentration, but not leaf N, P, Ca, Mg, or Fe concentration. Annual yield was increased by K rate only in 1979, but cumulative yield was positively related to K rate.

Open Access

The objective of this study was to determine the most advantageous time to collect cuttings of Chinese pistache, a commonly recommended ornamental shade tree that is difficult to propagate by cuttings. In 1993, calendar date and degree days (daily mean temperature -7.2C) were used to estimate an appropriate cutting time. The greatest percentage of rooted cuttings occurred in male cuttings harvested on 13 May 1993 (397 degree days) and treated with 17,500 mg·liter-1 IBA or in male cuttings harvested on 20 May 1993 (482 degree days) and treated with either 8750 or 17,500 mg·liter-1 IBA. In 1994, cutting time was associated with calendar days, degree days, and morphology. The most rooted cuttings (44%) were from green softwood cuttings taken on 9 May 1994, which was 380 degree days from orange budbreak using a threshold temperature of 7.2C. Orange budbreak was characterized by separation of the outer bud scales such that the orange, pubescent inner bud scales were visible. Cuttings taken on 9 May 1994 and treated with 8750 mg·liter-1 IBA produced the most primary and secondary roots and the longest primary roots per cutting. Male Chinese pistache cuttings should be collected from green softwood or red semi-softwood stems when about 380 to 573 degree days have accumulated after orange budbreak. Chemical names used: indolebutyric acid (IBA).

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`Dodd' pecan seedlings [Carya illinoinensis (Wangenh.) K. Koch] were chilled at 6C for 0 to 1800 hours in 300-hour intervals and percent budbreak and days to budbreak recorded. Chilling duration required for ≥ 50% budbreak was 900 hours. Chilling > 900 hours increased budbreak percentage and reduced time to budbreak. `Dodd' seedlings chilled at 1, 5, or 9C for 0 to 2500 hours in 500-hour intervals had more lateral budbreak after 1000 hours of chilling at SC than at 1 or 9C. When chilling hours ranged from 1500 to 2500, 1C increased budbreak of the first lateral bud compared with 5 or 9C. As chilling was increased from 1000 to 2500 hours, the days to budbreak declined, and the uniformity of budbreak increased.

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Abstract

Nitrogen was applied as a ground application at the recommended rate based on leaf analysis, or at 25, 50 or 100% of that rate injected through a trickle irrigation system in combination with 3 rates of water. Leaf N was not influenced by treatment. Fruit yield resulting from the ground application or the 100% and 50% injection treatments were equal, whereas the 25% injection rate gave variable results. Injection treatments had no marked effect on fruit size or fruit quality. N distribution within the tree was uniform where the trickle irrigation rate was 7.6 liters per hour. N levels in the leaves were lower at 15.2 liters per hour.

Open Access

Abstract

Lateral apical meristems were collected biweekly from 15 July 1982 to 18 Mar. 1983 from 2-year-old ‘Redhaven’ peach [Prunus persica (L.) Batsch] trees grown under standard and meadow orchard cultural practices. Dissected buds were prepared for scanning electron microscope analysis, and representative samples were photographed. Meadow orchard trees were cut 20 cm above the soil immediately after fruit harvest (15 July), and thus, floral initiation and development was delayed until new growth occurred. Floral development in the standard trees began 7 weeks after harvest (late August) but did not begin in the meadow orchard trees until 13 weeks after harvest (early October). The sequence of floral development in both standard and meadow orchard trees began with petals followed by sepals, stamens, and the pistil. Standard trees produced numerous floral apices; however, floral differentiation was poor in the meadow orchard trees with only 5% to 10% of the buds initiating floral apices. The meadow orchard system thus may have limited use in central Oklahoma.

Open Access

Field experiments were conducted to quantify the effect of Ca supplied as gypsum in factorial combination with watermelon [Citrullus launatus (Thumb) Matsum and Nakai] cultivars Charleston Gray, Crimson Sweet, and Tri-X Seedless on yield and the elemental concentration of leaf and rind tissue. Also, the effect that ontogenetic changes and sectional differences had on the elemental concentration in rind tissue was investigated. The experiments were conducted at two locations in Oklahoma. Yield was not affected by Ca; however, mean melon weight was reduced at 1120 kg Ca/ha. Leaf Ca concentration increased linearly in response to Ca rate. `Tri-X Seedless' had lower leaf Ca and higher K concentrations than did `Charleston Gray' or `Crimson Sweet'. Fruit ontogeny (days from anthesis) and melon section (blossom or stem-end) interacted to affect elemental concentrations in the rind tissue. There was also a significant genotypic effect on elemental concentration in rind tissue. Increasing rates of Ca applied to soil reduced the incidence of-blossom-end rot (BER) in `Charleston Gray' melons. Calcium treatment did not affect flesh redness or soluble solids concentration (SSC) of watermelon.

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Abstract

Vegetative and fruiting shoots were tagged in Oct. 1982 and 1983 on ‘Squirrel’, ‘Stuart’, and ‘Cape Fear’ pecan trees [Carya illinoensis (Wangenh) C. Koch], and flowering was determined the following years. One-year-old shoots were sampled from vegetative and fruiting shoots of each cultivar on 14 Oct. 1982, 9 Feb., 11 Apr., 14 Oct., and 24 Nov. 1983, and 6 Jan. and 17 Apr. 1984 and analyzed for reducing and nonreducing sugars and starch concentrations. Fruiting reduced return bloom of ‘Cape Fear’ in 1983 and 1984, and ‘Stuart’ in 1983. Sugar and starch concentrations varied inversely. Sugar concentrations were increased in November, January, and February, and starch concentrations were greatest during October and April. The total carbohydrate concentration in fruiting shoots of each cultivar was greater or equal to that of vegetative shoots in all but one instance. The degree of return fruiting was positively associated with cultivars with early fruit ripening dates.

Open Access

The influence of fruiting stress on shuck decline, nut quality, and premature germinaiton was evaluated on trees of pecan [Carya illinoensis (Wangenh.) C. Koch]. Fruit at the liquid endosperm state were removed from trees with a mechanical shaker to reduce crop load by 0%, 25%, 41%, 56%, or 77%. Shuck decline and premature germination decreased and kernel quality increased with a reduction in crop load. An excessive fruit load or fruit stress elevated the incidence of shuck decline, previously referred to as shuck disease, tulip disease, shuck die-back, or late season shuck disorder; decreased kernel development; and increased premature germinaiton. Shucks were dissected from fruit ranging from healthy to those with premature shuck opening and examined by scanning electron, transmission electron, and light microscopy. Fungal growth was detectable, but only after tissue degeneration had occurred. Thus, results indicate the onset of shuck decline is caused by stress associated with an excessive crop load and not a pathological disorder. Fungal growth is a secondary, not a primary, factor in deterioration of shucks with decline.

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The hypersensitive response in resistant plants exposed to incompatible pathogens involves structural changes in the plant cell wall and plasma membrane. Cell wall changes may include pectin deesterification resulting in release of methanol. The time course of methanol production was characterized from `Early Calwonder 20R' pepper (Capsicum annuum L.) leaves infiltrated with the incompatible pathogen, Xanthomonas campestris pv. vesicatoria (Doidge) Dye race 1 (XCV). In the first time course experiment, leaves were infiltrated with either 108 colony-forming units/mL of XCV or water control. Leaf panels (1 × 5 cm) were excised after dissipation of water soaking, then incubated in vials at 24 °C. Headspace gas was analyzed at 6-hour intervals up to 24 hours. The rate of methanol production from resistant pepper leaves infiltrated with XCV was greatest during the first 12 hours after excision. In another experiment, leaf panels were harvested at 6-hour intervals up to 24 hours after inoculation and incubated for 12 hours at 24 °C to determine the relationship between the interval from inoculation to leaf excision and methanol production. The highest rate of methanol production was obtained when the interval between bacterial infiltration and leaf excision was 18 hours. The relationship between methanol release and changes in the degree of methylesterification (DOM) of cell wall pectin was determined in near isogenic lines of `Early Calwonder' pepper plants resistant (20R) and susceptible (10R) to XCV race 1. Cell walls were prepared from resistant and susceptible pepper leaves infiltrated with XCV or water. XCV-treated resistant leaves had 18% DOM and 9.7 nmol·g-1·h-1 of headspace methanol, and the susceptible leaves had 48% DOM with 0.2 nmol·g-1·h-1 methanol. Susceptible and resistant control leaves infiltrated with water had 55% and 54% DOM, respectively, with no detectable methanol production. Increased methanol production in resistant pepper leaves inoculated with XCV coincided with an increase in cell wall pH. Intercellular washing fluid of resistant pepper leaves had a significantly higher pH (6.9) compared to susceptible leaves (pH 5.1) and control leaves infiltrated with water (pH 5.1). Both 10R and 20R pepper leaves infiltrated with buffer at increasing pH's of 5.1, 6.9 or 8.7 had increased methanol production. Since deesterified pectin is more susceptible to degradation, demethylation may facilitate formation of pectic oligomers with defensive signalling activity.

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Nitrogen was applied to mature pecan (Carya illinoinensis Wangenh. C. Koch.) trees annually as a single application at 125 kg·ha-1 N in March or as a split application with 60% (75 kg·ha-1 N) applied in March and the remaining 40% (50 kg·ha-1 N) applied during the first week of October. Nitrogen treatment did not affect yield, and had little effect on the amount of N absorbed. Nitrogen absorption was greater between budbreak and the end of shoot expansion than at other times of the year. Substantial amounts of N were also absorbed between leaf fall and budbreak. Little N was absorbed between the end of shoot expansion and leaf fall, or tree N losses met or exceeded N absorption. Pistillate flowers and fruit accounted for a small portion of the tree's N; ≈0.6% at anthesis and 4% at harvest. The leaves contained ≈25% of the tree's N in May and ≈17% when killed by freezing temperatures in November. Leaves appeared to contribute little to the tree's stored N reserves. Roots ≥1 cm diameter were the largest site of N storage during the winter. Stored N reserves in the perennial parts of the tree averaged 13% of the tree's total N over a three year period. Current year's N absorption was inversely related to the amount of stored N, but was not related to the current or previous year's crop load.

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