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- Author or Editor: C.B. Ely x
- Journal of the American Society for Horticultural Science x
Photosynthetically active radiation (PAR) was measured at two times of day (8:00 am and noon Central Standard Time) in a 915 × 915-cm area of a 1006 × 915-cm gable roof greenhouse. PAR measurements were taken across a grid at 40-cm intervals, a total of 529 data points. Spatial variation of PAR in the greenhouse was evaluated through contour plots and the geostatistical technique of semivariogram construction. Semivariograms provide a visual guide to the degree of spatial correlation of a variable, allowing a quantification of the distance at which variables cease to be spatially correlated (the range) Measured PAR contained distinct zones of lowered values, a function of overhead greenhouse structures, wall-hung electrical boxes, and tall plants in adjacent greenhouses. Although the amount of PAR changed over time, zones of high and low PAR remained relatively constant, except at the sides of the greenhouse. Constructed semivariograms revealed that PAR contained strong spatial correlation (up to a 350-cm separation) as measured in the north-south direction, moving parallel to greenhouse bench placement. When PAR measurements perpendicular to benches (east-west) were used in directional semivariograms PAR was found to be completely random, plotting as a horizontal line called a nugget effect. Thus, plants placed perpendicular to the greenhouse benches (east-west) would not be affected by the spatial correlation of PAR.
Abstract
Temperatures for several post-bloom periods were correlated with days from full bloom to ‘Bartlett’ pear maturity. Date of maturity based on pressure test showed a high negative correlation (r = -.88) with mean temp above 40°F for the 36 days following bloom. The peak thermal period occurred 26-30 days after bloom, with the highest correlation on the 28th day. Days to maturity had a higher correlation with accumulated mean temp above 45°F than with degree hr above 45°F for the same periods. Base temp of 38.5°F to 50°F gave r values greater than -.85 in this prediction method. Mean temp between 41.5°F and 68.5°F on the 28th day had a linear correlation r of -.71 with days to maturity. Equal temp increments were more effective at min levels than at max levels for accelerating maturity. The post-bloom thermal period affecting maturation coincides with the stage of cell division and most effective time for application of chemical thinning sprays.
Abstract
Cuts were generally more prevalent on mechanically harvested peaches than on those hand harvested, although they were usually within acceptable limits. Bruise development during storage was variable and often not significantly higher on machine harvested fruit than on those hand harvested. Fruit position within bulk bins appeared to influence subsequent bruise development. A prototype portable dumper-sorter did not significantly increase fruit injuries. Providing fruit were of comparable maturity, injuries to postbloom regulator-treated fruit were comparable to those untreated. The development of rots during storage was the greatest source of unmarketable fruit and is regarded as the most serious problem related to the mechanical harvesting of peaches for fresh market.
Abstract
Examination of flowers of carrot (Daucus carota L.) using the scanning electron microscope revealed that some cytoplasmically male-sterile genotypes exhibit flower abnormalities that may be associated with reduced pollination and seed set. Such abnormalities, evident in many inbred lines, may carry over to the male-sterile F1 parents used to produce 3-way hybrids and probably affect insect pollinator activity.
Environmental factors such as rainfall may reduce the efficacy of foliar-applied soybean [Glycine max (L.) Merrill] oil in reducing pest mortality. Greenhouse studies were conducted to investigate the influence of rain on the retention of soybean oil and the influence of soybean oil and rainfall on surface morphology of apple [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] and peach [Prunus persica (L.) Batsch (Peach Group)] leaves and stems. `Contender' peach and `Golden Delicious'/Malling 27 apple trees were grown in 19 L pots in a greenhouse (23 ± 9 °C) and sprayed with soybean oil (1%) emulsified with the adjuvants Latron B-1956 or K1. Twenty-four hours after treatment, the trees were subjected to simulated rainfall of 0.0, 0.25, 1.25, or 2.54 cm. A negative linear relationship existed between rainfall and oil retention. Peach leaves receiving 0.25, 1.25, and 2.54 cm rainfall retained 81%, 38%, and 18% of the applied oil, respectively. Oil retention by apple leaves was also negatively related to rainfall. For both species, a negative linear relationship existed between oil retention on stems and rainfall. There was no effect of emulsifier on retention of 1% soybean oil after rain on apple leaves or on the retention of 8% to 11% soybean oil on the stems of apple and peach. Scanning electron microscopy revealed that epicuticular wax occurred as striations on apple and peach leaves. The wax morphology on peach and apple stems appeared as thin plates and platelets, respectively. The wax morphology of leaves and stems of both trees was not affected either by the soybean oil emulsions or rain. Both emulsions induced stomatal closure in leaves and peach stems, however, stomates opened after rainfall of 1.25 or 2.54 cm. The lenticels appeared to be unaffected by either emulsion. Results illustrate that rainfall of 2.54 cm washed off a major portion of the applied oil. Thus, respraying may be needed under natural climatic conditions with rainfall ≥2.54 cm to restore the efficacy of applied soybean oil.
Polyphenols were analyzed in expanding buds and developing leaves of pecan [Carya illinoensis (Wangenh.) C. Koch] cultivars with varying responses to Cladosporium caryigenum (Ell. et Lang. Gottwald), the organism causing scab. Plant tissue extracts were examined by high-performance liquid chromatography using a water: methanol gradient to separate polyphenolic components on a C-18 reversed phase column. A diode-array detector was used to identify profile components by retention times and computer matching of ultraviolet spectra to standard compounds in a library. Concentrations of these polyphenols were compared throughout the growing season in leaves of pecan cultivars with low (`Elliott'), intermediate (`Stuart'), and high (`Wichita') susceptibility to scab; during susceptibility to infection by Cladosporium caryigenum from 16 cultivars; and in `Wichita' leaf discs with and without scab lesions. The major polyphenolic constituent of tissues for all cultivars was identified as hydrojuglone glucoside, which was detected in intact buds and leaves throughout the growing season. Hydrojuglone glucoside concentration increased concomitantly with leaf expansion and then declined slowly. Juglone was barely, if at all, detectable, regardless of leaf age. No correlation was found between cultivar susceptibility to pecan scab and the levels of either juglone or hydrojuglone glucoside in the healthy leaves of 16 cultivars. Leaf tissue with scab lesions had significantly higher juglone and hydrojuglone glucoside levels than leaf discs without scab lesions. Chemical names used: 4-8-dihydroxy-1-naphthyl b-d-glucopyranoside (hydrojuglone glucoside); 1,5-hydroxy-naphthoquinone (juglone).
Peach-to-nectarine mutations are associated with broad pleiotropic effects. The present study addresses the heritability of nectarine-specific effects in three hybrid families. A comparison of peach and nectarine siblings showed that nectarine fruit were smaller (less fresh weight), rounder, darker, redder, and had higher levels of sugars and organic acids. These heritable characteristics are similar to effects of spontaneous peach-to-nectarine mutations described previously.
Four greenhouse leaf inoculation methods for screening Japanese plum (Prunus salicina L. and hybrids) for resistance to Xanthomonas campestris pv. pruni (Smith) Dye were compared for repeatability, ability to differentiate among plant genotype responses, and correlations with field ratings. Clonally propagated trees were inoculated artificially in a greenhouse by immersing leaves in 2.5 × 108 cfu/ml inoculum (DIP), rubbing the adaxial side of leaves with a slurry of 2.5 × 108 cfu/ml inoculum and Carborundum powder (CARB), infiltrating leaves with 5 × 105 cfu/ml inoculum using a needle-less syringe (INFS), and infiltrating with 5 × 106 cfu/ml inoculum (INF6). No greenhouse method was superior in all assessment categories. The CARB method was most repeatable (t = 0.78) but had a low Spearman's correlation (rs = 0.29), indicating that greenhouse rankings did not correspond closely with field rankings. The INF6 method was unsuitable because it did not differentiate between plant genotypes. The DIP method appeared most suitable, having moderate repeatability (t = 0.46) for four observations per leaf and moderate Spearman's correlation with field performance (rs = 0.56). The INF5 method may be appropriate for identifying bacterial spot resistance that is associated with resistance in the leaf mesophyll.
Abstract
The stems of 3 clones of Dianthus were studied at weekly intervals from August through November and the cold-hardiness as well as the peroxidase isoenzyme complement was determined. The hardening patterns showed indications of the typical plateau, this occurring at −10 to −14°G in November. The time of initiation of hardening correlated well with the winter-hardiness of the clones, the hardiest clone undergoing hardening 2 to 3 weeks before the tender clone. As determined by acrylamide gel electrophoresis of the stem extracts, the 2 winter hardy clones showed a gradual synthesis of 2 to 4 new peroxidase isoenzymes during the hardening period, whereas the tender clone showed only a relatively weak initiation of one isoenzyme. The formation of the new isoenzyme preceded the period of hardening by several weeks to more than a month, depending on the specific isoenzyme and the clone.
Abstract
Storing ‘McIntosh’ apples (Malus domestica Borkh.) initially in 1.0% or 1.5% CO2 plus 1.0% O2 at 3°C (LO) was more effective in retarding firmness loss than initial storage in 4.5% or 5.0% CO2 plus 3.0% O2 at 3° (SCA), indicating that early exposure to LO suppressed the subsequent rate of softening in SCA. ‘McIntosh’ firmness retention, determined 1 day after storage and after 7 days at 20°, decreased with fruit maturity for all LO and SCA storage regimens, but mature fruit tended to soften more rapidly in SCA after being exposed initially to LO. Initial storage in SCA for >75 days with subsequent storage in LO (in 1984) did not result in firmer apples than those stored continuously in SCA. The initial exposure period in LO needed to induce retention of apple firmness depended on cultivar and temperature. For ‘McIntosh’, ‘Spartan’, and ‘Golden Delicious’ cultivars, respectively, maximum post-storage fruit firmness was reached after 7.5, 4.5, and 1.5 months of initial exposure to LO at 0° and after 4.5, 3.0, and 3.0 months at 3°. Poststorage evolution of CO2 and C2H4 and the severity of senescent disorders generally decreased with continuing storage in LO, but the incidence of low-O2 injury increased. Poststorage ethanol evolution increased with exposure to 1.0% O2 in ‘McIntosh’ apples stored at 0°, and ‘Spartan’ apples held at either 0° or 3°. Chemical name used: butanedioic acid mono(2,2-dimethylhydrazide) (daminozide).