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  • Author or Editor: L. Mills x
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Abstract

Low temperature injury to flower buds of peach [Prunus persica (L.) Batsch.] and sweet cherry [Prunus avium L.] and to one-year-old shoots of peach and apricot (Prunus armeniaca L.) during fall and winter was more severe on trees treated with paclobutrazol (PP 333) than on those not treated. Paclobutrazol had no measurable effect on cold resistance of apricot buds or cherry shoots. The average date of 1st bloom was advanced by one to 2 days in all 3 species by paclobutrazol.

Open Access

Crop-specific tailoring of fertilizer composition and timing of application reduces expense and runoff pollution. We examined the effects N forms and ratios have on growth, development, and utilization of nutrients in poinsettia (Euphorbia pulcherrima Willd. Ex Klotz.). Rooted cuttings of poinsettia `Freedom' were grown to flowering (10 weeks) in aerated solution culture under greenhouse conditions. Treatments consisted of five N ratios (percent ammonium: percent nitrate) of 100:0, 75:25, 50:50, 25:75, and 0:100 with a total N concentration of 150 mg·L–1. Dry mass for all plant parts and height increased as the ratio of NO 3 increased. Leaf and bract areas were greatest with ratios of 25:75 and 50:50, respectively. Plants receiving 100% NH 4 + exhibited severe ammonium toxicity symptoms and uptake of all macronutrients was suppressed. Average weekly uptake of NH 4 + , NO 3 , P, and K was significantly affected by the treatments. Maximum uptake of NO 3 and K occurred with 100% NO 3 , P with 25:75, and NH 4 + with 100% NH 4 + . Uptake averaged across all treatments was divided into physiological growth stages (GS) to identify peak demand periods. The greatest uptake of NH 4 + and NO 3 was from the beginning of treatments to floral induction (GSI). Uptake of P, K, and Mg peaked at GSII, floral induction to visible bud. Visible bud to anthesis (GSIII) had the lowest uptake for all nutrients. These results demonstrate how NH 4 + : NO 3 ratios and stage of development can influence growth and nutrient absorption.

Free access

Abstract

As ‘Bing’ cherries (Prunus avium L.) matured, the quality characteristics changed rapidly but not consistently from year to year over 9 years. Color increased rapidly and at similar rates in all years. Soluble solids increased rapidly during years when the crop was light, but slowly when the crop was heavy. When crops were light, the fruit was full sized before color reached fresh market standards and there was no further growth as the fruit continued to mature. With heavy crops the fruit increased in size until they began to shrivel. Early in maturation the fruits were very firm, but they softened rapidly during the early fresh market stage, then more slowly.

Open Access

Abstract

Several aspects of hardiness behavior in ‘Bing’ cherry and ‘Elberta’ peach fruit buds were compared. Cherries averaged 2.1°C hardier than peaches. The difference was least in late fall and early spring, and greatest during winter. High temp caused the minimum hardiness level of peaches to rise by mid-winter; cherries not until late winter or early spring. Cherries hardened more rapidly than peaches during cold days. During dormancy cherry and peach buds hardened when temp was below -1.1 to -2.2°, dehardened when above that level. Hardening rates up to 1.9° per day for peaches and 2.8° for cherries were observed. Cherry buds hardened by cold days lost 6.1° of hardiness in 4 hr when exposed to 24°C.

Understanding of fruit bud hardiness in peach and cherry has progressed far enough that use of low temp control measures during winter, based on critical temp from laboratory evaluations, seems feasible.

Open Access

The relationship between heat tolerance and cold hardiness was examined during the winter of 1992-93. Dormant canes of Cabernet Sauvignon were collected from an experimental vineyard at approximately two to three week intervals. Samples were held overnight at 0-3 C. Subsamples were removed from storage and subjected to either room temperature for 4 1/2 hours, 45 C for 35 minutes followed by room temperature for 4 hours or held at 0-3 C. Samples were then subjected to either heat treatment (52, 54, 56, 58, or 60 C for 30 minutes) or low temperature exotherm analysis.

Pretreatment at 45 C improved the heat tolerance but did not change cold tolerance. Holding samples at room temperature resulted in a slight improvement in heat tolerance. Additional implications of these findings will be presented.

Free access

Abstract

Chemical regulation of cold hardiness is a fascinating objective for pomological research. In the past 5 years gibberellic acid (GA) and N-dimethylamino succinamic acid (Alar) have been reported to increase fruit bud hardiness of peaches (3, 4, 7). Trees treated with these two chemicals and 2-chloroethane phosphonic acid (Ethrel) were exposed to -11°F on December 30, 1968, permitting us to observe their effects on resistance of fruit buds to cold injury.

Open Access

An increase in mechanical pruning of Concord grapevines in Washington has led to a marked increase in yield. In 1993 the average yield for the 20,000 plus acres was slightly greater than 12 ton/acre. As part of a long term study, initiated in 1987, to evaluate the effects of mechanical pruning on Concord yield and fruit quality, we have also followed bud cold hardiness and winter injury over several years. Cold hardiness was monitored using low temperature exotherm analysis of excised buds. Winter injury was evaluated by visual examination of bud and cane tissues collected from vines with different croploads. In 1990 the average yield for mechanically pruned vines was 13T/ac and for balance pruned vines about 8T/ac. Winter injury during December 1990 showed significantly less injury to mechanically pruned vines whether primary, secondary or tertiary buds were examined. During the winter of 1991-92 and 1993-94 bud cold hardiness of individual vines showed no relationship to cropload per vine.

Free access

Abstract

Flower buds from 10 ‘Bing’ cherry (Prunus avium L.) and 5 ‘Elberta’ peach (Prunus persica [L.] Batsch) orchards were tested for cold resistance each week for 3 years during the dormant and pre-bloom periods. The cold resistance of dormant buds was most affected by temperature prior to sampling. Additionally, buds from certain sites were consistently more resistant than buds from others. Elevation, soil type, and cultural practices are the site characteristics likely to influence cold resistance of buds. During the pre-bloom period differences among sites were closely related to bud development which, in turn, was associated with elevation and temperature.

Open Access

Abstract

(2-Chloroethyl)phosphonic acid (ethephon) applied Sept. 8, 1971 at 250 and 500 ppm delayed sweet cherry (Primus avium L.) bloom 3 to 5 days, thereby reducing spring freeze injury and increasing yield. Preliminary data from a nonfrost year indicate no deleterious effect of treatment on maturity or quality.

Open Access

Nutritional levels of mature vs. young leaves of Anthurium (Anthurium andraeanum Linden.) cultivars were determined over a seven year period. Nutritional levels for essential nutrients tested (B, Ca++, Cu++, Fe++, K+, Mg++, Mn++, Mo-, P, and Zn++) were determined with inductively coupled plasma emission spectrometry. Kjeldahl N was determined with a flow injection analyzer. The young leaf, 90% mature, was determined to be the most accurate predictor of the nutritional status of anthuriums. These values were established for the cultivars `Kozohara', `Nitta Orange', `Kaumana', and `Ozaki'.

Free access