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  • Author or Editor: J. A. Flore x
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Abstract

The strawberry (Fragaria X ananassa L.) ‘Midway’ and ‘Guardian’ were grown runnerless at several within-row spacings (8-47 cm). The proportion of dry matter allocated to fruit was negatively correlated with spacing distance for ‘Guardian’ (r = 0.68), but positively correlated for ‘Midway’ (r = 0.91). Total crown weight was positively associated with plant-spacing distance for ‘Guardian’ (r = 0.88) but not for ‘Midway’ (r = 0.05). Specific leaf weight was positively correlated with spacing for both cultivars.

Open Access

The commercial strawberry Frageria × ananassa and several clones of F. chiloensis and F. virginiana were preconditioned in growth chambers under the following conditions: 500 μmol m-7s-1 PAR and 20° day, 10° night or 30° day and 20° night. After at least 3 weeks of preconditioning at the two different temperature regimes, leaf photosynthetic rate (A) was determined for temperatures ranging from 10 to 35° in 2-3° increments with an open gas exchange system under laboratory conditions. The objective was to determine if F. virginiana and F. × ananassa can photosynthesize at higher temperatures than F. chiloensis, and if any of these would acclimate to higher temperatures. F. chiloensis did not acclimate to higher temperatures, and bad maximum A between 16 and 20°. F. virginiana did acclimate to higher temperatures, with maximum A for the low temp treatment between 18 and 24°, and for the high temp treatment between 24 and 30°. The commercial cultivars of `Earliglow' and `Redchief' acclimated to higher temperature and responded similar to F. virginiana.

Free access

Abstract

CO2 assimilation (A), leaf conductance to water vapor (gl), mesophyll conductance (gm), and water use efficiency (WUE) were compared for two cultivars of highbush (Vaccinium corymbosum L.) and a wild diploid lowbush blueberry species (Vaccinium darrowii Camp.) in response to PPF, CO2, temperature, and vapor pressure deficit (VPD) to determine if apparent tolerance of V. darrowii to high temperature and drought conditions resulted from differences in gas exchange characteristics. Cultivar differences between ‘Bluecrop’ and ‘Jersey’ in A were not significant when expressed on a leaf area, leaf dry weight, or total chlorophyll basis. Maximum CO2 assimilation rates for V. darrowii were about 35%, 50%, or 40% lower than highbush cultivars when expressed on a leaf area, leaf dry weight, or total chlorophyll basis, respectively. Differences between ‘Bluecrop’ and ‘Jersey’ were also non-significant for mesophyll conductance, transpiration, CO2 compensation points, and water use efficiency. CO2 assimilation maximized between 600-800 µmol·s–1·m–2 photosynthetic photon flux (PPF) for all three genotypes and the temperature optima ranged between 18° and 26°C for ‘Jersey’, 14° and 22° for ‘Bluecrop’, and 25° and 30° for V. darrowii. As temperature was increased from 20° to 30°, leaf conductance (gl) to water vapor was lower and water use efficiency was higher for V. darrowii, compared to ‘Bluecrop’ but not ‘Jersey’. There was a 50-65% reduction in gl as VPD was increased, but only 10–20% reduction was observed in A. Leaf conductance to water vapor was reduced for V. darrowii, which restricted intercellular CO2. Since crosses are possible between highbush and V. darrowii, it is possible that heat tolerance and/or drought resistance could be improved in Highbush blueberry through the incorporation of genes from V. darrowii.

Open Access

Abstract

A model which predicts terminal and spur leaf emergence of sour cherry (Prunus cerasus L. cv. Montmorency) grown near East Lansing, Michigan was developed from biological and temperature observations made in orchards near Egg Harbor, Wisconsin. Leaf number of spur and terminal shoots was more highly correlated with degree-day accumulation at a base of 4°C starting April 19, than with time. Leaf number on individual shoots was linear with respect to degree-day accumulation; however, not all growth on an individual tree was synchronous, and the plot of average leaf number vs. time was slightly curvilinear. Terminal buds set about 350 and 850 degree-days after first leaf emergence for spur and terminal shoots, respectively, regardless of location. Leaf size increased linearly with degree-day accumulation until full leaf expansion. At maturity terminal leaves were about 50% larger in area than spur leaves. Foliage growth was greatest during stage I and early stage II of fruit growth, and may compete with the fruit for assimilates needed for growth.

Open Access

Abstract

Hybrid geraniums (Pelargonium × hortorum Bailey) cv. Sooner Red were grown at temperatures ranging from 10–32°C and at various quantum flux densities. The time to visible bud stage (<0.5 cm diameter) was negatively correlated to quantum flux density at a given temperature. The time required from visible bud to flower stage was negatively correlated with temperature while light had no effect. Leaf thickness, number of palisade layers, and specific leaf weight were negatively correlated with temperature, and specific leaf weight was positively correlated with quantum flux density at a given temperature. Net photosynthetic rate ranged from 5–38 mg CO2 dm-2hr-1 for temperatures of 10-37° and was optimum at 20-32°. The Q10 of respiration for hybrid geranium leaves was about 2.2.

Open Access

Abstract

Changes in surface characteristics of the adaxial and abaxial cuticular membranes of expanding ‘Red-haven’ peach [Prunus persica (L.) Batsch] leaves were followed and related to wettability and to retention and penetration of foliar-applied compounds. Epicuticular wax deposition increased with leaf development until full expansion, the maximum being 50 to 65 μg cm−2. Although wax fine-structure was not prominent on expanding leaves, localized areas of crystalline wax occurred on both surfaces of fully expanded leaves. The 2 surfaces differed markedly in the composition of the epicuticular wax. Although triterpenoid acids, alkanes and primary alcohols were present on both surfaces, sterols and esters were predominant on the adaxial surface. Marked changes in composition occurred with leaf age. The contact angles formed by aqueous droplets on the adaxial surface increased with leaf development and attained the highest value only after full leaf expansion; on the abaxial surface the contact angle increased sharply and approached a maximum at 70 to 80% full expansion. Retention of aqueous solutions decreased with leaf expansion. Permeability of the cuticular membrane, as indexed by transpirational loss and penetration of 14C-NAA (naphthaleneacetic acid), decreased progressively with increasing leaf age. These findings are discussed in relation to spray application and penetration of foliar-applied chemicals.

Open Access

The partitioning of photosynthates labeled by 14CO2 in exposed and shaded `Empire' apple (Malus domestica Borkh.) branches was examined at 1, 3, 5, and 10 weeks after bloom. Extension shoots, nonfruiting spurs, or fruiting spurs were labeled separately to examine which shoot types exported to the fruit at each time. The general partitioning patterns were observed with autoradiography, while label accumulation in fruit was determined by oxidation and scintillation counting. At each treatment time, half of the branches was preconditioned with artificial shade (to 35% full light) for 48 hours before labeling and returned to the shade for a 2-day translocation period. One and 3 weeks after bloom, extension shoots showed little export to fruit; nonfruiting and vigorous fruiting spurs exported label to weak spurs and extension shoot tips. Shade had no major effect on partitioning patterns at 1 and 10 weeks, but essentially eliminated export from extension shoots at 3 weeks and greatly reduced export to fruit 5 weeks after bloom, as observed on the autoradiograms. At 5 weeks after bloom, the shading effect was equal to a 2-week delay in export. By 10 weeks after bloom, all shoot types were exporting most of the 14C fixed to fruit. The photosynthate support of the fruit before fruit set seemed to strongly depend on the spur canopy, especially when the extension shoots were exposed to low light.

Free access

Abstract

Two sour cherry (Prunus cerasus L.) cultivars ‘Montmorency’ and ‘Meteor’ were evaluated over two seasons to determine the relative importance of different components of yield. A path coefficient analysis was performed to determine the direct and indirect effects of primary, secondary, and tertiary components on limb yield. Fruit number, fruit weight, the number of lateral buds and spurs, and fruit set were found to be the most important components affecting limb yield in both cultivars. However, the fruiting habits of the two cultivars were significantly different. ‘Montmorency’ produced 68% of its fruit on lateral buds on 1-year-old wood, while ‘Meteor’ had 70% of its fruit on 2-year-old spurs. When the data were standardized by dividing by limb cross-sectional area, ‘Meteor’ had a higher flower bud density (number of flowers/cm2) and yield efficiency (grams of fruits/cm2) than ‘Montmorency’. Although ‘Meteor’ had higher limb yields than ‘Montmorency’, the ‘Montmorency’ trees sampled had about four times more limbs than ‘Meteor’, and, therefore, higher tree yields.

Open Access

A simulation model for determining flower bud phenological stages and fruit growth as a function of daily maximum and minimum temperatures was developed for `Montmorency' sour cherry (Prunus cerasus L.). The models were developed and tested with observations collected in the three major sour cherry production areas in Michigan located in northwestern, western central, and southwestern sections of the lower peninsula. Observations of flower bud phenology and fruit diameter were collected at 3- to 7-day intervals, in spurs and terminal shoots across multiple years. Nonlinear equations using accumulation of growing degree-days (base 4 °C) as an independent variable were fitted to observed flower bud phenological stages and fruit diameter, expressed as percentage of final fruit diameter. Simulated bud phenology stages were in agreement with observed data. Mean differences of simulated vs. observed dates of early phenological stages in the three production areas were between 4 and 1 days for side green and near 0 days for tight cluster, while during later stages (e.g., first bloom and full bloom) mean differences ranged from -2 to 0 days. Means differences of predicted fruit diameter were in the range of 0 to -3 days. Needing only daily temperature data, these simulation models have potential applicability in improving the timing and efficiency of management decisions related to crop phenology, such as pest control, fertilization, and irrigation.

Free access

Abstract

Conjugation of 14C-1-naphthaleneacetic acid (NAA) was followed in leaf discs of apple, apricot, grape, orange, peach and pear. NAA was metabolized by all crops studied. Free NAA and 2 metabolites that chromatographed with naphthylacety1-β-D-glucose (NAG) and naphthylacetylaspartic acid (NAAsp) constituted 90% of the radioactivity recovered, NAG was the major metabolite (45-90%) followed by NAAsp (5-30%) and NAA (2-22%). Conjugation was most complete in orange (98%), intermediate in apple, apricot, peach and pear and least in grape (68%).

Open Access