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Open access

A. N. Lakso

Abstract

Six-year-old ‘Empire’/Malling 7 (M7) apple (Malus domestica Borkh.) trees were left unpruned or pruned moderately during dormancy, and early-season leaf area development patterns were examined. Pruning markedly shifted leaf area distribution from spur to extension shoot. Leaf area at and shortly after bloom nearly doubled in the unpruned trees due to the increased percentage of the leaf area in rapidly developing spurs; however, the final total leaf areas were not affected significantly by the pruning. Leaf area development in all trees slowed dramatically around full bloom. Yields were reduced in the pruned trees primarily due to fewer flower clusters. Leaf areas per tree correlated well with percentage of sky values from fisheye photography.

Open access

A. N. Lakso

Abstract

A technique for characterizing apple (Malus domestica Borkh.) tree canopies using fisheye (hemispherical) photography is described. The technique has the advantages of speed of sampling and analysis, and of providing permanent records of canopy structure. Photographs were taken inside the canopy, and the percentage sky visible determined by densitometry. The percentage sky in the photographs was correlated to the light climate at the site of the photograph.

Free access

M. Bepete and A.N. Lakso

To determine relative dry-matter partitioning to early-season growth of extension shoots vs. fruits under competitive conditions in the shade, heavily cropping branch sections of `Empire' apple (Malus ×domestica Borkh.) were girdled and shaded to 15%, 40%, and 60% of available light for 9 days, while control branches were girdled and fully exposed. Treatments were applied at both 17 and 27 days after bloom, when fruit diameters averaged 13 and 23 mm, and the number of unfolded leaves on extension shoots averaged 13 and 19, respectively. Fruit diameters, extension shoot lengths, and numbers of unfolded leaves were monitored on the treated branches. Shoot growth was not affected by shading at either growth stage. Fruit growth rate was similar at 100% and 60% available light, but declined 25% at 40% available light and 50% at 15% available light. These results indicate that shoot growth has priority over fruit growth for partitioning in light-limiting conditions early in the season.

Open access

A. N. Lakso and R. C. Musselman

Abstract

Interior diffuse light readings were taken in trees of semi-dwarf ‘Wayne’ and ‘Golden Delicious’ apple (Malus domestica Borkh.) on days of varying cloudiness. Interior light to shaded spurs was found to be greatest when the total light outside the tree was 60 to 90% of maximum, due to higher diffuse light with haze or light cloudiness. Diffuse light available to a shaded site within the canopy is a function of exterior diffuse light levels and canopy density as affected by cultivar. Calculations of whole canopy photosynthetic potential from light data and photosynthetic light response, indicate that haze or cloudiness is needed to obtain maximum whole canopy rates.

Open access

R.S. Johnson and A.N. Lakso

Abstract

The relationship of leaf area and stem weight, with stem length at different times during the year, was studied on 5 apple (Malus domestica Borkh.) cultivars. Leaf area was related linearly to stem length, but the slope differed by up to 2-times between cultivars. Stem dry weight increased curvilinearly with respect to stem length and showed less variation among cultivars than did leaf area. These 2 relationships combined indicated that the stem constitutes an increasing proportion of the total shoot weight with increasing stem length. Dormant stems had a greater weight per unit length than stems of growing shoots. Both stem length and leaf area showed strong fitting linear relationships with accumulated growing degree-days, but the stem length relationship showed less variability among cultivars than did leaf area.

Open access

R.S. Johnson and A.N. Lakso

Abstract

A computer model simulating the C balance of a growing ‘Jonamac’ apple (Malus domestica Borkh.) shoot was constructed to estimate the time of first net carbohydrate export from the shoot. The model was based on measurements of net photosynthesis and dark respiration rates and estimates of the dry weight in the different components of the shoot. Under the prevailing weather of 1981, the model indicates that a shoot growing to a final length of 50 cm became a net exporter of carbohydrates 19 days after budbreak, a time corresponding to a shoot 4 cm long with 10 unfolded leaves. Assuming the same early growth rates, a shoot with a final length of 2 cm starts exporting at 15 days after budbreak. The total export of carbohydrates remains higher from short shoots than long shoots until 36 days after budbreak, indicating that short shoots supply greater amounts of carbohydrates to the rest of the plant during this early period. The model estimates the total import of carbohydrates from reserves of about 165 mg for the long shoot and 80 mg for the short shoot. In each instance, these reserves only accounted for about 20% of the total carbohydrates used by the shoot up to that point. The remainder was supplied by current photosynthates.

Open access

R.S. Johnson and A.N. Lakso

Abstract

A computer model of a growing apple (Malus domestica Borkh.) shoot was used to estimate the effects of light and temperature on the C balance of a shoot. Long-term average solar radiation (langley/day) and maximum and minimum temperatures from Geneva, N.Y., were used as weather inputs. To simulate other weather conditions, solar radiation was increased or decreased by 150 langley/day, and maximum and minimum temperatures increased or decreased by 5.6°C. Both a short shoot of 2 cm and a long shoot of 50 cm final length were simulated. The model output indicated that increased light reduced carbohydrate import and caused earlier and greater export. Increased temperature increased carbohydrate import and the subsequent rate of carbohydrate export. The short shoot had a greater initial rate of C export and continued to export more total carbohydrates than the long shoot for about 30 to 50 days after budbreak. Slow leaf area development at a given temperature had little effect on carbohydrate import but delayed the beginning of export.

Open access

D. C. Ferree and A. N. Lakso

Abstract

Three hand pruning systems (annual, biennial, and triennial) and 2 combinations of mechanical hedging and hand pruning were compared on 6 cultivars of apple (Malus domestica Borkh.) on Mailing (M) 26 planted in 1968 at a spacing of 3.6 × 6 m. In general cultivars responded similarly to the pruning treatments. After 6 years the pruning treatments had no apparent influence on trunk circumference and tree height, but hedging decreased tree spread. There were similar light levels with all pruning treatments. Inserting limb spreaders and pruning annually had the highest labor requirements and was among the better treatments in inducing larger fruit size, accumulated yield/tree, yield/trunk cross sectional area and revenue/tree. Hedging plus biennial pruning had a smaller labor requirement and was equivalent to annual pruning in fruit size, accumulated yield/tree, yield/trunk cross sectional area and revenue/tree. Hedging followed by annual pruning resulted in the lowest number of fruit/tree, accumulated yield/tree and yield/trunk cross section and was considered the least desirable treatment.

Open access

A. N. Lakso and S. G. Carpenter

Abstract

Treatment of headed-back 1-year-old dormant shoots of ‘Monroe’, ‘McIntosh’ and ‘Wayne’ apple (Malus domestica Borkh.) with 1% naphthaleneacetic acid (NAA) in latex paint was relatively ineffective and gave inconsistent results; however, treatment of mechanically hedged shoots on established trees gave statistically significant reductions in regrowth, by reducing bud break of dormant buds on older wood. Regrowth in ‘Monroe’ trees was reduced with daminozide primarily by reducing shoot length.

Free access

L. Corelli Grappadelli, A.N. Lakso, and J.A. Flore

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.