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Free access

Richard P. Marini, John A. Barden, and Donald Sowers

Three-year-old `Campbell Redchief Delicious'/MM.111 [Malus domestica (Borkh.)] trees were subjected to a factorial arrangement of annual pruning treatments (removal of excess scaffold limbs vs. no removal, heading the terminal extension shoot on scaffold limbs vs. no heading) plus a treatment involving gradual removal of excess scaffold limbs. Six years after treatments were initiated, pruning treatment did not influence tree height or trunk size. Tree spread was greatest for nonheaded trees. Although yield, yield efficiency, and gross returns were reduced by either type of pruning, there was significant interaction between limb removal and heading. Compared to no limb removal or heading, limb removal plus heading reduced cumulative gross returns by ≈ $12,800/ha.

Open access

Bruce Schaffer, John A. Barden, and Jerry M. Williams

Abstract

Deblossomed ‘Tribute’ strawberry (Fragaria × ananassa Duch.) plants had increased [14C]-photosynthates in untreated leaves 48 hr after treatment with 14CO2. The summed quantity of radioactivity in the untreated leaves and fruit of fruiting plants approximated that in the untreated leaves of deblossomed plants. There was no effect of deblossoming on the amount of 14C in the crown or roots. Autoradiographs showed that the majority of 14C was in the expanding leaves. Therefore, increased leaf production rates, which often result from deblossoming strawberry plants, may be attributed to an increase in photosynthates partitioned to the expanding leaves.

Open access

Karen L. Kerkhoff, Jerry M. Williams, and John A. Barden

Abstract

Leaf loss increased net photosynthesis (Pn) or delayed senescence of the remaining leaves in several plant species (2, 3, 7, 8). Strawberries are commonly defoliated during planting and after fruiting. The objective of this study was to determine the effects of partial defoliation on Pn rates and growth of the strawberry.

Open access

Richard P. Marini and John A. Barden

Abstract

Summer pruning of ‘Starking Delicious’, ‘Golden Delicious’, or ‘Stayman’ apple (Malus domestica Borkh.) trees in mid-August (about 14 weeks after full bloom) did not suppress shoot growth the following year, as compared to similar pruning prior to budbreak in early April. ‘Stayman’ trees pruned in June had more regrowth than those pruned in August. A 1% naphthaleneacetic acid (NAA) solution applied to the summer pruning cut prevented regrowth. The increase in trunk and branch circumference was reduced by August pruning, as compared to dormant pruning. Summer pruning did not influence total bloom the year following treatment, but summer pruning for 2 consecutive years reduced the amount of bloom on 2-yr-wood. Cutting to the first spur on 2-year-wood in August did not suppress shoot growth the following year as compared to heading back to 4 leaves on current season's wood.

Open access

Richard P. Marini and John A. Barden

Abstract

Summer pruning of vigorous ‘Starking Delicious’ apple (Malus domestica Borkh.) trees in mid-August (14 weeks after bloom) increased light penetration throughout the tree canopy for the remainder of the season. Light levels were lower in summer pruned trees than in similarly dormant pruned control trees the season following treatment. Relative light penetration measured with a selenium cell on clear days was similar to diffuse light penetration measured with a quantum sensor on overcast days until late summer. During late summer, when the developing fruit caused the branches to spread, diffuse light penetration on overcast days was greater than the penetration of direct light on clear days. Reduced light penetration the year following summer pruning resulted in lower specific leaf weight (SLW) of interior leaves as compared to interior leaves on dormant pruned trees. Specific leaf weight of peripheral leaves on dormant pruned trees declined in October, while SLW of leaves on summer pruned trees did not decline. The delayed decline in SLW may have been due to improved light conditions and/or delayed leaf senescence. Regardless of treatment, SLW of interior leaves did not decline in October.

Open access

Richard P. Marini and John A. Barden

Abstract

Autoradiography was used to examine the movement of assimilate from basal leaves of first-year, container-grown greenhouse Mailing Merton (MM) 111 apple trees (Malus sp.) exposed to 14CO2 either 2 or 21 days following summer pruning. Two days after summer pruning, the majority of 14C was transported to the roots regardless of treatment. Control trees exhibited a similar pattern of transport 3 weeks after summer pruning, while in summer-pruned trees, photosynthate moved primarily to regrowth. Prevention of regrowth with naphthaleneacetic acid (NAA) resulted in transport of photosynthate primarily to the roots.

Open access

Bruce Schaffer, David L. Bubenheim, and John A. Barden

Abstract

Net photosynthesis (Pn), transpiration (Tr), and stomatal conductance for CO2 (gs) were determined at 26° ± 1°C for leaves on intact and excised apple shoots at different vapor pressure gradients (VPG’s). Pn, Tr, and gs of leaves on intact and excised shoots responded similarly to changes in VPG. Pn and gs were not affected directly by VPG. Tr increased as VPG increased since stomatal closure did not counterbalance the increased VPG.

Free access

Richard P. Marini, John A. Barden, John A. Cline, Ronald L. Perry, and Terence Robinson

The influence of rootstock on average fruit weight was evaluated for a subset of data from a multilocation NC-140 apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] rootstock trial. Data for eight dwarf rootstocks were collected at four locations for 2 years. Analysis of covariance was used to evaluate the effect of rootstock on average fruit weight when crop density or number of fruit per tree was included in the linear model as a covariate. When number of fruit harvested per tree was used as a covariate, average fruit weight was not affected by rootstock in either year in Ontario. In Michigan and Virginia, rootstock and number of fruit per tree, but not the rootstock × number of fruit interaction, were significant, so common slopes models were used to estimate least squares means for average fruit weight. In general, trees on M.27 and P.1 produced the smallest fruit, and trees on B.9, M.9 EMLA, and Mac.39 produced the largest fruit. In New York the interaction of rootstock × number of fruit was significant, so least squares means were estimated at three levels of number of fruit per tree. Both years, at all levels of number of fruit, trees on M.26 EMLA produced the smallest fruit and trees on M.27 EMLA produced the largest fruit. Average fruit weight was most affected by number of fruit per tree when Mark was the rootstock. In general, results were similar when crop density was used as the covariate, except that trees on M.27 EMLA did not produce small fruit in Michigan and Ontario.

Open access

John A. Barden, Terry B. G. DelValle, and Stephen C. Myers

Abstract

Individual scaffold limbs on 5-year-old ‘Red Prince Delicious’ apple (Malus domestica Borkh.) trees on five rootstocks were unpruned or pruned in Aug. 1981 or Feb. 1982 using three severities at each time. Responses to summer and dormant pruning were similar; no significant interactions occurred. In Dec. 1982, branch circumference was inversely related to pruning severity. Compared to the control, all pruning severities decreased shoot number and increased mean shoot length in 1982; only the most severe pruning suppressed total shoot growth. Flowering and fruiting in 1983 were inversely related to pruning severity.

Open access

Robert F. Polomski, John A. Barden, Ross E. Byers, and Dale D. Wolf

Abstract

Terbacil, a photosynthetic inhibitor, and shade applied to apple (Malus domestica Borkh) limbs and whole trees altered the contents of fruit nonstructural carbohydrates and induced fruit abscission. Shade (92%) from 5 to 15, 10 to 20, 15 to 25, 20 to 30, and 25 to 35 days after full bloom (DAFB) induced fruit abscission. At 15 and 20 DAFB, fruit from limbs shaded for 10 days contained less total nonstructural carbohydrates (TNC) than fruit from limbs shaded for 0 or 5 days. Terbacil at 50 and 100 ppm applied to whole ‘Redchief Delicious’ trees at 15 DAFB markedly inhibited net photosynthesis. Fruit dry weight, TNC, total sugars, and reducing sugars declined with increasing rates of terbacil and 100 ppm resulted in abscission of all fruit. Trees treated with 0 and 50 ppm retained 4.6 and 1.4 fruit per cm2 of limb cross sectional area (LCSA), respectively. Terbacil at 75 ppm and 92% shade were applied to whole ‘Redchief Delicious’ trees at 18, 23, and 28 DAFB. Fruit dry weight and contents of total sugars and reducing sugars were lowered by shading and terbacil. Shade for 5 or 10 days induced total fruit drop. Terbacil at 75 ppm resulted in 0.8 vs. 2.9 fruit per cm2 of LCSA on the controls. Chemical name used: 5-chloro-3-(1,1-dimethylethyl)-6-methyl-2,4(1H,3H)-pyrimidinedion (terbacil).