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A rootstock planting was established with `Starkspur Supreme Delicious' apple (Malus dornestica Borkh.) on nine rootstock near Blacksburg, Va. Five uniformly sized fruit per tree were sampled 1 week before normal harvest and three five-fruit samples were taken at harvest. Rootstock had no consistent effect on the proportion of red surface, which averaged ≈90% Ground color was most yellow for fruit from trees on M.26 EMLA and least yellow from trees on M.27 EMLA, OAR1, and MAC24. Starch was lowest for fruit from trees on MAC9 and (Ottawa) 0.3 and highest from trees on OAR1 and MAC24. Firmness differences were neither large nor consistent and ranged from 71 to 78 N. Soluble solids concentrations (SSC) of fruit were consistently high for fruit from trees on MAC9 and 0.3. A maturity index was calculated from the two harvest samples per year. Data for SSC, starch ratings, and ground color were ranked, and the highest maturity index was for fruit from trees on 0.3, MAC9, and M.26 EMLA.
Abstract
There was no effect of rootstock on the net photosynthesis (Pn) of 1-year-old vegetative, containergrown ‘Delicious’ trees in 2 experiments. Rootstock effects on specific leaf weight (SLW) were slight in one experiment, and absent in another. There was no influence of rootstock on shoot growth, leaf number, transpiration rate (Tr) or dark respiration (Rd), each of which was determined in one experiment. These data fail to support reports of differences in Pn within a given cultivar on various rootstocks.
Hurricanes or strong winds occasionally damage apple trees in the northeastern and mid-Atlantic regions of the U.S. Following the wind event, trees may be leaning or may be lying flat on the ground with extension root damage. Commercial growers generally pull trees upright while the ground is still moist and support the tree or just the trunk with various types of posts providing support to a height of about 60 to 200 cm above ground. In some cases the trees are pulled partially upright and propped up with boards or sand bags may be placed on the upwind side of the tree. Research data are not available for comparing various methods of treating the trees following wind damage, but field observations indicate that trees perform well if trees are pulled upright within 2 or 3 weeks after the wind event. Data from rootstock research plantings from several states indicate that tree anchorage is influenced by the combination of scion cultivar and root-stock. In Virginia in 1989, Hurricane Hugo brought wind gusts of about 95 km·h–1 when the ground was completely saturated by heavy rains. Trees in several plantings designed to evaluate rootstocks or cultivars were evaluated for the extent of leaning following the storm. The percentage of leaning trees on M.26 EMLA was <10% for `McIntosh' and `Golden Delicious' and 40% for `Delicious'. Susceptibility of trees on M.7A was also influenced by scion cultivar, with 0% for `Golden Delicious' and `Empire', 2% for `Redchief Delicious', and 88% for `TripleRed Delicious'.
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.
Abstract
Young container-grown apple (Malus domestica Borkh.) trees and mature bearing trees were summer pruned either before or after shoot extension had ceased. Net photosynthesis, dark respiration, and transpiration of shoot leaves were increased by summer pruning, while stomatal resistance was decreased as compared to dormant pruned controls. These effects were more pronounced and of longer duration in basal leaves of container-grown trees and interior leaves of orchard trees than in distal or peripheral leaves, respectively.
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.
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.
Abstract
Changes in photosynthetic parameters in ‘Stayman’/Malling Merton (MM) 111 apple (Malus domestica Borkh.) trees measuring 5 m wide and 4 m high were studied for an entire growing season. Parameters investigated included penetration of photosynthetically active radiation (PAR), changes in spur leaf net photosynthetic (Pn) potential, dark respiration (Rd) and specific leaf weight (SLW). As measured by changes in PAR penetration, canopy development was generally complete by mid-May. Pn, Rd, and SLW were modified by canopy position. SLW was influenced by the previous light environment as peripheral canopy leaves had higher SLW’s than interior leaves.
Abstract
Several summer pruning treatments were applied in August to ‘Stayman’/Malling Merton (MM) 111 apple (Malus domestica Borkh.) trees measuring 4m high and 5m wide to examine the resulting changes in light climate. Diffuse photosynthetically active radiation (PAR) increased immediately by about 1/5 on the periphery and 1/10 within the canopy from 2 types of summer pruning. These changes in PAR had no effect on net photosynthetic (Pn) potential, dark respiration (Rd), or specific leaf weight (SLW) determined 21 and 54 days after pruning. One method of summer pruning reduced penetration of PAR into inner canopy positions the year following treatment.
Abstract
Two experimental growth regulators, CGA-15281 (beta-chloroethyl-methyl-bis-benzyloxy-silane) and an analogue, CGA-17856, induced leaf abscission in peach (Prunus persica (L.) Batsch). Responses paralleled temperature following treatment. Older leaves were more responsive than younger ones and abscission occurred prior to leaf senescence. Applications prior to rainfall indicated about 6 hours without wetting was needed for maximum chemical activity. CGA-17856 tended to cause more leaf abscission than CGA-15281.