Terminal Shoot Length Research Articles

Exposure of red spruce seedlings to acid mist: importance of droplet composition just prior to drying periods.

Two-year-old red spruce (Picea rubens Sarg.), raised from seed collected at five locations from Maine to North Carolina, were exposed in a greenhouse to either sulphuric or nitric acid mist (median pH 2-85). Exposures were performed three times a day, four days a week over an eleven-week period during the growing season. Each exposure consisted of 4 h of misting followed by a 3.75 h drying period. Immediately before each drying period, acidic droplets were either left to dry directly on the foliage or were removed by a 15 min deionized water (diw) rinse. When sulphuric acid droplets dried directly on the foliage, visible injury developed and to a lesser degree the same was true for nitric acid. When acidic droplets were replaced with dim before each drying period, foliar injury did not develop despite misting for hundreds of hours at pH values well within the range that has caused visible injury in previous experiments. When acidic droplets dried directly on foliage, needle dry weight was reduced, but differences between sulphuric and nitric acid exposure were not found. No treatment effects were found on terminal shoot length. Treatment responses among seedlings from different seed resources were similar, with greater variation found within provenances than between provenances. We conclude that the composition of liquid on foliage at the end of wet deposition events and the processes occurring during drying periods are important factors in determining the response of red spruce to acidic cloudwater.

067 SHOOT ORIENTATION AFFECTS PEACH SHOOT AND FRUIT GROWTH

One-year old fruiting shoots averaging 50 cm in length were tagged according to naturally-occurring orientations ranging from vertical to horizontal throughout the canopies of dormant `Encore' peach (Prunus persica L Batsch) trees. Following fruit set, tagged shoots were thinned to two or three fruit per shoot. Fruit diameter, terminal shoot extension, and shoot orientation were measured at intervals throughout the season. Fruit were harvested at uniform maturity based on ground color for assessment of fresh weight, diameter, percent red blush, and red color intensity. A linear relationship (p=.001) was found between final fruit size and initial orientation, with fruit diameters 6 percent larger on shoots initially oriented horizontally than those initially vertical. Fruit size differences were not detected until the last two to three weeks of growth. Fruit size response to orientation was found to be independent of light. Red color development was not influenced, probably due to fairly uniform light environments within the canopies. Terminal shoot length was linearly related to initial orientation, with shoots initially oriented horizontally having the least terminal shoot extension. Development of lateral shoot growth in relation to shoot orientation will be discussed.

Variation in shoot growth components among western larch families

Shoot growth components, including predetermined growth, free growth, number of stem units, and mean stem unit length, were evaluated over two growing seasons (8th and 9th) for their contribution to variation in lateral shoot length of 14 families of western larch (Larixoccidentalis Nutt.). All families produced some free growth stem units in both years, averaging 21 and 20% of the total number of stem units in years 8 and 9, respectively. Significant variation was detected among families in total number of stem units and predetermined growth stem units in both years, in mean stem unit length and terminal shoot length at age 8, and in lateral shoot length and tree height at age 9. Lateral shoot length and terminal shoot length were highly correlated with each other, as well as with the total number of stem units and predetermined growth stem units in the lateral shoot. Free growth stem units in the lateral shoot at ages 8 and 9 were not significantly correlated with 8- and 9-year terminal shoot growth or height at age 9. However, the total number of stem units in lateral shoots was well correlated with 8- and 9-year terminal shoot length and with 9-year height. The implications of these results for early selection for increased height growth are discussed.

Chilling of Endodormant Peach Propagules: IV. Terminal Shoot Growth of Cuttings, Including Gibberellic Acid Treatments

Cuttings from peach (Prunus persica (L.) Batch cv. Johnson Elberta) trees were subjected to five chilling durations (20 to 76 days) at seven temperatures (0 to 14C) and five concentrations of gibberellic acid [GA, (0.0 to 1 mm)]. There was a significant increase in terminal shoot length with longer chilling treatments. Cuttings treated at 2 to SC had the longest shoots, and shoot length decreased, in order, following treatment at 10, 0, and 14C. Treatment with the highest concentration of GA, resulted in the longest terminal shoots. Interactions between GA and chilling durations indicated that either higher concentrations of GA, or longer chilling treatments increased terminal shoot growth. Thus, endogenous promoters, like GA, are evidently produced or released during chilling. Sensitivity to GA, was also important. Chemical name used: Gibberellic acid (GA3).

Chilling of Endodormant Peach Propagules: III. Budbreak and Subsequent Growth of Physiologically Dwarfed to Near Normal Seedlings

We studied the response of physiologically dwarfed (PD) to near normal peach [Prunus persica (L.) Batsch] seedlings (`Johnson Elberta' seeds) to various chilling treatments. Peach seedlings were obtained by forcing seeds that had been subjected to a brief stratification treatment. Seedlings were divided into four types (groups) according to the length of the primary stem and the presence and size of lateral branches. The seedlings were used in a chilling study with treatments of five durations (20 to 60 days) at four temperatures (2 to 14C). Terminal shoot growth and lateral budbreak were recorded 17 days after forcing. Shoot and leaf dry weight were obtained after seedlings had grown for 64 days. Budbreak and growth improved with the duration of the chilling treatment. Generally, 7C was the best chilling temperature, with 2 or 10C only slightly less effective. Treatment at 14C did not promote budbreak or growth. Budbreak and growth had significant interactions between treatment duration and temperature. The seedling type and treatment duration interaction was significant for terminal shoot length, lateral budbreak, and leaf dry weight, but were probably the result of differences between the seedling types before treatment and not true interactions with the length of the treatment. There was a significant interaction between the seedling type and treatment temperature on terminal shoot growth. Subsequent shoot growth did not differ significantly between the seedling types after similar chilling treatments. Thus, shoot growth was the best indicator of the chilling process of `Johnson Elberta' peach seedlings. Indicators of dormancy removal such as lateral budbreak or terminal shoot growth after 17 days forcing were not good predictors of subsequent seedling growth.

Spatiotemporal distribution of epicormic shoots and their architecture in branches of Fraxinuspennsylvanica

Epicormic shoots in the branch systems of Fraxinuspennsylvanica var. subintegerrima (Vahl) Fern, (green ash) were more common on lower order shoots and arose periodically over a number of years, resulting in a greater number in older crown regions. Nevertheless, considerable variation existed among trees, ranging from 3 to 34 epicormic shoots per branch sample. Epicormic shoots were generally located near the distal end of parent shoots, suggesting their origin from persistent buds in these regions. The mean divergence angle of epicormic shoots was almost 10° greater than that of nonepicormic shoots. Mean length did not differ between epicormic and nonepicormic shoots, but the length of daughter terminal shoots extending epicormic shoots was considerably less than the length of those extending nonepicormic shoots. The number of lateral shoots produced by the two shoot types did not differ. The significance of epicormic shoot production to crown development and maintenance is discussed.

Reduced Rates and Multiple Sprays of Paclobutrazol Control Growth and Improve Fruit Quality of `Delicious' Apples

`Gardiner Delicious'/MM.lO6 apple (Malus domestics Borkh.) trees were initially sprayed in 1985 with paclobutrazol (PB) at 250 mg.liter-1 at tight cluster and again on 10 and 25 June and 29 July. From 1986 through 1988, PB sprays of 85 or 100 mg·liter-1 were applied at either petal fall (PF) + 2 or PF + 4 weeks and one to two additional sprays were applied per year when growth resumed. Promalin was applied to one group of trees that received PB starting at PF + 2 weeks. PB reduced terminal, lateral, and total shoot growth the year of application and in subsequent years. Although average shoot length of lateral and terminal shoots was reduced, the greatest reduction in growth occurred because PB prevented spurs from growing into lateral and terminal shoots. Compared to unsprayed trees, PB reduced pruning time in all 4 years by 23% to 70%. PB increased bloom only the first year after application, but increased fruit set for 2 years due to a carryover effect. Application of PB in 1985 caused a reduction in fruit size, sometimes in soluble solids concentration, length: diameter (L : D) ratio, and pedicel length. Promalin either overcame the reduction in the ratio or increased it in 1986. Reduced rates of PB in subsequent years caused few adverse effects on the fruit. PB increased flesh firmness when applied at PF + 2 weeks but not at PF + 4 weeks. Trees treated with PB produced fruit with higher flesh Ca and less bitter pit, cork spot, and senescent breakdown following regular air storage. Chemical names used: ß -(4 -chlorophenyl)methyl α -(1,1-dimethylethyl) -1H-l,2,4-triazole-1-ethanol (paclobutrazol, PB); gibberellins A4+7 plus N-(phenylmethyl) -1H-purine-6-amine (Promalin).

Effects of growth regulators on growth and fruiting of own-rooted ‘Golden Delicious’ apple trees

Established tissue-culture propagated own-rooted cultivar ‘Golden Delicious’ apple ( Malus domestica Borkh.) trees were treated with paclobutrazol at a dosage of 40 mg cm −2 of trunk cross-sectional area (average of 1.48 g per tree) via trunk drench at the end of the fifth growing season. They responded the second season after application. Treatment with the triazole GA biosynthesis inhibitor had more effect on vegetative growth than on flower cluster or fruit number. It reduced terminal shoot length and tended to reduce fruit yield and seasonal net photosynthesis on a leaf area basis. Weight per fruit was not changed but fruit length tended to be slightly reduced whereas russeting index was increased. Promalin (GA 4 + 7 + BA) applications to paclobutrazol-treated trees did not alter growth or fruiting. Despite the fact that paclobutrazol inhibited terminal shoot growth, treated trees went into biennial bearing as readily as untreated trees after a heavy fruit load season. Vegetative growth was vigorous the “off year” and terminal shoot growth was no longer inhibited by paclobutrazol. Applications of GA 4 + 7 to trees during the “off-year” did not affect vegetative growth that season or fruiting the following season. “On year” yield tended to be reduced from trees that had been treated with paclobutrazol 5 years earlier.

Patterns of Abies fraseri Regeneration in a Great Smoky Mountains Spruce-Fir Forest

PAULEY, E. F. AND E. E. C. CLEBSCH (Graduate Program in Ecology, University of Tennessee, Knoxville, TN 37996-1610. Pattems of Abiesfraseri regeneration in a Great Smoky Mountains spruce-fir forest. Bull. Torrey Bot. Club 117: 375-381. 1990.-Abiesfraseri (Pursh) Poir. (Fraser fir) has incurred high mortality from infestation by Adelgespiceae Ratz. (balsam woolly adelgid). Vegetational changes in the spruce-fir forest since Adelges infestation have included a large increase in the density of Rubus canadensis L. (thomless blackberry). Size and age structures, microsite and aspect distributions, and growth of Abies seedlings (stems < 137 cm tall) were quantified on Mt. Collins, Great Smoky Mountains National Park in 1988 to determine pattems of co-occurrence between Abies seedlings and Rubus. The majority (87%) of seedlings were c25 cm tall, and most (62%) were at least five years old. No germinal (< 1 year old) Abies were found. Dead wood substrates and bryophyte-covered surfaces both supported more seedlings than expected by chance. Seedling growth trends showed a recent increase in terminal shoot length and recent decreases in lateral shoot lengths, suggesting a combination of normal growth pattems and recovery from Adelges infestation. Effects of Adelges infestation were noted for 26% of all seedlings and were more frequent among older seedlings. Density of Abies seedlings was low at high Rubus densities, but seedling shoot growth showed no clear relationship with Rubus density. Rubus appeared to interfere with establishment or survival of Abies seedlings but not with annual growth.

Effects of paclobutrazol and of ethephon on cropping and vegetative growth of ‘Crimson Gold’ nectarine trees

Cultivar ‘Crimson Gold’ nectarine trees ( Prunus persica (L.) Batsch) were treated with paclobutrazol (PP333) as a trunk drench and fruits were thinned either by hand or by a spray with ethephon. No interactions between PP333 and ethephon were found. PP333 decreased fruit drop and increased yield, whereas ethephon had no effect. A higher percentage of crop was harvested at the first picking from PP333-treated trees, but the level of soluble solids was lower than that for fruits from untreated trees. Hand-thinning and ethephon at 120 mg l −1 increased the percentage of fruits picked on the first picking. Vegetative growth was reduced by PP333, both in terms of terminal shoot length and relative trunk girth increment. PP333 advanced bloom the year after treatment, but reduced the number of flowers injured by frost, resulting in almost a double yield. Shoot growth was reduced the year after the application of PP333.

Shoot production in Douglas-fir branches

Of the 3981 shoots present in 1986 on 16 Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) branches, 6–12 years old, only 1933 produced new shoots in 1987, and of these only 311 produced more than one shoot. Length of new terminal shoots was determined primarily by the length of the parent shoot (R2 = 0.57). Shoots that did not elongate had blunt buds, &lt; 1 mm long, with no leaf primordia; shoots that elongated had pointed buds, &gt; 2 mm long, with many leaf primordia. Buds &lt; 1 mm long survived up to 3 years without elongating; needles on these shoots survived an additional 2 years. Parent shoots longer than 13 cm all elongated. The percentage of parent shoots &lt; 14 cm long that did not elongate, and would have subsequently died, increased with (i) decreasing parent shoot length; (ii) increasing whorl number along the main axis of the branch (toward the branch base); (iii) decreasing total elongation of all shoots on the branch, a measure of branch vigor.

Growth, Leaf Mineral Nutrition, and Leaf Water Status of Mature Apple Trees Subjected to Various Crop Loads and Soil Water Conditions

Abstract Mature fruiting and defruited ‘McIntosh’/M.26 apple (Malus domestica Borkh.) trees were exposed to natural rainfall or to no rainfall with the use of under-canopy tent-like covers. With covers present, fruit diameter tended to be less and, on one occasion, soluble solids concentration and fruit firmness increased. Trunk growth was reduced more by fruit than by covers. Trunk growth of fruiting trees did not respond to covers, whereas trunk growth of defruited trees was reduced by covers. Fruit load and reduced soil water content did not affect terminal shoot length. In one experiment, specific leaf weight (SLW) was less for fruiting trees than for defruited trees. Fruiting increased foliar N, P, Ca, and Mg and decreased K concentration. On a leaf-area basis, K was again lower in cropping trees while other nutrients remained mostly unchanged. With tent covers, trees generally had less foliar N, P, and K based on either concentration or amount per unit of leaf area. Leaf water potential was lower for trees with fruit and tended to be lower for trees with tent covers. Leaf stomatal conductance was higher for fruiting trees than for defruited trees and higher for trees without tent covers than for trees with tent covers.

Growth and Fruiting of Apple and Cherry Trees as Affected by Trunk Looping

Abstract Trunk looping of several apple cultivars on seedling roots reduced terminal shoot growth and trunk enlargement below the loop and increased root suckers. Growth was reduced most in the early years of tree growth. In the 5th, 6th, and 7th growing seasons, annual trunk enlargement was not affected, but growth suppression in the 2nd, 3rd, and 4th years reduced final trunk diameter measurements after seven seasons. Similarly, terminal shoot length was suppressed greatest in the early years and to a lesser extent in the 5th through the 7th growing seasons. Fruit number was unaffected by looping in the 5th growing season, but looping increased fruit number and fruit/cm2 trunk cross-sectional area in the 6th and 7th seasons in ‘Golden Delicious’, ‘Starkrimson Delicious’, and ‘Northwest Greening’, but not ‘Stayman’.

Sample Size Estimates for Peach Tree Growth and Yield Experiments

Abstract Trunk cross sectional area (TCA), TCA enlargement, yield, yield efficiency, and terminal shoot length were recorded for each of 10 peach [Prunus persica (L.) Batsch] trees in plantings ranging in age from 4-15 years. Sample variances were used to estimate the number of trees per treatment needed to detect differences of a desired magnitude in experiments comparing 2 treatments. In general, 30 trees per treatment were required to detect a 15% difference in TCA and yield, while more than 40 trees per treatment were needed to detect a similar difference for TCA enlargement and yield efficiency. Twelve trees per treatment and 6 to 22 shoots per tree, depending on cultivar, could be expected to detect a 15% difference in terminal shoot length.

The Influence of Summer Pruning and Cropping on Growth and Fruiting of Apple

Abstract Trees of apple [Malus domestica Borkh. cvs. Jonathan/Malling (M) 26] were summer-pruned each August from 1978-1980 by heading all shoots longer than 10 cm, and their response was compared to trees receiving only a light dormant-pruning by thinning-out cuts. Cropping treatments were a full crop or defruiting in June. Final length of shoot regrowth on summer-pruned trees was 82% and 76% less than terminal growth of control trees in 1979 and 1980, respectively, but terminal shoots produced the year following pruning were 55% and 62% longer on summer-pruned tress than on controls in 1979 and 1980, respectively. Summer-pruned trees with a full crop had 13% shorter terminal shoot length than defruited trees in 1979, but cropping had no effect in 1980. Trees with a full crop had a smaller annual increase in trunk cross-section than defruited trees, but were not affected by summer pruning. Summer pruning restricted tree canopy dimensions, resulting in 43% less canopy volume than control trees in 1979 and 1980, increased canopy openness to light penetration, and hastened flower opening. Pruning treatments did not affect fruit set. Fruit yield per tree was reduced by summer pruning, but yield per canopy volume was not affected. Fruit size was decreased by summer pruning in 1979 but was increased in 1980. Fruit soluble solids were reduced by summer pruning in 1979 and 1980, fruit color was increased in 1978 and 1980, but not in 1979. Flesh firmness was unaffected by summer pruning.

Effects of Disbudding on the Shoot Mortality, Growth, and Bud Production in Red and Sugar Maples

In studies of insects boring in maple buds, the effects of bud destruction on the growth and form of trees and branches are difficult to measure because the infestations vary greatly. To determine these effects, small red maple trees, 3–4 ft tall, and branches on red and sugar maple trees, 15–18 ft tall, were disbudded at 4 intensities on May 9, 1962. Measurements made 10 months later revealed that sugar maple was very sensitive to all levels of disbudding. After complete disbudding, 70% of the 1961 and 10% of the 1960 terminal shoot growth was killed and the terminal function was not assumed by any of the adventitious shoots. In comparison with the controls, the removal of all terminal buds of sugar maple branches caused about 65% reduction in terminal shoot length; 35% in total shoot length; 45% in 1962 shoot diameter; 15% in 1961 shoot diameter; and 47% in bud production. Removal of only the distal terminal bud caused the same pattern of damage, but the growth reductions were less severe. Red maple, which was much less sensitive to disbudding than sugar maple, produced a statistically significant reduction of the measured variables only when all buds were removed. Ten percent of the 1961 terminal shoots were killed by complete disbudding and 1.5% by removal of all terminal buds. Small red maple trees and branches on large trees were very similar in their reaction to the treatments. The findings are discussed relative to recent literature on auxin production.