Lateral Shoot Growth Research Articles

325 Evaluation of `Meeker' Red Raspberry Freeze Tolerance using Whole-plant Growth and Root Electrolyte Leakage Viability Tests

In Spring 1996, `Meeker' red raspberry root cuttings were planted into a sandy loam soil in 30 cm tall x 27 cm diameter black plastic containers. During Mar. 1997, a second bottomless container was placed over the overwintering canes of half of the plants. The second container was filled with the same sandy loam soil to simulate ridging of the plants. All plants were grown using standard cultural practices on an outdoor, gravel nursery bed. Freeze tolerance of potted whole plants and excised root sections was measured at 5 °C intervals between -5 and -20 °C in a series of laboratory freeze tests conducted during Jan. 1998. Electrolyte leakage data were used to calculate the index of injury for excised roots while whole-plant response to freezing was determined by measuring the subsequent growth of floricane lateral shoots and of primocanes. After 1 month in the greenhouse, results indicated the dry weight of primocanes harvested from plants that were exposed to -20 °C was 56% of the nonfrozen control primocane dry weight. Primocane dry weight from plants exposed to -5, -10 and -15 °C was not different from the controls. Similar results were obtained for the percent of floricanes that were alive and for the dry weight of laterals produced by these floricanes after 3 months in the greenhouse. The whole-plant freeze test results indicated plants at the lowest temperature, -20 °C, were injured but not killed. Root index of injury of single potted plants averaged 5%, 15%, 29%, and 58% at -5, -10, -15, and -20 °C, respectively.

The effect of reduced quantities of photosynthetically active radiation on Fraxinus pennsylvanica growth and architecture

The quantity and quality of light have significant effects on tree growth and architecture that can be highly variable depending on the shade tolerance of the species. A study was conducted to determine the effect of decreased availability of photosynthetically active radiation (PAR) on the growth and architecture of green ash (Fraxinus pennsylvanica var. subintegerrima (Vahl) Fern.), a moderately shade-tolerant species. Twenty-four seedlings were planted in each of five shade treatments (4, 8, 20, 40, and 100% of full sun, respectively). Measurements made over a 2-year period revealed that with decreased PAR levels there was generally a reduction in leaf thickness, number of shoot units per shoot, shoot-unit length, shoot growth, branching frequency, lateral shoot growth, and shoot biomass. However, in moderate reductions of PAR, there were increases in shoot unit numbers, overall shoot length, and branch numbers. The overall effect of heavy shading was to produce a tree with little height growth and a poorly developed crown.Key words: Fraxinus, shading, seedling morphology, shoot unit, light quantity, architecture.

Timing and Severity of Summer Pruning Affects Flower Initiation and Shoot Regrowth in Sweet Cherry

To examine the effect of timing and severity of summer pruning on flower bud initiation and vegetative growth, 4-year-old `Bing' cherry trees (Prunus avium L.) were pruned at 31, 34, 37, 38, or 45 days after full bloom (DAFB) with heading cuts 20 cm from the base of current-season lateral shoot growth, or at 38 DAFB by heading current-season lateral shoot growth at 15, 20, 25, or 30 cm from the base of the shoot. The influence of heading cut position between nodes also was examined by cutting at a point (≈20 cm from the shoot base) just above or below a node, or in the middle of an internode. Summer pruning influenced the number of both flower buds and lateral shoots subsequently formed on the shoots. All of the timings and pruning lengths significantly increased the number of both flower buds and lateral shoots, but differences between pruning times were not significant. There was significantly less regrowth when shoots were pruned just below a node or in the center of an internode, rather than just above a node, suggesting that the length of the remaining stub may inhibit regrowth somewhat. The coefficient of determination (r2) between flower bud number and regrowth ranged from -0.34 to -0.45. In young high-density sweet cherry plantings, summer pruning may be useful for increasing flower bud formation on current-season shoots. The time of pruning, length of the shoots after pruning, and location of the pruning cut can influence subsequent flower bud formation and vegetative regrowth.

Induction and Culture of Apex of Axillary Shoots of Papaya in Vitro from Mature Field-grown Trees

The papaya (Carica papaya L.) is a tropical fruit tree grown in many coastal region of Colima. The experiments were conducted to optimize cultural requirements for induction and culture of shoot of C. papaya cv. Red Lady in vitro. The crown, fruits, and leaves were removed from 1-year-old trees in the field for stimulate growth of lateral shoots with application of 289 μM gibberellic acid solution along steam surface. Apex (2 × 2 mm) of the shoots induced were established in Drew and Smith (DS) medium containing 1 μM 6-benzylaminopurine (BAP) and 1 μM naphthaleneacetic acid (NAA). After 90 days of establishment, the explants were transferred to a multiplication medium consisting of DS medium containing different concentrations of BAP and NAA (0:0, 2:0.1, 2:0.5, 2.5:0.5 and 3:0.5 μM, respectively). Individual shoots were excised from the proliferating cultures and subcultured onto fresh medium at 30- to 40-day intervals. The shoot number induced of trees in the field was of 47.5 per plant. After three subculture of shoot the best multiplication factor per subculture (6.9) was when 2 or 2.5 uM of BAP and 0.5 μM of NAA were added to DS medium.

Effect of different types and concentrations of plant growth retardants on Sturt's desert pea ( Swainsona formosa)

Sturt's desert pea ( Swainsona formosa) has potential as a flowering pot plant, if the uneven and excessive vegetative growth can be controlled by the use of growth retardants. Ancymidol, chlormequat, daminozide, flurprimidol and paclobutrazol were applied to Sturt's desert pea (SDP) in glasshouse experiments. Paclobutrazol (PBZ) at 10 mg a.i./plant consistently produced a compact pot plant with more lateral shoots. Flurprimidol at 0.5 and 1 mg a.i./plant reduced main shoot growth but had little effect on lateral shoots. CCC had no significant effect. Ancymidol at 10 or 25 mg a.i./plant and daminozide at 2500 and 5000 mg a.i./plant produced less attractive plants with serious symptoms of toxicity. Suppression of lateral shoot growth required higher concentrations of PBZ and flurprimidol compared to the main shoot.

Effective Vegetative Growth Control of Apples with BAS 125W

When applied as a dilute spray (at 125 and 250 ppm), BAS 125W effectively reduced shoot extension growth on `York' Imperial (YI) and `Spartan' (S) apple trees but was less effectively on `Delicious' (D). In 1994, lateral shoot growth of YI/M.26 trees (1 to 2 m tall) from 10 May to 7 July was reduced (35 vs. 7 cm) by sprays applied on May 13. The initial surge of growth by vertical shoots was suppressed by the treatments (16 vs. 35 cm), but there was more regrowth (6.5 vs. 0.5 cm). Some leaf injury was seen on YI. The 1995 experiments were conducted on S/M.111 and D/M.111 in an orchard spaced 3.7 m by 7.3 m. On S, lateral shoot length on five dates from 7 June to 20 Sept. was reduced by the sprays (44 vs. 32 cm on 20 Sept.). The initial surge of growth by vertical shoots was suppressed by the treatments (30 vs. 85 cm), but there was more regrowth (34 vs. 4 cm). There were fewer apples that were <25% red and more that were 25% to 40% and 66% to 85% red. On D, lateral shoot length on five dates from 7 June to 20 Sept. was reduced by the sprays (51 vs. 38 cm on 20 Sept.). The growth of vertical shoots was not influenced by the treatments, possibly due to a light fruit load in the tops of the trees. Growers viewing the 1995 plots estimated enhanced income of $933/ha for D and $780/ha for S.

`Pinot noir' and `Riesling' Grapevines Respond to Water Stress Duration and Soil Water-holding Capacity

Glasshouse-grown `Pinot noir' and `Riesling' grapevines (Vitis vinifera L.) were subjected to one of four water stress durations [no water deficit (control); and water deficits imposed postbloom, lag phase, and veraison] in combination with three soil water-holding capacities (0%, 26%, and 52% gravel, by volume). Vines subjected to increasing water stress duration had less cumulative lateral shoot length and lower shoot count, leaf size, and berry weights than those not stressed. Soluble solids concentration (SSC) during maturation and pH at harvest also increased with increasing water stress duration, but titratable acidity was not affected. Transpiration and stomatal conductance also were reduced with increased water stress duration, but soil water increased, reflecting the larger leaf surface on vines with veraison-imposed deficits. Reducing water-holding capacity (by increasing the percentage of gravel in the soil) tended to increase berry weight and SSC but reduced lateral shoot growth. The 52% gravel treatments increased transpiration rate and stomatal conductance for `Riesling' but reduced them slightly in `Pinot noir'. Percentage of soil moisture was reduced linearly with reduced water-holding capacity. These results indicate that early irrigation deficits may advance fruit maturity of wine grapes with concomitant reductions in vegetative growth. Differential responses of these cultivars to soil water-holding capacity also should help to identify suitable wine grape cultivars as the wine grape industry expands into areas with low water-holding capacity soils.

Shoot Density Affects `Riesling' Grapevines I. Vine Performance

`Riesling' grapevines (Vitis vinifera L.) were subjected for 4 years (1987-90) to three shoot densities (16, 26, and 36 shoots/m of row) combined with three crop-thinning levels (1, 1.5, and 2 clusters/shoot) in a factorialized treatment arrangement. Weight of cane prunings per vine (vine size) decreased linearly with increasing shoot density and clusters per shoot. Cane periderm formation (in terms of percent canes per vine with >10 ripened internodes) was inhibited by increased shoot density, while vine winter injury (primarily bud and cordon) increased slightly in a linear fashion with increasing clusters per shoot. Canopy density and leaf area data suggested that fruit clusters were most exposed to sunlight at a shoot density of 26 shoots/m of row due to reduced lateral shoot growth and a trend toward slightly smaller leaves. Yield, clusters per vine, and crop load (yield per kilogram of cane prunings) increased with increasing shoot density and clusters per shoot, while other yield components (cluster weight, berries per cluster, and berry weight) decreased. Soluble solids and pH of berries and juices decreased with increasing shoot density and clusters per shoot, but titratable acidity was not substantially affected. Free volatile terpenes increased in berries and juices in 1989 with increasing shoot density, as did potentially volatile terpenes in 1990. Shoot densities of 16 to 26 shoots/m of row are recommended for low to moderately vigorous `Riesling' vines to achieve economically acceptable yields and high winegrape quality simultaneously.

946 GROWTH AND DEVELOPMENTAL RESPONSES OF POINSETTA TO CALCIUM NITRATE AND TO 6-BA

Some studies have shown that the presence of calcium ions greatly influence the growth of lateral shoots in poinsettia. Rooted cuttins were transplanted in 13.14 cm dia. plastic pots and grown on Metro-mix soil, fertilized with 20-10-S osmocote and watered as needed. Plants were sprayed with 300 & 600 ppm of ca(NO3)2. Others treated with 500 ppm of 6-BA, plus 300 and 600 ppm of Ca(NO3)2 and then with 500 ppn of 6-BA. Some plants were left without treatments as check. The average number of lateral bud breaks were highest on plants treated with 6-BA when compared to plants treated only with Ca(NO3)2 and the check. The number of lateral bud breaks increased from an average of 11 on the 5th day to 15 on the 30th day whenever 6-BA was applied. The average length of lateral shoots also increased from an average of 10mm the 5th day to over 23mn on the 30th day when 6-BA was applied, but the presence of Ca(NO3)2 at 300 ppm lateral shoot growth was greater than at 600 ppm. In general, the average growth rate in height increased in all treatments compared to the check and the presence of Ca(NO3)2 further increased the growth in height. Finally, the foliage growth rate (in diameter) was greatly influenced by 6-BA and 600 ppm of Ca(NO3)2.

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.

Lateral bud-burst and shoot growth in horizontally trained stems of low-pruned mulberry plants (Morus alba L.)

Lateral bud-burst and shoot growth in horizontally trained stems of low-pruned mulberry plants (Morus alba L.)

Cadmium accumulation and bioavailability in Coontail (Ceratophyllum demersum L.) plants

The aquatic vascular plant (Ceratophyllum demersum L.) was investigated as a potential biological filter for removal of Cd from wastewaters. Plants were grown in and harvested weekly from 0.10 M Hoagland nutrient solutions containing concentrations of Cd from 0.01 to 1.03 μg Cd mL−1. Tissue Cd was positively correlated to increased concentrations of Cd in solution. Concentration factors (CFs) of Cd in plants after one week were 13.3 for the 0.01 μg Cd mL−1 treatment; 451.4 for plants treated with 0.04 μg Cd mL−1, and 506.5 for plants treated with 1.03 μg Cd mL−1. Plants treated with 0.01 μg Cd mL−1 sustained tissue Cd concentrations almost 9-fold over those at week 1. However, after 5 weeks tissue Cd concentration in plants exposed to 1.03 μg Cd mL−1 had decreased 97% compared to the week 1 concentration. Growth measurements of dry weight, stem lengths, and lateral shoot growth were nagatively correlated to increased Cd treatments. Our results suggest that Coontail exposed to very low Cd concentrations (0.01 μg Cd mL−1) can take up and accumulate Cd. However, plants exposed to Cd at 0.04 μg Cd mL−1 or above did not accumulate Cd past one week.

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.

Chilling of Endodormant Peach Propagules: II. Initial Seedling Growth

We observed initial peach [Prunus persica (L.) Batsch] seedling growth after endodormant (ED) seeds (`Johnson Elberta') had been stratified for five durations (20 to 60 days) at eight constant temperatures (0 to 18C). Seedling growth increased and became more normal when seeds were stratified for longer durations at chilling temperatures. Stratification (St) at 0 to 6C (especially 2C) produced seedlings with more abnormal growth than St at higher temperatures (8 to 10C) at intermediate St durations (30 to 50 days). Growth of the primary stem increased with additional St (0 to 14C). Abnormal (epinastic) leaf development decreased following longer St treatments at 4 to 14C. Lateral shoot growth increased initially, then decreased after longer treatments at low temperatures (0, 4, and 6C) and decreased after St at higher temperatures (8 to 10C).

In vitro branching in relation to repeated subculture in two cultivars of Potentilla fruticosa

The in vitro branching pattern of two ornamental cultivars of Potentilla fruticosa L. was analyzed quantitatively with respect to repeated subculture. In both cultivars, in vitro multiplication occurred predominately by axillary branching. There was little callus and few adventitious shoots were produced. In the more vigorous cultivar, ‘Snowbird’, there were up to 5 orders of branching. In the other cultivar, ‘Pink Whisper’, there were rarely more than 3 orders of branching. In both cultivars, apical dominance was weak in vitro and all but the youngest axillary buds were released. Differences in branching appeared to be related to the degree of apical control of lateral shoot growth. In ‘Snowbird’, where control was weak, lateral branches grew vigorously producing several bud sites for higher order branching. For both cultivars, shoot multiplication was at its maximum at the beginning of the experiment and then declined to a more or less steady level. These patterns indicated that apical control was weakest at the beginning of the experiment and then increased during repeated subculture. Nevertheless, in ‘Snowbird’, there was evidence of a gradual increase in multiplication rate toward the end of the experiment.

Lateral shoot formation and flower-bud formation in apple in the first year after budding as affected by air temperature and exposure to red light

Under controlled environment conditions the effect of three air temperatures (16°, 21°, and 26°C) and of low-intensity red light during the night (at 21°C only) on the vegetative development and flower-bud formation of apple trees (cvs Rode Boskoop and Elstar) were evaluated in the first year after budding. Day and night temperatures were the same; soil temperature was 17°C. The vapour pressure deficit of the air was low (about 0.40 kPa at each temperature). Shoot growth increased with increasing temperature especially in the 16-21°C range. The growth effects were mainly reflected in lateral shoot growth. At 16°C lateral growth was poor (in ‘Boskoop’) or almost absent (in ‘Elstar’). At 26°C, lateral shoots was more evenly spread along the main axis than at lower temperatures. Exposure to red light had no effect on growth. Flowering on the main stem and on the lateral shoots were considerably less at higher temperature. The same held when only clusters with more than four well developed flowers were consid...

Advancement of `Riesling' Fruit Maturity by Paclobutrazol-induced Reduction of Lateral Shoot Growth

Paclobutrazol (PB) was sprayed on hedged `Riesling' (Vitis vinifera L.) vines at one of five concentrations (0, 1000, 2000, 3000, or 4000 mg·liter-1) as single annual applications over 3 years (1987-89). Observations were made on growth, yield, and fruit composition during the years of application and 1 year thereafter (1990) to test carryover effects. PB had no effect on vine vigor, expressed as weight of cane prunings, during the three application years, but reduced vine vigor linearly with concentration in 1990. Yield was reduced by PB in the first 2 years of the trial, while in one season cluster weight and berries per cluster were also reduced. °Brix was increased by PB during all 3 years of application; titratable acidity was reduced and pH increased in the first year of application. PB sprays significantly reduced lateral shoot length, mean leaf size on both main and lateral shoots, and total leaf area on main and lateral shoots. Winter injury to buds, cordons, and trunks was also reduced with increasing PB level. Residues of PB in fruit in the first year of application ranged from 9 μg·kg-1 at the 0-m·gliter-1 level to 638 μg·kg-1 at the 4000-mg·liter-1 level. PB shows promise as a viticultural tool for advancement of fruit maturity, with possible additional benefits such as improved vine winter hardiness. Chemical name used β -[(4-chlorophenyl) methyl]-α -dimethylethyl)-1-H-1,2,4-triazole-l-ethanol (paclobutrazol, PB).

Combined Effects of Spirea Aphid (Homoptera: Aphididae) and Nitrogen Fertilization on Shoot Growth, Dry Matter Accumulation, and Carbohydrate Concentration in Young Apple Trees

One-year-old apple trees were grown in pots in an unheated greenhouse with screened ends and were artificially infested with spirea aphid, Aphis spiraecola Patch. Spirea aphid density increased at a faster rate on trees receiving higher rates of nitrogen application. Accumulation of dry weights in all tree parts (leaves, lateral shoots, trunk, rootstock, and roots) during the growing season were affected by both spirea aphid and nitrogen fertilization. Spirea aphid reduced accumulation of dry weights of all tree parts harvested at the end of the first growing season. These reductions were still present when trees were harvested at the 10-leaf stage the next spring. Spirea aphid reduced lateral shoot growth at the end of the growing season and at the 10-leaf stage. Dry weights of all tree parts increased with increasing rates of nitrogen. The percentage and amount of nonstructural carbohydrates in all tree parts were reduced by spirea aphid feeding and were positively related to nitrogen rate. At the 10-leaf stage in the second season, similar results were obtained. Foliar N concentration increased linearly with increasing amount of N application in both infested and control leaves. Also, differences in leaf N concentration were found between infested and control leaves at each N application rate.

Antitranspirant, Water Stress, and Growth Retardant Influence Growth of Golden Pothos

Cuttings of Epipremnum aureum (Linden & André) Bunt. were soaked for 5 seconds in 5% Folicote or Stressguard antitranspirant solution, planted immediately or after 6 hours, and misted or not misted during the daylight hours for 2 weeks. Neither antitranspirant affected the growth of misted cuttings. However, in nonmisted cuttings, Folicote resulted in delayed first leaf unfolding and small plants. Misting improved shoot growth relative to not misting. In a second experiment, Stressguard sprayed on leaves of stock plants resulted in slow growth of cuttings taken from them, while Folicote had no effect. Water stress induced by delayed planting resulted in water loss and slow lateral shoot growth in both experiments. Application of uniconazole at the four-leaf stage at 0.05 to 0.4 mg/0.5-liter pot reduced stem elongation, leaf count, and the length of nodal roots. Uniconazole increased individual leaf size on the main shoot and promoted the growth of basal lateral shoots. While stem and total plant dry weights were reduced, total leaf dry weight was not affected by uniconazole. Uniconazole continued to provide good control on the elongation of newly emerged lateral shoots and promoted the production of more and larger leaves when evaluated 4 weeks after the main shoot was severed above the fourth basal node. Chemical name used: (E)-1-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-trizol-1-yl)-1-penten-3-ol (uniconazole).

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).