Increase In Trunk Cross-sectional Area Research Articles

Plant growth regulators to increase fruit set and yield of ‘Rocha’ pear trees in Southern Brazil

The aim of this study was to evaluate the effect of different aminoethoxyvinilglycine (AVG), thidiazuron (TDZ) and prohexadione calcium (P-Ca) rates sprayed at different timings on fruit set, yield, and fruit quality of 'Rocha' pear trees in different climatic conditions of Southern Brazil. The study was performed in two commercial orchards located in São Joaquim, SC (2015/2016) and Antônio Prado, RS (2016/2017). Plant material consisted of 'Rocha' pear trees grafted onto Pyrus calleryana and quince rootstock 'BA29' in São Joaquim and Antônio Prado, respectively. Treatments consisted of AVG, TDZ and P-Ca sprayed at different rates and timings. Trunk cross-sectional area increase, fruit set, thinned fruit, fruit per tree, yield, average fruit weight, projected yield, yield efficiency, fruit length, fruit diameter, L/D ratio, seed number, flesh firmness, and soluble solids content were assessed. Fruit set and yield were consistently increased by AVG in all experiments. Fruit set was not affected by P-Ca and was significantly decreased by TDZ. However, yield was positively affected by P-Ca 100 mg L-1 sprayed at full bloom + 7 days after full bloom and TDZ 10 mg L-1 at full bloom. Fruit size was consistently increased by TDZ.

Variability of survival and yield traits in cacao (Theobroma cacao L.) clones under marginal field conditions in Ghana

ABSTRACTIncreasing the genetic base of current parental cacao varieties grown in West Africa with clones that are able to perform well under marginal conditions could improve cacao production. Survival and yield of 30 different cocoa clones of more recent introductions were compared with five parental clones of improved cocoa varieties under natural field conditions in Ghana. A randomized complete-block design with five replications was used to evaluate the 35 clones for the following traits: percentage survival, increase in trunk cross-sectional area (TCSA), canopy spread, bean mass and bean yield. Significant (p < 0.05) clone effects for all traits and broad-sense heritability range of 0.16–0.51 were observed. Bean mass and bean yield varied from 0.90 to 1.44 g and 149 to 467 kg/ha, respectively. Bean yield and TCSA was positively and moderately correlated (r = 0.46; p < 0.01). Clones A 1/197, ICS 70 and MO 20 outperformed the best control clone for both survival and yield, which could be used in cacao breeding to improve production under marginal conditions in Ghana.

Genetic base-broadening of cacao for precocity and cropping efficiency

AbstractIntroduction of clones from genetic groups that are underrepresented in the pedigree of commercial cacao varieties in West Africa represents an important aspect of cacao improvement strategy of broadening the genetic base to overcome current yield stagnation of the crop. The objective of the present study was to determine the combining abilities of more recently introduced cacao clones for yield and cropping efficiency in the early bearing years. Seven recently introduced clones were crossed as males to five clones commonly used in the seed gardens in Ghana using a North Carolina II design. The 35 F1varieties and one commercial variety were evaluated in the field from June 2010 to March 2015 for four traits: increase in trunk cross-sectional area in the juvenile, and in the pod-bearing phases, bean yield and cropping efficiency. Though both GCA and SCA variances were significant for all traits, the ratios of GCA:SCA were much smaller than unity, indicating the importance of non-additive effects in the control of the traits. Among the set of clones therefore, prediction of F1variety performance cannot be based on the GCA orper se(average) performance of the clones. Six varieties were more precocious, and eight had higher cropping efficiencies than the standard variety. Bean yields ranged from 0.74 to 1.05 t/ha/year in the fourth and fifth years after planting among the top six varieties. The study provides evidence of the large potential for productivity increase through the use of cacao clones beyond Pound's early introductions into West Africa.

Genetic variation and combining abilities for vigour and yield in a recurrent selection programme for cacao

SUMMARYThe low genetic diversity of cacao germplasm collections in West Africa is often cited as a limitation to further yield improvement of the crop in its major production countries. Twelve clones obtained from first cycle selection for yield and clones available in international genebanks were tested for their combining ability for key agronomic traits by using these as males in crosses with five female clones available in the Seed Gardens in Ghana. Progenies obtained from a North Carolina II (NC II) mating design and standard varieties were planted at two sites that contrast in terms of soil fertility, rainfall total and distribution. Fifty-eight progenies obtained from the 5 × 12 incomplete NC II mating design and six other progenies, of which two were standard varieties, were evaluated at the more favourable location. At the less favourable location, 44 progenies of the NC II mating design and 20 other progenies, including the two standard varieties, were planted. A randomized complete block design with four replications was used at both locations. Progenies with PA 7 as female parent had better seedling survival at the location with poorer production conditions. Low levels of genetic diversity among female clones at 86 single nucleotide polymorphism loci was reflected in larger standard errors for the additive variance due to female parents relative to that due to male parents. Non-additive genetic effects were much larger than the corresponding additive variance components for all traits at each of the two locations. Average yields over the fourth and fifth years after planting ranged from 0·23 to 1·29 t/ha/year. The standard varieties were not among the best progenies for seedling vigour, yield or yield efficiency (yield per unit trunk cross-sectional area (TCSA) per year). Narrow-sense heritability estimates were higher for three estimates of tree vigour (estimated as increase in TCSA) than for yield traits. Heritability for yield efficiency was a moderate ofh2= 0·5 ± 0·23. The study indicates that further yield increments are attainable by selecting and crossing among the early cacao introductions into West Africa.

Influence of Citrus Source and Test Genotypes on Inoculations with Candidatus Liberibacter asiaticus

Assessments of the resistance of citrus germplasm to huanglongbing (HLB) can be expedited by inoculating plants under laboratory or greenhouse settings with the HLB bacterium, Candidatus Liberibacter asiaticus (CLas). Consistent rapid screening is critical to efficiently assess disease resistance among plant materials; however, a number of factors may govern the efficacy of such inoculations. Despite the rapidity at which HLB can spread in a grove, it often takes 8 to 10 months for high levels of CLas and HLB symptoms to develop even in highly susceptible sweet orange. Therefore, two experiments were conducted to assess factors that might influence efficiency in screening for HLB resistance. In one experiment, three test citrus genotypes (‘Kuharske’, previously shown to be HLB resistant; rough lemon, previously shown to be HLB tolerant; and ‘Valencia’, HLB susceptible) were bud grafted using CLas-infected buds from four different source genotypes. All bud source genotypes had similar levels of CLas titer, but citron, rough lemon, and Volkamer lemon were hypothesized to be better bud inoculum sources as they are more tolerant of HLB than ‘Valencia’. Among the three test genotypes over all sources of infected buds, inoculations of ‘Kuharske’ resulted in lower CLas titers and fewer HLB symptoms than inoculations of rough lemon or ‘Valencia’. Inoculations of rough lemon resulted in higher CLas titers and more pronounced HLB symptoms when it was inoculated using infected buds from rough lemon or ‘Valencia’. Grafting ‘Valencia’ with infected buds from Volkamer lemon resulted in less disease than when ‘Valencia’ was grafted with infected citron, rough lemon, or ‘Valencia’ buds. Overall, these results suggest that the source of CLas-infected buds used to graft-inoculate some genotypes will influence disease development. Trunk cross-sectional area increase for the year following infection was 3× higher in ‘Kuharske’ and rough lemon, compared with ‘Valencia’. ‘Kuharske’ had very low levels of CLas (30 CLas/µg DNA), whereas ‘Valencia’ (43,000 CLas/µg DNA) and rough lemon (6700 CLas/ µg DNA) had relatively high levels. As an alternative to graft-inoculating plants with CLas-infected buds, plants can be subjected to infestations of CLas-infected Asian citrus psyllid (ACP) as occurs naturally. Of interest is if transmission rates of CLas and the development of HLB in a genotype are greater when the ACP have been feeding on the same host genotype. An experiment was therefore conducted to assess transmission of CLas by ACP reared on CLas-infected rough lemon to five different genotypes (‘Carrizo’, ‘Flame’ grapefruit, rough lemon, ‘Temple’, and ‘Valencia’). These assessments were made using a detached leaf assay recognized as a faster method of gauging transmission rates of CLas than using whole plants. Higher percentages of ACP died when they were transferred from infected rough lemon to healthy ‘Carrizo’, and lower percentages died when they were transferred to rough lemon or ‘Flame’. However, CLas transmission by infected ACP occurred to at least some leaves of each genotype in each of the five different assays, with 70% or more leaves of each genotype becoming infected in at least one assay. Over all assays, there was relatively little variation among genotypes in the percentage of leaves becoming CLas infected and in the titer of CLas developing in infected leaves. However, there were relatively large differences in transmission rates among individual assays unrelated to differences among test genotypes. Because of the rapidity of the detached leaf assay, efforts are merited to improve consistency of this inoculation method.

Effect of two-spotted spider mite population (Tetranychus urticae Koch) on growth parameters and yield of the summer apple cv. Katja

Warabieda W. (2015): Effect of two-spotted spider mite population (Tetranychus urticae Koch) on growth parameters and yield of the summer apple cv. Katja. Hort. Sci. (Prague), 42: 167–175. The effect of two-spotted spider mite populations (Tetranychus urticae Koch) on the yield and growth parameters of the early-season apple cv. Katja was evaluated during a 3-year study. In the case of the colonisation of apple trees exceeding 1,462, 2,760 and 1,548 cumulative mite days (CMDs) in the subsequent years of research, a significant reduction of the cumulative yield (14 kg/tree) and of the cumulative trunk cross sectional area increase (5.7 cm2) was observed. No significant effect of spider mites on the average weight of the fruit was observed, while the pest affected fruit colouration. The calculated values of economic injury level were 60.5, 155.5 and 51.8 CMDs in subsequent years of the study, respectively. These values are much lower than the action threshold recommended in Poland and elaborated for the European red mite – Panonychus ulmi (Koch) on apple trees. The results suggest that the tolerance of early-season apple cultivars to T. urticae may be lower when compared to late-season varieties infested with P. ulmi; therefore, the decision to implement pest management for two-spotted spider mite should be taken at a lower infestation threshold than previously thought.

Influence of Irrigation Regime on Water Relations, Gas Exchange, and Growth of Two Field-grown Redbud Varieties in a Semiarid Climate

For three growing seasons (2003–2005) two newly planted, field-grown redbud (Cercis canadensis L.) varieties were subjected to three reference evapotranspiration (ETo)-based irrigation regimes (100, 66, and 33% ETo). Over this time period, water relations (pre-dawn leaf water potential), gas exchange (mid-day stomatal conductance), and growth data (trunk cross sectional area increase, tree leaf area, and shoot elongation) were measured. Pre-dawn leaf water potential (ψl) was more negative for trees receiving the least amount of irrigation, and for Mexican redbud [C. canadensis var. mexicana (Rose) M. Hopkins] trees. However, mid-day stomatal conductance (gs) was similar for Texas redbud (C. canadensis var. texensis S. Watson) trees across the three irrigation regimes, and was highest for Mexican redbud trees receiving the greatest amount of irrigation volume. Growth varied by variety and irrigation regime. Trunk cross sectional area increase was greatest for Mexican redbud trees, leaf area was highest for trees receiving the greatest amount of irrigation, and shoot elongation was greatest for trees receiving the 66% ETo irrigation regime. However, despite differing irrigation volumes, greatest gas exchange and growth was not necessarily associated with greatest irrigation volume. When considering conservation of precious water resources, these redbud varieties maintain adequate growth and appearance under reduced irrigation.

Impact of reflective groundcover on growth, flowering, yield and fruit quality in Gala apples in New Brunswick

Privé, J-P., Russell, L. and LeBlanc, A. 2011. Impact of reflective groundcover on growth, flowering, yield and fruit quality in Gala apples in New Brunswick. Can. J. Plant Sci. 91: 765–772. A 5-yr field study was conducted in New Brunswick, Canada, to assess the impact of a reflective groundcover (ExtendayTM) on Gala (Malus× domestica Borkh.) apple trunk cross-sectional area (TCSA), flowering, yield and fruit quality. Overall, a 25% increase in the total number of fruit per tree was realized with use of the 3-m wide reflective groundcover on the orchard floor between tree rows from full-bloom until 3 wk post-harvest; this translated to 26% greater total yield per tree and 16% greater yield efficiency. No overall effects on fruit quality at harvest were associated with use of the reflective groundcover. Trees with reflective groundcover exhibited a greater yearly percentage increase in TCSA (18.5%) than those without (15.0%); neither flowering nor fruit set was affected in any year. These increases in productivity were mediated by the enhanced canopy light environment provided by the reflective groundcover. The primary economic benefit to be derived from use of the ExtendayTM reflective groundcover in apple production in the Maritime region is through the capacity to produce higher-yielding crops of fruit on larger trees (increased yield efficiency), without compromising fruit quality. This improvement in production efficiency could translate to an increase in 4.5 t ha−1 of marketable fruit in New Brunswick.

Long-term Effects of Sod Competition on Peach Yield

Excessive vegetative growth in peach (Prunus persica) causes canopy shading that reduces fruit bud initiation in the canopy interior and increases pruning costs and time. Sod competition can reduce pruning but may also reduce yield. The objective of the present study was to measure the effects of increased sod competition [2- vs. 8-ft-wide vegetation-free areas (VFA)] on yield and quality of irrigated peach. Total pruning weight was reduced by sod competition in the first 4 of 7 cropping years. Subsequent years indicated no effect on vegetative growth due to sod competition. Annual increase in trunk cross-sectional area was reduced by sod competition in the first year of cropping and unaffected in subsequent years. Canopy development was reduced by sod competition in the first 2 years of cropping, which increased photosynthetically active radiation transmission through the canopy and increased fruit red color in the first year. The width of the VFA did not alter the relationship between total fruit number and total yield in any year; however, the total number of fruit per tree was reduced in all years and total yield was reduced in 6 of 7 years. Results suggest that dormant season pruning was removing a higher percentage of the crop bearing wood from the 2-ft VFA compared with the 8-ft VFA treatment, resulting in reduced yield per unit of dormant pruning. This indicates that pruning practices must be modified to leave more bearing wood in mature trees to maintain yield potential when sod competition is used to control vegetative growth.

Genetic Variability in Partitioning to the Yield Component of Cacao (Theobroma cacao L.)

Biomass partitioning of cacao (Theobroma cacao L.) was studied in seven clones and five hybrids in a replicated experiment in Bahia, Brazil. Over an 18-month period, a 7-fold difference in dry bean yield was demonstrated between genotypes, ranging from the equivalent of 200 to 1389 kg·ha-1. During the same interval, the increase in trunk cross-sectional area ranged from 11.1 cm2 for clone EEG-29 to 27.6 cm2 for hybrid PA-150 × MA-15. Yield efficiency increment (the ratio of cumulative yield to the increase in trunk circumference), which indicated partitioning between the vegetative and reproductive components, ranged from 0.008 kg·cm-2 for clone CP-82 to 0.08 kg·cm-2 for clone EEG-29. An examination of biomass partitioning within the pod of the seven clones revealed that the beans accounted for between 32.0% (CP-82) and 44.5% (ICS-9) of the pod biomass. The study demonstrated the potential for yield improvement in cacao by selectively breeding for more efficient partitioning to the yield component.

503 Effect of Source and Timing of Potassium Fertilizer on `Empire' Apple Tree Growth, Yield, and Fruit Quality

A field experiment was established in 1993 in a 3-year-old `Empire'/M.9 apple orchard. An incomplete factorial treatment design compared nitrogen only fertilization with nitrogen plus potassium fertilizer applied either on the ground with and without trickle irrigation or through the trickle irrigation system. Timing of potassium fertigation treatments compared season-long K fertigation to early season or late-season K fertigation. Results of main effects showed that K fertilization reduced trunk cross-sectional area increase, but increased yield, fruit size, and fruit red color. There was no benefit of fertigation compared to ground application of fertilizers plus trickle irrigation. There was no effect of source of K fertilizer (KCl vs KNO3) on tree growth, yield, fruit size, or color. Time of K fertigation showed that late-season K fertigation resulted in greater trunk cross-sectional area increase compared to early season fertigation or season-long fertigation. Fruit size was greatest when K fertigation was done in the early season. There was no effect of time of fertigation on yield or fruit red color. Potassium fertilization increased leaf K levels and reduced leaf Mg levels. Time of fertigation did not affect leaf K levels, but early season fertigation resulted in higher leaf N levels.

Growth and cropping of ‘Blanquilla’ pear trees treated with paclobutrazol

SummaryThe application of 1000 or 2000 mg l–1 paclobutrazol at full bloom or when shoots were 25 cm long, to trees carrying no crop, inhibited shoot growth, the effect increasing linearly with the concentration applied. However, total tree growth, measured by the relative increase in trunk cross-sectional area, was greatest in the treated trees. The application of paclobutrazol at full bloom resulted in a great reduction of fruit set and in the almost total loss of crop. However, when it was applied in conjunction with GA3, the effect was overcome and a normal crop was obtained. Microscopical observations on flowers sprayed with paclobutrazol showed that growth of ovules and nucellus was slowed down and the maturation of embryo sacs was retarded, effects that were overcome with the application of GA3. Growth of trees treated at bloom time with paclobutrazol was greater than that of trees either sprayed with paclobutrazol and GA3 or left unsprayed, and this was attributed to the loss of crop. Paclobutrazol...

068 EFFECT OF PRUNING SEVERITY ON APPLE TREE GROWTH, YIELD AND YIELD EFFICIENCY

`Empire'/M.26 apple trees which were planted in 1978 and trained to a Y-trellis were pruned differentially from 1989-1993. Trees were dormant pruned by removing from 1-4 scaffold limbs. The annual increase in trunk cross-sectional area (TCA), and the number and length of shoots removed during summer pruning increased linearly as the severity of pruning increased. The number of shoots removed during summer pruning from the most severe pruning treatment was more than double that of the least severe treatment Cumulative fruit number and yield were reduced linearly with increasing severity of pruning while average fruit size was increased only slightly by severity of pruning. Light interception was reduced with increasing severity of pruning. Tree efficiency of converting light energy into fruit (g fruit/MJ PAR intercepted) was linearly reduced with increasing pruning severity. Most of the reduction in conversion efficiency appeared to be due to reduced partitioning of resources into fruit since partitioning index (g fruit/unit increase in TCA) was more highly correlated to pruning severity than to conversion efficiency. Conversion efficiency and partitioning index accounted for a greater portion of the yield variation than did light interception indicating that the influence of pruning on yield was more a function of changing internal physiology than reduced light interception.

EFFECTS OF SOIL MANAGEMENT ON TREE GROWTH, FRUIT SET, YIELD, AND FRUIT QUALITY OF SPARTAN APPLES ON M.9 ROOTSTOCK

Four soil management treatments were applied from 1991 to 1993 to `Spartan'/M.9 apple trees planted in 1987. Geotextile, straw mulch, composted manure mulch, and grass sod were used to control weed growth in a 1-m-wide band under the trees. The experiment was a randomized complete block design with two blocks and seven trees per treatment; data was taken from the five inner trees in each plot. Trees in straw mulch showed the largest increase in trunk cross-sectional area (+45.6%) over the three years; those in the geotextile showed the second largest (40.7%). Straw mulch also resulted in the largest yield 2 years out of 3. Fruit set and fruit quality were also assessed, and trees in manure mulch and grass sod set the least fruit in each season. Fruit from the grass sod treatment remained harder in storage, and both straw mulch and grass sod have a higher proportion of grade A fruit (57 of total fruit).

Prunus Rootstock Affect Long-term Orchard Performance of `Redhaven' Peach on Brookston Clay Loam

Performance of `Redhaven' peach [Prunus persica (L.) Batsch.] propagated on nine experimental Prunus rootstock was evaluated over 8 years beginning in 1984, in a randomized complete-block experiment with 10 replications on a Brookston clay loam soil type near Harrow, Ont. This experiment was part of an interregional NC-140 peach rootstock experiment. Significant rootstock-induced effects were noted for increase in trunk cross-sectional area, cumulative tree height and spread, cumulative number of root suckers, yield, average fruit weight, yield efficiency, winter injury, cold hardiness, and tree survival. None of the clonally propagated rootstock gave satisfactory overall performance. All trees on GF655-2, 80% on GF677, 60% Self-rooted, and 50% on GF1869 were dead by the eighth year. In addition, suckering was a major problem on GF1869 and a moderate problem on GF655-2. `Citation' induced the most scion dwarfing but had the lowest yields and low yield efficiency. When yield, yield efficiency, fruit size, and tree mortality were considered together, the four peach seedling rootstock performed better than the other Prunus rootstocks and were ranked as follows: Siberian C, Halford, Bailey, and Lovell. Of these, the first three could be recommended with the most confidence to commercial growers who grow peaches on fine-textured soils in northern regions.

Growth and yield responses of almond (Prunus amygdalus) to trickle irrigation

Growth and yield responses of developing almond trees (Prunus amygdalus, Ruby cultivar) to a range of trickle irrigation amounts were determined in 1985 through 1987 (the fifth through seventh year after planting) at the University of California's West Side Field Station in the semi-arid San Joaquin Valley. The treatments consisted of six levels of irrigation, ranging from 50 through 175% of the estimated crop evapotranspiration (ETc), applied to a clean-cultivated orchard using a line source trickle irrigation system with 6 emitters per tree. ETc was estimated as grass reference evapotranspiration (ET0) times a crop coefficient with adjustments based upon shaded area of trees and period during the growing season. Differential irrigation experiments prior to 1984 on the trees used in this study significantly influenced the initial trunk cross-section area and canopy size in the 50% ETc treatment and 125% ETc treatment. In these cases, treatment effects must be identified as relative effects rather than absolute. The soil of the experimental field was a Panoche clay loam (nonacid, thermic, Typic Torriorthents). The mean increase in trunk cross-sectional area for the 3-year period was a positive linear function (r 2 = 0.98) of total amounts of applied water. With increases in water application above the 50% ETc treatment, nut retention with respect to flower and fertile nut counts after flowering, was increased approximately 10%. In 1985 and 1987, the nut meat yields and mean kernel weights increased significantly with increasing water application from 50% to 150% ETc. Particularly in the higher water application treatments, crop consumptive use was difficult to quantify due to uncertainty in estimates of deep percolation and soil water uptake. Maintenance of leaf water potentials higher than −2.3 MPa during early nut development (March through May) and greater than −2.5 MPa the remainder of the irrigation season (through August) were positively correlated with sustained higher vegetative growth rates and higher nut yields.

APPLE TREE GROWTH DURING TWO SEASONS FOLLOWING SOIL PREPLANT TREATMENTS

The effect of soil preplant strategies winter solarization and methyl bromide fumigation were compared to a non-treated control on apple tree growth. Treatments were applied in the fall after removal of an existing orchard with spring planting of 'Jonee' and 'Smoothee Golden Delicious' on M.26 EMLA rootstock. Soil fumigation significantly increased shoot length in first year, trunk cross-sectional area increase during two seasons, and bloom and set in second year. The control and winter solarization treatments were similar in all responses. Foliar Mn concentrations were significantly lower with fumigated trees in second years compared to other two treatments, which were similar.

Survival and Growth of Peach Trees Planted in Killed Bahiagrass at an Old Orchard Site

More peach [Prunus persica (L.) Batsch.] trees survived when planted in killed bahiagrass (Paspalum notatum Flugge `Paraguayan-22') sod growing between previous orchard tree rows (98%) than when planted in previous tree sites (81%) or in previous tree rows, but halfway between previous tree sites (79%). The previous orchard was removed Nov. 1986, and new trees were planted Feb. 1987. Surviving trees in the killed sod grew better than trees at the other two sites. Tilling the sites before planting did not affect nematode populations or tree survival and growth. Soaking the tree roots in a fenamiphos solution (1 g·liter-1) for 20 minutes before planting resulted in 79% tree survival vs. 93% survival for the nonsoaked trees. Fenamiphos sprayed under the trees at a rate of 11.2 kg·ha-1 during the spring and fall of the planting year did not change nematode populations, tree survival, or tree growth. The fenamiphos sprays reduced the increase in trunk cross-sectional area by 3 cm2 for trees in the sod. Other than leaf Zn concentration, which was low, concentrations of the elements were within the sufficiency range for Georgia for all treatments. Trees planted in the killed sod had an increased leaf K concentration and decreased leaf Mg concentration when compared with trees planted in the rows. Chemical name used: ethyl 3-methyl-4-(methylthio)phenyl (1-methylethyl)phosphoramidate (fenamiphos).

Influences of uniconazole on growth, fruiting, and photosynthetic activity of tissue culture-propagated own-rooted apple trees

Tissue culture-propagated (TC) own-rooted ‘Gala’ and ‘Triple Red Delicious’ apple trees grown at three planting densities were not treated (TC control) or were treated with annual uniconazole sprays or two trunk drenches starting with the third or fourth growing season. Budded (BUD) trees on M. 7a rootstock were also included as controls. After both the fifth and sixth growing seasons, the cultivars grown and the treatments applied had more influence on the attributes measured than did planting densities. Flowering and yield were greater on ‘Gala’ trees compared with ‘Triple Red’ for the fifth, but not the sixth season. The tree propagation method did not influence flower numbers and yield of ‘Gala’ trees in either the fifth or the sixth growing season but flower numbers were greater on BUD compared with TC trees of ‘Triple Red’ for both seasons. Flowering of TC ‘Triple Red’ trees tended to be increased by uniconazole treatment. Uniconazole applied by the trunk drench method markedly retarded vegetative growth of ‘Gala’ trees during the fifth season but flowering was reduced the following season. The trunk cross-sectional area of control TC trees for both cultivars increased more than for BUD trees but uniconazole treatment slowed trunk cross-sectional area increase so that treated TC trees were maintained at nearly the same size as BUD trees. Overall, ‘Triple Red’ leaves had higher chlorophyll concentrations than ‘Gala’ leaves, but there were no differences between BUD and TC leaves for net photosynthetic rate (Pn), stomatal conductance for water (g sw), relative chlorophyll concentration, or specific leaf weight (SLW). Uniconazole treatment increased mean seasonal Pn, g sw, relative chlorophyll, and SLW compared with controls.

Application of GA4+7 to Stem Enhances Carambola Seedling Growth

Growth response of containerized carambola (Averrhoa carambola L.) seedlings to GA applied to trunks in lanolin paste were studied under glasshouse conditions. Gibberellic acid at 0, 250, 500, or 750 mg·liter and an untreated control (no lanolin) were used. Internode length and increases in plant height and trunk cross-sectional area (TCA) did not differ for control and 0 mg·liter plants, but mostly increased with concentration of GA. Increase in TCA was determined in a second study with control and treated plants, using 500 mg GA/liter. Mean recommended graftable size (7 mm) was reached in 47 days in plants that were GA treated, and 93 days in control plants, suggesting that GA may be used to shorten nursery time for producing graftable carambola seedlings. Chemical name used: gibberellic acid (GA.,+,).