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Jessica M. Cortell and Bernadine C. Strik

In Spring 1993 and 1994, mature trailing `Marion' blackberry (Rubus L. subgenus Rubus Watson) plants were pruned to 0, 4, 8, and 12 floricanes. In 1994, yield per cane was higher for plants with 4 floricanes compared to plants with 8 or 12 floricanes. In Summer 1993, there was a trend for lower primocane dry mass with a higher floricane number and a significant reduction in primocane branch dry mass with an increase in floricane number. Total plant, fruit, floricane, and lateral dry mass increased linearly with floricane number. Results were similar for floricane components in Summer 1994; however, there were no treatment effects on primocane or branch dry mass and there was a significant linear increase in crown dry mass with floricane number. By Winter 1994-95, there were no treatment effects on primocane or crown dry mass. Plants without floricanes produced more primocanes per plant than plants with floricanes in 1993 but not in 1994. Plants without floricanes produced primocanes that had a significantly lower percent budbreak the following year (1994) than plants with floricanes. Primocanes produced by plants without floricanes had more nodes per branch and a greater average branch cane length than those from plants with floricanes the previous season. The number of nodes per primocane tended to decrease with an increase in floricane number per plant in 1994 and 1995. There was no significant effect of floricane number per plant the previous season on fruit per lateral, fruit mass, or yield per plant the following season in either treatment year (1993 + 1994). However, in 1994, plants without floricanes the previous year had the lowest yield per cane. Topping primocanes at 30 cm in 1993 and 1994 had few significant effects on yield components the following season. Thus, `Marion' blackberry can compensate for reduced fruiting cane number through an increased percent budbreak on remaining canes. While there were differences in primocane dry mass among treatments after harvest in 1993, there were no differences by mid-winter in either 1993 or 1994. Although plants grown without floricanes in 1993 had more primocanes, these canes had a lower percent budbreak the following season. Consequently, in this study we did not see increased yield in plants grown without floricanes the previous season. This was perhaps because primocanes were not trained as they grew, a practice that improves light exposure to the canes and may increase flower bud initiation.

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P. C. Crandall and J. K. L. Garth

Abstract

Butanedioic acid mono-(2,2-dimethylhydroxide) (daminozide) at concentrations ranging from 2000-8000 ppm applied when primocanes were 45 cm tall (12–16 nodes) greatly increased the early yield of ‘Heritage’ raspberries (Rubus idaeus L.). The addition of (2-chlorethyl)phosphoric acid (ethephon) at 300 ppm tended to further increase the effectiveness of the daminozide treatments. None of the treatments significantly affected the total primocane height. Microscopic examination of the axillary buds of untreated primocanes revealed that first signs of floral development occurred soon after the growth regulators were applied.

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Gina E. Fernandez and Marvin P. Pritts

The objective of this experiment was to determine the effects that altering the probable source-sink relationships would have on subsequent growth and yield components under field conditions. The balance between vegetative and reproductive growth was altered by imposing light stress (shading) on various growth phases, or removing primocanes, floricanes or fruit. Removal of primocanes significantly increased yield the year of removal. However, if primocane removal coincided with canopy shading, this increase in yield was not achieved. Overall, a significant negative correlation existed between 1991 and 1992 yields. Treatments with high yields in 1991 had low yields in 1992, and visa verca. This evidence-suggests that: 1) primocanes and floricanes are competing for light, not photosynthates during the flowering and fruiting period and 2) altering the balance of vegetative and reproductive growth one year had a significant effect on growth the subsequent year.

Open access

Harry Jan Swartz, Susan E. Gray, Larry W. Douglass, Edward Durner, Christopher S. Walsh, and Gene J. Galletta

Abstract

Thornless blackberry plants were trained on 2 trellis types to determine the effect of primocane-floricane separation on plant productivity. Plants grown on a divided canopy had less shaded primocanes and more productive floricanes than those grown on a single canopy. Light interception was correlated positively to an increase in number of fruit per raceme and soluble solid/acid ratio. Dormant pruning had no effect on light interception or yield.

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Maria E. Cramer, Kathleen Demchak, Richard Marini, and Tracy Leskey

relocated, so there were three replicates of all six treatments. Two primocane-fruiting red raspberry cultivars, Josephine and Polka, were used in 2016 and 2017. These cultivars were double-cropped and were chosen for their ability to provide fruit

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G. Fernandez and M. Pritts

Seasonal changes in growth, photosynthetic rates, temperature, and light response curves of `Titan' red raspberry (Rubus idaeus L.) were obtained from potted plants grown under field conditions. Primocane dry weight accumulation underwent two phases of linear growth at the beginning and the end of the season, but growth slowed during fruiting. This slower rate of dry weight accumulation also coincided with an increase in root dry weight. Primocane NAR and SLA were highest early in the season. Light response curves differed depending on cane type and time of year. Floricane photosynthetic rates (A) were high during the fruiting period, while primocane A rates remained steady throughout the season. Both primocane and floricane leaflets displayed a midday drop in A rate, with a partial recovery in late afternoon. Photosynthetic rates of both primocane and floricane leaves were very sensitive to high temperatures. Temporal convergence of sink demand from fruit, primocanes, and roots occurs when plants experience high temperatures. This may account for low realized yields in raspberry and the high level of yield component compensation typical of source-limited plants.

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Gina E. Fernandez and Marvin P. Pritts

Seasonal changes in growth, mean maximal photosynthetic rates, and the temperature and light response curves of `Titan' red raspberry (Rubus idaeus L.) were obtained from potted plants grown under field conditions. Primocane dry weight accumulation increased steadily at the beginning and the end of the season, but growth slowed midseason during fruiting. The slower midseason dry-weight accumulation rate coincided with an increase in root dry weight. Primocane net assimilation rate (NAR) was highest early in the season. Floricane photosynthetic rates (A) were highest during the fruiting period, while primocane A remained steady throughout the season. Primocane and floricane leaflets displayed a midday depression in A under field conditions, with a partial recovery in the late afternoon. Photosynthetic rates of primocane and floricane leaves were very sensitive to temperature, exhibiting a decline from 15 to 40C. Light-response curves differed depending on cane type and time of year. A temporal convergence of sink demand from fruit, primocanes, and roots occurs when plants experience high temperatures. These factors may account for low red raspberry yield.

Open access

Stanley R. Nehrbas and Marvin P. Pritts

Abstract

Effects of annual pruning, alternate-year mowing, and primocane suppression on yield and its components for ‘Titan’ and ‘Royalty’ summer-bearing raspberries (Rubus idaeus and R. neglectus) were measured for 2 consecutive years. Cumulative yield was highest for primocane suppression and lowest for alternate-year mowing. Path analysis revealed that cane number per plant and number of fruitful laterals per cane were the most important yield components for both cultivars. Alternate-year mowing plots had higher cane numbers per plant than other treatments, but fewer fruitful laterals in the bottom and middle thirds of the canes. Annual primocane suppression increased numbers of fruitful laterals in the bottom and middle thirds of canes, resulting in increased yield compared to other treatments. Productivity was related to the amount of photosynthetically active radiation entering the canopy.

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Fumiomi Takeda

NAA at 0.25% to 1.0% applied in late May on the basal portion of thornless blackberry (Rubus, subgenus Eubatus) primocanes inhibited lateral shoot growth in the treated area and reduced the number of primocanes. However, regrowth occurred near or below ground from axillary buds not contacted by NAA. Rates of (0.25% and 0.12570 NAA did not affect the terminal or lateral growth above the treated area. The reduced number of basal lateral shoots facilitated machine harvesting. Chemical name used: napthaleneacetic acid (NAA).

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Hermen Malik, Douglas D. Archbold, and C.T. MacKown

Partitioning patterns of fertilizer N in container-grown `Chester Thornless' blackberry (Rubus spp.) were determined over two growing seasons following application of 15NH4 15N03. The roots and primocane tissues comprised the majority of the plant biomass each year. The N concentrations of primocane and floricane leaves were lower in 1988 than 1989, but were higher than in any other tissues each year. Foliar N values were followed by those for fruit, roots, and canes. As determined by isotope partitioning ratios, primocane cane, leaf, and fruit 15N enrichment from fertilizer N was higher than in other tissues in 1988. In 1989, when only stored 15N was available, the floricane was the most enriched, followed by the fruit and roots. Thus, newly acquired N was allocated to primocane tissues, fruit, and roots. Stored fertilizer N was allocated to all tissues from the roots and floricanes, but a significant amount remained in the floricanes. After two seasons. the plants retained only 27% of the total fertilizer N initially acquired.