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Raspberry root growth during fruiting appears to be a strong sink for assimilates, and may decrease carbon availability for fruits and, consequently, cane yield. Both floricanes and primocanes may contribute to root carbon supply in raspberry during fruiting. To test this, `Tulameen' raspberry canes were grown outdoors in containers filled with perlite and peat (1:1). One-half of the plants were girdled and the rest were nongirdled. Within each girdling treatment, either 0 or 3 primocanes were allowed to grow. Treatments were applied at early bloom (10 May), and 50% fruit harvest occurred the first week in June. Fruit number and yield per plant decreased in girdled plants and plants without primocanes compared with nongirdled plants and plants with primocanes. Individual fruit fresh weight was not affected by treatments, but individual fruit dry weight and the dry weight to fresh weight ratio was higher in girdled plants without primocanes than in the other treatments. Neither girdling nor the presence of primocanes affected dry weight allocation to primocanes or floricanes. Root dry weight was higher in girdled plants with primocanes than in nongirdled plants without primocanes. It appears that primocanes supply carbon to roots during fruiting, and subsequently, roots mobilize carbon to floricanes. Thus, roots appear to serve primarily as a translocation pathway for carbon from primocanes to floricanes. However, when primocane growth is suppressed, root carbon is mobilized to support floricane development. If carbon flow from roots to floricanes is restricted, fruit number and yield is significantly decreased.

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Carrizo citrange [Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.] seedlings were budded with `Hamlin' orange [Citrus sinensis (L.) Osb.] and subjected to 3 bud forcing treatments: (1) topping [T] by removing the seedling above the bud union; (2) lopping [L] by cutting half way through the seedling above the bud union and breaking the rootstock over; or, (3) bending [B] the seedling top over and tying it to the base of the plant. As scion buds emerged and grew, plants were sacrificed for dry weight measurements; also, the portion of the rootstock seedling above the bud union was exposed to 14CO2 at 3 stages of scion development. Plants with seedling tops attached (B,L) gained more dry weight and fibrous roots than T seedlings. Scion elongation was greater for B plants than for T plants. Plants usually flushed twice regardless of bud forcing treatment. No treatment differences were noted for time of flushing or scion bud emergence. Labeled photosynthate from attached rootstock leaves was translocated to scions during both flushes suggesting that recently fixed C enhanced scion growth for B and L plants.

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Low yields have been observed in annual production systems in raspberry (Rubus idaeus L.) compared with annual yields in perennial systems. This yield reduction could be related to a depletion of root carbohydrates and its consequent detrimental effect on fruit number or size. Additionally, primocanes could play an important role in the carbohydrate dynamics in an annual system and may also affect yield. Two experiments were carried out in 2003 and 2004 to determine the importance of root carbohydrates and primocanes in fruiting and yield components of ‘Tulameen’ red raspberry in an annual production system. In the 2003 experiment, girdled floricanes were compared with nongirdled controls. Girdling before bloom decreased fruits per cane and consequently yield per cane compared with controls, whereas girdling at the end of bloom had no effect. Root dry weight accumulation at the end of the fruiting season was significantly less in both early and late girdled compared with nongirdled plants. In 2004, floricanes were completely girdled or nongirdled at midflowering. Additionally, three primocanes were permitted to grow in one-half of the nongirdled and girdled plants, whereas primocanes were completely removed from the other half. Girdling and removal of all primocanes resulted in 100% plant mortality. In the presence of primocanes, floricane girdling had no effect on yield compared with the nongirdled treatments. There was a reduction in root dry weight in the nongirdled + primocane removal treatment compared with the treatments in which three primocanes were present. In the presence of primocanes, however, root dry weights were similar in both girdled and nongirdled plants. These results suggest that root carbohydrates are important in determining fruit number and yield in the annual system, and reductions in root carbohydrate during early flowering results in decreased yield. However, roots appear to quickly convert from source to sink status, and as the season progresses, both floricanes and primocanes act as sources to replenish root carbohydrate reserves. Carbohydrate dynamics appear to be similar between the annual production system and the traditional perennial system; however, because the annual system begins with limited carbohydrate reserves resulting from root pruning that occurs during removal from the nursery, yields are lower than those seen in perennial systems.

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Annual production systems for red raspberry (Rubus idaeus L.) have been proposed for off-season production or for increasing crop diversity in warm winter climates. However, yields in these annual systems are low compared with annual yields in perennial production systems. The yield reduction may be from the root pruning that occurs during removal and shipment of the canes from the nursery. This would result in significant root loss and may decrease the availability of root carbohydrates for reproductive development. To investigate this, ‘Cascade Delight’ red raspberry plants were root pruned during dormancy, and growth and fruiting of these plants were compared with non root-pruned controls the next season. Dry weights of all organs except floricane stems increased throughout the growing season; however, root pruning decreased root, floricane lateral, and total fruit dry weight compared with no root pruning. The yield decrease observed in root-pruned plants was because of a decrease in flower and fruit number per cane compared with the control. Total carbohydrate concentration in roots of root-pruned and non root-pruned plants decreased significantly between pruning and budbreak; however, root carbohydrate concentration and content were always lower in root-pruned compared with non root-pruned plants. The lower root carbohydrate availability in root-pruned compared with non root-pruned plants during budbreak apparently limited flower bud formation/differentiation, resulting in decreased yield. These results suggest that yields in annual red raspberry production systems are limited because of the loss of root carbohydrates during removal from the nursery. Management practices that increase yield per plant (e.g., by ameliorating root loss) or increase yields per hectare (e.g., by increasing planting density) are needed to render the annual production system economically viable.

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Cool night temperatures have been reported to induce ovary swelling and consequent fruit deformation in bell pepper (Capsicum annuum L.), resulting in unmarketable fruit. This response is a serious limitation to the success of winter production systems for bell pepper. Limited work has been done with other types of sweet pepper, so it is unknown how universal this response is. Furthermore, most prior work has examined effects on ovary diameter only, and there is limited characterization of other ovary traits in response to cool night temperature. The objectives of the present study were to determine the effects of low night temperature on ovary characteristics in different sweet pepper cultivars and to determine the parts of the ovary that are most affected by these factors. Three types of sweet pepper (bell, long-fruited, and cherry) were exposed to 22/20 or 22/12 °C day:night temperatures and flowers at anthesis were continuously harvested throughout the experiments. Ovary fresh weight (FW), diameter, and length across all types (and cultivars within type) were greater under 22/12 °C compared with 22/20 °C. The increase in ovary FW was the result of increases in both ovary wall and placenta FW. In general, all cultivars exhibited increases in ovary size under 12 °C compared with 20 °C night temperature. Differences in ovary FW resulting from night temperature became more pronounced with time. These results indicate that low night temperature effects on ovary swelling may be a universal response among sweet pepper types. Three to 4 weeks are required for maximum swelling response, suggesting that flower buds must be exposed to low night temperatures within the first week after flower bud initiation, because previous work found that flower bud initiation in bell pepper takes ≈4 weeks. However, the duration of low night temperatures necessary for this response remains unknown.

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Two experiments were conducted with Swingle citrumelo [Citrus paradisi (L.) Osb. × Poncirus trifoliata (L.) Raf.] and Cleopatra mandarin (C. reticulata Blanco) seedlings budded with `Hamlin' orange [C. sinensis (L.) Osb.] to determine the effects of rootstock shoots on nursery tree growth. All experiments were conducted in a greenhouse. Plants were forced by cutting off the rootstock above the bud union (C), or by bending the rootstock shoot above the bud union and tying it to the base of the plant (B). In one experiment, rootstock leaves for B plants were subjected to 4 levels of shade: (1) no shade; (2) 70% shade; (3) 90% shade; or 95% shade. In another experiment, rootstock shoots of B plants were subjected to 4 levels of defoliation: (1) no defoliation; (2) approximately 33% defoliation; (3) approximately 66% defoliation; and (4) complete defoliation. Scion stem and leaf dry weights, leaf area and number, and shoot length were less for plants with shaded rootstock tops than for nonshaded plants. Stem and leaf dry weights and leaf area of scion flush 1 were less at 90 and 95% shade than at 70% shade. Defoliation of rootstock tops reduced scion stem and leaf dry weights, leaf area and number, and shoot length compared to nondefoliated plants. Most scion growth measurements were reduced more by complete defoliation than by partial defoliation.

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Some physiological and biochemical properties of melting flesh (MF) and non-melting flesh (NMF) peaches [Prunus persica (L.) Batsch] were determined during ripening for 5 days at 20 °C. Respiration rates and ethylene production of MF ‘Flordaprince’, MF ‘TropicBeauty’, NMF ‘UFSun’, and NMF ‘Gulfking’ were measured at different harvest skin ground color-based maturity stages. The MF cultivars at harvest were mostly preclimacteric or at the onset of ripening. The NMF cultivars generally had higher ethylene production at harvest and throughout ripening than the MF cultivars; thus, the NMF fruit had started ripening on the tree before harvest. Some of the NMF fruit harvested at more advanced stages quickly became postclimacteric during the storage period. Quality determination after fruit ripening showed that MF ‘TropicBeauty’ had the highest soluble solids content (SSC), but also the highest titratable acidity (TA). The NMF cultivars had lower TA than the MF cultivars. NMF ‘Gulfking’ consistently had high SSC/TA, which was the result of it having the lowest TA. The NMF cultivars retained firmer texture than the MF cultivars during ripening. The flesh firmness of the NMF cultivars was four to five times greater than that of the MF cultivars. To investigate the reason for this significant textural difference, the activities of the cell wall modification enzymes pectin methylesterase (PME) and polygalacturonase (PG) were quantified in all four cultivars at advanced ripeness stages. PME activity appeared to be more directly related with peach fruit softening than PG activity.

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Experiments were conducted in north Florida and south Georgia to determine the effects of H2CN2 sprays on vegetative and reproductive growth of blueberry. In Florida, mature, field-grown `Misty' southern highbush (Vaccinium corymbosum L. hybrid) blueberry plants were sprayed to drip with 0, 10.2, or 20.4 g·L-1 of H2CN2 [hereafter referred to as 0%, 1.0%, and 2.0% (v/v) H2CN2] on 20 Dec. 1996 and 7 Jan. 1997. During the following winter, mature `Misty' southern highbush and `Climax' rabbiteye (V. ashei Reade) plants were sprayed to drip with 0, 7.6, or 15.3 g·L-1 of H2CN2 [hereafter referred to as 0%, 0.75%, and 1.5% (v/v) H2CN2] on 17 Dec. 1997 and 6 Jan. 1998. For all experiments, plants were dormant and leafless, with slightly swollen flower buds, at the time of spray applications. Generally, H2CN2 sprays increased the extent and earliness of vegetative budbreak and canopy establishment and advanced flowering slightly. The number of vegetative budbreaks usually increased linearly with increasing spray concentrations. In Florida, H2CN2 [0.75% to 1.0% (v/v)] sprays increased mean fruit fresh weight and yield, and shortened the fruit development period (FDP) compared to controls. However, H2CN2 sprays ranging in concentration from 1.5% to 2.0% (v/v) resulted in significant flower bud injury and reduced total fruit yield compared to controls. In south Georgia, 27 of 37 field trials conducted between 1991 and 1998 on several rabbiteye and southern highbush cultivars indicated that leaf development was significantly enhanced by H2CN2. H2CN2 shows potential for increasing early fruit maturity, fruit size, and yield of southern highbush and rabbiteye blueberry cultivars with poor leaf development characteristics in low-chill production regions. Chemical name used: hydrogen cyanamide (H2CN2).

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Four low-chill peach cultivars were evaluated for vegetative and reproductive growth, fruit quality, and yield in north central and central Florida. Twenty-trees (five of each cultivar) were planted at each site in Feb. 2002. Prior to budbreak in the spring of 2004 and 2005, three shoots of average length and diameter were selected at a height of 1.5–2.0 m and the number of vegetative and flower buds was recorded for each shoot. Percentage of bloom was estimated, and the number of open flowers on selected shoots was measured weekly. Trees were harvested twice per week starting in mid-April in central Florida, and in late April in north central Florida. Total number and weight of marketable fruit was measured for each tree. Ten representative fruits were selected from each tree at each harvest. Fruit were measured for blush, weight, and size. Soluble solids, TAA, and pressure were determined for five fruit from each 10-fruit sample. Preliminary results indicate a higher mean number of blind nodes in central Florida and a higher mean number of flower buds in north central Florida. In central Florida, 90% bloom was about 4 days earlier than north central Florida. Fruit number and individual fruit size, weight, and marketable yield were higher in north central Florida than in central Florida. Fruit blush was higher in central Florida than in north central Florida and tended to increase as the season progressed. In north central Florida, blush decreased slightly throughout the season.

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The effect of climate was observed on fruit quality of four low-chill peach cultivars (Flordaprince, Flordaglo, UFGold, and TropicBeauty). The cultivars were evaluated in three locations (north–central, central, and southwest Florida). Soluble solids content (SSC), titratable acidity (TA), SSC:TA ratio, fruit weight, blush, and fruit development period (FDP) were determined. Longer FDPs were observed at the north–central location than at the southwest location. Fruit development and the expression of quality attributes were affected by location during fruit growth with higher color and SSC and shorter FDP occurring under warmer conditions. Within locations, ‘UFGold’ had the shortest FDP except at the southwest location where its chilling requirement may not have been met. At the central and southwest locations, ‘UFGold’ also tended to have lower TA values and higher SSC;TA ratios than the other cultivars.

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