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Gina E. Fernandez, Laura M. Butler, and Frank J. Louws

Strawberry (Fragaria × ananassa) `Chandler' plants from three sources were grown in the annual hill plasticulture system during two growing seasons (1996-97 and 1997-98). These trials evaluated the yield and vegetative performance of bareroot plants from Prince Edward Island and Ontario, Canada, and plug plant tips that were rooted in North Carolina but obtained from Ontario Canada. At the end of the season, total and marketable yields and fruit weight were not different among the plant sources. In addition, plants from all three plant sources produced equivalent yields on a weekly basis. Monthly whole plant harvests revealed that plant source did not affect leaf area, root, crown, leaf, flower or fruit dry weight during most of the growing season. In addition, plant growth parameters (specific leaf area, leaf area ratio, leaf weight ratio, and root to shoot ratio) in general did not differ among plant source in any 1 month. Plant growth did show shifts in dry weight allocation and leaf area as the season progressed that were uniform among plant sources, with the majority of the growth occurring in the spring in the two months prior to harvest. This uniformity among plant sources will allow future research to emphasize plant production practices that may reduce the risk of pest and disease problems or optimize production practices favored by growers.

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Bruce R. Roberts, Henry F. Decker, Kenneth J. Bagstad, and Kathleen A. Peterson

Two biosolid-containing waste media [sewage sludge compost and incinerated biosolids (flume sand)] were tested individually, together, and in combination with a commercial growing medium for growing wildflower sod in greenhouse trials over a 3-year period. A medium composed of flume sand and Metromix (7:3 weight/weight) in 7.5 {XtimesX} 10.5 {XtimesX} 2-inch deep (19 {XtimesX} 27 {XtimesX} 5-cm) plastic trays seeded at 20 oz/1000ft2 (6.1 g·m-2) with cosmos (Cosmos bipinnatus), cornflower (Centaurea cyannis), plains coreopsis (Coreopsis tinctoria), white yarrow (Achillea millefolium) and purple coneflower (Echinacea purpurea) produced a suitable wildflower sod in 10 to 12 weeks. A single application of slow release fertilizer (Osmocote 14-14-14, 14N-4.2P-11.6K) applied as a top dressing had no significant effect on sod development; however, a 4-mil [0.004-inch (0.10-mm)] polyethylene barrier placed in the base of each container resulted in increased dry weight accumulation and a higher root to shoot ratio relative to sod grown without plastic.

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J.A. Anchondo, M.M. Wall, V.P. Gutschick, and D.W. Smith

Growth and yield responses of `New Mexico 6-4' and `NuMex R Naky' chile pepper [Capsicum annuum L. var. annuum (Longum Group)] to four Fe levels were studied under sand culture. A balanced nutrient solution (total nutrient concentration <2 mmol·L-1) was recirculated continuously to plants potted in acid-washed sand from the seedling stage to red fruit harvest. Plants received 1, 3, 10 or 30 μm Fe as ferric ethylenediamine di-(o-hydroxyphenyl-acetate). Plant growth was determined by leaf area, specific leaf area [(SLA), leaf area per unit dry weight of leaves], instantaneous leaf photosynthetic rates, and dry matter partitioning. Low Fe (1 or 3 μm Fe) in the nutrient solution was associated with lower relative growth rates (RGR), increased SLA, and higher root to shoot ratios (3 μm Fe plants only) at final harvest. High Fe levels (10 or 30 μm Fe) in the nutrient solution were associated with an increased yield of red fruit and total plant dry matter. RGR of low-Fe young chile plants was reduced before any chlorotic symptoms appeared.

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Puffy Soundy, Daniel J. Cantliffe, George J. Hochmuth, and Peter J. Stoffella

Several levels of P were supplied via floatation irrigation to `South Bay' lettuce (Lactuca sativa L.) transplants to determine the optimum P concentration necessary. Plants were propagated by floating flats (ebb and flow system) in a nutrient solution containing P at either 0, 15, 30, 45, or 60 mg·L-1 in summer and fall experiments, and either 0, 15, 30, 60, or 90 mg·L-1 P in a factorial combination with 60 or 100 mg·L-1 N in a winter experiment. Adding more than 15 mg·L-1 P had minimal effect on growth. Transplants produced with 0 P grew poorly, regardless of the level of N applied. Nitrogen at 100 mg·L-1 improved the response of shoot growth to any level of P, but adversely affected root growth compared with N applied at 60 mg·L-1. In general, relative growth rate was improved, while net assimilation rate was reduced at all levels of P. High-quality transplants had a root to shoot ratio of about 0.25, total root lengths between 276 and 306 cm, and total root area between 26 and 30 cm3 in a 10.9-cm3 cell volume. Only 30% of the plants produced without P could be pulled from the transplant flats, whereas 90% could be pulled when P was added. Pretransplant P hastened maturity and increased lettuce head weight at harvest in the field. This work suggested that at least 15 mg·L-1 P, supplied via floatation irrigation to a peat + vermiculite mix, was required to produce a transplant with sufficient roots for ease of pulling, rapid field establishment, and earlier harvest.

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Fred T. Davies Jr., Constantino M. Calderón, and Zosimo Huaman

The influence of arbuscular mycorrhizal fungi (AMF) [two Peruvian mixed isolates, a pure isolate of Glomus intraradices] and the flavonoid, formononetin, were tested on growth, yield, and leaf elemental concentration of the Peruvian potato (Solanum tuberosum L.) `Yungay'. Plants started from tissue culture-produced prenuclear minitubers of `Yungay' were subjected to seven treatments, which included noncolonized (non-AMF) plants fertilized with Long Ashton nutrient solution modified to supply P at 11 and 44 μg·mL-1. All AMF plants received low P (11 μg·mL-1) and were inoculated with either a sierra-maize mixed isolate, sierra-papa mixed isolate, pure isolate of G. intraradices, sierra-maize mixed isolate + formononetin, or a sierra-papa mixed isolate + formononetin. Plants were grown in 3-L containers under shade house conditions in Lima, Peru. Non-AMF plants at low P had the poorest growth, while high P plants had the greatest overall growth. All AMF plants had greater growth, including a higher root to shoot ratio, higher phosphorus use efficiency [(g tuber)/(g P/kg tissue)], and a lower leaf to tuber ratio (indicating greater leaf efficiency in producing tuber dry matter), compared to non-AMF plants at low P. The mycorrhizal inoculation effect (MIE) ranged from +44% to +57%, indicating that `Yungay' was moderately to highly mycorrhizal dependent. Plants colonized with the sierra-papa isolate + formononetin had the same tuber development and leaf to tuber ratio, compared to high P, non-AMF plants. Formononetin increased extraradical hyphae formation. Mycorrhizal enhancement was in part due to greater P, Fe, and Mg uptake, a higher phosphorus-use efficiency and greater extraradical hyphae formation.

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Sudeep Vyapari, Edmund L. Thralls, and Michele S. Scheiber

A study was conducted to evaluate establishment of root-bound vs. nonroot-bound container-grown Plumbago auriculata Lam. in a landscape. A total of 144 plants were transplanted from #1 containers in a rain-out shelter at Mid-Florida Research and Education Center, Apopka, Fla., in June 2004. The field soil type was amended with composted yard waste. The three treatment types used for the study were: 1) root-bound plants; 2) root-bound plants with a vertical slice made through the root ball at a 90° angle; and 3) nonroot-bound plants. To evaluate the effect of these three treatments during the course of establishment period, harvesting was done once every 2 weeks. Data on growth indices (height × width × width), shoot dry weight, root dry weight, and length of the longest root were recorded. The experimental design was a completely randomized design consisting of three treatments, 12 harvest dates (days after planting), and four replicates per harvest date. Plants were maintained according to the best management practices recommended by the UF/IFAS, and were irrigated once a day using microirrigation. Experimental data were analyzed for significance of correlation among variables using SAS version 9.1. Results of the correlation and regression analysis indicated that the increase in the shoot dry weights (g), root dry weights (g), growth indices (m3), and root: shoot ratio had significant relationship with the harvest dates. Correlation among harvest dates and shoot dry weight, root dry weight, or growth indices was found to be positive. However, results of the study indicated that as the number of days after planting increased, the root to shoot ratio decreased.

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David R. Sandrock, Timothy L. Righetti, and Anita N. Azarenko

Cornus sericea L., Weigela florida (Bunge) A. DC., and Euonymus alatus (Thunb.) Sieb were grown outside in 3.8-L plastic containers for 345 days (1 Apr. 2001 to 11 Mar. 2002). Nitrogen (N) was applied at rates (NAR) of 25, 50, 100, 200, and 300 mg·L–1 and delivered as aqueous double-labeled 15N depleted NH4NO3 (min 99.95% atom 14N). In all species, root, shoot, and total plant dry weight increased with increasing NARs while root to shoot ratios decreased. Similarly, root, shoot, and total plant N increased with NAR for each species, and at each NAR more N was stored in the roots than in the shoots. Estimation of fertilizer N uptake determined by the total N method was higher for all species and at each NAR than estimation of N uptake determined by the fertilizer 15N tracer method. Fertilizer N uptake efficiency determined by the total N method was highest at 25 mg·L–1 and decreased as NARs increased. In contrast fertilizer N uptake efficiency determined by the fertilizer 15N tracer method was lowest at 25 mg·L–1 and increased or remained relatively constant as NARs increased. Differences in N uptake and N uptake efficiency can be attributed to overestimation by the total N method due to the inclusion of nonfertilizer N and underestimation by the fertilizer 15N tracer method due to pool substitution. Corrected N uptake efficiency values can be calculated by adjusting the original data (total N or 15N uptake) by the distance between the origin and the y intercept of the regression line representing the data.

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Carolyn F. Scagel

Using several different ericaceous ornamental species, we compared the growth, mineral nutrition, and composition of plants in response to growing media amended with varying proportions of sphagnum moss peat (peat) or coir dust (coir). Plants were grown for 16 weeks in media consisting of 80% composted Douglas fir bark with 20% peat, 20% coir, or 10% peat and 10% coir. Sixteen weeks after planting, decreases in extractable P were larger in peat-amended medium than the coir-amended medium, while decreases in extractable NH4-N and NO3-N were larger in the coir-amended medium. In general, leaf and stem dry weight, the number of leaves and stems, and total stem length increased with increasing proportion of coir in the medium while root dry weight either increased (Kalmia latifolia), decreased (Rhododendron, Gaultheria), or was not influenced by increasing the proportion of coir in the medium. The composition of the growing medium also influenced aspects of plant marketability and quality including: leaf greenness (SPAD), plant form (e.g., number of leaves per length of stem), and partitioning of biomass (e.g., root to shoot ratio). Nutrient uptake and fertilizer use was significantly different between the media types. Depending on the cultivar, we found that the coir-amended medium resulted in higher uptake or availability of several nutrients than peat-amended medium. Up take or availability of N, P, K, Ca, and S was enhanced for several cultivars, while uptake or availability of Mg, Fe, and B was similar between media types. Most cultivars/species growing in the coir-amended medium had higher production or accumulation of proteins and amino acids in stems than plants growing in peat-amended medium, while the production of proteins and amino acids in roots was lower in plants growing in coir-amended than in peat-amended medium. For the cultivars/species we tested, coir is a suitable media amendment for growing ericaceous plants and may have beneficial effects on plant quality.

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Conny W. Hansen and Jonathan Lynch

Whole-plant biomass accumulation, P dynamics, and root-shoot interactions during transition from vegetative to reproductive growth of `Coral Charm' chrysanthemum (Dendranthema ×grandiflorum Ramat.) (Zander, 1993) were investigated over a range of P concentrations considered to be deficient (1 μm), adequate (100 μm), and high (5 mm). In nondeficient plants, transition from vegetative to reproductive growth resulted in reduced relative growth rate and root and shoot biomass accumulation. Reproductive plants showed a higher commitment of the whole plant to the production of developing flowers than to leaves and roots, whereas, in vegetative plants, the highest component production rate was in leaves. This indicates changes in the source-sink relationships during transition from vegetative growth making developing flowers stronger sinks for photoassimilates than roots. Phosphorus allocated to developing flowers was predominantly lost from leaves. Phosphorus-deficient plants showed characteristic P-deficiency symptoms and favored root growth over shoot growth regardless of growth stage. Phosphorus availability in nondeficient plants affected root growth more than shoot growth. No substantial differences in shoot biomass production, relative growth rate, and CO2 assimilation rates were observed in adequate-P and high-P plants. However, the root component production rate, root to shoot ratio, root length ratio, specific root length, specific root area, root mass to leaf area ratio, and root respiration increased in adequate-P plants compared with high-P plants, which indicates that high root activity was maintained without affecting shoot biomass in buffered P conditions. Our results suggest that the high P concentrations used in many horticultural systems may have no benefit in terms of shoot growth and may actually be detrimental to root growth.

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Kelly J. Prevete, R. Thomas Fernandez, and William B. Miller

Boltonia asteroides L. `Snowbank' (Snowbank boltonia), Eupatorium rugosum L. (eastern white snakeroot), and Rudbeckia triloba L. (three-lobed coneflower) were subjected to drought for 2, 4, and 6 days during the fall and spring. Leaf gas exchange, leaf water potential, growth, and carbohydrate partitioning were measured during drought and throughout the following growing season. Leaf gas exchange of B. asteroides was not affected by drought treatment in the fall, not until day 6 of spring drought, and there were no long-term effects on growth. Transpiration and stomatal conductance of R. triloba decreased when substrate moisture decreased to 21% after drought treatment during both seasons. Assimilation of drought-treated R. triloba decreased when substrate moisture content decreased to 12% during spring but was not affected by drought in the fall. There was a decrease in the root-to-shoot ratio of R. triloba that had been treated for 4 days, which was attributed to an increase in the shoot dry weight (DW) of treated plants. Reductions in spring growth of E. rugosum were observed only after fall drought of 6 days, and there were no differences in final DWs of plants subjected to any of the drought durations. Spring drought had no effect on growth index or DW of any of the perennials. Boltonia asteroides and R. triloba had increases in low-molecular-weight sugars on day 4 of drought, but E. rugosum did not have an increase in sugars of low molecular weight until day 6 of drought. Differences in drought response of B. asteroides, E. rugosum, and R. triloba were attributed to differences in water use rates.