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Dennis P. Stimart

The Allen Centennial Gardens are instructional gardens managed by the Department of Horticulture, University of Wisconsin-Madison. Twenty-two garden styles exist on the 2.5-acre (1.0-ha) campus site with a primary focus on herbaceous annual, biennial and perennial ornamental plants. The gardens are used for instruction mostly by the Department of Horticulture and secondly by departments of art, botany, entomology, landscape architecture, plant pathology, and soils. Class work sessions are limited due to the gardens' prominence on campus, high aesthetic standards, space restrictions, and large class sizes. Undergraduate students are the primary source of labor for plant propagation, installation and maintenance; management; and preparation of interpretive literature. Work experience at the gardens assists students with obtaining career advances in ornamental horticulture. Future challenges include initiating greater faculty use of the gardens for instruction and creating innovative ways to use the gardens to enhance instruction.

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Rozlaily Zainol and Dennis P. Stimart

Genetic analysis of a white double-flowering Nicotiana alata is being investigated. Self-pollination of the double-flowering plant produced all double progeny. Reciprocal hybridization of the double-flowered selection with N. alata cultivars produced nondouble F1 progeny that segregated 3:1 (nondouble to double) in the F2 generation. Reciprocal backcrosses of F1 plants to the parents resulted in nondouble progeny when backcrossed to the nondouble parent and 1:1 segregation when backcrossed to the double parent. Intercross of F1 plants resulted in progeny segregating 3:1. Double flowering habit has been transferred to white, red, salmon, green, and bicolor N. alata. Results suggest double flowering is under nuclear control regulated by a recessive allele.

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Rozlaily Zainol and Dennis P. Stimart

A double-flower form of Nicotiana alata Link & Otto was characterized genetically as a monogenic recessive trait expressed when homozygous. Reciprocal crosses demonstrated no maternal effect on expression of double flowers. A single dominant gene expressed in the homozygous or heterozygous state caused the single-flower phenotype. The symbol fw is proposed to describe the gene controlling double-flower phenotype.

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Kenneth R. Schroeder and Dennis P. Stimart

Three percent hydrogen peroxide (H2O2) was diluted with deionized water (dH2O) to 0.75%, 0.38%, 0.19%, 0.09%, or 0.05% H2O2 plus 1.5% sucrose for use in evaluation of Antirrhinum majus L. (snapdragon) cut flowers. Other vase solutions used as controls included; 300 ppm 8-hydroxyquinoline citrate (8-HQC) plus 1.5% sucrose; dH2O plus 1.5% sucrose; and dH2O. A completely random design with 7 replicationss was used. Flowering stems of three commercial inbreds and one F1 hybrid of snapdragon were cut when the first five basal florets opened. Each stem was placed in an individual glass bottle containing one of the eight different treatments. Flowering stems were discarded when 50% of the open florets wilted, turned brown, or dried. Postharvest life was determined as the number of days from stem cutting to discard. Addition of H2O2 to vase solutions at rates of 0.19 and 0.09% resulted in postharvest life not different from that obtained with 8-HQC plus sucrose. Hydrogen peroxide plus sucrose extended postharvest life of snapdragon cut flowers 6 to 8 days over dH2O and 5 to 7 days over dH2O plus 1.5% sucrose.

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Dennis P. Stimart and James F. Harbage

The role of the number of adventitious roots of Malus domestics Borkh. `Gala' microcuttings in vitro on ex vitro root and shoot growth was investigated. Root initiation treatments consisted of IBA at 0, 0.15, 1.5, 15, and 150 μm in factorial combination with media at pH 5.5, 6.3, and 7.0. IBA concentrations significantly influenced final root count and shoot fresh and dry weights, but not plant height, leaf count, or root fresh and dry weights at 116 days. Between 0 and 0.15 μm IBA, final root counts were similar, but at 1.5, 15, and 150 μm IBA, root counts increased by 45%, 141%, and 159%, respectively, over the control. The pH levels did not affect observed characteristics significantly. There was no significant interaction between main effects. A significant positive linear relationship was found between initial and final root count. The results suggest a limited association between high initial adventitious root count and subsequent growth. Chemical name used: 1 H -indole-3-butyric acid (IBA).

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Kenneth R. Schroeder and Dennis P. Stimart

A phenol-sulfuric acid assay was used to quantify non-specific neutral carbohydrates in Antirrhinum majus L. flowering stems of three inbreds and their hybrids. Flowering stems 40 cm long were harvested with five to six florets open and flower, leaf, and stem tissue separated, freeze-dried, and finely ground. Carbohydrates were extracted from the tissue with 95% ethanol in a 70 °C water bath and combined with a 5% w/v phenol solution and concentrated sulfuric acid. Glucose equivalents were determined with a spectrophotometer at absorbance of 490 nm. Averaged over tissue type, results were genotype dependent, ranging from 213 to 291 μg glucose equivalent per mg dry tissue with a LSD0.05 = 13. Flowers had the highest concentration of 340 μg/mg dry tissue, followed by stems, then leaves with 36% and 38% lower concentrations, respectively. Carbohydrate concentrations in two inbreds were compared when grown under cool (16 °C) and warm (29 °C) conditions. A genotype x environment interaction exists with inbred 3 exhibiting no reduction, 6% increase, and a 45% reduction in carbohydrate concentration when grown in warm conditions, while inbred 2 exhibited 15%, 23%, and 37 % reductions for flowers, leaves, and stems, respectively. Overall, there were 10% and 21% reductions in carbohydrate concentration for inbreds 2 and 3, respectively, when plants were grown under warm conditions.

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Kenneth R. Schroeder and Dennis P. Stimart

Postharvest longevity (PHL) is important in determining quality and consumer preference of cut flowers; thus, it remains a pressing problem for the florist industry. Information on genetics and heritability of cut flower PHL is lacking. This study focused on determining gene numbers and inheritance of Antirrhinum majus L. cut flower PHL. An inbred backcross population was generated from a yellow short-lived (YS; 6d PHL) and a white long-lived (WL; 14 d PHL) inbred. F1 hybrids were backcrossed reciprocally three times to each parent. Parental backcross (BC) populations contained 55 to 65 lines. Lines within each BC generation were self-fertilized three generations by single-seed descent without selection to produce BC1S3, BC2S3, and BC3S3 generations. Cut flowers from all generations were evaluated together for PHL in deionized water. Gene numbers were estimated using confidence intervals and the proportion of non-parental BC lines. Continuous variation, estimates of a minimum of two to four genes controlling PHL, and significant environmental variation suggest selection for increased PHL would be successfu,l but slow. A negative correlation between PHL and yellow flower color was detected in this study. In spite of that fact, mean PHL of the yellow flowered inbred lines improved 1 to 2 d when backcrossing to YS and 3 to 4 d when backcrossing to WL without selection. Thus, inbred backcrossing to a long-lived parent with selection for flower color should make acquisition of longlived colored lines attainable.

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Kenneth R. Schroeder and Dennis P. Stimart

Hypocotyls from Antirrhinum majus L. were excised at 2 weeks of age from seedlings grown under a 16-hour photoperiod or continuous darkness. Explants were cultured on modified Murashige-Skoog (MS) medium containing 0, 0.44, 2.22, 4.44, 8.88, or 44.4 μm BA to investigate adventitious shoot formation. Excised hypocotyls from eight commercial cultivars, three inbred lines, and an F1 hybrid between two of the inbreds were cultured on MS medium containing 2.22 μm BA to assess genotypic effects on adventitious shoot formation. The influence of seedling age was assessed by excising hypocotyls from seedlings at 6, 10, 14, 18, 22, 26, or 30 days. Optimal conditions for adventitious shoot formation on excised hypocotyls included: seedling growth in a lighted environment, use of hypocotyls from 10-day-old seedlings, and culture on medium containing 2.22 μm BA for 3 weeks. Under these conditions, up to a 5-fold improvement in number of shoots per hypocotyl over previous studies was achieved. Adventitious shoot formation was genotype-dependent and appeared to be a dominant trait. Chemical name used: N 6-benzyladenine (BA).

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Kenneth R. Schroeder and Dennis P. Stimart

Gibberellic acid (GA3) and photoperiod were used in combination in an effort to reduce generation time of Antirrhinum majus L. Four commercial inbred lines of A. majus were started from seed and grown in a glasshouse in winter 1993-94. GA3 was applied as a foliar spray every 2 weeks at 0, 144, 289, 577, or 1155 μm starting 5 weeks after seeds were sown. Supplemental lighting (60 μmol·m–2·s–1) from 0600 to 2000 hr and night interruption from 2300 to 0300 hr was used throughout the experiment. Data were collected weekly on plant height and leaf count from the start of GA3 treatments through anthesis. Time to flowering was determined as days from seed sowing to anthesis. GA3 treatment of A. majus under a long-day photoperiod increased time to flowering, plant height and leaf count. It would appear that long-days may have overridden the floral induction effects of GA3.

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Kenneth R. Schroeder and Dennis P. Stimart

Flowering stems from three commercial inbreds and their F1 hybrids of Antirrhinum majus L. were cut when the first eight basal florets opened. Tops of the stems were removed above the eighth floret and florets were removed leaving two, four, six, or eight open florets on a stem. A completely random design with 10 replications was used. Flowering stems were placed in plastic storage containers 35 × 23 × 14 cm (L × W × H) with 2.5 L deionized water for postharvest evaluation. Evaluation took place under continuous cool-white fluorescent light (9 μmol·m–2·s–1) at 24°C Postharvest life was determined as the number of days from cutting to discard when 50% of the open florets on a flowering stem wilted, turned brown, or dried. Results showed postharvest life increased as the number of open florets on a stem decreased. Mean postharvest life increased as much as 4.7 days when only two florets remained on a stem. These results indicate a direct relationship between number of florets on a cut flower stem and postharvest life.