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  • Author or Editor: Dennis Stimart x
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Abstract

Excised embryos from Acer griseum (Franch.) Pax., A. mandshuricum Maxim., A. maximowiczianum Mig. (A. nikoense Maxim.) and A. triflorum Kom. germinated within 21 days when incubated in a lighted environment on wick cultures moistened with a solution of 10 mg/liter gibberellic acid (GA3). Cotyledon and epicotyl growth of A. maximowiczianum embryos were greatest when treated with GA3. Embryos of A. maximowiczianum incubated with 6-ben-zylamino purine (BA) or 6-furfurylamino purine (kinetin) developed the longest roots while those treated with indoleacetic acid (IAA) or naphthaleneacetic acid (NAA) remained tightly coiled and dormant. Excised embryos incubated in darkness or intact seeds placed in all treatments failed to germinate. In A. maximowiczianum 3 sites of dormancy delay germination: pericarp, seed coat, and embryo.

Open Access

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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Abstract

Axillary shoot growth on scions of poinsettia (Euphorbia pulcherrima Wild, ex Klotz) was regulated by grafting nonbranching (‘C-1’) and self-branching (‘Amy’, ‘Glory’, ‘Super Rochford’) cultivars on each other. Branching of ‘C-1’ was increased when scions were grafted onto self-branching rootstocks and branching was decreased on self-branching cultivars grafted onto ‘C-1’ rootstocks. Initiation of axillary bud growth was promoted on younger nodes of ‘C-1’ when grafted onto self-branching rootstocks. Increased branching propensity of ‘C-1’ scions grafted onto rootstocks of self-branching types continued even after vegetative cuttings were rooted. Axillary bud activity was unaffected by leaf removal. Results suggest that axillary bud activity is governed by shoot and root interactions of the plant and that axillary shoot growth is governed by some endogenous factors translocated from the roots across the graft union to the shoot.

Open Access

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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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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Leaf impressions were made from two short-lived (4 and 5 d) inbreds, a long-lived (11 d) inbred, and their hybrids (8 and 9 d) of Antirrhinum majus L. using Super Glue and glass microscope slides. Leaves were taken from mid stem, pressed on glass slides (under side down), spread with a small amount of Super Glue, set for 3 to 4 s. Then, the leaf was peeled off leaving a permanent impression in the glue. Slides were placed under a microscope equipped with a video imaging system and computer images were taken to facilitate counting of stomatal complexes. Number of stomata ranged from 10,400 to 21,300 per cm2 of leaf. A LI-COR LI-3100 area meter (LI-COR, Inc. Lincoln, Neb.) was used to measure total leaf area of 40-cm cut flower stems of each accession. Stomata per flowering stem ranged from 1,074,000 to 2,282,000, with the long-lived inbred having the fewest stomata, the hybrids intermediate with 11% to 21% more, and the short-lived inbreds having 40% to 113% more stomata per stem. It appears long postharvest life of A. majus is associated with flowering stems with fewer stomata per cut stem.

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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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Efforts to improve postharvest longevity of fresh-cut flowers has only recently turned toward selection and breeding. Conventional methods to extend keeping longevity of cut flowers depend on use of chemical treatment placed in holding solutions. Postharvest longevity studies were initiated with Antirrhinum majus L. (snapdragon) to determine: if natural genetic variation existed for cut-flower longevity, the inheritance of the trait, heritability, and associated physiology. Evaluation of commercial inbreds held in deionized water revealed a range in cut-flower longevity from a couple of days to 2.5 weeks. The shortest- and longestlived inbreds were used as parents in crosses to study the aforementioned areas of interest. Information will be presented on inheritance of cut flower longevity based on populations evaluated from matings for generation means analysis and inbred backcross method. Also presented will be information on stomata, transpiration, carbohydrate, fresh-weight change, and forcing temperature relative to postharvest longevity.

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Cut flowers of Antirrhinum majus L. (snapdragon) P1, P2, F1, F3, and F2 × F2 plants were harvested after the first five flowers were open and were evaluated for postharvest longevity to further evaluate genes conditioning postharvest longevity. F3 progeny evaluated were derived by selfing F2 selections of long keeping, mid-range, and short keeping types. F2 × F2 progeny evaluated were derived from crosses within and between postharvest longevity categories. Populations for evaluation were grown in the greenhouse in winter 1998-1999 in a randomized complete-block design according to standard forcing procedures. Thirty plants of each genotype were held in the laboratory in deionized water under continuous fluorescent lighting at 22 °C for postharvest assessment. The end of postharvest life was defined as 50% of the flowers drying, browning, or wilting. Data will be presented on postharvest longevity and allelic relationships within populations.

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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.

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