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Abstract
After warm stratification for 6 weeks, depulped seeds of Liriope muscari L. ‘Variegata’ and Ophiopogon japonicus (Thunb) Ker. germinated 77 and 74%, respectively, compared to about 25% for intact fruits. About 65% of the seedlings of variegated liriope exhibited some form of variegation, with several variagation patterns evident.
Cephalotaxus species are needle evergreens offering the aesthetic qualities of Taxus, yew, yet are heat- and drought-tolerant, sun- and shade-adaptable, and resist deer browsing. They are adaptable to nursery and garden cultivation in USDA hardiness zones (5)6–9. Unfortunately, the various species are frequently confused in the American nursery trade due to their extreme similarity in morphology. Recently, molecular data have been widely applied in the taxonomic studies, especially DNA sequencing. The chloroplast gene rbcL of Cephalotaxus has been sequenced for determining species relationships. The preliminary results show that C. oliveri Mast. has 10 base changes from C. drupacea Sieb. et Zucc., while only one base difference occurred between C. drupacea and C. harringtonia (Forbes) Koch. There are between one and 10 base substitutions among C. fortunei Hooker, C. koreana Nakai, and C. sinensis (Rehd. et Wils.) Li. Compared with other closely related conifers, Cephalotaxus has a substantial number of differences among species except between C. drupacea and C. harringtonia, which may not be distinct species. Detailed data relative to gene sequencing, growth morphology, and horticultural characteristics should lead to correct identification of species and great horticultural uses. Furthermore, the method of rbcL sequence can be applied to distinguish other morphologically homogeneous ornamental plants.
Buddleia taxa were assessed for two-spotted spider mite (Tetranychus urticae Koch) resistance using a leaf disk bioassay, a novel shell vial bioassay and a field trial. Leaf pubescence and chemistry were examined for their role in two-spotted spider mite resistance. Results from bioassays and field sampling identified highly resistant taxa including B. fallowiana Balif. `Alba' and B. davidii × B. fallowiana Franch. `Cornwall Blue' as well as susceptible taxa including B. davidii Franch. `African Queen' and B. lindleyana Fort. ex Lindl. `Gloster'. The shell vial bioassay was an accurate predictor of field resistance to spider mite. Leaf pubescence was quantified by calculating the collective length of trichome branches per square millimeter of leaf surface area [effective branch length (EBL)]. EBL values ranged from 39 to 162 mm·mm-2 of leaf surface area among Buddleia taxa. Resistance was positively correlated with increased pubescence. Removal of pubescence by peeling resulted in increased oviposition of two-spotted spider mites. Exposing female two-spotted spider mites to a methylene chloride extract of B. davidii × B. fallowiana `Cornwall Blue' using a modified shell vial bioassay resulted in reduced oviposition and a methylene chloride extract of B. davidii `African Queen' resulted in no difference in oviposition when compared with a control. While pubescence is the best indicator of resistance to the two-spotted spider mite in Buddleia taxa, it is possible that defensive compounds are involved.
Cephalotaxus Sieb. and Zucc. (plum yew) species and cultivars have become popular because of their sun and shade tolerance, resistance to deer browsing, disease and insect tolerance, and cold and heat adaptability. Unfortunately, the nomenclature and classification in the literature and nursery trade are confusing due to their extreme similarity in morphology. In this study, amplified fragment-length polymorphism (AFLP) markers were used to discriminate taxa and evaluate genetic differences among 90 Cephalotaxus accessions. A total of 403 useful markers between 75 and 500 base pairs (bps) was generated from three primer-pair combinations. Cluster analysis showed that the 90 accessions can be classified as four species, C. oliveri Mast., C. fortunei Hooker, C. harringtonia (Forbes) Koch., and C. ×sinensis (a hybrid species); four varieties, C. fortunei var. alpina Li, C. harringtonia var. koreana (Nakai) Rehd., C. harringtonia var. nana (Nakai) Hornibr., and C. harringtonia var. wilsoniana (Hayata) Kitamura; and eight cultivars. Suggested names are provided for mislabeled or misidentified taxa. The Cephalotaxus AFLP data serve as a guide to researchers and growers for identification and genetic differences of a taxon, and a model to establish a cultivar library against which later introductions or problematic collections can be cross-referenced.
Although differential thermal analysis has been routinely used to evaluate cold hardiness, the relationship of deep supercooling ability and plant survival are not well understood. In this study, we compared the seasonal profiles of changes in low-temperature exotherm (LTE) occurrence with visually determined cold hardiness of Acer rubrum L. `Armstrong', Fraxinus americana L. `Autumn Purple' and Zelkova serrata (Thunh.) Mak. `Village Green' growing in three locations representing plant cold hardiness zones 8b, 7b, and 5a. Between December and February, LTEs in Acer rubrum `Armstrong' and Fraxinus americana `Autumn Purple' occurred at temperatures around 10 to 25C lower than the lowest survival temperatures. The mean difference between LTEs and lowest survival temperature was not significant for Zelkova serrata `Village Green' from January to April and for Acer rubrum `Armstrong' and Fraxinus americana `Autumn Purple' in March. Data indicated that LTEs could be used as an estimate of lowest survival temperature in Zelkova serrata `Green Village' but not in Acer rubrum `Armstrong' and Fraxinus americana `Autumn Purple'. This study demonstrated that LTEs may not reliably estimate cold hardiness in all species that deep supercool. Factors other than freeze avoidance ability of xylem may limit stem survival at temperatures above the LTE.
Abstract
Acer rubrum L. ‘October Glory’ cuttings taken on 15 June 1984 were subjected to short day (SDT) (800-1700 HR) or short day plus night interruption treatments (NIT) (800-1700 plus 2200-200 HR) from 25 July until 22 Oct. 1984. Additional cuttings taken on 14 Aug. were subjected to the same photoperiod treatments from 10 Sept, until 22 Oct. For the 15 June cuttings, the NIT treatment induced significantly greater percent budbreak than the SDT, but did not induce significantly greater overwinter survival. Cuttings of 15 June that broke bud under NIT had significantly greater stem length and dry weight than cuttings that broke bud under SDT. SDT and NIT cuttings of 15 June that broke bud had significantly greater percent root carbohydrates, total grams of carbohydrates, and percent overwinter survival then cuttings that did not break bud. For the 14 Aug. cuttings, 1% of the cuttings broke bud, yet 95% (SDT) and 90% (NIT) of the cuttings survived the winter, and no difference in cutting carbohydrate levels, except stem starch, existed between the two treatments.
Abstract
Rooting of light-grown cuttings of mung bean [Vigna radiata (L.) R. Wilcz.] was stimulated by wounding and by the ethylene-releasing compound (2-chloroethyl)phosphonic acid (ethephon) at 0.1, 1.0, and 10.0 mg/liter with a maximum response at 1 mg/liter. The inhibitor of ethylene synthesis, aminoethoxyvinylglycine (AVG), at 10 µm, significantly decreased root number in wounded cuttings, but ethephon overcame this inhibition. Rooting in wounded cuttings was stimulated by indolebutyric acid (IBA) at a concentration of 5 × 10−6 m but root numbers decreased by 56% with AVG + IBA. Application of ethephon or IBA, and extensive wounding, caused an upward redistribution of roots away from the base of the cuttings.
Abstract
A tissue infusion method was used to demonstrate nitrate reductase activity in the leaves of Vaccinium corymbosum L. grown with 3 N sources and in 2 pH regimes. Activity was not detectable by the extraction and assay of homogenized leaves of Kalmia latifolia L., Leucothoe catesbaei Gray, Malus sylvestris Mill., Pieris japonica D. Don., and Rhododendron catawbiense Michx. or in the roots of Leucothoe and Zea mays L., but it was detectable in both leaves and roots by the tissue infusion method.
The Department of Horticulture has introduced over 20 new plants into the Georgia and southern nursery trades. The program serves as a conduit for evaluating and distributing plants from the U.S. National Arboretum, Arnold Arboretum, individuals and nurseries. Propagation requirements and cold hardiness estimates are determined for most of the potential introductions. Cooperating nurseries provide real-world assessments of container and field cultural criteria. Further, plants are tested under field conditions at the Department's research farm. Plants are promoted through lectures, articles, and distribution to any interested Georgia nursery. Numerous trade, popular, and refereed articles were spawned from the program. Selected plants have been provided to commercial tissue culture labs for stock increase.
To date, the University has realized no financial return. A genuine need exists to generate income from royalties to sustain and enlarge the program.
A list of the Georgia introductions will be available to all participants and several of the more notable introductions will be discussed.
Abstract
Fruit pulp extracts of Liriope muscari (Decne.) Bailey were analyzed chromatographically and spectrophotometrically to determine which compounds were responsible for their blue-black color. A trihydroxy series of mon-oglycosylated anthocyanidins (delphinidin, petunidin, malvidin) were isolated. The malvidin glycoside appeared to be involved in a co-pigment complex with at least a flavone, explaining the neutral pH-stable blue color. Previous work indicated that a water-soluble seed germination inhibitor was present in the pulp. Nine bands were collected as fractions from Sephadex column chromatography. Each fraction was monitored by paper chromatography before use in a bioassay that tested for germination inhibitors. Several fractions significantly inhibited seed germination of Cucumis sativus L. ‘Poinsett’. Four classes of phenolic compounds were identified from the chromatograms: anthocyanins, anthoxanthins, phenolic acids, and a tannin-like polyphenol. Phenolic acids and the tannin-like substance were most prevalent in the 3 most toxic fractions. A mixture of these 3 fractions caused seed germination inhibition exceeding that attained by the individual fractions. Caffeic acid was tentatively identified as one of the phenolic acids present. Results indicated that germination inhibition is due to the combined action of several phenolic compounds.