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Various cultivars of strawberry (Fragaria ×ananassa Duch.) were stored for 42 h under an atmosphere of 15% CO2 to determine whether their firmness would be enhanced. Compared to initial samples and stored control samples, enhanced firmness was found in 21 of the 25 cultivars evaluated. The CO2 had no effect on color, as measured by Hunter `L', `a' and `b', or on soluble solids concentration (SSC) or pH. There were significant differences among cultivars in firmness; Hunter color `L', `a', and `b'; SSC; and pH.
Abstract
The rooting of strawberry runner tips was studied in relation to soil moisture tension in the rooting medium and soil moisture supplies to the mother plants. In the first weeks of runner establishment the rate and amount of top growth was controlled largely by the moisture supply to the mother plant. Growth was decreased as moisture stress on the mother plant was increased. For the most part, root habit of the runner was independent of influence from the mother plant. Variations in soil moisture tension in the rooting medium had little influence on top growth of the runner except for leaf area but did influence root growth significantly. Secondary root growth was restricted by both very wet and very dry soil conditions. The results confirmed that the initial number of main roots formed and their penetration was independent of moisture tension in the rooting medium. Organic matter additions to the rooting medium did not influence moisture effects appreciably.
The game-show format, used recurrently in an undergraduate-level, introductory plant propagation course, fostered a friendly, competitive incentive for students to master facts and concepts critical to understanding processes in plant physiology. Because student teams, rather than individuals, served as the contestants in each game, and because game points were never translated into grade points, participants and observers learned from and enjoyed the exercises without anxiety. Propagation-specific clues and questions were prepared for “Wheel of Fortune,” “Win, Lose, or Draw,” and other games. These were followed up at the end of each semester with several play-off rounds of a plant propagation variant of “Jeopardy!”, which served as an excellent means of course synthesis and review of key concepts. The format allowed for liberal use of humor as an effective pedagogical tool and resulted in the hands-on contributions of former students in construction of new game quizzes and puzzles for subsequent semesters.
The only method for large scale production of pure hybrid seed in Zinnia elegans involves the use of male sterile individuals. The male sterile trait, however, is a three gene recessive which at best produces only 50% male sterile progeny from seed. Since no method of clonal propagation is available, seed-produced female lines require labor intensive field roguing to insure removal of all normal flowered individuals. Clonal micropropagation was investigated as a means of mass producing male steriles for use as female lines. Sterilization procedures were developed for seed and axillary bud explants. Shoot proliferation media containing various levels of BAP, 2ip, and kinetin were screened using in vitro germinated seedling explants of the inbred line `Orange Starlight'. Microshoots demonstrated a high rooting percentage after 2 weeks on basal medium without growth regulators. Plantlets were easily acclimated in 1 to 2 weeks in a high humidity environment. In vitro derived plants of identified male sterile plants were phenotypically evaluated as to their suitability for use in field production.
The only method for large scale production of pure hybrid seed in Zinnia elegans involves the use of male sterile individuals. The male sterile trait, however, is a three gene recessive which at best produces only 50% male sterile progeny from seed. Since no method of clonal propagation is available, seed-produced female lines require labor intensive field roguing to insure removal of all normal flowered individuals. Clonal micropropagation was investigated as a means of mass producing male steriles for use as female lines. Sterilization procedures were developed for seed and axillary bud explants. Shoot proliferation media containing various levels of BAP, 2ip, and kinetin were screened using in vitro germinated seedling explants of the inbred line `Orange Starlight'. Microshoots demonstrated a high rooting percentage after 2 weeks on basal medium without growth regulators. Plantlets were easily acclimated in 1 to 2 weeks in a high humidity environment. In vitro derived plants of identified male sterile plants were phenotypically evaluated as to their suitability for use in field production.
`Fantasia' nectarines (Prunus persica L.Batsch) were either stored immediately at 0.5C or subjected to a 48-h delay at 20C in air or with 5% CO2 in air before storage. Samples were evaluated at harvest and after 18, 25, 32, 39 and 46 days storage in air or in 5% O2 with 0%, 4%, 8%, or 12% CO2. All samples were evaluated at optimum ripeness. A combination of delayed storage and elevated CO2 in storage effectively delayed chilling injury (CI) symptoms. Control of CI increased with increasing CO2 level in delayed and nondelayed treatments. Delayed storage was not effective without elevated levels of CO2 in the storage atmosphere. Fruit that was stored without delay did not soften normally during the ripening period and developed a dry, rubbery texture. The effect was enhanced as CI progressed, resulting in increased firmness of ripened fruit with increased storage time. The delayed storage treatments softened normally during ripening, but CI fruit had a dry, mealy texture. Internal conductivity measurements correlated well with CI development. Off-flavors were detected at the higher levels of CO2 storage.
In vitro cell cultures of huckleberry and bilberry are sources of phytochemicals for use as food colorants and bioactive chemopreventives. Shoot cultures provide a convenient, presterile source of explants for production of callus rich in extractable pigments or other chemicals. Efficient callus formation only occurs with good-quality shoots. In this study, liquid and gelled support systems were compared in terms of their effect on shoot growth. Gellan gum-based support resulted in excellent shoot proliferation and suitable shoot length for huckleberry cultures, whereas bilberry performed slightly better on agar and agar/gellan gum support. Bilberry had a more-rapid growth rate than huckleberry. Hyperhydricity was found with the use of rafts for both species. These shoot cultures have been used as vegetative explants for callus, and have produced vivid anthocyanins in solution cultures.
Abstract
Nitrogen zinc nitrate solution was applied to 18 species of container-grown woody ornamentals to determine if Zn levels could be increased and related to increased growth and plant quality. In 13 species there was an increase in Zn concentration as compared to untreated plants. Quality was improved in 3 species without a related increase in Zn content. Fe and Mn concentrations were unaffected in most species and no phytotoxicity was observed.
Use of a liquid media during micropropagation has promoted improved proliferation and rooting response in several species. In this experiment, a double phase system (a combination of liquid and agar solidified medium) was applied to three cultivars of miniature roses (Rosa chinensis var. minima) to determine the effects on shoot quality and subsequent ex-vitro rooting. Applications of liquid media to the surface of agar solidified media were made at 0, 2, and 4 weeks. Evaluation via computerized image analysis after eight weeks of proliferation revealed equal or greater values for shoot length, area and weighted density (equivalent to fresh weight) for cultures receiving overlay, regardless of timing, compared to the solid media control. Additionally, application of a liquid overlay improved rooting response by up to 20% over the control and resulted in a tendency for a greater number of roots of greater length and area than the treatment without liquid media overlay.
Polyphenols were analyzed in expanding buds and developing leaves of pecan [Carya illinoensis (Wangenh.) C. Koch] cultivars with varying responses to Cladosporium caryigenum (Ell. et Lang. Gottwald), the organism causing scab. Plant tissue extracts were examined by high-performance liquid chromatography using a water: methanol gradient to separate polyphenolic components on a C-18 reversed phase column. A diode-array detector was used to identify profile components by retention times and computer matching of ultraviolet spectra to standard compounds in a library. Concentrations of these polyphenols were compared throughout the growing season in leaves of pecan cultivars with low (`Elliott'), intermediate (`Stuart'), and high (`Wichita') susceptibility to scab; during susceptibility to infection by Cladosporium caryigenum from 16 cultivars; and in `Wichita' leaf discs with and without scab lesions. The major polyphenolic constituent of tissues for all cultivars was identified as hydrojuglone glucoside, which was detected in intact buds and leaves throughout the growing season. Hydrojuglone glucoside concentration increased concomitantly with leaf expansion and then declined slowly. Juglone was barely, if at all, detectable, regardless of leaf age. No correlation was found between cultivar susceptibility to pecan scab and the levels of either juglone or hydrojuglone glucoside in the healthy leaves of 16 cultivars. Leaf tissue with scab lesions had significantly higher juglone and hydrojuglone glucoside levels than leaf discs without scab lesions. Chemical names used: 4-8-dihydroxy-1-naphthyl b-d-glucopyranoside (hydrojuglone glucoside); 1,5-hydroxy-naphthoquinone (juglone).