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  • Author or Editor: M. A. L. Smith x
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The regenerative capacity of mature pecan [Carya illinoinensis (Wangenh.) K. Koch] embryonic tissues was demonstrated after pretreating mature nuts to eliminate associated endogenous contaminants. Cultured cotyledon segments were induced to form adventitious roots in a medium with 50 μm NAA. A regeneration medium with 20 μm BA and 5 μm IBA stimulated prolific axillary shoot production from the embryonic axis without causing cotyledon abscission. Cotyledon retention was essential for shoot initiation and long-term development. Eighty-five percent of the shoots emerging from embryonic axes formed at the cotyledonary nodes. Thirty percent of the microshoots rooted on an auxin-free medium after preculture in a medium with 20 μm IBA. TDZ (25 μm) stimulated callus production from the cotyledonary nodes and radicles. Adventitious buds emerged on the callus surface and internally in callus. Chemical names used: a -naphthaleneacetic acid (NAA); 6-benzylaminopurine (BA); indole-3-butyric acid (IBA); N-phenyl-N'-1,2,3-thidiazol-5-ylurea (TDZ).

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Micrografting is an effective technique for elimination of viruses, early diagnosis of grafting incompatibilities, rejuvenation of mature tissue, and bypassing the juvenile phase in fruit trees. Current micrografting procedures are difficult, impractical, expensive, and generally result in an inefficient rate of successful graft production. In order to alleviate some of these limitations, a unique apparatus was designed to splice the in vitro-derived scion and rootstock together during the micrografting process. The dual-layer device was constructed with a pliant outer layer to facilitate manipulation during the grafting of micro-scale plants, and a delicate, absorbent inner layer to cushion the plant tissue and retain hormones and other compounds. These chemicals are slowly released at the grafting zone to alleviate oxidation and enhance callus formation at the cut surface of scion and rootstock. After healing, it is easy to remove the grafting apparatus from the grafted plant without damaging the tissues. This apparatus may be used to unite a scion and a rootstock with different stem diameters. Shoot-tip cultures of `McIntosh' and `M-7' apple and `North Star' sweet cherry, and in vitro seedlings of lemon, orange and grapefruit were used as a source of in vitro scions and rootstocks. Successful graft unions were developed, and the grafted plants were transplanted into the greenhouse environment Micrografted plants were sectioned to determine the anatomical characteristics of the graft union.

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Micrografting is au effective technique for elimination of viruses, early diagnosis of grafting incompatibilities, rejuvenation of mature tissue, and bypassing the juvenile phase in fruit trees. Current micrografting procedures are difficult, impractical, expensive, and generally result in an inefficient rate of successful graft production. To alleviate some of these limitations, a unique apparatus was designed to splice the in vitro-derived scion and rootstock together during the micrografting process. The dual-layer device was constructed with an outer layer of aluminum foil, with flexibility to facilitate manipulation during the grafting of micro-scale plants. A delicate, absorbent inner layer of paper toweling cushions the plant tissue. It also may be treated with hormones and other compounds. After healing, it is easy to remove the grafting apparatus from the grafted plant without damaging the tissues. This apparatus may be used to unite a scion and a rootstock with different stem diameters. Shoot-tip cultures of `McIntosh' and M.7 apple and `North Star' sour cherry, and in vitro seedlings of lemon, orange, and grapefruit were used as a source of in vitro scions and rootstocks. Successful graft unions were developed, and the grafted plants were transplanted into the greenhouse environment.

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A whole plant microculture (WPMC) screening system facilitated rapid, quantitative appraisal of salt stress effects on `Micro-Tom' miniature dwarf tomato. Axillary bud explants were micropropagated on a hormone-free control medium (conductivity = 3.3 dS m-1), gradually introduced to treatments with increasing NaCl or Na2SO4 concentrations via biweekly subculture to fresh media (7,6, 12.8, or 18 dS m-1), and monitored over a subsequent 5 week culture period. Non-intrusive video image analysis techniques were adapted to quantify morphometric (shoot growth rate, area, and length; root length and area) and photometric (ruler and tissue quality) plant responses. Shoot growth was only slightly inhibited at 7.6 and 12.8 dS m-1, but was severely stunted and distorted on high salt (18 dS m-1) media. Root growth inhibition (significantly shorter and thinner primary rants) was first evident at 12.8 dS m-1 after 3 weeks of treatment. At 18 dS m-1, conspicuous retardation of root growth relative to controls could be gauged after only one week. Shoot tip chlorosis was observed in the lowest salt-supplemented treatment after three to four weeks of culture, but overall shoot yellowing at the two highest conductivities was marked after only a few days. Chlorosis symptoms were not uniform within treatments. Cell osmotic concentration showed a linear increase with increasing medium salinity. The WPMC system expedited time course observations of stress symptom development, paralleled stress response trends observed in solution culture tests, and provided an excellent vehicle to investigate plant adaptation to saline conditions.

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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.

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Dry edible beans (Phaseolis vulgaris) represent an inexpensive way to incorporate protein into the diet as a food ingredient, but beans contain unpleasant flavors and several anti-nutritional factors that limit their use without first processing with long heat treatments. `Great Northern' bean flour was processed using either static or specially designed dynamic (continuous) processing methods. The dynamic process treated flour slurries at temperatures up to 124°for 20 sec. The slurries were quick-frozen and freeze-dried after frozen storage periods of 0, 8, 24, 120, or 504 hr. The flours were analyzed for sensory properties, emulsifying activity, foaming properties, and trypsin inhibition. The heat treatments improved sensory attributes of the flour. The foam capacity and foam stability decreased in heat-treated flours. Trypsin inhibitor activity was at a minimum level immediately following thermal processing, but increased with time in frozen storage prior to drying. Minimal thermal processes cannot be relied upon to inactivate trypsin inhibitors.

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Many plants can produce bioactive chemicals with medicinal or health benefits, which has stimulated a whole new research effort aimed at extracting & improving natural phytochemicals. Begonia is a rich source of biologically-active phytochemicals and an excellent donor for natural anthocyanin pigments. High levels of triterpene compounds and a host of potentially-useful flavonoids have been isolated from Begonia sp., which may account for its frequent use as a medicinal plant remedy in a diverse array of cultures worldwide. Deliberate shifting of the physical and chemical microenvironments can have a significant effect on anthocyanins and precursors produced in vitro. This realization offers the potential to thoroughly screen and study valuable phytochemicals from Begonia. Begonia genotypes from 3 species were screened to identify callus induction techniques. Contamination inherent in the vascular system of one genotype, along with spontaneous organogenesis, were found to be recurrent problems. These were partially alleviated by light and growth regulator treatments. Studies comparing callus and in vitro vegetative tissues as resources for phytochemical extraction are scheduled.

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The influence of spectral irradiance on in vitro anthocyanin production in white friable callus of cranberry cultivars `Stevens', `Searles', and `Ben Lear' was examined by modifying cool white fluorescent lamp emission. Filters were used to shift spectral balance to blue, yellow, and red wavelengths at different PPF levels within a span of 30 to 150 μmol m-2s-1. White, friable, dark-grown calli—originally derived from shoots and leaves of shoot culture stock plants—were maintained approximately 6 months with subculture every 4 wk. Uniform callus masses were then subcultured to pigment induction medium and transferred to treatment microenvironments. Visual and machine vision analysis of pigmentation was assessed weekly for one month. Higher PPF levels stimulated the most rapid anthocyanin synthesis. Calli in the blue treatment produced the greatest pigmentation within the first two weeks. All three cultivars responded similarly to the treatments, however, pigmentation was slightly more intense in `Ben Lear' at higher PPFs. Results indicate spectral irradiance significantly affects anthocyanin synthesis in cranberry callus cultures, and suggest that manipulation of the physical microenvironment is an important consideration in development of efficient in vitro natural pigment production systems.

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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.

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Polyphenolic compounds (particularly anthocyanins, proanthocyanidins, and other flavonoids) from some fruits and vegetables have significant and diverse impacts on human health preservation. While it's well recognized that some of the polyphenolics in foods we consume have a protective and proactive role against disease, very little has been known about how they accomplish this feat. A range of bioassays (in vitro and in laboratory animals) were adapted to examine compounds extracted from berry fruits, and separated into distinct fractions by vacuum chromatography. The proanthocyanidin class of compounds, as well as mixtures of proanthocyanidins and other flavonoids, were significantly bioactive against both the promotion and initiation stages of chemically-induced carcinogenesis. Potent antioxidant activity was not confined to particular fractions, but was present in several classes of compounds. Identification and characterization of the bioflavonoids is complicated both by apparent interactions between related compounds that occur together within horticultural fruits, and interferences from some substances (pectins and complex sugars) that depress observed response in bioactivity assays.

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