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Chamchuree Sotthikul and Pimchai Apavatjrut

Propagation of Curcuma roscoeana in vitro was done successfully by culturing 0.5 × 1.0 mm shoot tips from young buds onto modified MS (1962) + 0.25 mg·L–1 kinetin. The bud-derived new plantlets could be multiplied on a new medium. Stem explants 10 mm in size, measured from base of the plantlets longitudinally cut in half, were the most suitable culture explants providing 2.8 new healthy plantlets/cultured explant. Explants from 4, 6, and 8 weeks old plantlets were more suitable than those of 2 weeks old when grown on agar or in liquid medium. From a histological study, it was found that new buds developed from preexisting meristems. The buds, like root initiation, could also occur directly from initial culture explants, not through callus. The plantlets obtained could successfully be transferred into growing pots, having a 95% survival rate.

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Janet S. Mrosek and Stephen C. Myers

The relationship between cell division, nonstructural carbohydrates and fruit size was investigated using 5-year-old `Encore' peach [Prunus persica (L.) Batsch]. The trees, which were trained to two opposing scaffolds, were selected for uniformity based on tree size and floral bud density. One-year-old shoots ranging in size from 20 to 30 cm were tagged from throughout the canopy. At anthesis, one entire scaffold was thinned of 75% of its flowers, leaving 25% in the mid-section of each shoot. The opposing scaffold served as the control. Samples were taken at three intervals for histological analysis: Anthesis, 30 days, and 45 days after full bloom. Nonstructural carbohydrates were analyzed on samples taken at five intervals: Anthesis, 10, 20, 30, and 45 days after full bloom. Volumetric size increased 29% by 30 days after full bloom, and 64% by 45 days after full bloom. Final fruit size (volumetric) was increased 8% by harvest.

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Sharon Bates, John E. Preece, John YOPP, and Robert Trigiano

Dissected white ash seeds were placed on a MS basal medium containing 10 μM TDZ and 1 μM 2,4-D. Adventitious buds formed directly and indirectly on cotyledons and hypocotyls that were in contact with the medium. Histological observations after 7 days from initiation indicated early divisional events originated directly in subepidermal layers on adaxial portions of the cotyledons. As these cells divided, the growth ruptured the epidermis. Bud-like structures were seen at 3 weeks. After transfer to a secondary medium containing 3 μM TDZ, 1 μM BA, and 1 μM IBA, some of adventitious buds elongated. Efforts (gibberellin, etiolation, ABA, and silver nitrate treatments) to increase the number of elongated buds have been unsuccessful. Excised adventitious shoots were rooted under mist and established in the greenhouse.

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K.R. Malueg, S.E. Schlarbaum, E.T. Graham, and R.N. Trigiano

Development of Cornus florida L. pollen was monitored using standard paraffin histological techniques and light microscopy. Terminal buds (putative floral buds) were collected over a 6 weeks from mature landscape trees located on The Univ. of Tennessee Agricultural Campus, Knoxville. Examination of samples taken at 3- to 7-day intervals revealed variations in development representing 1- to 2-week differences between florets in a single inflorescence, florets on the same tree, and florets from different trees. Floral initiation occurred before 19 July in the 2 years of this study. Pollen development followed typical angiosperm stages: tapetal cells were multinucleate, pollen tetrads were tetrahedral, and meiosis occurred late in the developmental period. Pollen grains appeared morphologically mature by early September in both years.

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Carl E. Motsenbocker, Marshall D. Sundberg, and Yuehe Huang

Two lines of tabasco pepper (Capsicum frutescens) were previously identified that differ significantly in ease of fruit detachment force. Greenhouse-grown plants of these lines, `McIlhenny Select' and `HP', were investigated for differences in cell organization in the fruit-receptacle area and the separation zone at different developmental stages. Histological examination indicated that fruit of `HP', which requires greater force to separate, exhibited a larger region of sclerified cells within the fruit-receptacle area. In contrast, fruit of `McIlhenny Select', the line that detaches easier, had fewer sclerified cells in this region. Cell sclerification increased for both lines with increasing fruit maturity. The fruit-pedicel separation zone in both lines is distal to the sclerified region and is composed of parenchymatous fruit tissue. The separation zone for `HP' includes at least 10 additional distal cell layers in the fruit septal region than `McIlhenny Select'.

Open access

Hiroshi Watanabe

Abstract

Continuous gamma irradiation during polyembryogenesis was tested to determine if the number of embryos could be reduced in ‘Marukinkan’ (Fortunella japonica Swingle), a polyembryonic Citrus relative, and effectively increase the number of F1 hybrids in crosses. The number of embryos in untreated plants was 10.9, and this number was reduced with increasing exposure rate to 2.4 at 500R/day. The percentage of monoembryonic seeds in untreated plants was 1.1, and this was raised with increasing exposure rate to 34.0% at 500R/day. Cytological and histological observations of polyembryogenesis showed that early adventive embryonic cell divisions were retarded severely by gamma-rays (500R/day), and most of them could not develop beyond the stage of small globular proembryos consisting of 1 to 4 cells. These proembryos finally disappeared, but the fertilized embryo generally survived, probably because of a division earlier than those of adventive embryos and a vigor afforded to fertilized cells.

Open access

Michael Marcotrigiano, Pamela A. Morgan, Harry J. Swartz, and Jennifer Ruth

Abstract

A phenotypic and sexual analysis of Fragaria vesca ‘Albo-Marginata’ determined that the leaf variegation was of chimeral origin. Stable periclinal chimeras were established in vitro from runner tips. Plants were transferred to proliferation media containing 0.5 μm IBA, 0.3 μm GA3, and BA at either 0, 1.3, 4.4, or 13.2 μm. Whereas the histogens of field-grown runner plants remained stable, more than 90% of the plantlets propagated in vitro varied from the original explants. Most variants were albino or were green, but some were mericlinal chimeras. Histological evidence indicated that many shoots were adventitious, arising from basal callus tissue or petioles. Chemical names used: 1H-indole-3-butanoic acid (IBA); gibberellic acid (GA3); N-(phenylmethyl)-1H-purin-6-amine (BA).

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Maryke A. Cleland, Cynthia Jones, and Mark H. Brand

An interspecific hybridization program involving five species of Impatiens was initiated to delineate incompatibility barriers. With the exception of one cross, no viable hybrid seed was recovered. Fluorescence microscopy revealed foreign pollen tubes to reach ovules in all crosses, although not all ovules were approached. A histological study involving I. auricoma Baill. and I. walleriana Hook f. ensued to confirm the presence of hybrid embryos. Developing I. walleriana × I. auricoma and reciprocal hybrid embryos were compared to self embryos. Development of hybrid embryos was delayed as early as five days post-pollination. I. walleriana × I. auricoma embryos continued to develop for 8 days post-pollination, but did not reach a size greater than a 5-day self embryo. Excessive endosperm was observed in the hybrid. I. auricoma × I. walleriana embryos continued to enlarge up to ovary abortion but did not reach a size greater than a 7-day self embryo and little to no endosperm developed. Disintegration of ovules included disorganization and collapse of the endosperm, and vacuolization and loss of turgidity of the embryo.

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X. Wang, J.T.A. Proctor, S. Krishna Raj, and P.K. Saxena

Ginseng is a very valuable agricultural species grown for its root, which contains pharmacologically active constituents. One limiting factor for expansion of ginseng production is an efficient method for mass propagation. Currently, seeding is the principal method of propagating ginseng, but the embryo of ginseng seeds at harvest is immature. A stratification schedule consisting of a cool-warm-cool temperature treatment over 18-22 months is required for embryo development and seed germination. An alternative for the efficient production of ginseng is mass propagation through the use of in vitro culture techniques. The objective of this work was to develop a highly efficient system for regeneration of ginseng. The efficacy of three auxins, viz. 2,4-D, NAA and dicamba, were compared for the induction of somatic embryogenesis in American ginseng. Somatic embryos formed on ginseng cotyledonary, zygotic embryo, and shoot explants after 8 weeks of induction by the auxins. Significantly more somatic embryos were induced by culture of any of the ginseng explants on media supplemented with 5 μmol·L-1 2,4-D than any other auxin treatment. Histological and SEM studies confirmed that the regenerants were somatic embryos. Somatic embryos germinated and developed into normal plants in 3-6 months. The development of a regeneration system for ginseng using somatic embryogenesis is a necessary first step for mass propagation and the improvement of American ginseng.

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Martin C. Goffinet, Mary Jean Welser, Alan N. Lakso, and Robert M. Pool

Northeastern U.S. grape growers have become more knowledgeable about many aspects of grape production, including pruning and training, canopy management, nutritional recommendations, pest and disease management strategies, vineyard floor management, etc. Important to all these aspects is a firm understanding of vine structure and development. Yet, there is no current publication on vine growth and development that growers and researchers can consult to gain an understanding of the organs, tissues, and developmental processes that contribute to growth and production of quality vines in the northeastern U.S. climate. A concerted effort is underway to secure enough information on how vines are constructed, grow, and develop in the northeast so that a publication useful to a wide audience can be produced. Our objective is to consolidate information already on hand that can help explain the internal and external structures of grapevines that are pertinent to the needs of northeast growers, to add information that is lacking by collecting and examining vine parts, and to work toward integrating vine structure with vine physiology and viticultural practices. Over the past decade, organs of various native American, French hybrid, and vinifera varieties have been collected from vineyards at Cornell's experiment stations and from growers' vineyards in the Finger Lakes and Lake Erie regions. Much quantitative data on vine development have been collected and interpreted. Lab work has included dissections of organs, histological and microscopic examination, microphotography, and the production of interpretive diagrams and charts. A list of the subject matter and examples of visual materials will be presented.