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Somatic embryogenesis was induced from internodal callus of `Scania', `Improved White Sim', and `Sandra' carnation (Dianthus caryophyllus L.). The optimum protocol for the induction of somatic embryogenesis included initiation of callus in liquid basal Murashige and Skoog medium supplemented with 3.0 μm 2,4-D followed by transfer to liquid basal medium lacking 2,4-D for embryo development. Somatic embryos originated from single cells and early embryonic development proceeded conventionally (i.e., via globular, heart-shaped, and torpedo stages), but clearly developed apical or root meristems were not always formed. A few embryos developed into seedlings and were acclimatized to ex vitro conditions. Chemical name used: 2,4-dichlorophenoxyacetic acid (2,4-D).

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Abstract

Embryo sac formation in borage (Borago officinalis L.) was of monosporic, Polygonum type. Zygotic embryogenesis resembled the Piperad type (Myosotis Variation) without a suspensor after the four-cell stage with free nuclear endosperm. Cotyledons were initiated 4 days after pollination (DAP) and grew rapidly until 12 to 14 DAP, with seed maturity at 18 DAP. There were two patterns of in vitro somatic embryo development from embryogenic callus: 1) from single cells, which proceeded through typical zygotic embryo stages; or 2) from groups of cells that developed as a meristem. The advanced stages of somatic embryogenesis were characterized by abnormal cotyledon and hypocotyl morphology and incomplete apical development.

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Abstract

On current season’s growth of sour cherry (Prunus cerasus, cv. Montmorency) injury induced by (2-chloroethyl)phosphonic acid (ethephon) occurred at and below the nodes in tissues adjacent to the 3 leaf traces supplying each leaf. In the secondary xylem close to the cambium, separation and breakdown of cell walls resulted in the formation of gum cavities; injury occurred also in cortical tissues adjacent to the leaf traces. In older portions of the branch more severe injury occurred where large gum cavities formed in the outer secondary xylem and in cortical tissues. Superficial swelling, cell proliferation and surface cracks occurred on the branches near the nodes accompanied by exudations of gum. Injury and cell wall dissolution may be related to cellulase activity stimulated by ethylene released from the break down of ethephon within the tissues.

Open Access

Poinsettia stem breakage reduces plant quality and marketability. The cultivar `Freedom' is susceptible to stem breakage; however, the severity of stem breakage varies with crop and year. The following four experiments were conducted to determine the factors that influence stem breakage of `Freedom' poinsettias: 1) Cutting Stem Diameter. Cuttings were graded by stem diameter into small (5.0–5.4 mm), medium (6.0–6.7 mm), and large (7.3–8.3 mm) cuttings. 2) Premature Lateral Shoot Development.Small (1- to 3-cm-long) leaves near the shoot tip of the rooted cuttings were excised to remove the lateral shoots from apical dominance prior to pinching, thus causing the lateral shoots to develop prematurely. 3) Container Spacing. The control group was spaced to 35.6 × 35.6 cm at the time of pinching. The plants in one treatment were spaced to 23.1 × 23.1 cm 25 days after pinching, and then spaced to 35.6 × 35.6 cm 11 days later. The plants in a second treatment were grown pot-to-pot for 36 days after pinch, at which time they were spaced to 35.6 × 35.6 cm. 4) Node Number. Plants were pinched to eight nodes, while the control group was pinched to 5 nodes. Tissue development in the stem crotch; i.e., the area of lateral stem attachment to the main stem, was observed by microscopic examination of paraffin-embedded samples from each experiment every 2 weeks until anthesis. Lateral shoot strength was quantified by hanging a plastic beaker from the lateral stem and gradually adding water until stem crotch failure occurred. We observed that stem strength increased as cutting stem diameter increased. Plants pinched to eight nodes produced weaker lateral shoots than those pinched to five nodes. Premature lateral shoot development and container spacing did not affect stem strength.

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Upper surface leaf lesions on `Sunburst' mandarin [(Citrus reticulata Blanco × (C. paradisi Macf. × C. reticulate)] associated with feeding by the citrus rust mite [Phyllocoptruta oleivora (Ashm.)] are more severe than those on other citrus cultivars. Development of leaf lesions on `Sunburst' mandarin and two other cultivars were examined by light and electron microscopy. Damaged leaves treated with a fungicide confirmed that the anatomical changes on `Sunburst' are an enhanced wound periderm response to feeding injury by rust mite and not the result of fungal invasion.

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The growth in diameter of large-(`Loring' and `Suncrest') and small-fruited (`Bailey' and `Boone County') peaches [Prunus persica (L.) Batsch] was recorded at weekly intervals from 175 days prebloom to ripening. Samples collected at three dates prebloom, full bloom (FB), and four dates postbloom, including ripe fruit, were sectioned and stained. Total cell count and mean cell size were determined for prebloom ovaries and postbloom mesocarp tissue. Large-fruited cultivars had significantly more cells (up to 3.7 times) than small-fruited cultivars at all sampling dates. Cell sizes increased dramatically with fruit development, but were similar for all cultivars within each sampling date. These results suggest that mesocarp cell count is the major difference between small- and large-fruited peach cultivars and that this difference is determined early in the growth of the ovary.

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Abstract

In vitro studies indicated that an isolated embryonic axis, or an intact embryo with all or part of its cotyledons, of a ‘Delicious’ apple (Malus Xdomestica Borkh.) produced only a single shoot and root. Adventitious shoot formation was observed when the embryonic axis was excised and the cotyledons were grown in vitro. The number of shoots formed increased as the length of the transverse cut surface was increased. More than 30 shoots per explant were obtained when both the proximal and distal one-third sections of the cotyledon (relative to the embryonic axis) were removed. An increase in shoot number per explant resulted in decreased shoot length. A polar phenomenon was observed in all excision treatments; adventitious shoot formation occurred only at the proximal cut end of the cotyledon.

Open Access

Abstract

Eleven suspected somatic mutations, consisting of 7 trees and 4 individual branches of the ‘Montmorency’ cherry, were compared with standard ‘Montmorency’ for phenotypic traits including tree height, trunk circumference, leaf area, crotch angle, resistance of flowers to frost injury, pollen germination, fruit set, individual fruit weight, fruit removal force, and yield. Differences occurred between some variants and ‘Montmorency’ controls for all characters except fruit removal force. All variants were tetraploid (2n = 32), as is standard ‘Montmorency’, with no evidence of cytochimerism.

Open Access

Anatomical differences in leaves of queen palm [Syagrus romanzoffiana (Chamisso) Glassman] showing visible K, Mn, and Fe deficiency symptoms are described. Potassium-deficient leaves showed less organization in the mesophyll than healthy leaves. Adaxial fibers increased in diameter. Chloroplast frequency was reduced overall, but most severely in areas of the leaf showing gross symptoms of the deficiency. Manganese-deficient leaves had reduced chloroplast frequency, especially in tissue near necrotic areas, and thicker and more fibers per unit length. Iron-deficient leaves had few chloroplasts throughout the mesophyll, and also thicker and more fibers per unit length.

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Abstract

Spray applications of aqueous emulsions containing methyl decanoate killed the terminal meristem. This action stimulated the development of axillary buds producing branched stems. Early symptoms of spray activity occurred at the initial points of contact of the spray material. The direction of external damage was influenced by gravity as the path of cell destruction followed the flow of the runoff spray material. Spray runoff damage downward on the stem was confined largely to the two outer cell layers. Methyl decanoate entered through the epidermal cells and the trichomes. Cells with dense protoplasts were more visibly affected than cells with few or no protoplasts. The methyl decanoate acted as a destructive agent of the nucleus through some kind of change in the properties of the nuclear membrane; this was manifested by dispersion of the nucleoplasm. Changes were observed in the color of the stained nuclei indicating progressive stages of cell destruction. The nuclear and cytoplasmic components appeared as a homogenous mass in the late stage of damage. In highly specialized cells lacking protoplasts, damage was not apparent until the final stage of tissue and organ destruction.

Open Access