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represented 12.1% ± 3.9%, the tuberous roots 6.3% ± 2.1%, and the fine roots only 3.9% ± 0.8% ( Fig. 21 ). Histological and histochemical study. Young roots have a small diameter; the parenchymatous cortex is limited to five or six concentric cambia

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intensity affects the expression of variegation, and 5) compare growth performance between variegated and WT plants under different light intensities. Materials and Methods Histology of variegated and WT leaf tissue sectors. Small pieces of

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A hybridization strategy for certain coloration could be developed based on accurate histological information of parental material together with the knowledge of heritability of color and color intensity. A sample of 12 Anthurium species and hybrids were histologically examined for pigmentation in spathes using a new method employing vacuum infiltration of spathe tissue with polyethylene glycol (PEG) prior to cross-sectioning. PEG infiltration displaces intercellular air spaces between cells. This method greatly improved the clarity of the cross sections and consequently improved observations of spatial localization of anthocyanins and chloroplasts. This infiltration method accurately identified the spatial localization of pigments for future breeding reference, notably among Anthurium species.

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A histological study of the initiation and development of adventitious roots in lightgrown cuttings of mung bean (Phaseolus aureus Roxb.) showed that cell divisions leading to adventitious root initiation occurred 20–24 hours after the cuttings were taken. Cell divisions began at the same time for control and naphthaleneacetic acid (NAA) treated cuttings indicating that NAA did not alter the timing of root initiation. The root primordia for both were well developed by 48 hours and the roots began to emerge by 72 hours. Intracellular changes in the cells destine for the initial divisions first became visible histologically at 12 hours. By 16 to 20 hours considerable intracellular change was observed, including enlargement of the nuclei and nucleoli and an increase in apparent cytoplasmic staining density.

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Histological analysis of somatic embryos derived from in vitro-grown lamina of Anthurium andraeanumshowed bipolarity with the presence of shoot and root poles connected by procambium. Vascular connections between the explant and somatic embryos were not observed. Storage of proteins, starch and raphides as well as a suspensor-like structure and an epidermis were observed in the somatic embryos. Origin of the somatic embryos was from a proembryonic cell complex or possibly from a single cell by direct embryogenesis. Both modes of somatic embryogenesis arose from the mesophyll.

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Abstract

Cracking behavior of tomato skins (Lycopersicon esculentum Mill.) was investigated using failure and relaxation tests. Skin specimens were taken in 2 directions to represent concentric and radial cracks. Normal tissue and tissue subjected to mechanical forces were examined to determine the resulting histological distortions. The relaxation test gave more information than the failure test. No difference was observed for longitudinal or transverse skin strength for failure or the relaxation test indicating isotropic behavior. The shape of the cells and deposition of cuting appeared to affect cracking behavior. Generally, cells elongated and flattened during the failure test and failed between cells walls.

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Abstract

The wound-healing process in cuttings of Pelargonium X hortorum L.H. Bailey cv. Yours Truly was studied using histological and histochemical techniques. Anatomical changes at the wounded surface of cuttings within 24 hours included deposition of a granular, amber-colored substance identified as suberin on the cell walls, in the intercellular spaces, and in the lumina of xylem vessels. Wound xylem, adventitious root primordia, and wound callus developed within 7 days. A periderm developed 14 to 21 days after wounding and its cell walls were suberized.

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Broccoli (Brassica oleraceae L. var. Italica cv. `Premium Crop') plants grown in perlite were supplied with nutrient solutions containing three levels of added boron (0.04 (severely deficient), 0.08 (moderately deficient) or 0.80 (normal) mg L-1). These treatments produced plants exhibiting either obvious (0.04 mg L-1) or no visual boron deficiency symptoms (0.08 and 0.80 mg L-1). At horticultural maturity, cross sections were taken in the upper and mid stem regions. The specimens were mounted on slides after being processed through a biological staining series. Boron availability was found to be correlated with the progressive internal deterioration of the stem which was observed histologically. An examination of staining patterns indicated that possibly a lignification process accompanies and contributes to hollow stem development. We have previously noted an increase in phenolic compounds and fiber content of broccoli produced under boron deficient conditions. The histological evidence of lignification further substantiates that boron deficiency induces changes in cell wall structure which may contribute to the development of hollow stem.

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Abstract

Scald was the major grade lowering defect resulting from mechanical harvesting of sour cherries for processing. Histological sections of scalded tissue showed no crushing or distortion of cells, but the epidermal cells appeared dense and the cell walls appeared to be thicker than those of nonscalded tissue. Since the cells of scalded tissue did not appear distorted, bruising apparently induced a chemical change as a result of membrane disruption bringing about discoloration. Microscopic examination indicated that darkened bruises on the epidermis of the cherries occurred prior to mechanical harvesting. Tannins were located primarily in the epidermal region, but during a 24-hour soak there was a slight movement of tannin into the outer cortical cells. Greater movement occurred in mechanically harvested cherries than in handpicked fruit. The cellular disruption resulting from bruising by mechanical harvesting possibly aided the movement of tannins. Scald was a major grade lowering factor when mechanically harvested cherries were soaked longer than 8 hours before processing.

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Abstract

Abscission layer formation during fruit maturation of sour cherry, Prunus cerasus L., occurred between the fruit and the pedicel. No abscission layer was formed between the pedicel and the spur. The abscission layer was first evident 12-15 days before fruit maturity. This layer was composed of 5-8 rows of cells in the transition zone between the fruit and pedicel and was first identified by its low affinity for haematoxylin. Cell separation occurred without rupturing of cell walls. Later cell wall collapse was apparent. Cells immediately distal and proximal to the line of separation were thin walled and prone to separate easily. No abscission layer was formed through the vascular bundles and no cell division was noted during layer formation. Abscission layer formation was observed in detached sour cherry fruit which was histologically similar to that observed in vivo. There was a close relationship between abscission layer formation and force required to separate the fruit from its pedicel. No abscission layer was observed, in the transition zone between the fruit and pedicel in the sweet cherry, Prunus avium L.

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