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biology, the present work aims to describe the morphology and anatomy of bisexual and functionally male flower types in pomegranate. Morphological and histological evaluations of hermaphroditic and male flowers were conducted using light microscopy (LM

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used for cell histology. Cell histology. For each harvested fruit, four pericarp samples were fixed overnight at room temperature in a 1 acetic acid:2 formaldehyde:5 ethanol solution. Sections of 3 μm thick were stained using toluidine blue and

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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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Blue light (320 to 496 nm) alters hypocotyl and stem elongation and leaf expansion in short-term, cell-level experiments, but histological effects of blue light in long-term studies of whole plants have not been described. We measured cell size and number in stems of soybean (Glycine max L.) and leaves of soybean and lettuce (Lactuca sativa L.), at two blue light fractions. Short-term studies have shown that cell expansion in stems is rapidly inhibited when etiolated tissue is exposed to blue light. However, under long-term light exposure, an increase in the blue light fraction from <0.1% to 26% decreased internode length, specifically by inhibiting soybean cell division in stems. In contrast, an increase in blue light fraction from 6% to 26% reduced soybean leaf area by decreasing cell expansion. Surprisingly, lettuce leaf area increased with increasing blue light fraction (0% to 6%), which was attributed to a 3.1-fold increase in cell expansion and a 1.6-fold increase in cell division.

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Abstract

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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New shoot growth of Carpinus betulus L. fastigiata was subjected to stock plant etiolation and stem banding (a 2.5-cm square of Velcro applied to the shoot base) treatments and sampled for histological study at intervals over a 16-week period of shoot development following etiolation. Effects of partial shading on histology of the stem were also investigated. Numerous histological changes were noted with stem development and stock plant treatment. Among these were a reduction in lignification of the secondary xylem and thickness of the periderm, and an increase in the percentage of sclereid-free gaps in the perivascular sclerenchyma with etiolation. Concomitant propagation studies revealed significant etiolation, shading, and banding effects on rooting percentages and root numbers. Rooting capacity was modelled using linear combinations of the widths of nonlignified secondary xylem, cortical parenchyma and periderm, as well as the percentage of gaps in the sclerenchymatic sheath remaining free of sclereids. It is proposed that the development of sclereids in potential rooting sites reduces rooting potential. The exclusion of light during initial shoot development retards sclereid development by up to 3 months following treatment, which correlates well with observed increases in the rooting potential of etiolated stems.

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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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Five-year old `Sharpblue' southern highbush blueberry plants (Vaccinium corymbosum L.) were self- and cross-pollinated (`O'Neal') to study peroxidase (POD) activity, isozyme patterns, and histological localization during fruit development. Cross-pollination resulted in larger and earlier-ripening fruit. Activities of soluble and bound POD were very high during fruit growth period I, with peaks at 10 and 20 days after self- and cross-pollination. Activity was much higher for cross-pollinated fruit. During fruit growth period II, POD activities were low in both pollination treatments. During ripening, soluble POD increased, then declined in both treatments. Bound POD activities increased during the color transition from blue to dark blue, with the increase greater in self-pollinated fruit. Banding patterns of soluble and bound POD isozymes and their histological localization varied by pollination treatment as well as fruit developmental stage. During fruit ripening, soluble POD activity appeared to be associated with color transition from light blue to blue, while bound POD activity appeared to be associated with color transition from blue to dark blue.

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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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