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Abstract

The standard method of preparing plant material by hand for histological study takes several days (1,2). A procedure is described herein which reduces processing time to 17 hours or less and provides tissues which are completely dehydrated and infiltrated. Up to 100 samples can be prepared within this time period. The method requires a minimum expenditure of time without sacrificing cytological detail.

Open Access

Abstract

Avocado (Persea americana Mill., cv. Simmonds) flowers and fruitlets were histologically examined to characterize the development of disfiguring bumps and ridges, as well as to investigate possible causes of the disorder. The outer cell layers of the ovary are damaged by a small, surface-feeding insect during and soon after anthesis. Bumps and ridges form as a result of cell proliferation in the pericarp directly beneath the wounds. Circumstantial evidence suggests that two species of flower thrips (Frankliniella) are the possible causal agents.

Open Access

Abstract

A study of the histology of the bud-graft unions involving a rose cultivar, Rosa × ‘Fire King’ and two rose understocks, R. multiflora, ‘Brooks’ and R. × ‘Manetti’, was made. These 2 combinations produce a growth phenomenon termed “brittleness”. The graft unions were characterized by large quantities of fragments of necrotic material in the understock-scion interface and delay in the reconstruction of the cambial cylinder with a corresponding decrease in thickness of the cylinders of cambial derivatives derived as a result of cambial activity.

Open Access
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Abstract

Severe symptom of internal bark necrosis (IBN) were noted when trees of ‘Red Delicious’ (‘Bisbee’ strain) on the EM II rootstock were grown hydroponically for 5 months in a complete nutrient regime supplemented with 50 ppm Mn. Lower levels of Mn resulted in less severe symptoms. Experimentally induced lesions were histologically identical to those occurring naturally in the field. Upon histochemical testing, frozen tissue sections obtained from trees grown in excess Mn regimes revealed localized and heavy accumulation of Mn in both incipient and well developed lesions. Localized accumulation of excess Mn may directly cause cell death and lesion formation.

Open Access

Abstract

The rooting substances of tomato (Lycopersicon esculentum Mill.) explants during root regeneration were studied. The root-promoting substances of the basic, acidic, and bound ether-soluble fractions of the plant extracts after paper chromatography were determined by a tomato hypocotyl test. The basic root-promoting substances in the basal hypocotyl region changed qualitatively, while those of the acidic and bound fractions decreased with rooting. It was found that in 5-day-old explants, the highest root-promoting substances were in the bound fraction, and in the basal hypocotyl region. Histological evidence showed the presence of preformed root primordia in the rooting region of 10-day-old tomato explants.

Open Access

Gaillardia pulchella is an annual wildflower with ornamental potential native to the South and Southern West part of the U. S. This experiment attempted to further describe the long day (LD) flowering requirement, approximate the length of the juvenility phase, and characterize apical events during floral initiation. Plants were transferred from short day to LD at various leaf numbers and the time to first flower was recorded from the onset of LD. A quadratic response described the data and indicated that a minimum of 19-20 expanded leaves were needed to flower most rapidly (49 days) once placed in LD. Histological results characterizing apical events will also be discussed.

Free access

Abstract

Ovary stimulation in cucumber (Cucumis sativus L. cv. Crusader) is accomplished rapidly after pollination. Increases in fruit growth are measurable within 24 hours. Experiments where styles were severed from ovaries at intervals after pollination indicate that the signal for ovary growth is received 12-18 hours after pollination. Histological examinations showed that at 12 hours pollen tubes have just penetrated beyond the base of the style into the ovary. Pollen tubes penetrated ovular tissue to accomplish fertilization 30-36 hours after pollination. This timing indicates that cucumber fruit-set is regulated by interactions between pollen tubes and pistillate tissue prior to syngamy.

Open Access

Cornus florida L. floral development was monitored using standard paraffin histological techniques and light microscopy. Terminal buds (putative floral buds) were collected over 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 July 19th in the 2 years of this study. Floral development followed typical angiosperm stages. Florets, although small, appeared morphologically mature by early September in both years.

Free access
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Abstract

The water economy of plants often is seriously unbalanced by root destruction or vascular occlusion induced by various rot organisms. Water absorption by the roots and water transport within the plants is impeded and wilting follows. Beckman (1) reviewed the literature on the histological and physiological changes in host plants infected with pathological wilts. Dimond and Edgington (2), studying the mechanics of water transport in healthy and Fusarium-vrilted tomato plants, pointed out the tremendous pressure deficits that are required to maintain normal water flow into leaves through partially plugged vessels.

Open Access

Abstract

More than 1000 higher plant species have been reported to regenerate in vitro via either somatic embryo formation or shoot formation (1, 9, 11, 12, 16, 27, 40, 42, 45, 46). Although many reports of plant regeneration are not accompanied by the necessary developmental or histological evidence for verification, it is apparent that most successes follow an organogenic rather than an embryogenic route. However, regardless of which developmental pathway is followed or the complexity of the protocol that is used ultimately to recover a complete plant, much of the work on in vitro regeneration can be described as empirical in nature.

Open Access