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  • Author or Editor: H. Paul Rasmussen x
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Abstract

The cover photograph is a scanning electron microscope image of pollen of Hibiscus rosa-sinensis L. clinging to the convoluted anther. The large pollen grains are mature and undoubtedly viable. The small pollen grain at the right is probably aborted pollen which is rather common in species hybrids. Some cellular structure of the anther wall is evident.

Open Access

Abstract

Chrysanthemum morifolium (Ramat.) cultivars showed a range of stem girdling responses when treated with the chemical pinching agents, a commercial pinching agent (OSO) and methyl decanoate (MD). Differential responses were attributed to the number of trichomes per unit area of the stem; resistant cultivars had more trichomes than susceptible cultivars. The stomatal number per unit of stem area was constant for all cultivars. Stem diameter was not a significant factor in the susceptibility of cultivars to girdling damage. Resistance was eliminated by damaging or removing the trichomes of a resistant cultivar. Similar treatment of a susceptible cultivar did not increase susceptibility. Susceptible cultivars absorbed more 14C MD than resistant ones. Injury was positively correlated with 14C MD uptake within cultivars. Methyl decanote did not enter the stem through epidermal cells adjacent to trichomes or the trichome itself, but rather through epidermal cells not in proximity of the trichomes.

Open Access

Abstract

A technique was developed which permits observations of a single rose petal segment through the stero-light microscope (SLM), scanning electron microscope (SEM), transmission electron microscope (TEM), and light microscope (LM). The procedure consisted of viewing the fresh tissue with SLM, fixing and post-fixing in glutaraldehyde and osmium, respectively, and dehydrating in ethanol. The alcohol in the tissue was subsequently replaced with increasing concentrations of iso-amyl acetate, the tissue critical point dried, coated with C, and viewed in the SEM. The tissue was removed from the SEM mounting stub, pressure embedded in epoxy resin at 28 kg/sq cm (400 psi), polymerized, sectioned, stained, and viewed with both the TEM and LM. The technique of pressure embedding samples in epoxy resin eliminated the problem of rehydration and subsequent dehydration of tissue following SEM observation. Furthermore, this new technique reduced the time required for observation with multiple microscopic optical systems, while still offering latitude in the time between the various steps which has been a drawback in previous techniques.

Open Access

Abstract

Scanning electron microscopy was used to measure epidermal hairs and drupelet morphology of raspberry fruit. Significant differences were found among cultivars and selections in drupelet size, total contact area between drupelets, and contact area with hairs between drupelets, hair density index, and hair length. Drupelet numbers also differed. Fruit strength, as measured by cohesiveness, was related to contact area between drupelets, whether hair-covered or not, in conjunction with total drupelet number. Hair density contributed to cohesion in some years with certain cultivars. Resistance to compression was most consistently correlated with total drupelet area and contact area between drupelets alone and in conjunction with hair density.

Open Access