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  • Author or Editor: W. C. Chang x
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Abstract

Menazon (S-(4,6 diamino-s-triazin-2-methyl) o,o-dimethyl phosphorodithioate) an organophosphate insecticide, and usnic acid, an allergen present in lichens, inhibited germination of mung bean (Phaseolus mungo L.). On the third day of germination, cotyledons were examined histochemically and ultrastructurally and the resultant photomicrographs showed abundant starch grains and protein bodies in the treated seeds compared to the controls. Electron microscopic examination showed extensive endoplasmic reticulum and ribosomes along with vacuoles and normal mitochondria in control tissue. In contrast, the presence of protein bodies and disruption of the cytoplasmic organization were conspicuous in the menazon- and usnic acid-treated mung beans. This suggests impaired utilization of food reserves during germination.

Open Access

Cryopreservation of pollen from two ginseng species —Panax ginseng L. and P. quinquefolium L.—was studied. Freezing anthers that served as pollen carriers to –40C before liquid N storage affected pollen viability little after liquid N storage. Anther moisture content affected pollen viability significantly when stored in liquid N. The ideal anther moisture content to carry pollen for liquid N storage was 32% to 26% for P. ginseng and 27% to 17% for P. quinquefolium. Viability of pollen from P. quinquefolium anthers with 25.3% moisture content changed little after 11 months of liquid N storage.

Free access

Eight open-pollinated peach families [Prunus persica (L.) Batsch] were selected from a germplasm collection that was screened for tolerance to Leucostoma persoonii (Nits.) Höhn. [imperfect state, .Leucocytospora leucostoma (Pers.) Höhn] following field inoculation. The eight peach families were either susceptible or tolerant to L. persoonii infection based on canker length measurements. Three open-pollinated seedlings per family were chosen for evaluation. Following artificial inoculation, measurements of hydraulic conductance per pressure gradient (Kh) were made on 2-year-old branch segments from the 24 seedlings, and safranin dye was used to mark the conductive xylem pathways. For the peach families tolerant to L. persoonii, the specific Kh of the canker branch segments was greater than that for the most susceptible peach families. The inoculated branch segments from the tolerant peach families maintained ≈15% to 30% of the water transport of control segments. Safranin dye movement indicated that the sapwood in inoculated branch segments of seedlings from the susceptible peach families was almost completely blocked. Isolation experiments indicated deeper penetration of the fungus into the xylem of seedlings of susceptible than tolerant families. Xylem dysfunction appears to be correlated with a reduction in Kh, and the seedlings in the tolerant peach families are better able to maintain water transport through the stem segment invaded by the fungus.

Free access