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S H Wittwer

Publications and source records attributed to S H Wittwer.

At least 19 recordsLinked to original sources
PubMed1972

Subcellular Localization of Zinc and Calcium in Bean (Phaseolus vulgaris L.) Tissues.

Two bean (Phaseolus vulgaris L.) cultivars differing in growth responses to zinc were examined for differences in uptake and subcellular localization of (65)Zn during a 15-day growth period. The zinc-sensitive cultivar Sanilac showed initially a much higher rate of absorption, which declined after 24 hours. The zinc-tolerant cultivar Saginaw showed a slow but steady rate of absorption for 10 days. In roots as well as in stem callus tissues of both cultivars, three-fourths of the absorbed (65)Zn was localized in the "cytoplasmic" supernatant fractions (containing ribosomes and vacuolar sap). Very little (less than 7%) (65)Zn was localized in the cell wall fraction. There was a much greater proportion of the absorbed (65)Zn localized in root mitochondria and nuclei of the zinc-sensitive Sanilac than in the zinc-tolerant Saginaw. Stem callus tissues, however, did not show such cultivar differences in zinc accumulation at the sub-cellular level.Calcium-45 distribution in the cultivar Redkote showed preferential affinity for cell walls both in roots and stem cellus tissue. The percentage of absorbed (45)Ca associated with cell wall fractions of roots gradually increased with a corresponding decline in the percentage of radioactivity associated with the cytoplasmic fraction. At 15 days, 57% of the total (45)Ca in the roots was localized in the cell walls. A similar, albeit less pronounced, preferential (45)Ca sorption on cell walls occurred for the callus tissue. Calcium-45 also accumulated at later stages in the nuclear fraction, but there was no mitochondrial accumulation.

Journal Article↗
PubMed1966

Senescence inhibition and respiration induced by growth retardants and N-benzyladenine.

Senescence of Grand Rapids leaf lettuce was greatly reduced at 3 storage temperatures by post-harvest treatment with N,N-dimethylaminosuccinamic acid (Alar) and 2-chloroethyltrimethylammonium chloride (CCC), but not with (6)N-benzyladenine (BA). Conversely, Alar and CCC were inactive on broccoli while BA was markedly effective. The deterioration and discoloration of mushrooms was inhibited by Alar with no effect observed from BA or CCC.The inhibition of senescence by BA and the growth retardants was not always associated with a reduction in respiration (O(2) uptake, CO(2) evolution). BA stimulated respiration and hastened senescence in leaf lettuce accompanied by a diametrically opposite effect from Alar and CCC. Thus, BA cannot be considered a universal senescence inhibitor. The variability of senescence responses induced by different chemicals on a variety of plant tissues suggests a dissimilar mode of action or a complex interaction with native growth substances.

Journal Article↗