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H H Smith

Publications and source records attributed to H H Smith.

At least 37 records · Page 2Linked to original sources
PubMed1973

Somatic mutational transients. 3. Response by two genes in a clone of Nicotiana to 24 roentgens of gamma radiation applied at various intensities.

Somatic effects of radiation intensity on the mutable V and stable R genes were detected in plants of a heterozygous clone (v(S3)/v(s), R/r) subjected to the same dose at four rates. The effects were compared by counting speckled and purple sectors in flowers from irradiated and control plants. Response curves were estimated from the mutant sector averages, observed over a period of transient response for successive mature flowers. A structure for integrating the mutational contributions from different flowers was provided by models. The average control mutation rates are 8,110 per 10(7) cells for the V gene, and 49.45 for R. At a constant intensity of 4320 roentgens/hour, average induced mutation rates per 10(7) cells per roentgen for V increase from 194 (at 24 r total dose) to 1,116 (at 3 r dose); the corresponding rates for R increase from 7.24 to 27.65. With these responses as standards, both genes at corresponding total doses yield lower rates at lower intensities. For the series of intensities 1.2, 0.6, 0.3 and 0.15 roentgens/hour, the decreases in mutation rate for the V gene are, respectively, 66, 148, 315, and 617 per 10(7) cells per roentgen. The corresponding decrements for R are 4.86, 8.70, 14.61, and 23.51. These effects are non-linear functions of intensity for both genes, but V is at least 13 times as sensitive as R. Radiation operating to extinguish a buffering system against final mutation can account for the dose and dose-rate effects observed.

Cell Division↗
PubMed1972

Parasexual interspecific plant hybridization.

Interspecific plant hybrids have been produced by parasexual procedures. Protoplasts of Nicotiana glauca and N. langsdorffii were isolated, fused, and induced to regenerate into plants. The somatic hybrids were recovered from a mixed population of parental and fused protoplasts by a selective screening method that relies on differential growth of the hybrid on defined culture media. The biochemical and morphological characteristics of the somatically produced hybrid were identical to those of the sexually produced amphiploid.

Journal Article↗