David G. Davis

In vitro culture of callus tissues and cell suspensions from okra (Hibiscus esculentus L.) and cotton (Gossypium hirsutum L.).

SummaryMethods are described for starting and maintaining callus-tissue cultures of twoMalvaceae, okra (Hibiscus esculentus L.) and cotton (Gossypium hirsutum L.). Okra callus was slow to initiate, but once started it was easy to maintain, in contrast to cotton, which was difficult to initiate and grow. Different media were required to establish the two species. The inclusion of 5 mg per liter of ascorbic acid aided in reducing the formation of black pigments in cotton callus. Hypocotyls of sterile young okra seedlings and leaves of cotton plants were used to produce the callus tissue. Rapidly growing cell suspensions of okra and cotton were obtained in B5 medium.

Epicuticular wax constituents of North American and European Euphorbia esula biotypes

Abstract The epicuticular leaf wax of four North American and one Austrian Euphorbia esula biotypes was examined as a potential source of chemotaxonomic information relative to intraspecies classification. Analysis (GC and GC/MS) shows general similarity of wax constituent character among all biotypes but differences in specific component yields between the North American and Austrian biotypes. Distinctive variation in occurrence of five triterpenes (α- and β-amyrin, δ-amyrenone, 24-methylenecycloartenol and lupeyl acetate) was observed between the North American and Austrian biotypes.

Effects of organic solvents on growth and ultrastructure of plant cell suspensions

Abstract The effects of organic solvents on the growth response and fine structure of batch-cultured plant cell suspensions were examined. The growth responses of the cells to organic solvents varied with the plant species, but in general the toxic effects of solvents increased in the following order: chloroform, DMSO (dimethyl sulfoxide), methanol, acetone, isopropanol, and ethanol. At 0.25% concentration, chloroform had no apparent effect on cell growth; however, ethanol inhibited growth at concentrations as low as 0.05%. Determinations of volatility and metabolism of 14 C-labeled solvents indicated that reductions in the concentrations of acetone and ethanol resulted primarily from evaporation. In contrast, [ 14 C]methanol losses resulted from metabolism and evaporation, while a reduction in DMSO concentration was mainly attributed to cellular metabolism. A microscopic examination of soybean cells treated with 1 and 2% acetone indicated that starch reserves, normally present in amyloplasts, were decreased. Furthermore, membrane abnormalities and cytoplasmic degeneration were more prevalent in these cultures. DMSO-treated soybean suspensions were associated with cellular hypertrophy accompanied by enlargement of nuclei and diminishing thickness of the cell walls. These results suggest that organic solvents can alter the growth and structure of cell suspensions; however, choosing a solvent that is compatible with a tissue and allowing ample time for volatilization may reduce adverse effects.

The characterization of esulone C and chemotaxonomy of jatrophane diterpenes in leafy spurge

Abstract A new jatrophane diterpene, esulone C, was isolated and characterized from the ether extract of the roots of a North Dakota accession of the noxious weed leafy spurge. The ether extracts of North Dakota, Oregon, Montana and Austrian leafy spurge accessions were chromatographically compared for the occurrence of jatrophane diterpenes relative to the taxonomy and biological control of leafy spurge.

ORGANOGENESIS IN LEAFY SPURGE (EUPHORBIA ESULA L.)

SummaryAll parts of leafy spurge seedlings can be regenerated when isolated and placed onto B5 medium. One-centimeter isolated hypocotyl segments were tested successfully for their usefulness as a bioassay system by comparing the response of auxins, herbicides, and cytokinins. Indole-3-acetic acid (IAA) was the most effective auxin to stimulate root formation. IAA was effective whether the hypocotyl segments remained on the same medium up to 60 days, or the segments were transferred to basal media after 2 or 5 days (pulse treatment). Pulse treatments with the other auxins resulted in stimulation of root formation; continuous or 5-day pulses of higher concentrations of indole-3-butyric acid,α-naphthaleneacetic acid and especially 2,4-dichlorophenoxyacetic acid and picloram formed excessive callus instead of roots. Picloram did not stimulate root formation, whether the treatment was continuous or pulse-treated. No roots formed with continuous picloram at 0.1 mg/liter or greater, but transfer to basal media did result in root and shoot formation at about 50% of the number formed on the controls. Lesser picloram concentrations had no effect. Shoots formed readily on untreated (control) segments, but continuous treatment with all three cytokinins, kinetin, zeatin, and zeatin riboside, increased the numbers of shoots about equally. Root formation was inhibited by the cytokinins at the higher concentrations (0.1 to 0.2 mg/liter). With the exception of a 5-day pulse of 0.04 mg/liter IAA, the auxins did not stimulate shoot formation, but generally inhibited shoot formation, even in pulse-treated cultures.

Phototoxicity of selected non-ionic surfactants to soybean Glycine max cell suspensions

Abstract The phytotoxicity of a series of linear alcohol ethylene oxide adduct non-ionic surfactants to achlorophyllous soybean Glycine max (L.) Merr. var. Wilkin cell suspensions was determined. The compounds tested were 1-dodecanol (12-0), four of its ethylene oxide (EO) adducts, and an adduct of 1-decanol with 6·7 (average) EO units (10- 6·7 ). Three of the dodecanol adducts were homogeneous surfactant preparations with 2,6 or 8 EO (12-2, 12-6, 12-8, respectively) and one had an average of 17 EO (12- 17 ). The 12-0 compound had no effect on cell growth. Its lipophilic EO adducts 12-2 and 12-6 stimulated growth slightly (less than 30%) at the lower concentrations (22 to 55 μ m and 7 to 26 μ m , respectively) 8 days after treatment. All compounds except 12-0 inhibited growth at the higher concentrations (ranging from 11 to 120 μ m , depending on the compound). Growth inhibition by these adducts increased with EO chain length from 12-2 to 12-8 and then decreased for the very hydrophilic 12- 17 . Growth was only slowed by surfactant treatments at intermediate concentrations and eventually the cells attained nearly the same maximum dry weight as untreated cells. The 10- 6·7 surfactant affected the cultures similarly, but not identically, to the 12-6 and 12-8 surfactants. The surface tensions of the treating solutions were measured. The concentrations of 12-6, 12-8, 12- 17 and 10- 6·7 at which phytotoxicity occurred were too low for micelle formation.