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Suspension cultures of Rosa sp., soybean (Glycine max L.), wheat (Triticum monococcum L.), sweet clover (Melilotus alba Desc.), Haplopappus gracilis Nutt., and rue (Ruta graveolens) produced ethylene. The amount varied with the species. The rate of formation in rose and Haplopappus cells paralleled growth but accelerated when the stationary phase was reached, after which the rate declined sharply. Light was not required for ethylene production. Exogenous ethylene could not replace 2,4-dichlorophenoxyacetic acid or naphthalineacetic acid in the cell cultures, and there was no stimulation of growth in the normal medium. Ethylene at 20 mm reduced growth of Ruta and rose cells by 30 and 20%, respectively. The amounts of ethylene produced by the cultures do not affect growth.
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The canavanine content of developing leaves of jack bean, Canavalia ensiformis (L.) DC., increases during leaf development. The leaf possesses the enzymes required for synthesizing canavanine by a cyclic series of reactions analogous to the ornithine-urea cycle. This reaction series involves the sequential formation of canaline, O-ureidohomoserine, and canavaninosuccinic acid.
The pattern of photosynthetic carbon metabolism was determined in tissue cultures of Portulaca oleracea. Four-carbon acids are the most heavily labeled photosynthetic products during short term exposure to (14)CO(2), containing greater than 40% of the total radioactivity incorporated. Phosphoglyceric acid and sugars account for only 10% of the label after equal exposure times. Other features of the CO(2) assimilation pattern in Portulaca callus tissue include a relatively large percentage of label located in various minor products throughout the time course studied, and a greater incorporation of (14)C into sugars in tissue cultures than occurs in leaves. Ultrastructurally, the chloroplasts and cells of the callus are like those in the mesophyll cells of Portulaca leaves. The requirement for Kranz anatomy for operation of functional C(4) physiology is discussed.
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Undifferentiated, highly chlorophyllous cell cultures; undifferentiated white cell cultures; green, shoot-forming cultures; and white, shoot-forming cultures of Digitalis purpurea L. were established and subcultured every 3 weeks in liquid media in the light or in the dark. The digitoxin content, the chlorophyll content, and the ribulose bisphosphate carboxylase activity of these cultures were assayed. The light-grown, green, shoot-forming cultures accumulated considerable amounts of digitoxin (about 20 to 40 micrograms per gram dry weight), and the white, shoot-forming cultures without chloroplasts accumulated about one-third that amount of digitoxin. The chlorophyll content and the ribulose bisphosphate carboxylase activity of the undifferentiated green cells were about the same as they were in the green, shoot-forming cultures, but the digitoxin content of the former was extremely low (about 0.05 to 0.2 microgram per gram dry weight), which is about the same as that in undifferentiated white cells without chloroplasts. Thus, it was concluded that the chloroplasts are not essential for the synthesis of digitoxin in Digitalis cells. The optimum concentrations of the tested compounds for accumulation of digitoxin were: benzyladenine, 0.01 to 1 milligram per liter; indoleacetic acid, 0.1 to 1 milligram per liter; alpha-naphthaleneacetic acid; 0.1 milligram per liter; and 2,4-dichlorophenoxyacetic acid, 0.01 milligram per liter.
The production of ethylene by melon (Cucumis melo cv Cantaloup charentais) tissues is stimulated during incubation in the presence of fungal glycopeptides extracted from Colletotrichum lagenarium, a pathogen of melon. These glycopeptides, called elicitors of ethylene, are found in the mycelium, the cell wall, and the culture filtrate. Elicitation of ethylene is a relatively early phenomenon and lasts for several hours. Upon purification of the crude elicitor extract by gel filtration and ion exchange chromatography, three elicitors were isolated. The three elicitors contained amino acid, sugar, and phosphate residues, and they have a decreased activity after partial chemical degradation of their sugar moiety.Elicitation of ethylene is not fungal species specific. Elicitors of phytoalexins, obtained from three Phytophtora species, enhanced ethylene biosynthesis in melon tissues.
Treatment of melon leaves or seedlings with elicitors of Colletotrichum lagenarium, a fungal pathogen of melon, increases chitinase activity. In treated leaves, chitinase is enhanced within the first 6 hours and becomes 2 to 10 times higher than in control leaves after 24 hours. Ethylene is increased simultaneously and is correlated with chitinase elicitation. In the presence of aminoethoxyvinylglycine, an inhibitor of ethylene synthesis, both elicitor-induced ethylene and elicitor-induced chitinase are inhibited. This inhibition is overcome by added exogenous ethylene. On the other hand, 1-aminocyclopropane-1-carboxylic acid the direct precursor of ethylene, triggers chitinase activity. Chitinase elicitation is thought to be a protein synthesis dependent process, as it does not occur in the presence of cycloheximide.
We report the use of Ni(2+) and Co(2+) on free-hand sections of soybean (Glycine max L.) and Bidens sp to localize polygalacturonates. In soybean only the hourglass cells of the seedcoat stain intensely. In the pod the epidermis of the outer pod wall and a few layers of subepidermal cells stain lightly, while that part of the funiculus adjacent to the seedcoat palisade epidermal cells stains heavily and the neck of the funiculus close to the pod also stains. In Bidens stem sections, the walls of the collenchyma stain most intensely.
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