The action of ethylene on the capacity of plant tissues to metabolize cyanide to beta-cyanoalanine was examined. Beta-cyanoalanine synthase (EC 4.4.1.9) catalyzes the reaction between cyanide and cysteine to form beta-cyanoalanine and hydrogen sulfide. Levels of beta-cyanoalanine synthase activity in tissues of 6 day old etiolated pea (Pisum sativum) seedlings were enhanced severalfold by 1 microliter per liter ethylene. The promotive effect of ethylene increased with increasing ethylene concentrations from 0.01 to 100 microliters per liter and with the period of exposure from 3 to 24 hours. Ethylene enhanced beta-cyanoalanine synthase activity in all regions of the seedling (shoots and roots, internodal regions, cotyledons). The promotive effect was eliminated by norbornadiene, a competitive inhibitor of ethylene action. Levels of beta-cyanoalanine synthase in seedlings of four other dicots (Phaseolus aureas, Glycine max, Lactuca sativa, Sinapis arvensis) and two monocots (Hordeum vulgares, Triticum aestivum) were also increased in response to ethylene. Our results suggest an important regulatory role for ethylene in the metabolism of cyanide by higher plants.

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The auxins indole‐3‐acetic acid (IAA) and 2,4‐dichlorophenoxyacetic acid (2,4‐D) stimulated ethylene production from gametophytes of the fern Pteridium aquilinum (L.) Kuhn. var. latiusculum (Desv) underw. ex Heller and sporophytes of the ferns Matteuccia struthiopteris (L.)Todaro and Polystichum munitum (Kaulf.) Presl. Treatment with Co2+ or l‐α ‐(2‐aminoethoxyvinyl)‐glycine (AVG) eleminated or significantly reduced the stimulatory effects of IAA. Treatment with 1‐aminocyclopropane‐1‐carboxylic acid (ACC) resulted in significantly greater rates of ethylene production from all tissues tested. Based on their response to auxin, ACC, AVG and Co2+, the ethylene biosynthetic pathway in these three lower vascular plants appears similar to that existing in angiosperms.

Although the use of hypochlorite to disinfect seeds is widespread, the effects on tissues isolated from them have been largely ignored. Disinfection of barley (Hordeum vulgare L. cv. Himalaya) half‐seeds with hypochlorite solutions of ≥1.0% (w/v) available chlorine caused the pericarp to separate from the underlying tissues. Aleurone layers isolated from these grains had lower rates of oxygen consumption and released significantly less protein, PO43− Mg2+, K+ and amylase (EC 3.2.1.1) into the medium in response to gibberellic acid (GA3) than layers isolated from grains disinfected with a 0.1% hypochlorite solution. Disinfection with 1.0% hypochlorite also quantitatively altered the spectrum of proteins released into the incubation medium by the layers in response to GA3.

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