Inhibition of Somatic Embryogenesis in Tissue 2Medicago sativaby Aminoethoxyvinylglycine, Amino-oxyacetic acid, 2, 4-Dinitrophenol and Salicylic Acid at Concentrations which do not Inhibit Ethylene Biosynthesis and Growth

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Abstract
Meijer, E. G. M. and Brown, D. C. W. 1988. Inhibition of somatic embryogenesis in tissue cultures of Medicago sativa by aminoethoxyvinylglycine, amino-oxyacetic acid, 2, 4-dinitrophenol and salicylic acid at concentrations which do not inhibit ethylene biosynthesis and growth. J. exp. Bot. 39: 263–270. The effects of aminoethoxyvinyglycine (AVG), amino-oxyacetic acid (AOA), 2, 4-dinitrophenol (DNP) and salicylic acid (SA) on ethylene production, tissue proliferation and somatic embryo-genesis in a recently developed rapid in vitro regeneration system of Medicago sativa L. were examined. Contrary to numerous publications, AVG, AOA and DNP did not affect the rate of ethylene biosynthesis, while SA even caused an increase in ethylene production. All four compounds were, however, potent inhibitors of somatic embryo formation in the M. sativa tissue cultures, even at concentrations which did not affect tissue growth. Generally, a 5-d exposure to the inhibitors reduced the number and quality of somatic embryos obtained. It is suggested that the inhibitors may not reach the site of action of enzymes involved in ethylene biosynthesis and may possibly block other biosynthetic pathways which are of crucial importance to somatic embryo development. The results indicate that a delicate differentiation process like somatic embryogenesis is very sensitive to metabolic perturbances. The results are also discussed in the light of other known effects of these four compounds on higher plants.