1997, Inhibiiors of ethylene responses in piants at the receptor level: Recent developments. -Physiok Plant, UKf: 577-582.. A number of organic molecules that appear to block the ethylene receptor have been discovered recently. For example, on irradiation with visible lighl. diazocyclopentadiene (DACPK gives rise to some potent but as yet unidentified inhibitor eompounds. Some synthetic cyclopropenes have been shown io bind to the ethylene receptor and prevent the physiological action of"ethyiene for extended periods. Cydopropene iCPi. 1-methylcyclopropene (1-MCPi and 3.3-dimethyIcyclopropene (3.3-DMCPi have been shown to prevent ethylene effects in a number of plants. As low a concentration as (1.5 nl I ' of k.MCP is sufficient lo protect carnation fDianthus caryophyttusi flowers for several davs against ethylene. and 0.7 nl Y' 1-MCP or CP will prevent the ripening of banana iMusa sapieniumi lor 12 days at 24°C, Some plant organs require higher concentrations of these inhibitors. Complete inhibition of ethyiene effects in pea seedlings requires treatment w iih 40 nl I ot 1 -MCP, These nov el inhibitors appear lo be suitable for many commercial applications inciuding extending the xase life of cut flowers and the display life of potted plants. Since l-.MCP apparentlv is non-toxic at concentrations that are active, it mav in fnture be available for regulating Ihe ripening of tniits and preventing the deleterious effect.s of ethylene in v egetables,

No abstract

1-Methy1cyclopropene (l-MCP), formerly designated as Sis-X, has been shown to be an effective inhibitor of ethylene responses in carnation flowers in either the light or the dark. The binding appears to be to the receptor and to be "permanent". A 6 h treatment at 2.5 nll-1 is sufficient to protect against ethylene, and 0.5 nll-1 is sufficient if exposure is for 24 h. As carnation flowers age, a little higher concentration appears to be needed. Most of the natural increase in ethylene production during senescence is prevented by treatment with 1-MCP. A closely related compound, methylenecyclopropane shows ethylene activity. A tritium labelled 1-MCP (60 mCi mmol-1 ) has been prepared. A higher specific activity is needed for more critical studies.

A 6-hour fumigation of flowering Begonia ×elatior hybrida Fotsch. `Najada' and `Rosa', B. ×tuberhybrida Voss. `Non-Stop', Kalanchoe blossfeldiana Poelln. `Tropicana', and Rosa hybrida L. `Victory Parade' plants with 1-MCP, (formerly designated as SIS-X), a gaseous nonreversible ethylene binding inhibitor, strongly inhibited exogenous ethylene effects such as bud and flower drop, leaf abscission, and accelerated flower senescence. The inhibitory effects of 1-MCP increased linearly with concentration, and at 20 nl·liter-1 this compound gave equal protection to that afforded by spraying the plants with a 0.5 STS mm solution. Chemical names used: 1-methylcyclopropene (1-MCP), silver thiosulfate (STS).

In the horticulturally important ornamental species Cyclamen persicum Mill., somatic embryogenesis is an efficient vegetative propagation method and the development of artificial seeds is an ultimate aim. This study aims at a systematic comparison of the proteomes of zygotic embryos, somatic embryos grown in liquid medium containing 30 or 60 g l(-1) sucrose, germinating embryos of both types and endosperm in order to obtain novel insights into seed and germination physiology. Using high resolution two-dimensional isoelectric focussing/sodium dodecylsulfate polyacrylamide gel electrophoresis (2D IEF/SDS PAGE), 74% of the proteins expressed in zygotic embryos were found in similar abundance in somatic embryos grown in 60 g l(-1) sucrose. Somatic embryos grown in 30 g l(-1) sucrose accumulated fewer protein species than those grown in 60 g l(-1). Selected proteins were identified following mass spectrometry (nano-LC-MS/MS). Four enzymes involved in glycolysis (UDP-glucose pyrophosphorylase, fructose bisphosphate aldolase, triosephosphate isomerase and glyceraldehyde-3-phosphate dehydrogenase GAPDH) were specifically induced in somatic embryos. 11S globulin proteins identified by MS were present in high levels in somatic embryos, zygotic embryos and endosperm, whereas 7S globulins were detected mainly in endosperm and zygotic embryos. These are the first storage proteins identified in C. persicum. Xyloglucans are known to be another group of seed storage compounds in C. persicum. Interestingly, xyloglucan endotransglycosylases were found to be highly expressed in endosperm tissue. We discuss the physiological implications of these observations.