Gravistimulation induced differential ethylene production in Antirrhinum majus L. cut flower stems with highest levels in the lower halves of the gravistimulated stems. Expression levels of three different 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS) genes, an ACC oxidase (ACO) and an ethylene receptor (ETR/ERS homolog) gene were studied in the bending zone after 9 h of gravistimulation. One of the ACS genes (Am-ACS3) was abundantly expressed in the lower halves but not in the upper halves of gravistimulated stems. This strongly suggests that Am-ACS3 is responsible for the observed differential ethylene production in gravistimulated stems. Am-ACO and Am-ETR/ERS gene expression was increased in both the lower and upper halves of gravistimulated stems, suggesting that they play no role in differential ethylene production.When gravistimulation was performed in an environment enriched with either 20 µ µ µ µL/L ethylene or 100 nL/L 1-methylcyclopropene (1-MCP), a slight stimulation of bending by 1-MCP and a slight inhibition of bending by ethylene were observed. The regulation and role of ethylene in gravitropism of cut snapdragon flowering stems is discussed.
INTRODUCTIONFlowering stems of a variety of bulbous (e.g. Gladiolus, Kniphofia and Tulipa) and herbaceous (e.g. Gerbera, Lupinus and Antirrhinum) plants often show elongation growth during their postharvest life and may show severe bending when stored or transported horizontally (Halevy and Mayak, 1981). Despite the commercial importance of such commodities, most research on gravitropic responses has been done with seedlings, hypocotyls, vegetative stems and specific gravi-responsive organs such as coleoptiles, epicotyls and grass-shoot pulvini. Only few reports have been published on the gravitropic response of flower stalks including dandelion, Kniphofia, Antirrhinum and
PCA score plot of the volatile compounds production rate of healthy and wounded potatoes over a period of 17 days storage at 20°C. Dots marked with a circle are samples that may have been cross-contaminated during the analysis. The mission of Wageningen U niversity and Research is " To ex plore the potential of nature to improve the q uality of life". U nder the banner Wageningen U niversity & Research, Wageningen U niversity and the specialised research institutes of the Wageningen Research Foundation have joined forces in contributing to finding solutions to important q uestions in the domain of healthy food and living environment. With its roughly 30 branches, 5 ,000 employees and 10,000 students, Wageningen U niversity & Research is one of the leading organisations in its domain. The uniq ue Wageningen approach lies in its integrated approach to issues and the collaboration between different disciplines.
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