Influence of Calcium and Magnesium on Ethylene Production by Apple Tissue Slices

Abstract

The decline in ethylene production in apple (Pyws malus L. cv. Golden Delicious) tissue slices during 24 hours Incubation in 600m orsorbitol and 10 m_liolar 2-(N-morpholno)ethanesulfonic acid buffer (pH 6.0) is recognized as a senescent ph The inclusion of very high concentrations (100 MiMolar) of Ca2+, Mge+, or Ca2+ plus Mg+ severely inhibited ethylene production duing the first 6 hours of incubation. However , after 6 hours and up to 24 hours the ethylene-forming system was stablized. These high concentrations of Ca2'+, Mg+, or Ca22 plus Me+ virtuafy Nated lpd peroxidation and protein leakage from these slices. Also conversion of 1-amncyciopropane-1-carboxylic-acid to eth-ylene and the influence of indokacetic acid on ethylene production was stabilized after 24 hours of incubation by these high concentrations of Ca2'+, Me+, Nd Ca2' plus Me+. Addition of divalent ionophores severely inhibited ethylene production, but this i n was prevented by Ca2' in concentrations greater than the ionophore. These data suggest that the loss of ethylene production by an tissue sices results from degradation ofmembranes. They support previous work that indicates that the ethylene-forming system, perhaps the segment of the pathway from 1-aminocycl-propane-l-carboxyic-l-acid to ethylene, resides in the plasma membrane.