Response of Developing Apple Fruits to Ethylene Treatment

Knee, M., Hatfield, S. G. S. and Bramlage, W. B. 1987. Responseof developing fruits to ethylene treatment.—J. exp. Bot.38: 972–979. Fruits of apple (Malus domestica Borkh. cv. Cox's Orange Pippin)were treated with various concentrations of ethylene usuallyfor 48 h to determine their response in relation to stage ofdevelopment. The main response recorded was the reduction byethylene of the delay in onset of rapid ethylene production(DEP) in individual fruits. Early in development low concentrationsof ethylene had little effect but DEP was progressively reducedby concentrations up to 10⁷ mm³ m^–3. As the fruit approachedthe natural onset of rapid ethylene synthesis concentrationsof 10² and 10³ mm³ m^–3 became increasingly effective.Increasing the duration of treatments with a fixed concentrationreduced DEP proportionately. Delay after harvest in applyinga 48 h treatment had little effect on the relation between DEPand concentration of ethylene applied. Although resistance todiffusion of gas in fruits increased during fruit developmentthis resistance was never large enough to affect the relationof concentration and response. Key words: ethylene, fruit ripening, Malus domestica     

Microsporidian Spore Discharge and the Transfer of Polaroplast Organelle Membrane into Plasma Membrane

Electron microscopic examinations of Glugea hertwigi and Spraguea lophii spores indicated the presence of a single plasma membrane; however, this membrane remained in the spore during the discharge of the sporoplasm from the spore. Although discharged spores retained the old plasma membrane, the extruded sporoplasms acquired a new plasma membrane. In order to determine where the new plasma membrane came from, we used two fluorescent probes with membrane affinities. The markers were tested on unfired and discharged spores. The probe, N-phenyl-1-naphthylamine (NPN), labeled the polaroplast membrane in addition to the apolar groups in the posterior vacuoles of unfired spores. After spore discharge, NPN label disappeared from the spore ghosts except for a slight fluorescence on residual plasma membranes. Much of the NPN-labeled membrane reappeared after spore discharge on the outer envelope of discharged sporoplasms. The probe chlorotetracycline (CTC) labeled calcium-associated membranes of spore polaroplasts. During spore discharge, the CTC fluorescence shifted from the polaroplast organelle of unfired spores to the outer envelope of discharged sporoplasms. These results indicate that the polaroplast organelle may provide the new plasma membrane for discharged microsporidian sporoplasms.