Non-invasive photoacoustic spectroscopic determination of relative endogenous nitric oxide and ethylene content stoichiometry during the ripening of strawberries Fragaria anannasa (Duch.) and avocados Persea americana (Mill.)1

relationship exists and that, concomitantly, NO may be employed as a post-harvest senescence retarding agent Employing non-invasive photoacoustic spectrometry, (Leshem and Wills, 1998; Leshem et al., 1998). This emissions of nitric oxide (NO) and ethylene in postcriticism particularly pertains to endogenous plant NO harvest strawberries and avocados were monitored. emissions which, in the above reports, were partially A clear-cut stoichiometric relationship was found based on data obtained from an invasive technique between the two gases: unripe fruit manifesting high whereby an NO-sensitive microprobe was inserted into NO and low ethylene levels—the converse in ripe fruit. the fruit tissue and therefore that the wounding caused, Findings are discussed in the light of putative control albeit minor, NO emissions which ordinarily would not of ethylene-promoted fruit senescence by endogenoccur. The present research addresses this contention by ous NO. using the recently renewed non-invasive and rapid PAS technique as described in the Materials and methods.