USING DENSITY-MEASUREMENTS TO STUDY THE EFFECT OF EXCISION, STORAGE, ABSCISIC-ACID, AND ETHYLENE ON PITHINESS IN CELERY PETIOLES

The density of excised 2-cm celery (Apium graveolens L.) petiole segme nts was highly correlated with a subjective evaluation of pithiness. L oss of density and the appearance of pithiness was stimulated by lengt hening the duration of storage, raising the storage temperatures above OC, and excising petiole segments. Segments excised from the upper tw o-thirds of the petiole lost less density during storage than segments excised from the bottom third of the petiole. Segments with initial h igh densities lost slightly less density during storage at 5C for 5 we eks than segments that were initially less dense. The extent of pithin ess development varied significantly among six cultivars held at 5C fo r 2 weeks. Treating whole petioles with 1 mu M abscisic arid for 4 day s significantly increased density loss. Exposing petiole segments to u p to 100 mu l . liter(-1) ethylene in humidified air for up to 2 weeks at 5C did not significantly change density over air controls. The los s of density and the development of pithiness in lightly processed cel ery petioles could be reduced by selecting resistant cultivars, monito ring water stress during growth, using only segments excised from the upper two-thirds of the petiole, and selecting segments with initial h igh densities.