The mechanism by which seal-packaging individual fruit in high density polyethylene film delays deterioration was ration of other perishable, living fruit items.The control of deterioration of fruit by plastic film had been generally explained by the modification of the concentrations of C02, 02, and ethylene (21). However, this theory was not supported by our data (1O, 13). Endogenous levels ofthe above gases were similar in fruit sealed in HDPE or not sealed, but their rates of physiological deterioration were altogether different. The major effect of sealing appears to be the provision of a watersaturated microatmosphere (8). This may alleviate water stress, which is important in controlling life processes (15, 20). However, so far only the inhibition of transpiration, shrinkage, and shriveling has been ascribed to the high humidity that is found in the microatmosphere of the sealed fruit (21). Therefore, we set out to investigate the hypothesis that sealing delays deterioration of lemon and bell pepper fruits by alleviating water stress. The importance of transpiration as a major process leading to physiological deterioration of citrus fruit has been demonstrated (7). This paper reports our attempts to relate water stress to various physiological parameters in sealed and nonsealed fruit. Lemons and peppers were selected for these studies because they responded very favorably to the seal-packaging technique. These fruits do not have the marked ripening and climacteric processes that could disturb our objective by masking the effects of the sealing per se on fruit behavior. Among the various techniques developed to extend fruit postharvest life, the use of plastic film is growing in importance because it is convenient in the many different conditions throughout the chain of handling from producer to consumer (8, 21). Ben-Yehoshua (8) found that seal-packaging individual fruit with a thin film ofHDPE2, 5 to 15 ,m in thickness, doubled storage life of various fruits. The flavor of the fruit was not spoiled; on the contrary, the sealed fruit maintained its normal flavor, as well as its firmness and fresh appearance for at least twice as long as nonsealed fruit. Surprisingly, sealed citrus fruit kept at 20C lost less weight and was firmer than nonsealed fruit at optimal (lower) temperatures.Seal-packaging delayed several parameters of physiological deterioration of fruit better than cooling; which is usually considered the best means of delaying senescence of detached living organs (1 1, 21). Accordingly, it is hoped that the elucidation of the mode of this action of seal-packaging would also help better understand the mechanism of senescence of detached plant organs and their causes. Such information might also be useful 2Abbreviations: HDPE, high density polyethylene; WSA, water-saturated atmosphere; WSD, water saturation deficit; AIS, alcohol-insoluble solids. In one pepper experiment, two other treatments were performed: WSA and sealed atmosphere with around 85% RH. The WSA was obtained by placing no...