Britex and Zivdar, water-based polyethylene waxes, were applied in commercial and experimental formulations as spray coating, a single dip, or double dips on `Murcott' tangerine (Citrus reticulate Blanco) fruits. Postharvest waxing of `Murcott' tangerine reduced weight loss but affected the sensory characteristics of the fruit. Charges in fruit weight loss and juice composition occurred in the waxed fruits after 4 weeks of storage at 5C plus 1 week of simulated retail handling at 17C. Changes in internal fruit atmosphere were related to fruit flavor quality.

The putative Ca 2؉ -channel blocker LaCl 3 prevented the gravitropic bending of cut snapdragon (Antirrhinum majus L.) spikes (S. Philosoph-Hadas, S. Meir, I. Rosenberger, A.H. Halevy [1996] Plant Physiol 110: 301-310) and inhibited stem curvature to a greater extent than vertical and horizontal stem elongation at the bending zone. This might indicate that LaCl 3 , which modulates cytosolic Ca 2؉ , does not influence general stem-growth processes but may specifically affect other gravity-associated processes occurring at the stem-bending zone. Two such specific gravity-dependent events were found to occur in the bending zone of snapdragon spikes: sedimentation of starch-containing chloroplasts at the bottom of stem cortex cells, as seen in cross-sections, and establishment of an ethylene gradient across the stem. Our results show that the lateral sedimentation of chloroplasts associated with gravity sensing was prevented in cross-sections taken from the bending zone of LaCl 3 -treated and subsequently gravistimulated spikes and that LaCl 3 completely prevented the gravity-induced, asymmetric ethylene production established across the stem-bending zone. These data indicate that LaCl 3 inhibits stem curvature of snapdragon spikes by preventing several gravity-dependent processes. Therefore, we propose that the gravitropic response of shoots could be mediated through a Ca 2؉ -dependent pathway involving modulation of cytosolic Ca 2؉ at various stages.Various aboveground plant parts, such as coleoptiles, hypocotyls, seedlings, grass-shoot pulvini, and flowering stems, respond to a change in a gravity vector by differential growth that leads to upward bending. Most of the work on negative gravitropism has been performed with seedlings and specific graviresponsive organs such as coleoptiles, epycotyls and grass-shoot pulvini (Kaufman et al., 1985; Migliaccio and Galston, 1987; Gehring et al., 1990; Brock et al., 1992; Kim and Kaufman, 1995). However, there have been several reports of gravitropism of stem-like organs (Rorabaugh and Salisbury, 1989; Kiss et al., 1997; Strudwick et al., 1997), vegetative stems (Meicenheimer and Nackid, 1994), and flowering shoots (Kohji et al., 1979; Halevy and Mayak, 1981;Woltering, 1991; PhilosophHadas et al., 1995 PhilosophHadas et al., , 1996 Fukaki et al., 1996). In this respect, the graviresponding spikes of snapdragon (Antirrhinum majus L.; Philosoph-Hadas et al., 1996) provide an excellent model system for investigating the gravitropic phenomenon in mature inflorescence stems.The common underlying mechanisms of negative gravitropism involve perception of the stimulus and its transduction into physiological processes that lead to a differential growth response (Salisbury, 1993). Gravity perception is considered to be accomplished by a mass pressure on the lower cell membrane following changes in organ orientation. This mass is believed to be either that of specific plastids, usually amyloplasts or chloroplasts, which sediment only in cells of a specific developmental stage...

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