Effect of petiole anoxia on Phloem transport in squash.

Translocation of (14)C-labeled assimilates in Early Prolific Straightneck squash (Cucurbita melopepo torticollis Bailey) through a 15-centimeter oxygen-deficient zone of the petiole was studied as a function of varying periods of anaerobiosis (N(2) atmosphere). Initiation of anaerobic conditions caused an immediate and rapid decline in translocation to about 35 to 45% of the pretreatment rate within 30 to 40 minutes. This inhibition response (first inhibition response) was transient, however, and full recovery to the pretreatment rate occurred during the ensuing 60 to 90 minutes. Following this adaptation response to anaerobic conditions, translocation continued unimpaired for extended periods of time, approaching, and in some cases exceeding, 24 hours. The second inhibition response was permanent and could not be reversed by supplying air during a subsequent 20-hour period.