Submitted to: Physiologia Plantarum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 17, 1995
Publication Date: N/A
Interpretive Summary: For a finite period following harvest, potatoes will not sprout and are physiologically dormant. Dormancy is gradually lost during storage and the resulting sprouting is detrimental to the nutritional and processing qualities of potatoes. Because of this, sprouting results in severe financial loss to producers. Sprouting is currently controlled by synthetic sprout inhibitors. The research being conducted in this lab is directed towards identifying key physiological processes regulating tuber dormancy and ultimately modifying these processes genetically. Previously, we have shown that the plant hormone abscisic acid (ABA) is required for the initiation and maintenance of tuber dormancy. In this paper, we show the effects of dormancy on the internal levels and metabolism of ABA were determined. ABA levels fell throughout postharvest storage although the rate of metabolism was constant. No specific level of internal ABA was correlated with the loss of dormancy. These results indicate that, although ABA participates in the initiation of tuber dormancy, other growth factors are involved in the termination of dormancy. The nature of these dormancy-breaking factors is currently being determined.
Technical Abstract: The effects of postharvest storage duration, and storage and incubation temperatures on the loss of innate tuber dormancy, endogenous levels of free and conjugated abscisic acid (ABA) and the metabolism of (+)- [3H] ABA were examined over three growing seasons in tubers of potato (Solanum tuberosum L. cv Russet Burbank). In tubers stored at 20 deg C, dormancy was lost and sprout growth began after 35 to 50 days of storage. In contrast, dormancy was lost after 50 to 80 days of storage at 3 deg C but subsequent sprout growth was initiated only after transfer to 20 deg C. After 35 days of storage, endogenous levels of free ABA were highest (860 +/- 35 pmol g-1 fresh weight) in tubers held at 3 deg C, intermediate (659 +/- 78 pmol g-1 fresh weight) in tubers transferred from 3 to 20 deg C seven days prior to analysis and lowest (471 +/- 18 pmol g-1 FW) in tubers stored at 20 deg C. Regardless of temperature, free ABA levels declined with increasing duration of storage. During postharvest storage, there was no change in the rate of ABA metabolism regardless of the dormancy status and/or growth potential of the tubers. These results demonstrate that ABA is readily metabolized by potato tubers and that the principal route of catabolism consists of the oxidative metabolism of ABA to phaseic and dihydrophaseic acids with minimal esterification to conjugated ABA. Further, these results suggest that a decline in endogenous ABA below a threshold level is not a prerequisite for the loss of potato tuber dormancy and the onset of sprout growth.