Tuber dormancy

Of the three general types of dormancy (Lang, 1987), Jerusalem artichokes display what is termed endodormancy, where an internal mechanism prevents sprouting even though the external 

Biology and Chemistry of Jerusalem Artichoke Helianthus tuberosus L. 

The tubers become dormant in the fall, prior to the actual completion of their development. For example, Steinbauer (1939) found the onset of dormancy (two cultivars) to be between August 28 and September 7 in the U.S. After this time, freshly dug tubers did not sprout even under suitable environmental conditions. The exact timing of the onset of dormancy varied between individual tubers on the same plant and with production location, cultivar, and other factors. Interestingly, the larger, more mature tubers were the last to enter into dormancy. Dormancy was initially established in the rhizomes and small, younger tubers and well before the completion of the maturation process and the first frost. The onset of dormancy appeared to be a gradual process thus, not all of the tubers on a plant became dormant simultaneously. 

The depth or degree of dormancy varies considerably among cultivars and within an individual cultivar such that one tuber will sprout while others are delayed considerably. In a study of 145 cultivars, Boswell (1932) found that the time required for 50% of the tubers to sprout when not subjected to a cold treatment to fulfill the dormancy requirement ranged from 54 to 200 days, with 5 to 6 months typical for most cultivars. Likewise, the degree of dormancy varied between seasons. Cutting the tubers did not alter the dormancy. Treatment with certain chemicals (e.g., ethylene chlorohydrin), however, could shorten the dormancy period, although a number of the chemicals tested also slowed the subsequent growth of the sprout (Steinbauer, 1939). 

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Many genetic studies in potato have focused on disease resistance. A summary of disease resistance genes and quantitative trait loci in potato has recently been published (Celebi-Toprak et al., 2005b). In addition, major quantitative trait loci have been identified for tuber dormancy (chromosome II), tuber eye depth (chromosome X), flesh color (chromosome IV), tuber shape (chromosome II) and uniformity of tuber shape (chromosome III) (Sliwka et al., 2008). 

Thornton, M. K., Lewis, M. D., Barta, J. L., Kleinkopf, G. E. (1994). Effect of nitrogen management on Russet Burbank tuber dormancy and response to CIPC. American Potato Journal, 71, 705. 

Tuber dormancy studies can be separated into three general types based upon the tuber material used and whether the dormancy requirement is fulfilled naturally or via an artificial induction of cell division. Each method has distinct advantages and disadvantages. The tuber material includes intact tubers, tuber slices in which cell division is induced using an auxin analogue in an aqueous... 

The compound is not effective when appHed as a preharvest dormancy agent on potatoes and it should not be used until injuries to the tuber coat have healed. Neither should it be appHed until some suberization has occurred, generally two weeks after storage at >10° C (23). CIPC is widely used outside the United States on a number of crops as a herbicide. 

Destefano-Beltran, L., D. Knauber et al. (2006). Effects of postharvest storage and dormancy status on ABA content, metabolism, and expression of genes involved in ABA biosynthesis and metabolism in potato tuber tissues. Plant Mol. Biol. 61(4-5) 687-697. 

Amylose is one component of starch, which is the most abundant carbohydrate storage reserve in plants. Carbohydrates such as starch function as a reservoir of energy for later metabolic use. It is found in many different plant organs, including seeds, fruits, tubers, and roots, where it is used as a source of energy during periods of dormancy and regrowth. 

An important factor determining the efficacy of radiation treatment of tubers and bulbs is the time delay between harvest and irradiation. The sprout inhibition is most pronounced if the irradiation of tubers and bulbs is applied shortly after harvest, when they are still in their dormancy stage. However, the dormancy period may vary among cultivars and cropping season, and is also dependent on the postharvest storage temperature. 

Sliwka, J., Wasilewicz-Flis, I., Jakuczun, H., Gebhardt, C. (2008). Tagging quantitative trait loci for dormancy, tuber shape, regularity of tuber shape, eye depth and flesh colour in diploid potato originated from six Solanum species. Plant Breeding, 127, 49-55. 

Initiate or terminate the dormancy of seeds, buds, and tubers. 

Bagni, N., Donini, A., Serafini-Fracassini, S., Content and aggregation of ribosomes during formation, dormancy, and sprouting of tubers of Helianthus tuberosus. Plant Physiol., 27, 370-375, 1972. 

The precise role of polyamines in the control of dormancy and the onset of cell division in Jerusalem artichoke tubers, and for that matter in plant development per se, remains in question. Evidence from arginine decarboxylase mutants of Arabidopsis does indicate a possible role in root meristem function (Watson et al., 1998). 

As mentioned previously, when dormant there are low amounts of polyamines in the tubers however, they are synthesized rapidly when dormancy is broken (Del Duca and Serafini-Fracassini, 1993 Serafini-Fracassini et al., 1984), the onset of which occurs very early in the G, phase. Likewise, immediately after the fulfillment of the dormancy, there was a marked decrease in arginine and glutamine (precursors of polyamines) and a corresponding increase in polyamines (Durst and Duranton, 1966 Serafini-Fracassini et al., 1980). 

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