Jerusalem artichoke growth, development, and field storage. I. Numerical assessment of plant part development and dry matter acquisition and allocation

Expanding commercial interest in the use of inulin as a bulking agent for artificial sweeteners, dietary fiber health supplement, fat replacement for processed foods, feed stock for fructose syrups, and a wide range of potential industrial products, has stimulated research on inulin-containing crops such as the Jerusalem artichoke. To better understand the developmental physiology of the crop and to identify potential breeding objectives, the temporal pattern of development of individual plant parts (shoots, branches, leaves, flowers, stolons, tubers, and roots) and the allocation of dry matter into the same plant parts were monitored in the cultivar 'Sunchoke' over the entire growing season and during in situ field storage during the early winter, 32 weeks after planting. While number of shoots (approximately 9) peaked in week 10, the number of branches (42.8), stolons (49.4), and tubers (85.5) reached a maximum 24-28 weeks after planting. Number of leaves (approximately 525) peaked between weeks 20-24 after planting, as did number of flowers (approximately 55). The Jerusalem artichoke allocated the major portion of its dry matter (dm) into aboveground plant parts during the first half of the growing season. Approximately 16 weeks after planting, the pattern of allocation shifted dramatically with: a) near cessation in the acquisition of dry matter; and b) the reallocation of existing dry matter from the aboveground organs into the tubers. By the 16th week after planting, 85% of the total dm was in the aboveground plant parts, but declined to 28% by the 30th week. Of the total dm, 92% was accrued during the first 16 weeks and only 8% thereafter. The shift in dry matter resources coincided with a dramatic decrease in leaf number and in leaf and branch dry weight. By the end of the season, the harvest index reached 0.70 and the tuber yield 14.6 t dm ha(-1). Yield improvement could potentially be facilitated through lengthening the logarithmic period of carbon fixation and by earlier tuber induction and development.