Breaking tuber dormancy in Helianthus tuberosus L. and interspecific hybrids of Helianthus Annuus L. × Helianthus tuberosus
Tubers of Helianthus tuberosus L. are dormant after production in the late fall until the next spring. In the wild, tuber dormancy is broken after exposure to winter cold, resulting in sprouting and shoot development in the spring when conditions are favorable. The dormancy period typically limits H. tuberosus populations to one growth cycle per year. An efficient method for breaking tuber dormancy is needed to have an additional growth cycle per year in a breeding program, which could take place in winter inthenurseryorthegreenhouse allowingforincreased breedingefficiency.Theobjective of thisresearch was to compare chemicaland cold temperature treatments for artificially breaking tuber dormancy in 12 genotypes of H. tuberosus and interspecific hybrids of Helianthus annuus L. 3 H. tuberosus. Five cold exposures (2, 4, 6, 8, 10 weeks at 2 8C), three plant hormones (ethylene, cytokinin, and gibberellic acid), and one untreated control were examined. Gibberellic acid was the best chemical treatment, initiating plant growthwithin6.5to11.5daysinthemajorityofgenotypestested.Thebestcoldtreatment was exposure to 2 8C for 8 weeks, where plant growth began 63.6 to 67.5 days after treatment initiation. Although longer cold treatments shortened the time to emergence while in the greenhouse, the penalty of the long cold treatment per se was too long to be useful. The gibberellic acid treatment strategy described here may not need further optimization, because it is short enough to allow for two growth cycles of H. tuberosus per year.
Gibberellic acid effect on tuber dormancy of Jerusalem artichoke under greenhouse conditions
Department of Plant Science, Faculty of Agriculture and Technology, Rajamangala University of Technology Isan, Surin Campus, Thailand Department of Plant Science and Agricultural Resources, Faculty of Agriculture, KhonKaen University, Muang, KhonKaen, Thailand Peanut and Jerusalem Artichoke Improvement for Functional Food Research Group, Khon Kaen University, Muang, KhonKaen, Thailand Department of Agricultural & Biosystems Engineering, Iowa State University, Ames, Iowa, USA Department of Plant Pathology and Microbiology, Iowa State University, Ames, Iowa, USA *Corresponding author e-mails: sanun@kku.ac.th
United Nations Convention on the Law of the Sea 1982, A Commentary
Volume VI is the sixth substantive volume to be published in the series. It deals with the work of the First Committee at the Third UN Conference on the Law of the Sea, namely the international seabed area. The volume thus embraces the deep seabed mining regime set out in Part XI of the 1982 Convention on the Law of the Sea together with the 1994 Agreement on its implementation. Completion of this commentary was delayed first by the consultations and negotiations that commenced in 1990 and led to the 1994 Agreement and the entry into force of the Convention. It was further delayed until the Assembly of the International Seabed Authority approved the detailed mining regulations in 2000. Additional supplementary material can be found at UNCLOS 1982 Commentary: Supplementary Documents.