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Abstract
Changes in primary root number (RN), root dry weight (RDW), and shoot dry weight (SDW) on newly rooted stem cuttings of 7 woody ornamental plants were evaluated over 18 or 24 weeks after either no root removal or root removal where remaining RN equalled 25%, 50%, or 100% of the average RN at transplanting. Regardless of root removal treatment or season (February, June, or July), increases in primary RN occurred after transplanting and preceded increases in RDW and SDW. RDW and SDW increased progressively and together after primary RN ceased increasing. Cuttings started in February attained maximum RN in 12 to 18 weeks after transplanting, whereas those started in June and July required 6 weeks. Results suggest that stem cuttings of woody plants have a minimum, species dependent, primary RN which must be attained before measurable shoot growth is initiated.
Controlled pollinations were made between five hemlock (Tsuga) species from eastern North America and Asia, resulting in over 5700 germinating seedlings. A subset of putative hybrid seedlings from each cross was tested for authenticity by various DNA marker systems. The most reliable and useful system for verifying hybrids was amplified fragment-length polymorphism (AFLP) markers. Hybridizations between the eastern North American species, T. canadensis [L.] Carriere and T. caroliniana Engelm., and the Asian species, T. chinensis (Franch.) E. Pritz., were used as a model to test the inheritance, reliability, and ease of use of these markers. Using AFLP markers, we were able to verify 58 hybrids between T. caroliniana and T. chinensis, one hybrid between T. caroliniana and T. canadensis, but could find no definitive hybrids between T. canadensis and T. chinensis. Results using other marker systems, including RAPD, SCAR, ITS, and SSR, are also presented.