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- Author or Editor: M. Warmund x
- Journal of the American Society for Horticultural Science x
Abstract
Experiments were performed on ‘Cherokee’ blackberry (Rubus sp.) floral buds and cane tissue collected from field plantings on 12 Jan. and 18 Feb. 1987 to determine the susceptibility of floral primordia, phloem, and xylem to freezing injury after exposure to 16C for 0, 4, 12, 24, or 48 hr. Before rest completion in January, floral primordia, phloem, and xylem subjected to 16C were hardier than those tissues tested in February when rest was completed. Floral primordia and cane tissues dehardened slowly with time at 16C before rest completion. After rest was completed, the rate of deacclimation of floral primordia and xylem increased. Some blackberry canes were subjected to two thawing episodes at 16C for 4 hr. In January, phloem and xylem of canes thawed twice were as hardy or hardier than those tissues in samples thawed once. Conversely, two thawing episodes in February resulted in greater xylem injury than a single episode, but two episodes did not affect the hardiness of the phloem. The number of thawing episodes did not affect floral bud hardiness at either sampling date.
`Jonagold'/Mark apple (Malus domestica Borkh.) trees that were chip-budded in Washington and Illinois on 31 Aug. or 21 Sept. 1989 were sampled in Apr. 1990 to determine if magnetic resonance imaging (MRI) could be used to nondestructively examine vascular continuity or discontinuity between the rootstock and scion. Images could be placed into three categories based on signal intensity: 1) the rootstock, bud shield, and the bud or new scion growth had a high signal intensity; 2) the rootstock and the bud shield had a high signal intensity, but the scion had a low signal intensity; and 3) the rootstock had a high signal intensity, but the bud shield and scion had a low signal intensity. High signal intensity was associated with bound water in live tissue and the establishment of vascular continuity between the rootstock and scion. Azosulfamide staining and destructive sectioning confirmed that vascular continuity was established when the rootstock, bud shield, and scion had a high signal intensity in images, whereas budding failure occurred when the bud shield and/or the scion had a low signal intensity. Additional trees that had wilted or weak scion growth were collected from Illinois in June 1990. Parenchyma tissue was found in the scion adjacent to the bud shield that interrupted the vascular tissue. Poor scion growth on trees from the 21 Sept. budding in Washington may be attributed to insufficient growth of rootstock and/or scion tissues at the union in the fall.