Red huckleberry is an indigenous Vaccinium sp. from southeastern Alaska to central California along the Pacific coast and Cascade Mountain ranges, with small disjunct populations reported in southeastern British Columbia (Vander Kloet, 1988). The berries are tart, rather than sweet, and are harvested commercially from the wild for processing. Bearing red leaves in autumn and red berries that remain on the plants into late autumn or early winter, red huckleberry has potential for managed commercial fruit production and as an edible ornamental plant. Adaptability to a range of growing sites, vigorous growth, upright habit, and the potential for mechanical harvesting are important traits of this species for breeding programs and commercial production (Barney, 2003).
Little research has been published regarding sexual propagation practices for red huckleberries. Various temperature regimens can affect Vaccinium sp. germination. Although Stark and Baker (1992) reported 70% germination of V. membranaceum at a constant 20 °C, some Vaccinium sp. need temperature fluctuations to germinate (Baskin et al., 2000; Minore et al., 1979; Stushnoff and Hough, 1968; Vander Kloet, 1983). Relatively low germination percentages and a slow germination process are a characteristic of red huckleberry seeds (Vander Kloet, 1983). Vander Kloet (1983) reported up to 47% germination of freshly extracted red huckleberry seeds under a temperature regime of 22 °C day/5 °C night with a 14-h photoperiod (time after harvest of berries not reported). The study also included a 28 °C day/13 °C night temperature treatment with a 14-h photoperiod resulting in 21% germination, but detailed information about the process of germination (i.e., how seeds germinate over time) was not given.
Gibberellic acid (GA) is used to help break seed dormancy of many angiosperms (Taiz and Zeiger, 2002). For instance, at 4 weeks after treatment with 900 ppm GA3, Dweikat and Lyrene (1989) found 50% of V. corymbosum seeds had germinated, whereas only 4% of nontreated seeds had germinated. Higher concentrations of GA3 failed to significantly increase germination. In contrast, GA treatments failed to influence V. ashei seed germination (Ballington et al., 1976). Similarly, Austin and Cundiff (1978) reported that neither GA4+7 nor GA4+7 plus benzyladenine stimulated V. ashei seed germination, although GA4+7-treated seedlings reached transplant size 2 to 4 weeks earlier than did control seedlings or seedlings from GA3-treated seeds. Additionally, Maznaya and Lyanguzova (1999) found that imbibing nonstratified seeds of V. uliginosum for 48 h in 100 to 500 mg/L GA3 solutions increased the germination percentages from 3% to between 65% and 80%.
Devlin and Karczmarczyk (1975, 1977) determined that without germination enhancement treatments, V. macrocarpon seeds are photoblastic (i.e., require light to germinate) and suggested an interaction between the need for light and GA treatments. Devlin and Karczmarczyk (1975) determined that V. macrocarpon seed germination was enhanced in the dark when seeds were soaked with GA after they were treated with concentrated sulfuric acid. The seedcoat is a barrier for the uptake of exogenously applied GA and dark germination was enhanced by GA treatments after seed scarification with concentrated sulfuric acid. In fact, treatment with 1000 ppm GA enhanced seed germination in the light and dark (Devlin and Karczmarczyk, 1977). Smagula et al., (1980) also determined that early germination of V. angustifolium seeds kept in the dark was stimulated by GA at 500, 1000, 2000, or 4000 ppm. Unlike V. ashei, V. angustifolium seed germination increased with increased GA concentrations in the light.
Therefore, the objectives in conducting this research were to develop a regression model of the germination process for red huckleberry seeds and to use the regression model to assess the effects of temperature and GA concentration on cumulative germination percentage, rate, and lag time of red huckleberry seeds.
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