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Janine O. Haynes and Wallace G. Pill

Purple coneflower seeds following priming (-0.04 MPa, 10 days, 15C, darkness) osmotically in polyethylene glycol 8000 (PEG) or matrically in expanded no. 5 vermiculite had greater germination rate and synchrony at continuous 20C or 30C than untreated seeds, but germination percentage was unaffected. Inclusion of 5.5 × 10-2 M gibberellic acid (GA3 as ProGibb Plus 2X, Abbott Laboratories, N. Chicago, Ill.) further improved germination rate and synchrony at 20C, but not at 30C. In a greenhouse study (30C day/27C night, July-August natural light), seeds primed in PEG or vermiculite containing G A3 compared to untreated seeds had 6 percentage points higher maximum emergence (ME), 3.3 fewer days to 50% ME, 1.9 fewer days between 10% and 90% ME, 116% greater shoot dry weight, and 125% longer leaves at 16 days after planting in peat-lite. Inclusion of ethephon (0.01 m, as Florel) either alone or with GA3 during priming provided no benefit to seed germination or seedling emergence. Moistened vermiculite substituted for PEG solution as a priming medium for purple coneflower seeds, the priming benefit on seedling emergence and growth being enhanced by 5.5 × 10-2 m G A3 inclusion in the priming media.

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Janine G. Haynes, Wallace G. Pill, and Thomas A. Evans

Switchgrass (Panicum virgatum L.) is one of the perennial, native, warm-season grasses recommended as a component of wildflower meadows. Seed treatments to alleviate low seed vigor and seed dormancy of switchgrass would enhance establishment of either plug transplants or seedlings after direct sowing into the meadow. “Heavy” seeds (45.5 mg/50 seeds) of open-pollinated switchgrass stored under cool and dry conditions (average 13 °C, 30% relative humidity) for 24 months had higher germination percentage than “light” seeds (26.0 mg per 50 seeds). In factorial combination, the heavy seeds were subjected to acid scarification (8 M H2SO4 for 5 min), sodium hypochlorite treatment (5.25% NaOCl for 15 min), and moist chilling (prechilling in 0.2% KNO3, for 14 days). Acid scarification followed by NaOCl treatment additively increased germination, a response that was associated with marked corrosion of the lemma margin in the distal region of the caryopsis, as observed by scanning electron microscopy. Prechilling the seeds following acid scarification and NaOCl further increased germination. All three treatments combined (acid scarification, NaOCl, and prechilling) almost doubled the final emergence and greatly increased seedling shoot dry mass in both a warm and cool postsowing environment. However, the effectiveness of these seed treatments was lost after 32 months of dry storage.

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Janine G. Haynes, John M. Smagula, and Paul E. Cappiello

Stem cuttings were harvested in April from four clones of containerized bunchberry(Cornus canadensis L.) forced in the greenhouse and in June from the same four clones growing in the field. April cuttings that had produced rhizomes by transplant time produced the greatest mean number and weight of shoots during the first growing season compared to April cuttings without rhizomes, June cuttings with rhizomes, or June cuttings without rhizomes. In a second study, cuttings and single-stem divisions were taken in July; divisions produced a greater mean number of shoots than did stem cuttings when compared at the end of Oct. A third study evaluated the effect of K-IBA application to lateral buds on subsequent rhizome production, and the effect of cutting node number (two vs. three nodes) on root or rhizome development. Treating lateral buds with K-IBA was not inhibitory to rhizome formation and elongation. Compared to two-node cuttings, three-node cuttings produced greater mean rootball size, rhizome number, and rhizome length; nearly twice as many of the three-node cuttings formed rhizomes as did two-node cuttings. A fourth study showed that cuttings rooted for 5 or 6 weeks in a mist enclosure generally exhibited greater shoot and rhizome production by the end of the first growing season than cuttings rooted for 8 or 9 weeks. This was despite the finding that cuttings rooted for longer durations (8 or 9 weeks) possessed larger rootballs and greater rhizome numbers at transplant time compared to cuttings rooted for shorter durations (5 to 6 weeks). Chemical name used: indole-3-butyric acid (K-IBA).