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  • Author or Editor: Jayne Zajicek x
  • Journal of the American Society for Horticultural Science x
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Seeds of tickseed (Coreopsis lanceolata L.) and purple coneflower [Echinacea purpurea (L.) Moench] were primed in aerated solutions of distilled water or 50 or 100 mM salt (potassium phosphate, pH 7.0) at 16C for 3, 6, 9, or 12 days. Coreopsis seeds primed in the 50 mM buffer germinated the most rapidly and uniformly, and, under stress conditions in the greenhouse, resulted in a faster-growing, more-uniform crop than other treatments. Seeds primed in distilled water and the 50 mM buffer germinated faster and at higher rates at suboptimal temperatures in the laboratory than nonprimed seeds. Priming of Echinacea purpurea seeds for 6 or 9 days in distilled water or in the 50 mM buffer resulted in faster, more-uniform germination than other treatments. Seedling emergence under stress conditions was improved by all priming regimes, with best emergence occurring in treatments that lasted > 3 days. Priming also increased germination rates of E. purpurea at suboptimal temperatures in the laboratory.

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Growth of potted Ligustrum was controlled by uniconazole at 3.0 mg a.i./pot. Uniconazole inhibited growth by inducing shorter internodes with smaller diameter and by reducing secondary branching and new leaf production. As a result, the total leaf area of the treated plants was 6396 less than the control plants. The chlorophyll content of recently expanded leaves was 27% lower in treated than in control plants, even though there were no visual differences in leaf color. Leaves of treated plants also had a 28% higher stomatal density than the control. The liquid flow conductance of Ligustrum was 3.7 × 10-14 m·s-1·Pa-1 and was similar for plants in both treatments. Differences in daily water, use between the two treatments began to appear at the same time as differences in growth. Total water use of treated plants was 13% less than that of the control. When daily water use was normalized on a-leaf-area basis, water use between treatments was similar, suggesting that differences in total water use were primarily due to differences in leaf area. For plants in both treatments, peak sap flow rates in the main trunk ranged between 60 and 100 g·h-1·m-2. Leaf conductance, transpiration rates, and water potential were also similar for treated and control plants. Chemical name used: (E)-1-(4-chlorophenyll) -4,4, -dimethyl-2-(l,2,4-triazo1-l-y1)-l-penten-3-ol (uniconazole).

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Growth of potted hibiscus (Hibiscus rosa-sinensis L.) was limited either by pruning or by a soil drench of `uniconazole at 3.0 mg a.i. per pot. Both treatments changed the water use of hibiscus. Five days after treatment with uniconazole, plants showed reduced water use, an effect that became more pronounced with time. Water use of pruned plants was reduced immediately after pruning, but soon returned to the level of the control due to the rapid regeneration of leaf area. Pruned or chemically treated plants used 6% and 33% less water, respectively, than the control. Chemically treated plants had a smaller leaf area, and individual leaves had lower stomatal density, conductance, and transpiration rate than control plants. Under well-watered conditions, the sap flow rate in the main trunk of control or pruned plants was 120 to 160 g·h-1·m-2, nearly three times higher than the 40 to 70 g·h-1·m-2 measured in chemically treated plants. Liquid flow conductance through the main trunk or stem was slightly higher in chemically treated plants due to higher values of leaf water potential for a given sap flow rate. The capacitance per unit volume of individual leaves appeared to be lower in chemically treated than in control plants. There was also a trend toward lower water-use efficiency in uniconazole-treated plants. Chemical name used: (E)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-l-yl)-1-penten-3-ol (uniconazole).

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Abstract

Seedlings of Baptisia australis (L.) R. Br. and Liatris aspera Michx., grown in prairie soil with no additional P, benefited significantly from inoculation with Glomus etunicatum Becker and Gerd., regardless of whether they were adequately watered or moderately or severely drought-stressed. In the presence of additional P, growth of severely droughted inoculated seedlings for both plant species was not significantly greater than noninoculated plants. When the influence of four Glomus species on growth of the two forbs was compared under drought-stress conditions with no supplemental P, growth of both plant species was signficantly improved by all fungal species compared to noninoculated controls. Preinoculated seedlings of both plant species were transplanted into disturbed-site soils with indigenous vesicular-arbuscular mycorrhizal (VAM) fungi present and subjected to severe moisture stress. After 12 weeks, inoculated seedlings were significantly larger than noninoculated seedlings for all soil types, with or without additional fertilizer (0.15 kg P/m3 + 0.075 kg N/m3). Under conditions of drought stress and low fertility, preinoculated seedlings of both B. australis and L. aspera grew significantly larger than noninoculated seedlings.

Open Access

Abstract

Seedlings of blue wildindigo [Baptisia australis (L.) R. Br.], rough gayfeather (Liatris aspera Michx.), and butterfly milkweed (Asclepias tuberosa L.) were grown in either a 1 soil : 1 sphagnum peat : 1 perlite (by volume) or 1 soil : 1 sand medium (v/v), amended with 0.00, 0.29, or 0.58 kg P/m3, and inoculated with Glomus etunicatum Becker and Gerd., G. fasciculatum (Thax. sensu Gerd.) Gerd. and Trappe, G. macrocarpum Tul. and Tul., G. mosseae (Nicol. and Gerd.) Gerd. and Trappe, or remained noninoculated. The objective was to determine whether vesicular-arbuscular mycorrhizal (VAM) fungi can establish and enhance plant growth, and how this would be affected by soil amendments. Replications were transplanted into the field to determine whether VAM pretransplant inoculation increased host growth and flowering. In the greenhouse, total dry weight of the three wildflower species grown in 1 soil : 1 sand (v/v) medium with no P was significantly improved by addition of most mycorrhizal species tested, but the response varied among plant species. At 0.29 kg P/m3, fewer mycorrhizal growth responses were evident. No growth responses were evident at 0.58 kg P/m3. B. australis was the only species that benefited from mycorrhizal inoculation in the 1 soil: 1 sphagnum peat: 1 perlite (by volume) medium at 0.00 and 0.29 kg P/m3. There were no differences in tissue P content within the three species when VAM-inoculated plants at 0.00 kg P/m3 were compared to noninoculated controls. At 0.29 kg P/m3 in the 1 soil : 1 sand medium, inoculated seedling tissue P increased, but in the 1 soil : 1 sphagnum peat : 1 perlite medium, noninoculated controls had significantly higher tissue P contents compared to inoculated seedlings. In the field, height and inflorescences per plant for the wildflowers were improved by VAM inoculation during the 2nd growing season.

Open Access