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  • Author or Editor: John. E. Erwin x
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Jasmonates are a class of plant hormones involved in plant defense and stress responses. For example, jasmonate-induced defense responses in Lycopersicon esculentum include increases in activity of proteinase inhibitors, polyphenol oxidases, and peroxidases. As part of our efforts to reduce or control greenhouse pest infestations, we hypothesized that methyl jasmonate (MeJA) could induce these biochemical changes in common greenhouse crops. We studied Impatiens wallerana `Super Elfin Pink', L. esculentum `Big Boy', Petunia ×hybrida `Bravo Lavendar', Viola ×wittrockiana `Imperial Beaconsfield', Coleus ×hybridus `Wizard Jade', Nicotiana alata `Saratoga Lime', Pelargonium ×hortorum `Pinto Pink', and Tagetes erecta `Antigua Primrose'. Polyphenol oxidase and peroxidase activity was studied in the first four species, and proteinase inhibitors were studied in all eight. We sprayed plants with 0, 5 × 10-6, or 10-4 molar MeJA and made measurements after 24 hours. We detected a small increase in polyphenol oxidase activity of plants treated with 10-4 molar MeJA; 5 × 10-6 molar had no effect, and L. esculentum had the highest polyphenol oxidase activity. Peroxidase activity was not affected by MeJA. I. wallerana had the highest peroxidase activity, L. esculentum and V. ×wittrockiana had the lowest. 5 × 10-6 molar MeJA increased proteinase inhibitor activity in most species, and 10-4 molar increased activity in every species except P. ×hortorum.

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Our objectives in this study were to identify the flowering response of Kalanchoe spp. to photoperiodic treatments and characterize flowering and vegetative characteristics of flowering plants. Twenty vegetatively propagated Kalanchoe spp. were grown under one of four photoperiodic treatments: 1) short days (SD; 8-h photoperiod) for 16 weeks; 2) night interruption lighting (NI; 2000 to 0200 hr) for 16 weeks; 3) SD for 8 weeks then transferred to NI for 8 weeks; or 4) NI for 8 weeks then transferred to SD for 8 weeks. Kalanchoe beauvardii, K. behariensis, K. fedtschenkoi, K. longiflora, K. marmorata, K. marnieriana, K. streptantha, K. tomentosa, and K. vigueridoi did not flower under any treatment. Kalanchoe laetivirens and K. rosei had minimal flowering when exposed to NI followed by SD, whereas K. pumila had minimal flowering when exposed to SD followed by NI. Kalanchoe glaucescens, K. laciniata, K. manginii, K. nyikae, K. rotundifolia, K. uniflora, and K. velutina flowered when exposed to SD for 8 or 16 weeks, and node number below the inflorescence and days to first open flower for these species increased when NI preceded SD. Kalanchoe millotii flowered under a 16-week SD treatment only. No plants flowered when grown under only NI. We classified K. glaucescens, K. laciniata, K. manginii, K. millotii, K. nyikae, K. rotundifolia, K. uniflora, and K. velutina as obligate SD plants. Flower diameter, total flower number, total color index, shoot length, branch number, and leaf length and width varied among species. Based on these ornamental characteristics, we identified K. glaucescens, K. laciniata, K. manginii, K. nyikae, K. uniflora, and K. velutina as potential ornamental flowering potted plants.

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Five cuttings from different node positions on stock plants were taken from each of 3 Clematis cultivars (Jackmani, Contesse de Bouchard, and Gypsy Queen) and Clematis purpurea plena elegans. Actively growing plants with 5 nodes were acquired. Node number increased from 1 at the base of the plant to 5 at the tip of the plant. Cuttings were treated with or without 0.1% IBA (indole-3-butyric acid) and placed in 1 of 5 different media: 100% washed sand (WS), 50% washed sand and 50% sphagnum peat (WP), 50% sphagnum peat and 50% perlite (SP), 100%) perlite (PT), or 50% sphagnum peat plus 25% perlite plus 25% vermiculite (PV). Rooting date, primary and secondary root number, and root dry weight were collected after 8 weeks. `Gypsy Queen' showed the earliest rooting with the greatest root development. Jackmani showed the worst rooting. Media WS and PT showed the best rooting whereas WP and SP showed the worst. Cuttings taken from the first 3 nodes rooted the best. As node position increased root number and dry weight decreased and time to root increased. Application of IBA had no significant effect on time to root or degree of rooting.

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A phone survey was conducted to assess the total impact of the floriculture industry on the Minnesota economy. Data were collected from wholesale growers, garden center retailers, chain stores, and florists. Information was gathered on `hard good' sales associated with greenhouse produced plants as well as plant sales. In addition, data on labor and salaries associated with the production, distribution, and retailing of plants and goods associated with the floriculture industry was collected. This data will be provided to local flower growers organizations to enable these groups to actively lobby for their concerns within the state.

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Lypcopersicum esculentum cv `Money Maker' seeds were germinated at constant 20C. Three days after germination seedlings were randomly divided into 3 groups and placed into 3 growth chambers maintained at 23/17, 20/20, or 17/23C (day/night temperature) (DT/NT). Irradiance and photoperiod were maintained at 250 μmol s-1 m-2 and 12 hrs, respectively. At the 2 leaf stage, plants in each chamber were divided into 3 groups of 3 plants each to receive a growth regulator treatment. Growth regulator treatments consisted of spray applications of either ancymidol (52ppm), GA3 (12ppm), or water applied every 3 days for 21 days. Measurements were taken on internode length and chlorophyll content after 21 days. Internode length increased as the difference (DIF) between DT and NT increased (DT-NT). Exogenous applications of GA3 overcame inhibition of stem elongation resulting from a -DIF environment. Application of ancymidol did not significantly decrease stem elongation in a -DIF environment. Temperature regime had a significant impact on chlorophyll content per mg dry weight. In contrast, growth regulator applications had a significant impact on chlorophyll content cm-2. There was no significant impact of either temperature regime or growth regulator treatment on the chlorophyll a/b ratio.

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The interaction between day/night temperature (DT/NT) and irradiance during the photoperiod prior to the inductive night on Pharbitis nil (L.) cv. Violet flower induction was studied. Plants exposed to 12 or 18 °C NT did not flower regardless of DT. When NT was 24 or 30 °C, percent flowering plants increased progressively as DT increased from 12 to 30 °C. Percent flowering plants and total flower bud number per plant was greatest when seedlings were induced with a 24 or 30 °C DT/30 °C NT regime. DT/NT did not affect the node number to first flower. Irradiance did not affect flowering. Temperature effects on P. nil flowering could be described as a function of average daily temperature, where flowering increased as temperature rose from 22 to 30 °C.

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Rose plants (cvs `Royalty' and `Lovely Girl') in an established canopy were cut back to node 1, 3, 5, 7, 9, 11, or 13 from the base of the stem at harvest. Harvest was defined as the reflexing of the outermost petal. Most rose stems were composed of 13 nodes, therefore, pruning to the 13th node involved removing the flower only. Three leaf removal techniques were evaluated: 1) no leaf removal, 2) removing the node leaf only, or 3) removing all leaves on the stem. Total break number increased as the node position which stems were cut back to increased. For instance, break number increased on `Lovely Girl' from 1.8 to 2.6 breaks as node position increased from 1 to 13. The number of lateral breaks which developed into marketable flowers also increased as the node position which stems were cut back to increased. `Lovely Girl' flower number increased from 0 to 2.6 flowers per stem as node position increased from 1 to 13. Leaf removal reduced the number of marketable flowering shoots. For instance, flowering shoots decreased from 2.6 to 1.4 per stem on stems cut at the 13th node following removal of all leaves on that stem. `Royalty' had more lateral breaks than `Lovely Girl' but also had more non-flowering lateral breaks following pruning. Commercial implications of this research will be discussed.

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Nephrolepis exaltata (L.) Schott `Dallas Jewel' plants were grown for 92 days under 16 day/night temperature (DT/NT) regimes and two photoperiods for a total of 32 environments. Temperatures ranged from 15 to 30 ± 1.5C. Photoperiod was either 9 hours (short days) or 9 hours plus a 4-hour night interruption (long days) using incandescent lamps. Photoperiod had no significant effect on either morphology or development rate. Frond length and leaflet count per frond were highly correlated with the average daily temperature (ADT). Frond length increased from 9.3 to 21.9 cm and leaflet count increased from 21 to 42 leaflets per frond as ADT increased from 15 to 30C. Solon count and frond orientation were highly correlated with the weighted difference (WDIF) between DT and NT. The weighted difference between DT and NT was equal to: (DT × photoperiod) - (NT × scotoperiod). The scotoperiod was inclusive of the night interruption. Stolon count increased as the weighted NT increased relative to the weighted DT, i.e., as WDIF decreased. In contrast, frond angle relative to the soil surface, i.e., frond orientation, increased as WDIF increased. Frond unfolding rate and total plant dry weight increased as temperature increased to ≈ 25C, then decreased.

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Parthenolide, a biologically active sesquiterpene lactone found in feverfew [Tanacetum parthenium (L.) Schultz. Bip.], has been indirectly linked to the antimigraine action of feverfew preparations. Commercial products of feverfew leaves vary widely in parthenolide content (0-1.0%/g dwt). No comprehensive studies have quantified parthenolide variation among feverfew populations or cultivars, and whether morphological traits are correlated with this natural product. In this study, 30 feverfew accessions were examined for parthenolide content, morphological traits, and seed origin. Statistically significant differences in parthenolide levels were found among the populations studied. Parthenolide content ranged from (0.012% ± 0.017 to 2.0% ± 0.97 /g dwt) as determined by HPLC-UV-MS. Higher parthenolide levels tended to be in wild material (0.41% ± 0.27) as opposed to cultivated material (0.19% ± 0.09). Parthenolide levels correlated with flower morphology: disc flower (0.49% = B1 0.36), semi-double (0.38% ± 0.13), double (0.29% ± 0.16), and pompon-like flower (0.22 ± 0.14). Leaf color also appeared to be indicative of parthenolide levels, with the light-green/golden leafed accessions showing significantly higher parthenolide content than darker-leafed varieties, but whether this was due to inadvertent original selection of a high parthenolide-containing golden leaf selection is not yet known. This study does show that further selection for improved horticultural attributes and natural product content is promising to improve feverfew lines for the botanical/ medicinal plant industry.

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