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Theodore W. Tibbitts and Uzoamaka B. Mokwunye

The cotyledons of marigold, Tagetes erecta L., developed epinasty when reflective surfaces were maintained under the seedlings. Plain aluminum foil or white-painted foil induced up to 360° curvature as the cotyledons extended, whereas no epinasty occurred over the exposed surface of potting mix or black-painted foil. A gray-painted foil induced intermediate epinasty. Dry-weight accumulation of the seedlings was not significantly affected by the epinasty.

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Nichole F. Edelman and Michelle L. Jones

(yellowing); or epinasty (downward curvature of the leaf or petiole) ( Abeles et al., 1992 ). The quality of ornamental plants may be reduced by exposure to ethylene during production, shipping, and retailing ( Jones and Edelman, 2013 ; Jones and Ling, 2012

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Nichole F. Edelman, Bethany A. Kaufman and Michelle L. Jones

, epinasty, senescence, and fruit ripening. Plant responses to ethylene depend on the concentration and exposure time (i.e., dosage) as well as the plant’s sensitivity to ethylene. Ethylene sensitivity varies by species, ranging from nonresponsive to highly

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Anish Malladi and Jacqueline K. Burns

signaling. PGRs can be thought of as components of large signaling networks that communicate information from one part of a plant to another. By way of four examples including the communication of 1) root anaerobiosis—epinasty, 2) soil moisture status

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Daniel K. MacKinnon, Dale Shaner, Scott Nissen and Phil Westra

, showing a very strong epinastic effect within 24 h of application ( Abeles et al., 1992 ; Blankenship and Kemble, 1996 ). This ethylene-induced epinasty (quantified by measuring the change in the angle of the leaves’ petiole in reference to the stem) can

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Mustafa Özgen, Sookhee Park and Jiwan P. Palta

Mitigation of ethylene promoted leaf senescence by lysophosphatidylethanolamine (LPE) was studied. Micropropagated `Russet Burbank' potato (Solanum tuberosum L.,) plantlets were grown on MS media in sterile culture tubes. After 2 weeks of growth, tubes were sealed and ethylene gas was applied to obtain 5 nL·L–1 final concentration in the culture tubes. Observations and measurements were taken two weeks after ethylene injection. Potato plantlets treated with ethylene showed severe leaf senescence symptoms such as epinasty, lack of growth, yellowing and axillary shoot formation. These observations indicate that apical dominance has been lost with ethylene treatment. The same experiment was repeated with different concentrations of LPE in the MS medium. Inclusion of 50 or 100 mg·L–1 of LPE in the medium mitigated the damage normally caused by applied ethylene. Leaves of plantlets exposed simultaneously to LPE and ethylene had significantly higher chlorophyll content and more healthy leaves compared to plantlets grown on medium lacking LPE. Results of this study suggest that LPE may have the potential to retard ethylene-promoted leaf senescence and may mitigate ethylene induced loss in apical dominance of micropropagated potato plantlets.

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Kim Patten, John Wang, Fred Katz, Don Riemer, Chuck Kusek and Herb Hopen

Tolerance of cranberry (Vaccinium macrocarpon Ait.) at different phenological stages to the postemergent broadleaf herbicide clopyralid (0.21 or 0.42 kg a.i./ha) was evaluated in Washington, New Jersey, Massachusetts, and Wisconsin. Tolerance varied among states, rates, and application times. Applications made during early shoot growth, especially at the high rate, usually resulted in the most crop injury (leaf cupping and epinasty and reduced yield); while applications at the low rate made after vegetative development occurred usually resulted in less or no injury. No phytotoxicity occurred when applications were made before shoot growth (Washington and New Jersey). Chemical name used: 3,6-dichloro-2-pyridinecarboxylic acid (clopyralid).

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Harlene Hatterman-Valenti*

Greenhouse studies were conducted to evaluate simulated drift injury to annual bedding plants. Dahlia, gazania, geranium, marigold, petunia, and salvia in the early stages of flowering were sprayed with either 2,4-D (dimethylamine salt) or dicamba (diglycolamine salt) at rates one-fifth, one-tenth, or one-twentieth the lowest labeled rate of for turfgrass. Interactions between species by time, species by treatments, and treatments by time were significant for visual injury. Species sensitivity from most sensitive to least sensitive was marigold > dahlia ≫ geranium = petunia > gazania = salvia. Dahlia was more sensitive to dicamba than 2,4-D while the opposite was true for marigold. Petunia flower initiation was reduced as dicamba or 2,4-D rate was increased. The duration of the trial may have limited flowering differences among treatments with the remaining species. Dahlia loss of apical dominance as an injury response was greater with dicamba than 2,4-D. Typical injury symptoms for dahlia included stem, leaf, and petiole epinasty along with multiple shoot growth. Gazania injury included slight leaf rolling and leaf stretching. Geranium injury included leaf curling and fewer flowers per cluster. Marigold injury included leaf node swelling and stem wall rupture with massive cellular proliferation. Petunia injury included stem and pedicel epinasty, curling of the outer portion of the corolla, and lower flower production. Salvia injury included stunting, slight flower stem curvature, and partial dieback of the terminal raceme.

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James P. Gilreath, Carlene A. Chase and Salvadore J. Locascio

Cucumber (Cucumis sativus L.) growth and yield in response to application of sublethal rates of 2,4-D at several developmental stages were evaluated in field studies during two seasons. In Expt. 1, prebloom applications of 2,4-D amine reduced plant vigor and increased foliar epinasty as rates increased from 0 to 112 g·ha-1. Early and total fruit yields also declined linearly as 2,4-D rates increased; 112 g·ha-1 2,4-D reduced early yield by 25% and total yield by 20%. In Expt. 2, plant vigor declined with increasing rates of 2,4-D applied at all four stages of development from first true leaf to early fruit enlargement; however, response at stage 1 differed with time after application. Epinasty increased with 2,4-D rate when applied at all developmental stages; however the severity of the response varied with time after application for stages 1, 2, and 3, but not for stage 4. Averaged over all developmental stages, vine length, fresh weight, and yield decreased linearly as rates increased. Early and total yields with 112 g·ha-1 were 22% and 19% lower than those of nontreated plants, respectively. Growth inhibition and yield decline, pooled across 2,4-D rates, were greater when exposure occurred at the earlier stages of development. Chemical name used: (2,4-dichlorophenoxy)acetic acid (2,4-D).

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Kiyoshi Yokota, Koichi Murashita, Masanobu Nonaka and Koichi Hirai

Since 1987 some chemicals have been examined for thinning of apple, while concidering the safety for humans, animals and bees. Ethyl 5-chloro-3 (1H) - indazorylacetate (Ethychlozate) had the same effect as Carbaryl on `Fuji' cultivor Suitable results were obtained by 40ppm solution spray at 2 to 3 weeks after full bloom. An addition of 300ppm Ethephon increased thinning effects on `Fuji'. But over thinning occured on `Tsugaru'. `Jonagold' and `Jonathan' by same concentration of Ethychlozate or Ethychlozate plus Ethephon.

Thinning effects were more severe on the lateral fruits than on the center fruits. The results were advantageous for apple growing in Japan as center fruits are very important. Epinasty, russet and other injuries caused by Ethychlozate sprayed were not recognized.