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The demand for new and/or improved herbaceous annuals and perennials continues to increase, making information on production and viability of these plants a necessity. In Louisiana and the Southern U.S., one of the greatest impediments to production of marketable herbaceous plants and their longevity is high temperature. Herbaceous plants have various stages of vegetative growth and flowering; high temperatures during these developmental stages can have a tremendous impact on plant metabolism, and thus plant growth and development. The goal of this research was to better understand the differences between heat tolerant (HT) and heat sensitive (HS) species and cultivars at various high temperatures in terms of whole plant growth, flowering, photosynthesis, carbohydrate content, electrolyte leakage, chlorophyll content and plant small heat shock proteins (HSP) expression levels. Salvia splendens Vista Series (HT), Sizzler series (HS); Viola witrokiana `Crystal Bowl Purple' (HT), `Majestic Giant Red Blotch' (HS), F1 Nature Series (HT) and F1 Iona Series (HS); Gaillardia × grandiflora `Goblin' (HT) and Coreopsis grandiflora `Early Sunrise' (HS) were grown from seed in growth chambers under 25/18 °C (day/night) cycles. Plants at 4, 6, and 8 weeks after germination were subjected to different high temperature treatments of 25 (control), 30, 35, 40, and 45 °C for 3 h. Results show that there was a significant difference in net photosynthesis, electrolyte leakage, soluble carbohydrate content and HSP levels between HT and HS cultivars. Effects of high temperature on plant growth, chlorophyll content, and number of days to flower, flower size, and marketable quality were also significantly different.

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Decline of sod quality during the transportation, storage, and transplant stages of sale is a primary economic concern of sod producers. However, the mechanisms of extending sod quality during storage, transportation, and transplantation remain unclear. This study was conducted to investigate the influences of selected plant metabolic enhancers (PMEs) seaweed (Ascophyllum nodosum Jol.) extract (SWE), humic acid [93% a.i. (HA)], and propiconazole (PPC), on sod tolerance to stress during storage and posttransplant root growth of tall fescue (Festuca arundinacea Schreb.) sod. The SWE + HA, and PPC were applied alone, or in a combination, to tall fescue 2 weeks before harvest. Photochemical efficiency (PE) of photosystem II was measured immediately before harvest. The harvested sod was subjected to high temperature stress (40 °C) for 72 or 96 hours. The heated sod was replanted in the field and posttransplant injury and root strength were determined. On average over 1999 and 2000, application of SWE (50 mg·m-2) + HA (150 mg·m-2), PPC (0.30 mL·m-2), and a combination of SWE + HA with PPC (0.15 mL·m-2), enhanced PE of preharvest sod by 8.5%, 9.1%, and 11.2%, respectively, and increased posttransplant rooting by 20.6%, 34.6%, and 20.2%, respectively. All PME treatments reduced visual injury except SWE + HA and SWE + HA + PPC in 1999. Extension of heat duration from 72 to 96 hours caused significantly more injury to the sod and reduced posttransplant rooting by 22.9% averaged over 2 years. The data suggest that foliar application of SWE + HA, PPC alone, or in a combination with SWE + HA, may reduce shipment heat injury and improve posttransplant rooting and quality of tall fescue sod. Chemical name used: 1-(2-(2,4-dichloropheny)-4-propyl-1,3-dioxolan-2yl)methyl-1-H-1,2,4-triazole [propiconazole (PPC)].

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Several components of whole-plant growth were compared among accessions of Fragaria chiloensis (FC) and F. virginiana (FV) grown at 23 and 31 °C daytime temperatures. The accessions loosely represented North American (NA) and South American (SA) provenances of FC and Kentucky (KY) and eastern Canadian (CN) provenances of FV. Differences in component values between species and by provenance and accession within species were observed at each temperature. Using the ratio of the component value at 31 °C to that at 23 °C as a basis for comparisons, whole-plant relative growth rate (RGR), leaf net assimilation rate (NAR), root RGR, and root: shoot ratio were reduced relatively more by high temperature in FC than FV, while crown RGR, leaf RGR, and leaves produced per day were not consistently affected by temperature or and did not differed significantly between species. While the SA FC exhibited higher values for nearly all components than the NA FC at both temperatures, both were affected similarly by high temperature. The CN FV exhibited somewhat greater sensitivity to high temperature than the KY FV, with significantly lower leaf NAR, crown RGR, and leaves produced per day in the former group.

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The membrane thermostability of Ilex cornuta Lindl. & Paxt. `Needlepoint' (Chinese holly), Ilex aquifolium L. `Albo-marginata' (English holly) and Ilex × `Nellie R. Stevens', a hybrid between Ilex aquifolium and Ilex cornuta, was determined using electrolyte leakage procedures with excised foliage and root tissue. The critical midpoint heat-killing temperature (T m) after a 30 min exposure for the foliage of `Nellie R. Stevens' (54.4±0.4) was approximately 1C greater than for Chinese (52.9±0.3) or English holly (52.9±0.4). The Tm for root tissue of English holly was higher (53.9±1.5) than either `Nellie R. Stevens' (51.7±0.3) or Chinese holly (50.1±0.3). The results of this study suggest that English holly can withstand the same or a greater degree of direct heat injury compared to Chinese holly. The poor performance of English holly in the southeastern United States is suggested to be its inability to withstand prolonged but sublethal high temperatures which do not cause direct membrane injury.

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broccoli varieties in their development under high temperatures. Heather et al. (1992) evaluated a collection of broccoli hybrids for heat tolerance and holding ability in summer productions on Long Island, NY. Those authors identified certain hybrids

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’s holly breeding program. Selection was based on its bright and abundant yellow fruits, pale yellow green stems, low broad habit, and superior heat tolerance. It is suitable for shade trees, backyard, park, and many other landscapes and gardens. Origin

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temperatures. Heather et al. (1992) evaluated a collection of broccoli hybrids for heat tolerance and holding ability in summer productions on Long Island, NY. These authors identified certain hybrids that yielded more marketable heads and that held their

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). Floral displays are prolific throughout the growing season in both high summer and low fall day/night temperatures at all locations—midsummer ( Fig. 1 ) and end of season. Thus, ‘Snowstorm’ is both heat- and cold-tolerant. Heat tolerance and its vigorous

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lines were conducted and followed by observation and line trials, as well as regional trials. A new, high-quality F 1 hybrid with heat tolerance was identified. Origin The breeding program was initiated during the autumn of 2005 with the inclusion of

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