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Eddo Rugini

Abbreviations: PA, polyamides. I acknowledge the support of the Ministry of Agriculture and Forestry “Piano Nazionale di Ricerca: sviluppo di tecnologie avanzate applicate alle piante,” and Claudio Taratufolo for technical assistance. The cost of

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Oded Sagee and Carol J. Lovatt

Maximum leaf NH3-NH4 + content and activity of the de novo arginine biosynthetic pathway occurred during the 1st week after transfer of 5-year-old rooted cuttings of the `Washington' navel orange (Citrus sinensis L. Osbeck) from 8 weeks of low-temperature stress [8-hour days (500 μmol·s-1·m-2) at 15 to 18C/16-hour nights at 10 to 13C]. Both aspects declined in parallel during the subsequent 4 weeks of 12-hour days (500 μmol·s-1·m-2) at 24 C/12-hour nights at 19C, which culminated in maximum bloom. Apical flowers of inflorescences initiated in response to 8 weeks of low-temperature stress exhibited maximum tissue concentrations of NH3-NH4 + and putrescine, and maximum activity of the de novo arginine biosynthetic pathway 1 week after transfer of the trees from the low-temperature induction to the higher temperature (flower buds were 7 × 5 mm, length/width). All three criteria decreased in parallel as flowers developed through Stage V (petal fall). In contrast, spermine concentration increased 7-fold during Stage IV of flower development (flower opening). By Stage V, ovaries contained about equal concentrations of putrescine, spermidine, and spermine. The activity of the de novo tyrosine biosynthetic pathway exhibited a pattern of change independent of flower NH3-NH4 + concentration. Observed changes were not due to increased organ weight or size and persisted when the data were expressed per milligram protein. The results of this study demonstrate that leaves and floral buds undergo parallel changes in N metabolism in response to low-temperature, stress-induced flowering and provide evidence that flower NH3-NH4 + content and putrescine synthesis via argine are metabolically correlated during flower development in C. sinensis.

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George F. Kramer, Chien Yi Wang, and William S. Conway

Pressure infiltration of `Golden Delicious' and `McIntosh' apples (Malus domestica Borkh.) with polyamides resulted in an immediate increase in firmness. `Golden Delicious' apples were 2.7 N (0.25 mM spermidine) to 6.7 N (1.0 mM spermine) firmer, while `McIntosh' apples were 2.2 N (0.25 mM spermidine) to 5.3 N (1.0 mM spermine) firmer than the water-treated control. During 28 weeks of storage at 0C, the differences between the polyamine-treated and water-treated apples were even larger. Similar results were observed with a 3% Ca treatment, but the Ca treatment reduced the rate of softening to a greater extent than did the polyamine treatments in `Golden Delicious'. Polyamides increased the endogenous levels of the polyamides infiltrated; however, the levels declined rapidly with time in storage. Both polyamine and Ca inhibited the development of chilling injury symptoms (brown core) in `McIntosh'. The influence of polyamines on ethylene production was negligible in both cultivars. The Ca treatment, however, inhibited ethylene evolution in `Golden Delicious'. Polyamides, thus, may affect apple softening through rigidification of cell walls rather than through interactions with ethylene metabolism.

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Kenneth G. McCabe, James A. Schrader, Samy Madbouly, David Grewell, and William R. Graves

’ salvia (PA = polyamide, PLA = polylactic acid, PU = polyurethane, TO = tung oil). Water-use efficiency is grams of plant dry weight divided by the liters of water required to produce the plant during 8 weeks of production under standard greenhouse

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Shiow Y. Wang and Miklos Faust

Ethylene biosynthesis and polyamine content were determined in normal and watercore-affected apple (Malus domestics Borkh. cv. Delicious). Fruit with watercore produced more ethylene and contained higher amounts of putrescine (PUT), spermidine (SPD), 1-aminocyclopropane-1-carboxylic acid (ACC), and 1-(malonylamino) cyclo-propane-1-carboxylic acid (MACC). The activities of ACC synthase and ethylene-forming enzyme (EFE) in watercore-affected fruit were also higher than in normal fruit. The EFE activity in severely affected flesh was inhibited, resulting in ACC accumulation and low ethylene production. S-adenosylmethionine (AdoMet) was maintained at a steady-state level even when C2 H4 and polyamides were actively synthesized in normal and affected fruit.

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M. Serrano, F. Romojaro, J.L. Casas, and M. Acosta

We have compared the ethylene and polyamine metabolism of senescing flowers from two cultivars of carnation (Dianthus caryophyllus L.), one showing climacteric (`Arthur') and the other non climacteric behavior (`Killer'). `Arthur' carnations showed the first symptoms of senescence at day 7, coinciding with maximum ethylene and CO2 production, a peak in the ethylene-forming enzyme (EFE) activity, and a 7-fold increase in free ACC content in respect to the initial value. In `Killer' carnations, however, onset of senescence was 15 days after harvest, and no ethylene or CO2 peak was detected. The lack of ethylene production was due to a constantly low level of free ACC and a low EFE activity. Free polyamine distribution was similar in the two cultivars at the preclimacteric stage, with the spermidine content being about three times that of putrescine. But as senescence progressed, this situation was reversed in `Arthur' carnation, with a predominance of putrescine during the senescence, while it was maintained in `Killer', with no significant changes during senescence. No free spermine was found at any stage of senescence in either cultivar. Thus, a correlation exists between ACC level, distribution of polyamides, and longevity of cut carnation flowers. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).

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Nader Soltani, J. LaMar Anderson, and Alvin R. Hamson

`Crimson Sweet' watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] plants were grown with various mulches and rowcovers and analyzed for relative growth rate (RGR), net assimilation rate (NAR), specific leaf area (SLA), leaf area index (LAI), and crop growth rate (CGR). Spunbonded polyester fabric (SB-PF) and perforated polyethylene film (PCP) rowcovers generally showed greater mean RGR, SLA and CGR than spunbonded polypropylene polyamide net (SB-PP), black plus clear combination plastic mulch and black plastic mulch alone. Plants on mulches and under rowcovers showed significant increases in RGR, NAR, and SLA over plants grown in bare soil. Carbon dioxide concentration inside the transplanting mulch holes was nearly twice the ambient CO, concentration. Growth analysis of sampled watermelon plants during early stages of development under various treatments was predictive of crop yield. Plants under SB-PF and PCP rowcovers produced the earliest fruit and the greatest total yield. An asymmetrical curvilinear model for watermelon growth and development based on cardinal temperatures was developed. The model uses hourly averaged temperatures to predict growth and phenological development of `Crimson Sweet' watermelon plants grown with and without rowcovers. Early vegetative growth correlated well with accumulated heat units. Results indicate a consistent heat unit requirement for the `Crimson Sweet' watermelon plants to reach first male flower, first female flower and first harvest in uncovered plants and plants under rowcovers. Greater variability was observed in predicting date of first harvest than first bloom.

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Heidi A. Kratsch, James A. Schrader, Kenneth G. McCabe, Gowrishankar Srinivasan, David Grewell, and William R. Graves

bioplastic polymers of PLA, polyamide, or polyurethane was shown to improve their integrity, stability, and water-use efficiency during plant production without sacrificing their biodegradation in soil ( McCabe et al., 2014 ). The objectives of this work were

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Bielinski M. Santos, James P. Gilreath, and Myriam N. Siham

(VIF), which consist of an impermeable layer of ethylene vinyl alcohol or polyamide in between polyethylene layers ( Gilreath et al., 2004 ; Hochmuth et al., 2003 ; Yates et al., 2002 ). These films are less permeable to fumigants than either low

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Valentina Schmitzer, Robert Veberic, Gregor Osterc, and Franci Stampar

bath for 1 h. Treated samples were centrifuged for 7 min at 12,000 g n . Supernatant was filtered through a polyamide filter (Chromafil AO-45/25; Macherey-Nagel, Düren, Germany) and transferred to a vial before injection in a high-performance liquid