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Mohamad-Hossein Sheikh-Mohamadi, Nematollah Etemadi, Ali Nikbakht, Mostafa Farajpour, Mostafa Arab, and Mohammad Mahdi Majidi

in tolerant to stress ( DaCosta and Huang, 2006 ; Sheikh-Mohammadi et al., 2017b ). Fig. 3. Effect of salinity stress on total nonstructural carbohydrates (TNC, A ) content, glutathione (GSH, B ) content, and superoxide dismutase (SOD, C

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Marianna Hagidimitriou and Teryl R. Roper

`Searles' (low yielding) and `Stevens' (high yielding) cranberry (Vaccinium macrocarpon Ait.) tissues were collected in 1990 and 1991 to determine the concentration of nonstructural carbohydrates in above-ground (uprights, woody stems) and below-ground tissue. Uprights had the highest total nonstructural carbohydrate (TNC) concentration, followed by woody stems, while below-ground tissue contained the lowest TNC concentration. Total nonstructural carbohydrate concentration in uprights increased early in the season, reached a maximum in late May, decreased as flowering approached, and remained low from late June to late August. The latter period corresponds to flowering, fruit set, floral initiation, and fruit development stages. In late August, when fruit were full size, TNC levels increased, reaching highest concentration in November as the plants were entering dormancy. Most TNC increase in the early season and the subsequent decrease were due to changes in starch. The increase of TNC late in the season was primarily due to increases in soluble carbohydrates. Total nonstructural carbohydrate concentration was greater in vegetative than fruiting uprights for the entire growing season. The lower TNC concentration in fruiting than vegetative uprights during flowering and fruit set was due to greater starch depletion in fruiting uprights. Seasonal changes in TNC in the two cultivars were similar; however, `Stevens' had generally higher TNC concentration and total dry weight as well as more fruiting uprights, fruit, and fruit weight per ground area. The low TNC concentration observed during fruit set and development suggests that the demands for carbohydrates are highest during that period and supports the hypothesis that competition for carbohydrate resources is one factor responsible for low cranberry fruit set.

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K.L. Hays, J.F. Barber, M.P. Kenna, and T.G. McCollum

This study was conducted to determine rooting characteristics, root carbohydrate content, and performance of 10 bermudagrass [Cynodon dactylon (L.) Pers.] genotypes exposed to drought. A greenhouse study was conducted twice to determine root distribution and carbohydrate content throughout the soil profile during simulated drought stress. Root distribution among genotypes and accumulation of total nonstructural carbohydrate within roots differed with depths. Root mass at 30, 60, 90, and 150 cm was significantly correlated with turf quality during drought stress (r = 0.72, 0.86, 0.80, and 0.81, respectively) only for one of the two tests. Root carbohydrate distribution was not significantly correlated with turf quality for the selected bermudagrass genotypes.

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Christopher J. French

Rooting of Rhododendron `Anna Rose Whitney' (R. griersonianum × `Countess of Derby') was delayed in cuttings from stock plants grown in full sun, compared to cuttings from plants grown in 80% shade. In the outer stem (extracambium tissues), concentrations of glucose, sucrose, soluble carbohydrate, and total nonstructural carbohydrates were higher in cuttings from shaded stock plants. In the inner stem (intracambium tissues), where rooting originates, fructose, starch, and nonstructural carbohydrates were lower in cuttings from the shaded stock plants. Rooting percentage was reduced by CO2 mist during propagation. At 7 days, during rooting with a CO2 enrichment to 1100 μl·liter-1, fructose in the inner stem was 3-fold higher than in cuttings rooted under atmospheric CO2 (340 μ1·liter-1). Under CO2 mist, total nonstructural carbohydrate concentration was higher in the inner stem throughout the rooting period. For both high stock plant irradiance and CO2 enrichment during propagation, there was an inverse relationship between fructose concentration in the inner stem and rooting. A possible mechanism for inhibition by fructose is proposed.

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Justine E. Vanden Heuvel and Joan R. Davenport

Carbohydrate supply has been hypothesized to limit fruit set in cranberry (Vaccinium macrocarpon Ait.), however the limitations to carbon gain throughout the season are currently unknown. These experiments investigated the effects of light, temperature, fruit presence, and defoliation on carbon production and partitioning in potted cranberry. Fruiting and vegetative uprights (short vertical stems which bear fruit biennially) reached similar asymptotes with respect to light response, but fruiting uprights reached saturation at a lower light intensity than vegetative uprights. Runners (diageotropic vegetative stems) had a lower asymptote, higher light compensation point, and greater rate of dark respiration than uprights. Temperature had little effect on net carbon exchange rate of uprights or runners. Before new growth, defoliation did not affect the concentration of total nonstructural carbohydrates in the vegetative uprights, or the partitioning of soluble carbohydrates to starch, even though uprights with lower leaf areas had higher net CO2 assimilation. At fruit set and again at fruit maturity, defoliation reduced total nonstructural carbohydrate concentration, while net CO2 assimilation was not affected. Carbohydrate production and partitioning within an upright was unaffected by the presence of a single fruit throughout the experiment.

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Bernard Gagnon, Yves Desjardin, and Roger Bédard

Abbreviations: DN, day-neutral; LT 50 , lethal temperature for SO% of flower buds; TNSC, total nonstructural carbohydrates. 1 Graduate student. 2 Research assistant. 3 Profcssor. We are grateful to the Agriculture Canada Research Station in Ste

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Timothy E. Elkner, J. A. Barden, M. M. Kushad, and D. D. Wolf

Fruiting spurs (`Red Prince Delicious') (RD) and shoots (`Sundale Spur Golden Delicious') (CD) with three leaf:fruit ratios and comparable nonfruiting spurs and shoots were girdled on 7 September 1988. An interaction between fruiting status and time existed for most parameters measured on both cultivars while there was no effect of leaf:fruit ratio. At 1 day after treatment (DAT) few differences existed due to fruiting status on either cultivar. At 8 DAT with RD and at 4 and 8 DAT with GD, Pn, transpiration (Tr), leaf water potential (ψ L), and nonreducing sugars were greater on fruiting than nonfruiting spurs and shoots while leaf resistance (RL), SLW, and starch were lower on fruiting spurs. In nonfruiting spurs and shoots Pn, Tr, and ψL tended to decrease while RL and SLW increased with time whereas m fruiting spurs and shoots most parameters remained constant. Total nonstructural carbohydrates, reducing sugars, and starch were greater in nonfruiting than fruiting spurs and shoots.

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Edward Bush, Paul Wilson, Dennis Shepard, and James McCrimmon

An experiment to determine the nonstructural carbohydrate composition and nodal survival (LT50) of common carpetgrass was conducted between 1993 and 1994 at Baton Rouge, La. Nonstructural carbohydrates in stolons were primarily sucrose [70-130 mg·g-1 dry weight (DW)] and starch (8-33 mg·g-1 DW). Total nonstructural carbohydrate (TNC) composition of stolons ranged between 30 to 165 mg·g-1 DW. Node survival following exposure to 2 °C ranged from 0% in August-sampled grass to 48% in December. The LT50 following acclimation under field conditions was -2 to -4 °C. Environmental factors influenced nonstructural carbohydrate composition, partitioning, and node survival. No relationship between TNC concentration and low-temperature tolerance was found. This research confirms previous reports that low-temperature tolerance of carpetgrass is very poor, and its culture may be limited to geographical areas having moderate winter temperatures.

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Mubarak S. Khalafalla and David A. Palzkill

Total nonstructural carbohydrates (TNC), starch, total soluble sugars, sucrose, and proline concentrations were monitored for 18 months in leaf tissue of two jojoba [Simmondsia chinensis (Link) Schneider] clones that differ in frost susceptibility. Seasonal changes in TNC and starch concentrations, with maxima in the winter and minima in summer, were significant. Sugar levels decreased from fall to spring and increased during early summer. The more frost-resistant clone (C-1) had significantly higher sugar concentrations during most of the study than the less frost-resistant clone (C-2). Proline concentrations largely followed the trends found for TNC. The C-1 clone had the higher levels of proline, except when C-2 was frost-injured. Growth trends were similiar between C-1 and C-2, with a major growth flush from March to May. Relatively high levels of starch preceded growth flushes.

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Justine E. Vanden Heuvel and Joan R. Davenport

Information on growth and carbon partitioning of cranberry uprights in response to soil N application is lacking. Therefore, two experiments were initiated on `Stevens' uprights to determine the effect of soil-applied N on tissue N, growth, net carbon exchange (NCER), and nonstructural carbohydrate production of uprights of `Stevens' cranberry. Tissue N concentration increased linearly with increasing soil N but was greater in vegetative uprights than in fruiting uprights. Current season growth on vegetative uprights was more responsive to tissue N than on fruiting uprights. Although chlorophyll concentration and NCER increased with increased soil N, upright starch concentration and often total nonstructural carbohydrate concentration decreased with increased soil N at midfruit development and preharvest, especially in vegetative uprights.