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Qi Zhou and Juan Carlos Melgar

nutrient partitioning patterns in mature trees and older trees to gain a better understanding of their requirements and potentially improve orchard nutrient management. Rational fertilization for fruit trees under field conditions should consider a balance

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Bernadine C. Strik and David R. Bryla

Fertilizer rate studies do not clearly determine the fate of the fertilizer in the plant or soil, or how the nutrient is partitioned within the plant. Nitrogen-cycling patterns have been studied in blackberry ( Malik et al., 1991 ; Mohadjer et al., 2001

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Jonathan M. Frantz and Peter Ling

; Huang and Yeh, 2009 ). It is therefore important to assess partitioning of biomass among leaves, stems, and flowers to determine the impact of any change in environmental management. The “best” performer or recommendations for management for a species

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Johan M.H. Stoop and David M. Pharr

The fleshy parenchyma tissue of celery [Apium graveolens L. var. dulce (Mill.) Pers.] petioles is the major storage tissue for the sugar alcohol mannitol and for the hexoses, glucose and fructose. In this study, we found that plants grown in the soilless mixture, Promix, fertilized weekly with a nutrient solution, or grown in a hydroponic container culture, differed in carbohydrate composition. However, plant growth was not affected. Higher mannitol and lower hexose concentrations were present in petioles from plants grown hydroponically. This was true in petioles that did not differ in total soluble carbohydrate concentration. The ratio of mannitol to hexose concentration in petioles was ≈2-fold higher for hydroponically grown plants compared to Promix-grown plants, and the higher ratio was maintained during the entire 12-week experimental period. Carbohydrate partitioning was also affected by petiole development within the plant. Sucrose and hexose concentrations were highest in mature petioles, whereas mannitol was relatively high in all petioles except the oldest ones. Because the mineral solution applied to the Promix-grown plants had a lower total salt concentration compared to hydroponically grown plants, we postulated that the salt concentration of the mineral solution might be an important factor affecting C partitioning in celery petioles. When plants were grown hydroponically at two different salt concentrations [electrical conductivity (EC) = 2.7 and 6.0 mS·cm-1], high mannitol-to-hexose ratios were observed in celery petioles of plants grown at high salt concentration (EC = 6.0 mS·cm-1), a result supporting the hypothesis that the salt environment might alter mannitol and hexose concentrations in a coordinated way. These data are consistent with the hypothesis that elevated mannitol levels may be a significant component of plant adjustment to salt stress, possibly adding osmotic adjustment and preventing inactivation of metabolic processes.

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Pradeep Kumar, Menahem Edelstein, Mariateresa Cardarelli, Emanuela Ferri, and Giuseppe Colla

different grafting combinations under Cd stress was determined in terms of plant growth, fruit yield and quality, SPAD index and chlorophyll fluorescence, chlorophyll and carotenoid content, and mineral element composition and partitioning in different plant

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Hala G. Zahreddine, Daniel K. Struve, and Salma N. Talhouk

species with ornamental traits, Malus trilobata (Schneid.) and Acer syriacum (Boiss. and Gaill.). The two species are not commonly grown in Lebanese nurseries and there are no reports on container production or nutrient partitioning of the species

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Patrick E. McCullough, Haibo Liu, Lambert B. McCarty, Ted Whitwell, and Joe E. Toler

Dwarf-type bermudagrasses [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davey] tolerate long-term golf green mowing heights but require heavy nitrogen (N) fertilizations. Inhibiting leaf growth with trinexapac-ethyl (TE) could reduce shoot growth competition for root reserves and improve nutrient use efficiency. Two greenhouse experiments evaluated four N levels, 6 (N6), 12 (N12), 18 (N18), and 24 (N24) kg N/ha/week, with TE at 0 and 0.05 kg·ha–1 a.i. every 3 weeks to assess rooting, nutrient allocation, clipping yield, and chlorophyll concentration of `TifEagle' bermudagrass grown in PVC containers built to U.S. Golf Association specification. Trinexapac-ethyl enhanced turf quality on every date after initial application. After 8 weeks, high N rates caused turf quality decline; however, TE treated turf averaged about 25% higher visual quality from nontreated turf, masking quality decline of high N fertility. `TifEagle' bermudagrass treated with TE had clippings reduced 52% to 61% from non-TE treated. After 16 weeks, bermudagrass treated with TE over all N levels had 43% greater root mass and 23% enhanced root length. Compared to non-TE treated turf, leaf N, P, and K concentrations were consistently lower in TE treated turf while Ca and Mg concentrations were increased. Root N concentrations in TE treated turf were 8% to 11% higher for N12, N18, and N24 fertilized turf than respective N rates without TE. Compared to non-TE treated turf, clipping nutrient recoveries were reduced 69% to 79% by TE with 25% to 105% greater nutrients recovered in roots. Bermudagrass treated with TE had higher total chlorophyll concentrations after 8 and 12 weeks. Overall, inhibiting `TifEagle' bermudagrass leaf growth appears to reallocate nutrients to belowground tissues, thus improving nutrient use efficiency and root growth. Chemical name used: trinexapac-ethyl, [4-(cyclopropyl-[α]-hydroxymethylene)-3,5-dioxo-cyclohexane carboxylic acid ethylester].

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Jonathan Frantz and Peter Ling

Bedding plant petunia (Petunia ×hybrida) is often produced with high nutrient concentrations as a cool-season crop. How a plant uses the nutrients supplied will depend in large part on the environmental factors influencing growth rate, such as light and CO2. Since more growers are considering using supplemental CO2 to improve energy efficiency for plant production, it is important to understand light and fertilizer levels needed for efficient production of high-quality plants. Using a multi-chamber controlled environment system, petunia plants were grown from seed for 6–8 weeks after transplanting into different light and CO2 environments and fed with either a low (7.1 mM N) or high (21.3 mM N) fertilizer regime. Plants were evaluated for appearance, harvested periodically, and separated into flower, stem, and leaf biomass. Biomass was then dried and analyzed with ICP-OES for essential macro- and micronutrients. Low-fertilizer-grown plants had consistently earlier and more flowers, but showed symptoms of nutrient deficiencies in the final few weeks of production at all light and CO2 levels. There were significant interactions between light and fertilizer treatments for different nutrients. Calcium uptake was greatly influenced by light level, Fe, P, and K were influenced by the fertilizer supply, and Mg and B were inversely influenced by fertilizer supply at high light. These data suggest new management strategies are needed to improve fertilizer use efficiency in different environments.

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Brian E. Whipker, Terri Kirk, P. Allen Hammer, and William B. Miller

`Nellie White' Easter lilies were grown under two day/night temperature regimes, a positive differential temperature (+DIF) of 15.5C night / 21C day temperature or a negative differential temperature (-DIF) of 19.4C night / 14.4C day temperature. At anthesis the plants were divided into 15 leaf-node segments, starting from the plant base (nodal position 0-15). The segments were further subdivided into leaf, stem and flower tissue parts, with fresh and dry weights being recorded, and tissue being analyzed for NH4-N, P, K, Ca, Mg, Na, Cu, B, Fe, Mn, and Zn.

Of the elements studied, only P content was statistically different at the DIF treatment × nodal position × tissue type interaction. Total 1eaf P per segment was higher in the -DIF plants, with the concentration increasing from 0.19 mg at nodal position O-15 up to the 1.34 mg at nodal position 46-60, compared to 0.16 and 0.76 mg, respectively, for the +DIF plants. There were also significant differences at the DIF treatment × tissue type, with -DIF leaf tissue having a higher total content of P, K, Mg, Ca, Na and B, while Cu was lower, than the +DIF leaf tissue. Results indicate that the distribution of nutrients in Easter lily plants are affected by growing temperature regimes.

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Dharmalingam S. Pitchay, Jonathan M. Frantz, and James C. Locke

Geranium (Pelargonium ×hortorum) is considered to be one of the top-selling floriculture plants, and is highly responsive to increased macro- and micronutrient bioavailability. In spite of its economic importance, there are few nutrient disorder symptoms reported for this species. The lack of nutritional information contributes to suboptimal geranium production quality. Understanding the bioenergetic construction costs during nutrient deficiency can provide insight into the significance of that element predisposing plants to other stress. Therefore, this study was conducted to investigate the impact of nutrient deficiency on plant growth. Pelargonium plants were grown hydroponically in a glass greenhouse. The treatment consisted of a complete modified Hoagland's millimolar concentrations of macronutrients (15 NO3-N, 1.0 PO4-P, 6.0 K, 5.0 Ca, 2.0 Mg, and 2.0 SO4-S) and micromolar concentrations of micronutrients (72 Fe, 9.0 Mn, 1.5 Cu, 1.5 Zn, 45.0 B, and 0.1 Mo) and 10 additional solutions each devoid of one essential nutrient (N, P, Ca, Mg, S, Fe, Mn, Cu, Zn, or B). The plants were photographed and divided into young, maturing, and old leaves, the respective petioles, young and old stems, flowers, buds, and roots at “hidden hunger,” incipient, mid- and advanced-stages of nutrient stress. Unique visual deficiency symptoms of interveinal red pigmentation were noted on the matured leaves of P- and Mg-deficient plants, while N-deficient plants developed chlorotic leaf margins. Tissue N concentration greatly influenced bioenergetic construction costs, probably due to differences in protein content. This information will provide an additional tool in producing premium geraniums for the greenhouse industry.