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Bruce W. Wood

/use. There are reports of Ni on Fe antagonism in which high Ni reduces endogenous Fe concentration and/or bioavailability ( Chen et al., 2009 ; Ghasemi et al., 2009 ; Hewett, 1953 ; Khalid and Tinsley, 1980 ; Koch, 1956 ; Kovacik et al., 2009 ; Misra

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Dean A. Kopsell and William M. Randle

Selenium and sulfur have similar chemical structures. This allows Se to be absorbed and incorporated in the same assimilation pathways as S. Onions (Allium cepa L.) are a crop with unique S metabolism, responsible for growth and flavor intensity. Because of the antagonistic behavior of the two ions, the effects of Se on S and Se nutrient depletion and tissue accumulation were investigated. `Granex 33' onions were grown in nutrient solutions with one concentration of S and increasing Se concentrations. Selenium was applied as sodium selenate (Na2SeO4) at concentrations of 0, 0.5, 1.0, 1.5, and 2.0 mg·L-1. Selenium depletion from the nutrient solution increased linearly with increasing Na2SeO4 treatment concentrations. Sulfur depletion increased and then decreased with increasing Na2SeO4 treatment concentrations. Selenium and S accumulation were highest in leaf tissues, less in root tissues, and lowest in bulb tissues at plant maturity. Selenium accumulation increased linearly with increasing Na2SeO4 for all tissues analyzed. Sulfur accumulation in leaf and bulb tissues was quadratic in response to increasing SeO4 -2, while S in root tissues decreased linearly with increasing Na2SeO4. Low concentrations of Na2SeO4 in our study enhanced S uptake and accumulation. Previously, Se was thought to competitively inhibit S uptake and metabolism.

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Francesco Giuffrida, Marianna Martorana and Cherubino Leonardi

( Greenway and Munns, 1980 ) and/or the possible increase in the requirements of a particular element, like phosphorus in tomato ( Awad et al., 1990 ), have been previously demonstrated. Antagonism phenomena in mineral uptake have also been observed as a

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Jorge B. Retamales, Claudio Valdes and Verónica Donoso

Bitter pit (BP) is the main physiological disorder of apples in Chile. Its incidence affects pre- and postharvest handling of the fruit and the profitability of this species. Since 1991, its control and prediction have been studied by this research team through field and laboratory trials. The BP incidence is linked to the fruit Ca concentration; however, fruit Ca analysis has not adequately predicted BP incidence in postharvest. Several authors have proposed Ca/Mg antagonism, which has been the basis to develop a predictive method through fruit Mg infiltration (IMG) 40 days before harvest. IMG has been massively used for two seasons in Chile, with 375 samples processed in 1997 and 1170 in 1998. The industry has been increasing its proportion of the samples processed, from 22% in 1997 to 71% in 1998. The most prominent varieties are `Granny Smith' (GS) > `Braeburn' (BR) > `Royal Gala' (RG) > `Red King Oregon' (RKO). The massive use of IMG has obtained predictive capacities (r 2 between BP predicted and BP after 3 months regular cold storage) of 0.8 for `Fuji'; 0.7 for GS, BR, and RG; and 0.58 for RKO. (This reduction in the predictive capacity with regards to the previous research under controlled conditions would, in part, be due to problems in obtaining fruit samples: non-uniform fruit size, inadequate sampling dates, diverse fruit numbers, etc.) Developments are underway to increase the geographical coverage of the service, the predictive capacity of the method for certain cultivars and productive areas and the number of samples processed.

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L.E. Parent, D. Isfan, N. Tremblay and A. Karam

Compositional nutrient diagnosis (CND) provides undistorted (linearized) variates amenable to principal component analysis (PCA) using a row-centered logratio transformation of foliar nutrient data. Our objectives were to carry PCA on raw or transformed nutrient data for carrot (Daucus carota L.) crops and to compare the critical value approach (CVA), diagnosis and recommendation integrated system (DRIS), and CND diagnoses using independent data. PCA conducted on percentage or log-transformed data produced similar multivariate structures difficult to interpret. PCA conducted on DRIS indexes and on row-centered logratios produced PCs (K-Ca+), (N+K-Ca-Mg+), and (P-Mg+) and PCs (K-Mg+), (N-Ca+), and (P-), respectively. Nutrient contrasts were easiest to interpret with CND and reflected either K-Mg antagonism or N dilution and Ca accumulation over time. CVA diagnosis of independent samples was generally not in line with DRIS or CND. DRIS and CND diagnostic indexes were highly correlated (r = 0.98 to 0.99). By summing bivariate DRIS functions, the DRIS index calculation procedure effectively row-centered the nutrient values for carrots. DRIS and CND index diagnosis indicated treatment-dependent Ca shortage. In contrast, CND PC diagnosis indicated overall stationary values for PC (N-Ca+) whatever treatment was applied. CND PC diagnosis is a multivariate (PCA) approach providing simplified computational effort and a theoretical basis for further improvements in foliar diagnosis.

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Steven McArtney, Dave Ferree, John Schmid, J.D. Obermiller and A. Green

A series of experiments were undertaken to compare the effects of individual and combined applications of GA4+7 and prohexadione-Ca (P-Ca) on scarf skin and fruit quality parameters on red strains of `Rome Beauty' and `Gala' apples. Three applications of GA4+7 at 10-day intervals beginning at petal fall (PF) significantly reduced scarf skin severity in all experiments. A single application of P-Ca at PF had no effect on scarf skin in one experiment but reduced scarf skin severity in two further experiments. Combining P-Ca with the first of three GA4+7 sprays as a tank mix reduced the severity of scarf skin more effectively than either material alone in two of three experiments at P < 0.05 and in all three experiments at P < 0.10. Combining P-Ca with the first application of GA4+7 as a tank mix generally reduced scarf skin as effectively as applying P-Ca and the first GA4+7 spray two days apart, although in one experiment, greater scarf skin control was achieved when P-Ca was applied 2 days after the first GA4+7 spray. A single application of P-Ca at PF consistently reduced, and three applications of GA4+7 consistently increased, mean fruit weight at harvest compared with the control. The economic benefits as a result of reducing scarf skin severity with P-Ca and GA4+7 sprays will need to be balanced against the negative effect of P-Ca on mean fruit weight. There is no antagonism between early season P-Ca and GA4+7 sprays for scarf skin control, and P-Ca may increase the efficacy of GA4+7 sprays for scarf skin control in apple.

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Katie J. Kammler, S. Alan Walters and Bryan G. Young

(ACCase) enzyme ( Senseman, 2007 ). Antagonism has been documented between these two modes of action when tank-mixed with reduced grass control resulting when sethoxydim was tank-mixed with primisulfuron, an ALS-inhibiting herbicide ( Young et al., 1996

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S. Christopher Marble, Andrew K. Koeser and Gitta Hasing

( Digitaria sanguinalis ); however, prodiamine was shown to be antagonistic in this tank mixture for control of eclipta ( Eclipta alba ). Determining synergism or antagonism of other common landscape herbicide tank mixtures for weed control is much

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Babak Madani, Marisa Wall, Amin Mirshekari, Alagie Bah and Mahmud Tengku Muda Mohamed

linked to a synergistic influence of K and N ( Premaratne and Oertli, 1994 ), whereas a decrease in leaf K at the 180 mg·L −1 Ca concentration may be related to antagonism between Ca and K ( Zharare et al., 2009 ). Papaya plant growth was unaffected by

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María José Jiménez-Moreno and Ricardo Fernández-Escobar

since symptoms of P excess has been observed at leaf P concentration of 0.21%. Excess P is usually expressed as the antagonism with other mineral nutrients such as Zn, Manganese, and other micronutrients ( Marschner, 2012 ; Safaya, 1976 ; Shane et al