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Li-Xiao Yao, Yong-Rui He, Hai-Fang Fan, Lan-Zhen Xu, Tian-Gang Lei, Xiu-Ping Zou, Ai-Hong Peng, Qiang Li, and Shan-Chun Chen

neutral with an isoelectric point of 6.73 ( Table 1 ). Fig. 1. Polymerase chain reaction (PCR) results of ferric chelate reductase genes of Citrus junos ( CjFRO s). CjFRO2 ( A ), 5′ terminal PCR products of CjFRO3 ( B ), and CjFRO4 ( C ), were

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Maritza Ojeda, Bruce Schaffer, and Frederick S. Davies

Root ferric chelate reductase (FCR) activity in Annona glabra L. (pond apple), native to subtropical wetland habitats and Annona muricata L. (soursop), native to non-wetland tropical habitats, was determined under Fe-sufficient and Fe-deficient conditions. Four-month-old seedlings of each species were grown hydroponically in a complete nutrient solution containing 90 μm Fe or no Fe. The degree of tolerance of Fe deficiency was evaluated by measuring root FCR activity, chlorophyll and Fe concentration in recently matured leaves and plant growth. Root FCR activity was higher in soursop than in pond apple in the nutrient solution with Fe. However, there were no differences in root FCR activity between species under Fe-deficient conditions. Root FCR activity in pond apple and soursop was not induced in the absence of Fe. Leaf chlorophyll index and Fe concentration, and dry weights of pond apple were lower when plants were grown without Fe compared to plants grown with Fe. Leaves of pond apple grown without Fe became chlorotic within 3 weeks. Lack of Fe decreased the chlorophyll index and Fe concentration in young leaves less in soursop than in pond apple. In contrast, the Fe level in the nutrient solution had no effect on dry weights of soursop. The rapid development of leaf chlorosis and low FCR activity of pond apple may be due to its native origin in wetland areas where there is sufficient soluble Fe for plant growth and development.

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Brandon R. Smith and Lailiang Cheng

., 1986 ; Marschner et al., 1986 ; Römheld and Marschner, 1983 ). In addition, roots can increase the activity of plasma membrane-bound ferric chelate reductase (FCR), which uses cytosolic NAD(P)H to cleave Fe(III)-chelates and reduce Fe 3+ to Fe 2

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Rebecca L. Darnell and Steven A. Hiss

Most Vaccinium species have narrow soil adaptation and are limited to soils that have low pH, high available iron (Fe), and nitrogen (N) primarily in the ammonium (NH4+) form. Vaccinium arboreum Marsh. is a wild species that can tolerate a wider range of soil conditions, including higher pH and nitrate (NO3-) as the predominant N form. This wider soil adaptation may be related to the ability of V. arboreum to acquire Fe and NO3- more efficiently than cultivated Vaccinium species, such as V. corymbosum L. interspecific hybrid (southern highbush). Nitrate and Fe uptake, and nitrate reductase (NR) and ferric chelate reductase (FCR) activities were compared in these two species grown hydroponically in either 1.0 or 5.0 mm NO3-. Nitrate uptake rate (on a whole-plant and FW basis) and root NR activity were significantly greater in V. arboreum compared with V. corymbosum. Iron uptake on a FW basis was also greater in V. arboreum, and was correlated with higher root FCR activity than was found in V. corymbosum. Increased Fe and NO3- uptake/assimilation in V. arboreum were reflected in increased organ and whole-plant dry weights compared with V. corymbosum. Vaccinium arboreum appears to be more efficient in acquiring and assimilating NO3- and Fe than is the cultivated species, V. corymbosum. This may partially explain the wider soil adaptation of V. arboreum.

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Sergio Jiménez, Jorge Pinochet, Anunciación Abadía, María Ángeles Moreno, and Yolanda Gogorcena

rhizosphere, exudation of reducing and chelating substances, and increase in ferric chelate reductase (FC-R) activity (reviewed in Schmidt, 1999 ), which reduces Fe 3+ and enables uptake via an Fe transporter ( Briat and Lobréaux, 1997 ). The FC-R increases

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Rebecca Darnell

Most Vaccinium species, including V. corymbosum, have strict soil requirements for optimal growth, requiring low pH, high iron, and nitrogen, primarily in the ammonium form. V. arboreum is a wild species adapted to high pH, low iron, nitrate-containing soils. This broader soil adaptation in V. arboreum may be related to increased efficiency of iron or nitrate uptake/assimilation compared with cultivated Vaccinium species. To test this, nitrate and iron uptake, and nitrate reductase (NR) and ferric chelate reductase (FCR) activities were compared in two Vaccinium species, V. arboreum and the cultivated V. corymbosum. Plants were grown hydroponically for 15 weeks in either 1.0 or 5.0 mm NO3 with 0.09 mm Fe. Root FCR activity was greater in V. arboreum compared with V. corymbosum, especially at the lower external nitrate concentration. However, this was not reflected in differences in iron uptake. Nitrate uptake and root NR activity were greater in V. arboreum compared with V. corymbosum. The lower nitrate uptake and assimilation in V. corymbosum was reflected in decreased plant dry weight compared with V. arboreum. V. arboreum appears to be more efficient in acquiring nitrate compared with V. corymbosum, possibly due to increased NR activity, and this may partially explain the wider soil adaptation of V. arboreum.

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Charalambos I. Siminis and Manolis N. Stavrakakis

Plant Soil 171 229 234 Brüggemann, W. Maas-Kantel, K. Moog, P.R. 1993 Iron uptake by leaf mesophyll cells: The role of the plasma membrane-bound ferric-chelate reductase Planta 190 151 155

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Rebecca L. Darnell, Bruno Casamali, and Jeffrey G. Williamson

rates and mineral nutrient preconditioning Tree Physiol. 27 901 909 Poonnachit, U. Darnell, R. 2004 Effects of ammonium and nitrate on ferric chelate reductase and nitrate reductase in Vaccinium species Ann. Bot. (Lond.) 93 399 405 Stockton, L.A. 1976

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Eva Bacaicoa and Jose María García-Mina

of iron deficiency susceptible and tolerant tomato genotypes and their reciprocal F-1 hybrids Plant Soil 241 97 104 De la Guardia, M.D. Alcántara, E. 2002 A comparison of ferric-chelate reductase and chlorophyll

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Lina Fu, Lijun Chai, Dekuan Ding, Zhiyong Pan, and Shu’ang Peng

solubilized by H + -ATPase-driven ( HA gene family) excretion of protons in the rhizosphere of roots ( Dell’Orto et al., 2000 ); it is then reduced by ferric chelate reductase encoded by the FRO gene family in the apoplast ( Robinson et al., 1999 ), and