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María José Jiménez-Moreno and Ricardo Fernández-Escobar

symptoms of P excess are similar to that of Zn deficiency. In fact, leaf Zn concentration in leaves of the control plants without P application was 24.5 ppm, whereas leaf Zn concentration of plants showing symptoms was 5.34 and 11.2 ppm in plants receiving

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Xing-Zheng Fu, Fei Xing, Li Cao, Chang-Pin Chun, Li-Li Ling, Cai-Lun Jiang and Liang-Zhi Peng

Zn is an essential micronutrient for plant growth and development. However, in citrus production, Zn deficiency is one of the most damaging and widespread nutritional disorders in both acidic and alkaline soils ( Srivastava and Singh, 2009 ). Zn

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Yong Zhang, Chunxia Fu, Yujing Yan, Yan’an Wang, Ming Li, Meixiang Chen, Jianping Qian, Xinting Yang and Shuhan Cheng

starch synthesis ( Hacisalihoglu et al., 2003 ). The apple is among the four most popular fruits in the world, and as an essential fruit for human health, high fruit quality is important. Zn deficiencies affect production and quality of all crops

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Bruce W. Wood

decades, on methods for correction of Zn deficiency in pecan ( Alban, 1955 ; Alban and Hammar, 1941 , 1944 ; Banin et al., 1980 ; Harper, 1960 ; Payne and Sparks, 1982 ; Sparks, 1976 ; Worley et al., 1980 ). Tree and orchard Zn-related requirements

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Hening Hu and Darrell Sparks

The effect of Zn deficiency on reproductive growth of `Stuart' pecan [Carya illinoensis (Wangenh.) C. Koch] was studied. At the most severe Zn-deficiency level, shoots were rosetted and produced neither. staminate nor pistillate inflorescences. At less severe Zn-deficiency levels, catkin length and weight decreased as Zn concentration in the leaf decreased. The number of fruits produced per shoot was reduced by Zn deficiency. Even though fruit abortion was not affected by Zn status of the shoot, fruit death and drying in situ increased with increasing Zn deficiency. Zinc deficiency dramatically suppressed fruit development and resulted in delayed and staggered shuck dehiscence.

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Dámaris L. Ojeda-Barrios, Eloísa Perea-Portillo, O. Adriana Hernández-Rodríguez, Graciela Ávila-Quezada, Javier Abadía and Leonardo Lombardini

, pesca y alimentación, 2008 ). In fact, Zn deficiency is common in commercial pecan tree orchards, frequently limiting productivity in Zn-poor soils ( Fenn et al., 1990 ; Sparks and Payne, 1982 ). Some of the consequences of Zn deficiency in pecan

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James L. Walworth, Scott A. White, Mary J. Comeau and Richard J. Heerema

above. Pecan trees growing in these soils are prone to Zn deficiency due to limited soil Zn availability ( Alloway, 2008 ; Malstrom and Fenn, 1981 ; Smith et al., 1980 ). Fenn et al. (1990) reported that water extractable Zn in a South Texas soil

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Hening Hu and Darrell Sparks

Leaves of `Stuart' pecan [Carya illinoensis (Wangenh.) C. Koch] with various levels of Zn deficiency were analyzed for physiological indicators of leaf vigor. Leaf chlorophyll content, stomatal conductance, and net photosynthesis were adversely affected by Zn deficiency. In leaves with severe Zn deficiency, each of these indicators increased 3- to 5-fold with a doubling of leaf Zn concentration, but stabilized as leaf Zn approached the sufficiency range (14 μg·g-1). High intercellular CO2 associated with low net photosynthesis indicates that stomatal aperture was not the cause of the reduction of net photosynthesis under Zn deficiency.

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Richard J. Heerema, Dawn VanLeeuwen, Marisa Y. Thompson, Joshua D. Sherman, Mary J. Comeau and James L. Walworth

reduced by Zn deficiency through its detrimental effects on pistillate flower production, the number of nuts set and matured, and final individual nut weight ( Hu and Sparks, 1990 ). In addition, there are major reductions in commercially important pecan

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Dariusz Swietlik

Zinc (Zn) deficiency is widespread throughout the world causing economic losses on a number of crops. Despite the fact that much information was generated during the last 20 years on Zn soil chemistry and its inorganic phase equilibrium, the mechanism controlling the amount of free Zn+2 present in the soil solution is not yet completely understood. This information is critical for the development of effective techniques of supplying Zn through the soil. As Zn moves very slowly through the soil, however, and a large portion of fruit tree root system occupies deep soil layers, foliar sprays with Zn are generally more effective than soil treatments in alleviating Zn deficiency symptoms. That is why many extension specialists recommend this approach. In view of the poor mobility of foliar-absorbed Zn in plants, however, we may need to reexamine this approach. Zinc foliar sprays may be effective in controlling Zn deficiency in leaves, but not in alleviating Zn deficiency in roots or subsequent flushes of growth. Also, the conditions under which fruit trees are most likely to respond to corrective Zn treatments are not well understood and the critical periods for Zn supply to assure optimal fruit set, fruit growth, and high fruit external and internal quality are not well defined. Field studies on fruit trees suggest that Zn deficiency must be quite severe to make the application of this element economically justifiable. In well-controlled greenhouse studies, however, growth responses were realized on plants only mildly affected by Zn deficiency. If considerable field variability may explain this discrepancy in the data, then future field research must use improved methodologies to properly quantify the impact of various levels of Zn deficiency on tree growth, fruit yield, and fruit quality.