Plant and Soil 241: 251–257, 2002. © 2002 Kluwer Academic Publishers. Printed in the Netherlands. 251 Uptake and transport of foliar applied zinc ( 65 Zn) in bread and durum wheat cultivars differing in zinc efficiency B. Erenoglu 1,2,4 , M. Nikolic 1 , V. Römheld 1 & I. Cakmak 3 1 Institut für Pflanzenernährung (330) Universität Hohenheim 70593 Stuttgart-Germany; 2 Cukurova University, Department of Soil Science and Plant Nutrition, 01330 Adana, Turkey; 3 Sabanci University, Faculty of Engineering and Natural Sciences, 81474 Istanbul, Turkey. 4 Corresponding author ∗ Received 3 April 2001. Accepted in revised form 13 February 2002 Key words: Triticum aestivum, Triticum durum, zinc, zinc efficiency, zinc transport via phloem, zinc uptake by leaf Abstract Using two bread wheat (Triticum aestivum) and two durum wheat (Triticum durum) cultivars differing in zinc (Zn) efficiency, uptake and translocation of foliar-applied 65 Zn were studied to characterize the role of Zn nutritional status of plants on the extent of phloem mobility of Zn and to determine the relationship between phloem mobility of Zn and Zn efficiency of the used wheat cultivars. Irrespective of leaf age and Zn nutritional status of plants, all cultivars showed similar Zn uptake rates with application of 65 ZnSO 4 to leaf strips in a short-term experiment. Also with supply of 65 ZnSO 4 by immersing the tip (3 cm) of the oldest leaf of intact plants, no differences in Zn uptake were observed among and within both wheat species. Further, Zn nutritional status did not affect total uptake of foliar applied Zn. However, Zn-deficient plants translocated more 65 Zn from the treated leaf to the roots and remainder parts of shoots. In Zn-deficient plants about 40% of the total absorbed 65 Zn was translocated from the treated leaf to the roots and remainder parts of shoots within 8 days while in Zn-sufficient plants the proportion of the translocated 65 Zn of the total absorbed 65 Zn was about 25%. Although differences in Zn efficiency existed between the cultivars did not affect the translocation and distribution of 65 Zn between roots and shoots. Bread wheats compared to durum wheats, tended to accumulate more 65 Zn in shoots and less 65 Zn in roots, particularly under Zn-deficient conditions. The results indicate that differences in expression of Zn efficiency between and within durum and bread wheats are not related to translocation or distribution of foliar-applied 65 Zn within plants. Differential compartementation of Zn at the cellular levels is discussed as a possible factor determining genotypic variation in Zn efficiency within wheat. Introduction Zinc deficiency is one of the most common micronu- trient deficiency in cereals, especially in wheat, signi- ficantly limiting grain yield, for example in Australia (Graham et al., 1992), India (Takkar and Walker, 1993), and Turkey (Cakmak et al., 1996a, 1999a). According to White and Zasoski (1999), the extent of Zn deficiency in soils is comparable with the ex- tent of many macronutrient deficiencies causing large economic losses. ∗ Fax: +49-711-4593295; Tel: +49-711-4592348. E-mail: beren@uni-hohenheim.de There are substantial differences in susceptibil- ity to Zn deficiency between cereal species and also among cultivars of a given species. The susceptibil- ity of cereals to Zn deficiency was found to decline in the order: durum wheat > oat ≥ bread wheat > barley > triticale > rye (Cakmak et al., 1997; Ekiz et al., 1998). Also diploid (AA), tetraploid (BBAA) and hexaploid (BBAADD) wheats differ greatly in their Zn efficiency (i.e., better growth and yield under Zn- deficient conditions). Among the diploid, tetraploid, and hexaploid wheats, the susceptibility of species to Zn deficiency declines in the order: tetraploid > hexaploid > diploid. Of the wheat genomes, A and B genomes exert increasing and decreasing effects on