1. Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, Japan
2. Department of Applied Biological Sciences, Nihon University, 1866 Kameino, Fujisawa, Japan
3. Departamento de Nutrici�n Vegetal, Estaci�n Experimental de Aula Dei, Consejo Superior de Investigaciones Cient�ficas, Apartado 13034, Zaragoza, Spain