Plants on right grown without added Co for 6 months (Alnus) 7 months (Myrica) or 9 months (Casuarina) showing symptoms of decreased growth.

• 右边植株进行缺氮水培，没加钴分别为六个月(Alnus)、七个月(Myrica)、九个月(Casuarina)出现生长迟缓。