LEAD AND MOLYBDENUM IN REED AND CATTAIL - OPEN VERSUS CLOSED TYPE OF METAL CYCLING

Uptake, leaching from living tissues, and the content in dry standing litter and in decaying plant material of lead and molybdenum were measured in two aquatic macrophytes: common reed (Phragmites australis (Cav.) Trin. ex Steudel) and narrow-leaved cattail (Typha angustifolia L.). The uptake of metals was not related to their supply in littoral sediments. The budget of the metals showed that, in spite of some interspecific differences, lead flowed passively through both plant species. Monthly rain precipitation removed 22% of the maximum amount of lead accumulated in cattail shoots. Substantial amounts of lead remained in dry standing litter of the two plant species for the next season. Conversely, molybdenum taken up in spring was retained in the shoots. Leaching of molybdenum from living tissues was negligible and dry standing litter of reed and cattail was devoid of this metal. Thus, the possible translocation of molybdenum from the shoots to underground organs in autumn is suggested.