**6.3 Fungicide toxicity**

The problem with the use of concentrated disinfectants and fungicides is that there is always a lengthy washing of stock plants in running tap water and distilled water to remove pathogens and, especially excess residues that may be lethal to the explants in the culture media. Our experience has indicated a possibility that there are some reactions between HgCl2 and aluminum foil. This suggests a possible affinity for chloride (Cl-) in that Al 3+ could be replacing Hg 2+. We observed that the foil was completely eaten up as a result of this reaction. Since stock plants were covered with aluminum foil throughout the disinfection, rinsing and culture excision processes which also took time, this could mean accumulation of aluminum deposits in the cultures, and hence possible aluminum toxicity to plantlets.

There are several studies undertaken and illustrate the deleterious effect of heavy metals such as aluminum and mercury on plant growth in the fields. However, such studies have not been accomplished in plant culture laboratories. It is possible that the poor performance of some plant cultures or explants might be attributed to the presence of residues of the strong disinfectants and fungicides used during decontamination process and toxicity of the heavy metals. However, research studies are needed to confirm or establish whether the use of such disinfectants and heavy metals *in vitro* culture contributes to plant culture toxicity or mortality.
