Pseudoreplication in experimental designs for the manipulation of seed germination treatments

In the published reports concerning the design of laboratory experiments ex amining signals that might trigger seed germination, there is currently a m isunderstanding of what might constitute correct replication of the experim ental treatment. This is particularly true for the study of dry heat, smoke and charcoal, where either an individual seed or a batch of seeds in a Pet ri dish or tray is being treated as the unit of replication of the experime ntal treatment, irrespective of whether or not those seeds were all subject ed to the experimental manipulation simultaneously. Under these circumstanc es, the application of the treatment is unreplicated, while samples nested within that single application have been replicated, and the Petri dishes/t rays are functioning solely as independent replicates of the variability in germination response within the seed batch used and variation within the p retreatment and post-treatment environments. Thus any observed difference i n germination may be due to the germination treatment but, potentially, it could also be due to any chance event affecting the treated sample. There a re a number of alternative experimental designs that avoid this problem. Th e essential point with these designs is that the application of the experim ental manipulation to each replicate should be separated in space by the us e of separate experimental equipment and/or in time by the repeated use of the same experimental apparatus.