CONTROL SYSTEMS. “Evidence is accumulating that major gene-switching events in plants, such as flowering, are regulated by complex control systems which ensures that development occurs only in the correct groups of cells at the appropriate time. A similar, or more sophisticated system might thus be expected to regulate alternation of generation.”
http://onlinelibrary.wiley.com/doi/10.1111/j.1469-185X.1994.tb01277.x/abstract