Gregor Johann Mendel is often described as the Father of Genetics. His discoveries regarding the inheritance of pea plants laid a solid foundation for the idea that genetic traits propagate from parents to children (generally) through dominant and recessive genes. Most of us have studied Mendel's work in our biology textbooks, and now it looks like some portions of it have to be rewritten :). It looks like contrary to inheritance laws the scientific world has accepted for more than 100 years, some plants revert to normal traits carried by their grandparents, bypassing genetic abnormalities carried by both parents.

Mutant plant inherits traits from grandparents (Courtesy: Purdue University)According to Robert Pruitt, a Purdue Department of Botany and Plant Pathology molecular geneticist, the mutant parent plants (Arabidopsis) apparently have hidden templates that contain genetic information from the previous generation! This information can be passed along to the offspring, and if the offspring finds that the genes from both its parents are abnormal/mutated, it might choose to use the template genes from its grandparents.
In this research, if both the parents have a mutation (the flowers were fused into tight balls), the child plant still can have a normal flower, inherited from the grandparent plants through template genes passed through its parents.
Even though a phenomenon called atavism has similar expressions (for example, a child might have his grandmother's nose), there is a big difference between the two. Atavistic genes are recessive genes that got suppressed in the parents due to the presence of a dominant gene, but were expressed in a child which lacks the dominant gene. In the case of the Arabidopsis plant, the grandparent genes are kept in a separate location in the parent, and are used in the child in case the parent genes are mutated/damaged.
This obviously introduces extra complexity into Mendel's Laws. If such behavior is found in animals as well, it is possible that it will be an avenue for gene therapy to treat or cure diseases. The study is published in the March 24 issue of the journal Nature.