Interference of the phosphodiesterase inhibitor aminophylline with the plant cell cycle

Aminophylline (an inhibitor of animal phosphodiesterases) interferes with a pleiotypic program in embryos and seedlings of Haplopappus gracilis, inducing a specific and reversible block of the cell cycle in G1 and G2, partial depression of RNA and protein synthesis and inhibition of the uptake of nucleosides and leucine. The analogy between these effects and those evoked in animal cells by various treatments leading to a rise in cAMP level is discussed.