The present invention provides methods for modulating the growth and/or yield of plants. In particular the methods comprise the use of agents which functionally inhibit the expression of plant D-like cyclin inhibitors including isolated polynucleotide sequences which interact with DNA or RNA encoding proteins capable of binding plant D-like cyclins. Further, the present invention provides recombinant polynucleotide sequences, vectors and host cells which encode proteins capable of binding to and inactivating the activity of plant D-like cyclin/cyclin dependent kinase complexes preventing plant cells from exiting the cell cycle. Methods for determining and agents which are inhibitors of the BRO cyclin dependent kinase inhibitor proteins which are capable of modulating plant cell cycle progression are also provided. Methods for the production of transgenic plant cells and plants with increased growth rates and yields when compared to wild-type plants are also provided.