Methods and compositions for modulating plant development are provided. Polynucleotide sequences encoding isopentenyl transferase (IPT) polypeptides are provided, as are the amino acid sequences of the encoded polypeptides. The sequences can be used in a variety of methods including modulating root development, modulating floral development, modulating leaf and/or shoot development, modulating senescence, modulating seed size and/or weight, and modulating tolerance of plants to abiotic stress. Transformed plants, plant cells, tissues, and seed are also provided.