The invention relates to stinging cells or isolated capsules and to their use in compositions and methods for efficient delivery of biologically active agents into a plant cell or plant tissue. The biologically active agent to be delivered by the methods of the present invention is selected from a nucleic acid, a peptide, a polypeptide, a plant hormone, an enzyme, an herbicidal agent, an anti-viral agent, an anti-bacterial agent and an anti-fungal agent. Particularly, the invention is related to compositions and methods for the efficient transformation of polynucleotide construct into a plant cell or tissue, to obtain transgenic plants.