T-DNA, or Transfer DNA, is a segment of DNA that is transferred from the bacterium Agrobacterium tumefaciens to the plant cell during the process of infection. This DNA integrates into the plant's genome, leading to the formation of tumors and the production of specific plant hormones. T-DNA carries genes that can alter the plant's growth and development. In biotechnology, T-DNA is utilized for genetic engineering in plants. Scientists can insert desired genes into T-DNA, allowing for the introduction of new traits, such as pest resistance or improved nutritional content, into crops. This method is a key tool in modern agricultural research and development.