Abstract: A method of producing a genetically transformed fluid-producing plant comprises:i) inserting into the plant tissue a gene or gene fragment controlling the expression of a target product, andii) regenerating a plant from said tissue, the genetically transformed plant being capable of expressing the target product in the fluid that it produces.There are also provided clones of genetically transformed fluid-producing plants which contain in their cells a chromosomal insert such that the target product is expressed in the fluids that the plants produce. There is further described a method of producing a protein or other target product which comprises:i) harvesting the fluid from a genetically transformed fluid-producing tree or plant, or a clone thereof, andii) recovering the target protein or other product from said fluid.