Low temperature of 2–5° C. accelerates the rate of formation of amino acids from reserve proteins in the endosperm of Heracleum sphondylium . It also brings about the accumulation of glycine and arginine in abundance. Experimental culture of excised embryos on synthetic media shows that these acids are particularly beneficial to embryo growth whilst alanine, the predominating acid at room temperature, is not. It is suggested that the rapid growth following low- temperature treatment results from the action of low temperature on protein breakdown.