Effect of amino acids glutamine (Gln), arginine (Arg), asparagine (Asn) and γ-amino-butyric acid (GABA), 3.5 mM each, and the control with 1% activated charcoal on cork oak gametic embryo growth per month. (A) RAI: relative size increment in projected area per month (month⁻¹). (B) RWI: relative fresh weight increment per month (month⁻¹).