When a green pod containing pea plant is crossed with a yellow pod containing pea plant in the progeny yellow pod containing plants are also produced, so green pod containing plant is

If green pod containing plant is homozygous (GG) and it is crossed with yellow pod containing pea plant (gg), only the plants which contains green pods (Gg) would be produced only if it is green pod containing plant is heterozygous (Gg), upon cross with yellow pod containing pea plant, would produce yellow pod containing pea plant also. Green pod producing plant can be GG/Gg  

                                                                (Green)      (Yellow)