Maleic hydrazide was applied to strawberry plants in an attempt to inhibit the growth of specific tissues within the developing achenes so as to trace their function as sources of stimuli to the developing receptacles.
Whole plants were sprayed at 1,500 p.p.m. at various intervals before and after the opening of the primary flower on the truss. Regular twice weekly sprays with various concentrations of 2-naphthoxyacetic acid at concentrations between 50 and 500 p .p .m. were also combined with the maleic hydrazide treatments. Observations were made on the development and final weight of all fruits, and values obtained for the percentages of achenes in which there were viable embryos at maturity. Achenes treated with maleic hydrazide at various intervals were examined to determine the effects of the treatment on the development of the embryo, endosperm, and nucellus. If treatment with maleic hydrazide was delayed until the third day after anthesis the receptacles were able to develop and to ripen successfully even though all the achenes on their surface were devoid of viable embryos. Maleic hydrazide at 1,500 p.p.m. was totally inactive as an inhibitor of receptacle expansion if treatment was delayed till later than the 10th day after anthesis.
It is concluded that the embryo is not the source of the growth stimulus which promotes the development of the receptacle, and that the endosperm probably does not become active as a major source of auxin-like substances until it has become cellular between 10 and 14 days after anthesis. The possible identity of the tissue controlling receptacle-growth in the period immediately following pollination and fertilization is discussed.