The Development of Embryo, Endosperm, and Nucellus Tissues in Relation to Receptacle Growth in the Strawberry

Maleic hydrazide was applied to strawberry plants in an attemptto inhibit the growth of specific tissues within the developingachenes so as to trace their function as sources of stimulito the developing receptacles. Whole plants were sprayed at 1, 500 p.p.m. at various intervalsbefore and after the opening of the primary flower on the truss.Regular twice weekly sprays with various concentrations of 2-naphthoxyaceticacid at concentrations between 50 and 5oop.p.m. were also combinedwith the maleic hydrazide treatments. Observations were madeon the development and final weight of all fruits, and valuesobtained for the percentages of achenes in which there wereviable embryos at maturity. Achenes treated with maleic hydrazideat various intervals were examined to determine the effectsof the treatment on the development of the embryo, endosperm,and nucellus. If treatment with maleic hydrazide was delayeduntil the third day after anthesis the receptacles were ableto develop and to ripen successfully even though all the acheneson their surface were devoid of viable embryos. Maleic hydrazideat 1, 500 p.p.m. was totally inactive as an inhibitor of receptacleexpansion if treatment was delayed till later than the 10thday after anthesis. It is concluded that the embryo is not the source of the growthstimulus which promotes the development of the receptacle, andthat the endosperm probably does not become active as a majorsource of auxin-like substances until it has become cellularbetween 10 and 14 days after anthesis. The possible identityof the tissue controlling receptacle-growth in the period immediatelyfollowing pollination and fertilization is discussed.