Parental self-hybridization

In order to obtain hybrid seeds, self-pollination and pollination by a sibling plant must be avoided. It is sought to develop a female parental line accepting pollen from other lines (cross-pollination), without reproduction of its own line. This can be achieved directly through emasculation, i.e., elimination of the pollenbearing organ, usually at the expense of large labor requirements. Other methods can be used to induce male sterility. 

Proceeding to two rings going-on one class, neutral derivatives of bicyclobutane with the two non-bridgehead carbons replaced by sp hybridized or trigonally coordinated atoms show self-destructive behavior for related reasons (see Chapter 19 by Hoz for a review of bicyclobutanes). Our suicidal species include the hypothetical bicyclobutane-2,4-dione (51) and its 1,3-disubstituted derivatives, recognized as squaraines (52) . The theoretical analysis of the parent diketo compound suggests the non-planar form also lacks the C-C bond. The 2,4-dibora compounds are experimentally known to be... 

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