Previous research suggests that the genetic information the pollen brings to the embryo and to the endosperm affects not only the vigour of the seed, but also the female parent plant photosynthesis capacity (Blanco, M., Doctoral thesis Univ. of Zaragoza, May 1972; Bosch, L., and Blanco, M., et al. MNL 52:122-123, 1978). The present work is to test for differential interaction between the plant and the seed produced on it, in respect to: (1) The relationship between their respective genetical constitutions, (2) specific genes, and (3) cytoplasmic effects.

The material was (a) Two inbred lines of quite different origins, each in an o2/o2 version and a +/+ version: A o2, A +, B o2, B +; (b) the F1 single cross, A o2 x B o2 (direct cross), and the reciprocal, B o2 x A o2; and (c) the F2 of both direct and reciprocal single crosses.

As treatments, the inbreds were self-pollinated; both classes of F1 plants were (1) not pollinated, (2) self-pollinated, (3) pollinated with each version of both parent lines (A +, A o2, B +, B o2); and both classes of F2 plants were self-pollinated.

The experimental design was "randomized plots" of 3 replications (one plot for each class of material and type of pollination; 25 plants per plot). The pollinated plants with ears not perfectly set were discarded. On each plant, 3 parameters were measured: (1) Refractometric reading of the stalk juice at maturity of the grain (34% moisture of the grain); (2) Dry weight of the ear/plant (15% moisture); and (3) Total dry weight/plant.

In each group of material (a, b and c) there were significant differences in reaction between corresponding treatments. This lets us advance that plants react specifically to the different classes of seeds, and vice versa. Such reactions depend on the relationship between their cytoplasms, genetic backgrounds and specific genes (o2 versus +). The results do not invalidate the hypothesis that in some cases the seed stimulates and increases the photosynthesis capacity of its mother plant.

Besides the working hypothesis, the homozygous o2 seeds in some of the cases were significantly superior in weight to the corresponding heterozygous seeds. Thus, "opaque 2" should not be considered a "defective" gene.

M. Blanco, P. Fontanet, A. Alvarez, J. Montserrat, and J. L. Blanco

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