It is well known that the "opaque-2" gene in homozygosis reduces the yield of grain. It is accepted that this yield reduction can be due, partly, to a defective action of this gene in the genesis of the seed and, partly, to a minor capacity of the vegetative part of the plant. To know the relative importance of these two factors, the plants of three different single crosses, homozygous for the gene "opaque-2", were divided in two classes, in relation with the class of pollination they received: (a) plants cross-pollinated, with pollen from normal plants; (b) Self pollinated (plants pollinated with "opaque-2" pollen. Both treatments of each hybrid were set up as one trial of 6 replications (21 plants per replication). For each treatment, the grain yield and the behavior of the plants, after maturity of the grain, were measured.

As expected, the plants pollinated with normal pollen produced vitreous kernels, and the plants pollinated with opaque-2 pollen produced opaque kernels. For opaque-2 treatment, yield was 12.4% higher in one hybrid (p < 0.05), but 3.32% and 6.55% smaller in the other two hybrids. These two last differences were at probability levels of 60% and 20% respectively.

After maturity of the grain, the following characters of the plant were measured:

(1) Number of plants remaining green (10 days after maturity, in two hybrids, and 40 days after maturity in the other one): The number was significantly greater in one opaque-2 pollen treatment (p < 0.001). For the other two hybrids, all the plants of both treatments had all the leaves dry. The number of plants with "green stalk" was greater in the three opaque-2 treatments. In two of the hybrids the difference was significant at the 0.01 level.

(2) Proportion of dissolved solids in the stalk juice, measured with a field refractometer (only the stalks that remained green after maturity were observed): The opaque-2 treatment was significantly higher in two hybrids (p < 0.05), and smaller in the third one (40% level).

These differences in grain yield and plant characters, related with the genetical differences of the fertilizing pollen, suggest that the genetic information that the pollen brought to the embryo and to the endosperm affected not only the vigor of the seed but also the physiology of the female parent plant. Mariano Blanco, on his Doctoral thesis (University of Zaragoza, May, 1972), describes his experiments with several inbreds and one single cross of normal genotype. He found that the character "refractometrical reading of stalk juice" of different plants of the same stock was influenced by the origin of the pollen and the type of fertilization: selfed plants had higher refractometrical readings than cross-pollinated plants, and different plants of the same stock had different readings when pollinated with pollen of different inbreds. Then, he pointed out: "The influence of different pollen seems to affect the chemical composition and proportions of the components of the dry matter of the plant. . . Such influences and inmediat reaction should be kept in mind because they can affect the yields in trials." We think that studies of the interaction between the seed and the mother plant offer possibilities for research in plant physiology and plant phenogenesis.

Luis Bosch, Mariano Blanco, Angel Alvarez, Antonio Pons & José L. Blanco

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