The restriction of two-line hybide rice development is low grain plumpness,which is decided by supplying power of source,transport power of flow,acceptant power and compatibility of store and temperature.

Five rice lines (varieties) with different genetic differentiation were crossed with eight indica cultivars for comparing and analyzing the grain plumpness among their hybrids.

The genetic analysis was made on grain plumpness of hybrids in indica japonica lines(IJLs) with different genetic differentiation mated with indica photo thermo sensitive male genetic sterile lines (PTMGS).

Although N application of spikelet promoting,spikelet sustaining or redundant fertilization would result in high grain plumpness, the size of hull was reduced, so that grain weight were also dropped.

Grain plumpness decreased by low temperature treatment during booting and grain filling period, and the visible effect of grain plumpness were founded from sixteen to twenty days after heading.

The inferior grains developed later, their endosperm cells were fewer but bigger than that of superior grains.

The results showed that S-3307 had different effects on superior and inferior grains.

By using two line hybrid rice Liangyoupeijiu and Peiliangyou 500, the RNA and protein contents in ovaries of superior and inferior grains were analyzed .

In the heading day of rice, the contents of the total RNA, mRNA in the superior grains (upperprimary branches grains) ovaries were higher than that in the inferior grains (lower secondary branches grains)ovaries, whereas, protein content lower than that of it.

For variety with good grain filling,the differences in the initial growth potential,maximum grain filling rate and mean grain filling rate were not obvious between superior grains and inferior grains.