Nucleic acid and protein synthesis and loss of vigour in germinating wheat embryos.

A study has been made of the RNA and protein synthesising systems of wheat embryos isolated from seed lots having high viability but differing in vigour. The rate of RNA and protein synthesis in wheat embryos during the early hours of germination is related to the vigour of the seed lot. The imposition of a stress factor, in the nature of a sub-optimal germination temperature, during germination of isolated wheat embryos magnifies the differences in rates of protein and RNA synthesis between high and low vigour seed. Using cell-free protein synthesising systems it has been demonstrated that an important difference between high and low vigour embryos lies in the relative levels of messenger RNA in the embryo. High vigour embryos contain relatively higher levels of poly A(+)-RNA (i.e. potential mRNA species) than lower vigour embryos and furthermore the level of poly A(+)-RNA in high vigour embryos increases during early germination whilst in lower vigour embryos the level decreases. The difference in poly A(+)-RNA levels accounts, at least partially, for the differences in rates of protein synthesis observed between embryos from high and low vigour wheat seed during early germination at both optimal and sub-optimal germination temperatures.