[The pollen tube growth of Pisum mutants under consideration of the free amino acids].

The germination of the pollen grains and the growth rate of the pollen tubes of eight mutants of Pisum sativum were compared with the parent line by in vitro investigations. All of the mutants studied showed a retardation of pollen tube growth as compared to the parent line, resulting in competitive elimination of some of the gametes in plants heterozygous for the respective mutant genes. The deficit of recessive plants in the progenies of heterozygous mutant strains of peas can be attributed to this retardation. Marked differences between the various mutants with regard to the levels of various free amino acids in their pollen grains were found. Certain amino acids may be present in greatly reduced concentration or may be present in excess. In some genotypes pollen tube growth can be stimulated by adding the deficient amino acid. This is especially true for proline, valine and threonine. As far as the other amino acids are concerned, the mutants studied showed varying reactions. The germination rate of the pollen grains is reduced by proline and threonine; germination is completely inhibited by glutamine. The amino acids isoleucine, histidine and cysteine retard pollen tube growth in all the mutants investigated. This is also true for leucine which, however, has a stimulating effect in one of the chlorophyll mutants.