Effects of flower node position on the mutable V and stable R loci in a clone of Nicotiana.

ENETIC analysis implying mutable alleles of the gene V to account for flower color variegation in a Nicotiana culture has been presented by SMITH and SAND (1957). These plants also contain stable genes for flower color and have been found useful for the study of interaction between environmental factors and genetic systems of varying stability (SAND 1957; SAND, SPARROW and SMITH 1960). The goal has been to elucidate differences and similarities between mutable and stable gene systems. Data are presented here for both somatic and germinal effects due to flower node position on a mutable allele of the V gene and on the stable R gene in a clone of Nicotiana. Results for flowers from various node positions are not homogeneous, but vary according to a pattern that is related to the sequence of node positions on the main flowering axis. It is inferred that metabolic changes associated with development of the branch, and correlated with growth rate, influence the mutation rates of both the stable and the mutable genes. This work has been summarized previously ( SAND 1960).