Sex Expression in Atriplex canescens: Genetics and Environment

The sex expression of 665 individually tagged plants of Atriplex canescens was recorded over a 7-yr period (1972-1978): 59% of the plants maintained constant sex expression; 41% changed sex. Sex ratios were determined for 20 naturally occurring A. canescens populations. In 19 4x populations, [female] s predominated with a mean ratio of 59.7 [female]:36.2~ [male] :4.1 [[female],[male]]. For the only 2x population, a 1~ [male]: 1 [female] ratio was observed. These results suggest a trioecious genetic system for 4x populations wherein XXXX genotypes are [female], XXYY genotypes are ~[male], and XXXY genotypes under ordinary circumstances are biased toward [female] phenotypic expression but are labile and may be [female],[male] , or [[female], [male]]. ~XXXY phenotypic expression as [male]s and [[female],[male]]s is apparently correlated with environmental stress.