Morphological differentiation of Chara aspera Detharding ex Willdenow and Chara galioides De Candolle under different environmental variables

Chara aspera Detharding ex Willdenow and Chara galioides De Candolle are two taxa that show close morphological similarities, making it difficult to determine their taxonomic position. Their identification is primarily limited to one reproductive character:
the diameter of the mature antheridia, which is larger in C. galioides. We attempted to
identify other differentiating characters and assess the validity of considering them as one or two different species. Both taxa were cultured under controlled environmental conditions. In the indoor experiment, 216 plants of both taxa were incubated under three different combinations of salinity, light and temperature. The measurements taken during and after the experimental period (9 weeks) included shoot elongation rate, the diameter of the main axis, length and width of spine cells, and length and width of anterior and posterior bract cells. According to our results, the morphometric data acquired from these measurements allow discrimination of C. aspera and C. galioides. These parameters are useful characters to differentiate these taxa and support the view that they represent independent species.