A study of the oospore characteristics in some Charophytes (Characeae) of Iran
Ahmadi, A.; Riahi, H.; Sheidai, M.; van Raam, J.C.
Charophytes produce a multilayered, pigmented and thick walled zygote, which is called oospore. Oospore dimensions and its wall ornamentation are useful characters in the taxonomy of Nitella species, but Chara species generally do not show details of oospore structure under the light microscope. We made SEM photographs of the oospores of 12 Chara taxa, one Nitella and one Tolypella species from Iran which generated proper data to differentiate between closely related Chara species. The ANOVA test of quantitative characters showed significant differences among the species for the oospore length, width and length to width ratio, the number of striae and fossa breath. Principal component analysis revealed that characters like the number of basal impression, oospore shape, largest polar axis, isopolarity index, fossa breath and number of striae, the membrane fibrous or not fibrous and membrane smooth or rough are the most variable characters among the species studied. UPGMA tree of oospore characters showed affinity between C. crassicaulis and C. vulgaris var. vulgaris and C. vulgaris var. longibracteata. However, C. grovesii, C. gymnophylla var. gymnophylla and C. gymnophylla var. rohlenae are placed close to each other in a separate subcluster. This is also true for C. contraria, C. socotrensioides and C. kirghisorum as they stand far from C. vulgaris varieties subcluster, forming a distinct group by themselves.