摘要：Morphotaxonomy, ecological preferences and biological characterization of algal
taxa of order Zygnematales (Conjugatophyceae, Chlorophyta), mainly the freshwater
species Spirogyra, Zygnema, and Mougeotia are still poorly understood and need
further in-depth investigations. In this study, different Spirogyra strains were
examined to characterize their abilities in conjugation and formation of zygospores
under different environmental conditions. We found that 16:8-h light:dark
photoperiod is the best condition to induce the conjugation and zygospore formation.
Moreover, the sexual reproduction was noticed to be triggered with increasing the
light intensity to 85 µmol photons m-2
s
-1
; no conjugation was observed at 35 µmol
photons m
-2
s
-1
. The attribute of conjugation under red and blue irradiance,
respectively, never equalized that in the white light even at elevated intensity. pH
value (7.5) was the most suitable niche for induction of sexual reproduction. An
increase of CO2 in the atmosphere, provided by NaHCO3 solution, did not enhance
sexual reproduction. Cultivation of the investigated Spirogyra strains on 0.003%
CaCl2-containing agarized Pringhsheim´s medium (1/2 conc. and without nitrogen)
induced the conjugation process as in case of CaCl2 omitted. UV radiation
completely inhibited the conjugation at all growth conditions.
关键词：environmental conditions; sexual reproduction; Spirogyra; zygospore
formation
