Formation and early development of tetraspores of Gracilaria lemaneiformis (Gracilaria, Gracilariaceae) under laboratory conditions

Morphological and culture studies of tetraspores of Gracilaria lemaneiformis were carried out under laboratory conditions. Relationships of germination rate, diameter and survival rate of tetraspores from 1st generation branches with grads of temperature and irradiance were determined, respectively. The result showed that 1st generation branches is in the majority of the tetraspores shedding and tetraspores from which had highest survival rates than other parts of the sporophytic plant. The time tetraspores used developing from giant unicells to diads, which both existed on the epidermis, then to tetraspores off the matrix, was only approximately 3 weeks all through. However, tetraspores spent more than two months developing into germlings of gametophytes. It was shown that temperature variation (10, 15, 25, 30 °C) with the light of 30 μmol m− 2 s− 1 had significant effects on the germination rate and diameter, but had no apparent effect on survival rate (ANOVA, P < 0.01). Germination rates of tetraspores reached the maximum at 20 °C, which was significantly higher than those at other temperature levels (P < 0.01), whereas 15 °C seemed to be optimal temperature for the diameter. All the three growth parameters (germination rate, diameter and survival rate) yield highly significant variations with irradiance treatments at room temperature (ANOVA, P < 0.01). The optimal germination rate was detected at the irradiance of 30 μmol m− 2 s− 1 (P < 0.01). The photon flux density which exceeds 480 μmol m− 2 s− 1 have apparently negative effect on diameter and survival rate.