J Integr Plant Biol. ›› 1955, Vol. 4 ›› Issue (2): -.

• Research Articles •    

Studies on Porphyra III. Sexual Reproduction of Porphyra

C. K. Tseng and T. J. Chang   

Abstract: 1. The carpogonium of Porphyra tenera Kjellm., when mature, sends out on one or both sides a filamentous projection on which the spermatia adhere. After fertilization, the projection gradually draws back into the carpogonium proper, showing that it is merely a temporary structure for effecting fertilization, and should not be identified with the true trichogyne of the Florideae, which is, in fact, a cell by itself with its own nucleus and withers after fertilization. As it is possible that the true trichogyne of the Florideae may be evolved from such a structure, it is suggested that the structure be called "prototrichogyne." In Porphyra dentata Kjellm. and P. suborbiculata Kjellm., prototrichogyne has not been found, although the protoplast of the carpogorfium apparently has the tendency to protrude outward but probably has been prevented from doing so by the thickness and toughness of the gelatinous membrane. Consequently, it is assumed that the tendency to form prototrichogyne is present in all Porphyra but owing to difference in the thickness of and toughness the gelatinous membrane, there are different grades of protrusion, from those which are scarcely noticeable to those which are very much elongated. 2. The spermatium of Porphyra tenera Kjellm., after adhering to the prototrichogyne, puts forth a very delicate process containing a thin strand of cytoplasm, which penetrates through the gelatinous membrane and through which the contents of the spepmatium pass into the female protoplast. The process is therefora similar to that repeatedly described by various European phycologists for P. umbilicalis (L.) Kuetz. In P. dentata Kjellm., similar spermatial processes have also been observed. It is assumed, there{ore, that this phenomenum is not unique to a few species, but is universal in all the species of Porphyra. Kunieda has described a totally different method of fertilization in which the spermatium is engulfed totally by the prototrichogyne. We have observed apparently similar phenomenum in P. tenera Kjellm. but after careful observation and experimentation, we have concluded that what seems to be an engulfed spennatium is actually the tip of the elongated prototrichogyne, broken away by folding or similar operation. 3. We have not observed the actual fusion of the sexual nuclei in the carpogonium, but we have seen, in many cases, the presence of spermatial nucleus inside the female protoplast, and in a few cases, the male nucleus almost comes in contact with the egg nucleus. In the prophase of the first cell division of the carpogonium, 5 pairs of chromonemata, two long and three short, in synapsis have been observed. In the prophase of the last cell division of the spermatial mother cells, 5 chromosomes have been seen; it is therofore concluded that fusion of the male and female nuclei must have taken place within the carpogonium. 4. Having observed 5 pairs of synaptic chromonemata in the prophase of the first cell division of the fertilized carpogonium, as well as 5 chromosomes in late prophase of the second and the third cell divesion of the carpogonium, we are led to the conclusion that meiosis has been effected in the first division of the carpogoninm and that the carpospores thus produced are haploid. Recently, Drew has raised the question whether the so-called carpospores of Porphyra are really products of sexual reproduction, and that for the time being it is better to avoid the using of the term "carpospore". From our studies, there should not be any more doubt that these spores are actually carpospores although they are, like those of Nemalion, haploid in nature.

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