New Observations on the Morphology and Structure of Marchantia polymorpha Gametophores in Sexual Reproduction Adaption

The morphology and structure of the gametophores of the liverwort Marchantia polymorpha were studied using light microscopy. New observations included:(1) The gametophores had distinct dorso-ventral differentiation and were highly specialized upright branches of the thallus bearing sex organs.(2) Two marginal ones of 9-11 rays of the female receptacle were distinguished by their slightly different sizes compared with others. There was no involucre between the two marginal ones. The dorsal region of the archegoniophore stalk was comprised of photosynthetic tissue,which extended laterally and formed two narrow grooves under the extended photosynthetic tissue. The ventral region of the stalk consisted of two-parallel rhizoid furrows half-wrapped by overlapping scales. (3) In contrast to the female archegoniophore,the antheridiophore stalk was smooth and no photosynthetic tissue or grooves were formed in the dorsal region. The umbrella-shaped female receptacle retained water,which could be released slowly along the grooves to form a tiny water flow,through which the spermatozoids swam to the archegonia. The morphology and structure of the Marchantia receptacles were adaptations to sexual reproduction,and can help us to understand the mechanism of fertilization in Marchantia.