Cytological Study on Induced Apospory in Ferns

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Abstract
A leaf or root detached from the sporophyte of apo-sporous prothallia of Pteridium aquilinum Kuhn var. latiusculum (Desv.) Und. was induced by detaching either roots or leaves from the sporophyte. The ability to induce an aposporous prothallium was limited to a few early leaves and roots of the young sporophyte. The prothallial outgrowth can originate from any part of the leaf; it is not correlated with such structures of leaf apex, vascular bundle, etc. Every sporophytic cell in the epidermis, mesophyll and cortex, except the guard cells, and elements of the vascular cylinder, can produce the gametophytic cell. The first indication of an aposporous outgrowth was the appearance of many large chloroplasts in the sporophytic cells from which the outgrowth originated. The prothallial outgrowth on the roots originates from epidermal cells near the growing point. The prothallial outgrowth was morphological and functionally a true gametophyte that bore sex organs from which a tetraploid sporophyte was sexually produced. The size of the nucleus, rhizoid, spermatozoid and antheridium of the aposporous diploid prothallium was in general, larger than the normal haploid prothallium. The tetraploid sporophyte exhibited many deviations from the normal morphology and physiology of the diploid sporophyte. For example, the tetraploid has an irregular shaped, thick leaf with an uneven surface compared with the diploid. Also the epidermal cells and stomata are larger in the tetraploid.