A Comparative Study of the Gametophytic Generation in thePolystichum aculeatumGroup (Pteridophyta)

Abstract

The gametophytic generation of the allotetraploid Polystichum aculeatum and its diploid parents, Polystichum setiferum and Polystichum lonchitis, was studied in order to compare their morphology, gametangial ontogeny, and breeding system. Six populations, two of each species, were selected for spore collection. Germination, gender expression, and antheridiogen experiments were established on agar and soil culture media. Germination percentage in the tetraploid was higher, and the only morphological difference was found in the length of marginal hairs that were also longer in P. aculeatum. Gender expression in the allotetraploid was a mixture of the diploids. Differences in gender expression of both diploids, with many male prothalli in P. lonchitis and many female ones in P. setiferum, may favor the formation of the hybrid that originated the allotetraploid. An antheridiogen system was observed in both P. aculeatum and P. setiferum, and each species responded to one another’s antheridiogen. In contrast, exudates from P. lonchitis failed to induce precocious maleness within the species but did induce an antheridiogen response in gametophytes of P. setiferum.