In Vitro Propagation of Rare and Endangered Serpentine Fern Species

Abstract

The carried-out studies concerned two serpentine fern species: Asplenium adulterinum and A. cuneifolium, as well as ferns not connected but also occurring on serpentine rocks, such as: A. septentrionale and Polypodium vulgare. The growth and development of gametophytes of all fern species were affected by Murashige and Skoog (MS) medium composition [Murashige and Skoog (Physiol Plant 15:473–497, 1962)]. Diluted MS medium to one half, and modified MS medium provided the best results in terms of fresh weight increase. The gametophytes growing in these two media (½ MS and MS own modification) had the correct shape and formed the most numerous gametophytes in the first and following rows. Measurements of the fresh weight of gametophytes of A. adulterinum and P. vulgare revealed that growth enhanced with sucrose concentrations between 20 and 30 g L−1. Lower sucrose concentration (5–10 g L−1), decreased the fresh weight of gametophytes and diminished their size. Higher sucrose concentration (40 g L−1) reduced gametophyte growth, though they did not show any discoloration or decay. A. septentrionale tolerated all the sucrose concentrations; it was only without sucrose in the medium that the fresh weight of gametophytes was smaller, as was also their number. The influence of several sugars, such as glucose, fructose, mannose, sucrose, maltose, and lactose (in the same concentration of 0.087 M) on growth and development of gametophytes was studied. The results of investigations showed that each of the fern species studied attained the best increase in the fresh weight, and produced the largest gametophytes in a medium supplemented with sucrose. Application of glucose provided similar results; with the exception of A. adulterinum, which preferred maltose in the medium, and A. cuneifolium, which grew equally well on medium with glucose and mannose. The remaining sugars, and particularly fructose, inhibited the increase of protallial fresh weight or caused its decay. Moreover, fructose turned out to be the most toxic: gametophytes of all studied fern species decayed when fructose was used in the medium.