Effects of pH, temperature and light intensity on spore germination and growth analysis of young sporophytes of Polypodium lepidopteris (Pteridophyta, Polypodiaceae)

Abstract

ABSTRACT Polypodium lepidopteris is a terrestrial fern from coastal vegetation, and is used as medicinal. This work analyzed the effects of pH, temperature and light levels on the spore germination and the relative growth rate (RGR) of young sporophytes. Fertile fronds were collected in Florianópolis, SC, Brazil. The effect of pH (4.0 to 6.7) on spore germinability was observed in a growing room at 25 ± 2ºC (22 mmol m-2s-1) under a 16h photoperiod. No statistical differences between treatments were found. The effect of different temperatures on the germinability was analyzed (20, 25 and 30ºC). The test was carried out in a germination chamber (17 mmol m-2s-1) under a 16h photoperiod. The germination was inhibited at 30ºC. The effect of natural light levels (54, 38, 22 and 8%) was analyzed. The highest germination percentages were verified at 22 and 8% of natural light. The growth analyses show statistical differences in the number of fronds and height of the longest frond between time 1 (283 days of spore inoculation) and time 2 (343 days of spore inoculation). Sporophytes of P. lepidopteris produced 1.33 ± 0.09 fronds per month. The RGR (relative growth rate) was 0.15 ± 0,009 cm cm-1month-1.