Leaf photosynthetic characteristics in eight shaded Malaysian filmy ferns

Abstract

The photosynthetic characteristics of eight Malaysian Hymenophyllaceae filmy ferns from shady habitats were investigated in this study. Chlorophyll content was highest in Trichomanes meifolium, followed by Cephalomanes obscurum, Hymenophyllum serrulatum, H. denticulatum, H. javanicum, H. acanthoides, H. exsertum and H. blandum, with values ranging from 3.3 to 8.6 mg/g fresh weight. Soluble protein content was remarkably high in H. serrulatum, with values of 53 ± 3.50 mg/g, followed by H. denticulatum, H. acanthoides, T. meifolium and the other species. Protein to chlorophyll ratios in the filmy ferns were low as expected, except for in H. serrulatum, H. acanthoides and H. denticulatum. Chloroplast number and size ranged between 34 to 138 per cell profile, and between 4.8 to 6.5 µm in diameter, in the Hymenophyllaceae. Quantum efficiency measurements in four Hymenophyllaceae spp. exhibited Fv/Fm values ranging between 0.73 to 0.81. The Hymenophyllaceae spp. also showed low in vivo CO2 assimilatory rates and light saturation points, ranging between 5 to 15 µmol CO2/m2/s and below 150 µmol/m2/s, respectively. The findings add further to our understanding on how the filmy ferns adapt and thrive in their humid and shady habitats.