A COMPARATIVE STUDY OF SPORE MORPHOLOGY OF THE SUBFAMILY CRYPTOGRAMMOIDEAE GENERA

Using the method of scanning electronic microscopy (SEM), a comparative study of twelve representatives of subfamily Cryptogrammoideae S.Linds. family Pteridaceae E.D.M.Kirchn. was carried out. A comparative study of morphological characters of investigated spores has revealed characters that allow considering the relatedness of the studied species to one subfamily – Cryptogrammoideae. These characters include: spore form is roundish-triangular, lociniate in proximal-polar and distal-polar positions; spore contour is low-crenate to smooth; distal side of the spore in an equatorial position is convex; rays of laesura are straight, raised over a sporoderm surface; exosporium is clearly defined from fine-granulate to verrucate.


INTRODUCTION
The first ideas about closely related taxa of the genus Cryptogramma R. Br. ex Richards were presented by Prantl (1882). From the Pellaea Link group of kinship he separated the genus Cryptogramma with subgenera: Cryptogramma, Onychium Kaulf, Llavea Lag, Anopteris (Prantl) Diels and Ochropteris J. Sm.
A distinct taxonomic group -subtrib. Cryptogrammaceae (cryptogrammoid ferns) as part of Polypodiaceae J.Presl a. C.Presl family -was separated in 1927 (Horvat, 1927). Later Christensen (1938) raised the subtribe rank to a tribe. 334 A.V. Vaganov By the middle of the XX century the leading pteridologists, including Pichi-Sermolli, but except Horvat and Copeland, in his works on the taxonomy of the genera Cryptogramma, Onychium and Llavea took them as the key genera among cryptogrammoid ferns. In 1963, Pichi-Sermolli (1963 in his monograph combined three genera of uncertain systematic position in the separate family Cryptogrammaceae Pic. Serm. of order Pteridales. Based on the similarity of external characters of the sporophyte the family included Cryptogramma, Llavea and Onychium. But the current stage of the study of fern systematics has allowed reviewing the taxonomic composition of the group. The application of molecular genetic methods in relation to the cryptogrammoid ferns group has shown the strongest relationship Onychium with Actiniopteris, and Cryptogramma and Llavea with Coniogramme (Zhang et al., 2005;Liu et al., 2008;Schuettpelz et al., 2007Schuettpelz et al., , 2008Christenhusz et al., 2011;Metzgar et al., 2013;Kuznetzov et al., 2014).
In the work about the ferns of Thailand Lindsay and Middleton (2009) specified a new combinationsubfamily Cryptogrammoideae as a part of the family Pteridaceae, transferred the family Cryptogrammaceae in its synonyms, and chose Cryptogramma as type genus. Currently, in articles on the molecular phylogeny of ferns the genera Cryptogramma, Llavea and Coniogramme are combined into a clade «Cryptogrammoid».
The purpose of the study is to find diagnostic characters of spore morphology of Cryptogramma, Llavea and Coniogramme to confirm the level of their relationship and evaluate whether they belong to the subfamily Cryptogrammoideae.

MATERIAL AND METHODS
Spores for the study were selected from herbarium materials stored in the herbarium of the V.L. Komarov Botanical Institute of the RAS (LE), the South-Siberian Botanical Garden, Altai State University (ALTB) and the Institute of Biology and Soil Science FEB RAS (VLA).
Spores were investigated using scanning electron microscope "Philips SEM 525-M", and electron-ion scanning microscope "Quanta 200 3D" situated in Tomsk Material Testing Center for collective use of the National Research Tomsk State University and JEOL JSM-6390LA Analytical Scanning Electron Microscope of Center for collective use of the V.L. Komarov Botanical Institute of the Russian Academy of Sciences (Saint-Petersburg). Spores were fixed using a carbon adhesive tape; to reduce the influence of the charge a method of thermal spraying by chromium, carbon or gold-palladium mixture in a vacuum sputtering plant. Spore surface was scanned in high vacuum at an accelerating voltage of 2 kV and a magnification of 1000 to 7000 times, and 10,000 to 16,000 times. The measurements of spores were carried out using "SIAMS MesoPlant" and "Photometer" programs.

DISCUSSION
The analysis of the results revealed the characteristic similar features of the spore morphology of the Coniogramme, Llavea and Cryptogramma species, namely the form of spores in the proximal-polar and distal-polar positions roundish-triangular, lociniate; spore contour low-crenate to smooth; in the equatorial position the distal side of the spore is convex; rays of laesura are straight, ascending above the sporoderm surface; exosporium clearly defined from fine-granulate to verrucate.
The data obtained by comparing of spore morphology and morphometric parameters allowed us to conclude that the inclusion of Coniogramme, Llavea and Cryptogramma in the subfamily Cryptogrammoideae and one «cryptogrammoids» clade in the modern system of the family Pteridaceae was justified.