保护措施：（1）对扇蕨进行就地保护和迁地保护；（2）采用分株繁殖和人工孢子繁殖，促使其复壮和扩展；（3）将分株繁殖和人工孢子繁育的个体回归原产地和适合扇蕨生长的生境，让其归化自然。; Neocheiropteris palmatopedata（Baker）Christ, a rare and endangered species endemic to China, has a scattered distribution only in central Yunnan, west Guizhou and southewest Sichuan provinces. To explore endangerment mechanisms and provide theoretical basis for the effective protection of N. palmatopedata, its morphological characteristics, cytology, growth characteristics, population and community structure, soil property, gametophyte development and morphological differentiation were investigated based on the extensive investigation of its distribution and destruction.
1. Morphological characteristics
A fan-shaped, pedatifid, palmate and reticulate fern, the central lobe of N. palmatopedata was occasionally pinnatifid. Sori were grown close to the midvein. Transverse section was made in different portion of petiole, showing a dictyostele. The vascular bundles of the petiole converge gradually and decrease in number from bottom to top. The vascular bundles were arranged in circularity, two of which were thicker than the others. In addition, two parts of xylem were seen in the both thicker vascular bundles, which was different from typical amphicribral bundle of ferns.
Chromosome number of N. palmatopedata was investigated. The result showed that the chromosome number was 2n=72 and the basic choromosome number is x=36, which differed from Gibby’s result—2n=70.
3. Growth characteristics
Growth status, phenology, propagation habit of N. palmatopedata were investigated. The result showed that it was exigent over humidity and light. Despite of its strong rhizome initiation, population growth was not affected by rhizome propagation.
4. Population and community structure
N. palmatopedata was scarce in population, and each population was isolated from each other. It was dominated by other species in the community, and its
geological distribution indicated obvious regional limit and ecological fragility of its distribution area.
5. Soil property
N. palmatopedata grew in brown-red soil, rendzina and red limestone soil, all with thick humus layer. Analysis of the soil chemical property showed organic matter, potent Ca and available Mg were key factors for growth and development of N. palmatopedata. When the humus soil under woods disappeared and the red soil appeared owing to primary vegetation destruction, the endangerment situation of N. palmatopedata was further aggravated.
6. Gametophyte development
The spores of N. palmatopedata were cultured in improved Knop’s medium, in-situ humus soil, red soil, sterile water respectively. Spore germination and gametophyte development were observed, and the impact of four culture methods on the gametophyte development and sexual reproduction was compared. The results showed that the mature spores were yellow-brown, monolete, and bean-shaped in equatorial view and elliptical in polar view. The germination was of the Vittaria-type and the gametophyte development of the Drynaria-type. The adult prothalli were cordate. Trichomes occurred in prothallus stage. Gametophyte culture process was susceptible to contamination of fungi, algae and moss.
7. Morphological differentiation
21 morphological indicators, including petiole length, lobe number, spore sori, spores etc. of 72 individuals from 6 populations of N. palmatopedata were determined. The significance of differences, morphological differentiation, and phylogeny relationship reflected between populations were studied with variance analysis, Euclidean distance clustering and COSINE clustering. The results showed:（1）Morphological indicators of significant differences and of no significant differences accounted for 4.76％ and 95.24％ respectively.（2）Variation in vegetative organs was less influenced by environment and more stable than that of the reproductive organ.（3）Morphological characteristics showed no significant differentiation at population level but certain differentiation in geographically different origins
8. Endangerment factors and conservation measures
Endangerment factors: (1）The history of its spreading and distribution area formed was not long owing to its late origin. (2）It was exigent over humidity, light and soil. (3）The long period of sexual reproduction and the low seedling rate at which gametophytes developed into sporophytes were the main reason for the endangerment of N. palmatopedata in sporophyte generation. (4）It couldn't enlarge distribution area by rhizome propagation. (5）Human-induced habitat loss and accompanying habit fragmentation likely accelerated the endangerment process.(6）Natural disaster such as drought was a factor causing the endangerment of N. palmatopedata that can’t be underestimated.
Conservation measures: (1）Introduce in-situ and ex-situ conservation. (2）Rejuvenate and expand N. palmatopedata by adopting division propagation and artificial reproduction by spores.(3）Return N. palmatopedata to nature by naturalizing the plants reproduced by division and spores to its home and habitats that suit its the growth.|