A Study On Micro-morphological Features Of Diaspores From The Alpine Meadow On The Eastern Qinghai-Tibet Plateau

Micro-morphological characters of seed or fruit surface have been used in taxonomy. There adaptive values have also been understood at some extent with more researches have been done. Micro-morphological characters of diaspores in 218 species belonging to 61 genera of 5 families from the alpine meadow on the eastern Qinghai-Tibet plateau were observed under SEM. The taxonomic and adaptive values have been discussed. We hope the results will provide micro-morphology data of diaspores to plant taxonomy and to plant adaptive study under such specific habitat of Qinghai-Tibet plateau. The main conclusions are as follows:1. Seed coat patterns of 54 species and 1 variety belonging to 12 genera of Leguminosae were divided into 12 types. The types of seed coat patterns are intersected between genera. Namely, one type of seed coat pattern may exist in different genera. This is inconsistent with delimitation of the genus. The combination of seed coat patterns, seed shape, hila shape and hila position is of taxomic significance at species level in genera Indigofera, Lespedeza, Caragana, Oxytropis, Hedysarum, Melilotus and Medicago. The types of seed coat patterns differed from the traditional division of subgenus in Astragalus and also differed from the division of sections in subgenus. The seed micro-morphology can be used in distinguishing species within a section.2. Seed coat patterns of 24 species and 1 varieties belonging to 5 genera of Gentianaceae were divided into 8 types. Seed coat patterns differed at some extent between genera, if combined with seed shape, they can be used in distinguishing genera. There is also similarity of seed micro-morphology between genera. They can also be useful in discussing relationship between genera. In respect of seed micro-morphology, the genera Halenia, Comastoma, Lomatogonium and Swertia are closely related. The types of seed coat ornamentations are consistent with the traditional division of sections in Gentiana. Seed coat ornamentations are of taxonomic significance at species level within a series in sect. chondrophylla.3. Seed coat patterns of 24 species, 2 subspecies, 3 varieties and 1 form belonging to 6 genera of Scrophulariaceae were divided into 10 types. Seed morphology and seed coat patterns can be used in dividing genera. The types of seed micro-morphology are consistent with the division of sections in Veronica. The types of seed micro-morphology are inconsistent with the infra-generic grouping of Pedicularis. Seed coat ornamentations are of taxonomic significance at species level within a series. Seed coat patterns are of little taxonomic significance at infra-species level.4. Fruit coat patterns of 82 species and 8 varieties belonging to 35 genera of Compositae were divided into 12 types. Fruit coat patterns are similar between genera closely related in traditional classification. The conservative values of achene micro-morphology are different between genera. It is higher in genera Leontopodium, Anaphalis, Ajania, Artemisia and Taraxacum. Species can be divided according to achene shape and fruit coat patterns in genera Heteropappus, Parasenecio, Senecio, Cremanthodium, Cirsium and Prenanthes. Achene shape and fruit coat patterns can be used in species dividing within a section in genera Aster and Artemisia. Fruit coat patterns are unvariable in Leontopodium, Ajania, Gerbera, Sonchus and Taraxacum.5. Fruit coat patterns of 18 species belonging to 3 genera of Cyperaceae were divided into 5 types. They are similar between some species belonging to Kobresia and Carex, the genera are closely related. The types of fruit coat patterns differed from traditional division of sections in Kobresia. The combination of fruit shape and fruit coat patterns can be used in distinguishing 6 species of Kobresia. The types of fruit coat patterns also differed from traditional division of sections in genus Carex.6. Micro-morphological structures of diaspores are of some adaptive value. There are phytolith verrucae on nutlet surfaces of some species in Cyperaceae. It is believed that fruit with silicon can resist pathogenic epiphyte. Membrane seed coats of some species in Gentianaceae and Scrophulariaceae may serve as keeping-warm structure, and may be an adaptation to alpine environment. Alveolate reticulations on seed surface and subtle reticulations in reticulation bottom of some species in Pedicularis may facilitate seed imbibing water when germinating. Small achene with pappus is fit for anemochory in Compositae. Mucilage on achene surface in Artemisia can fix small particles to create a microclimate for avoiding drying damage or absorb water quickly to germinate. It is also fit for myxospermy. Spinule on achene surface of Taraxacum may increase retention potential of plant diaspores to the coats of animals. It is fit for epizoochore.