Studies On The Improvement Of Seed Germination In Kobresia Sp. And Their Mechanism

Kobresia willd distributes mainly on the Qinghai-Tibet Plateau. All the Kobresia willds are perennial and most of them are dominant in the alpine grassland. Kobresia willds are very important high quality forages and ecological grass on the Qinghai-Tibet plateau. It is a high quality grass for livestocks. Kobresia plays an important role in keeping the balance of the ecological environment in Qinghai-Tibet plateau. However, the natural grassland degenerates heavily due to the excessive exploitation, mice, pests and climate changes. Ecological environment is worse and worse, which produces heavy influence on the animal husbandry in Tibet. In order to recover the depleted grassland, it is one of the most available methods to study the propagated characteristics on seed of Kobresia willd.Under natural condition, their germination rates are very low. The average germination rates without any pre-treatments are merely 4% and 2% in the lab and in the field respectively. Therefore, it is very important to make further studies on their dormant mechanisms to improve the germination rates of Kobresia willd.In this paper, the morphological characteristics on seed of Kobresia Willd(K.royleana,K.macrantha,K.choenoides,K.prattii,K.capillifolia,K.humilis and K.pygmaea)from Tibet are described and the mechanism that how different treatments improve the germination rates are explained and the germination rates of the seven kind seeds are improved ulteriorly.The seven kind seeds without any treatments are observed by scanning electron microscope and the seeds of K.royleana and K.choenoides treated with gibberellin,PEG,sulfuric acid and sodium hydroxide are also observed. Germination test is also carried out. The epidermic cell of K.royleana is thin and with some hiatus on it, and other seeds are all with thick carpodermis, strong protective tissues. The embryos are surrounded by the endosperms and located near the carpopodiums. The effects on the carpodermis are differently by treatments. The results were as follows: GA and PEG almost had no katogene to the carpodermis; the Sulphuric Acid has a very limitative effect, which is a little better than GA and PEG; and the Caustic Soda works the best, which improved the germination rates of the 7 species respectively from 91%, 0, 76%,69%,14%,21% and 0 to 96%,90%,93%,96%,74%,63% and 50%.The result also shows that the germination fastigium advances about 7～14 days.The thick carpodermis prevents the gas exchanging and the entering of water while the thick carpopodiums prevents the growing of the corcles, which are the contribution to the low germination rates under natural conditions. With the treatment of Caustic soda,the corneous layers are abscised uniformly; even the sclerenchymatous cells in the outer layer are destroyed; the cell spaces are also increased and the compact tissues in the middle are also rarefacted. As a result, the water and air would enter the seeds more easilier than before, so the germination rates are improved.