The Reproductive Ecology On Four Species Of Ephemeral Plants In Eremopyrum

Eremopyrum (Ledeb.) Jaub. et Spach is a small genus in tribe Triticeae (Poaceae) with eight species all over the world . In China, there are four species distributed only in the north part of Xinjiang. In Junggar desert, these species are typical ephemeral plants and are of very important ecological and applied value. In this paper, We observed and compared the characteristics of seeds germination, phenology, dynamics of biomass allocation , characteristics of breeding system and patterns of seed-set of the four species, and discussed the survival strategies of these species in the extreme environment of Junggar desert. The main results are as follow: 1) Phenotypic plasticity of seed germination has been involved in the four species, the seeds from the same mother plant show different germinability. This plasticity is engendered by environmental factors (especially temperature and precipitation) and the position of seeds on the mother plant. The dormant time of seeds at the lowest part of spikelets is at least one year and of the of spikelets others only about three months. The seeds from the same mother plant can germinate in both spring and autumn , but the number of the autumn germinated plants is much larger than that of the spring germinated plants. 2) The plants of the four species grew with rapid rhythms and the life spans of the spring germinated plants (only about 65 days) are shorter than that of the autumn germinated plants (about 100 days). 3) The life history traits of four species exhibite as typical r-strategists. The plants favore to allocate a greater proportion of resources to reproductive activities, their reproductive allocation can reach to 55～60% and is higher than that of most annual plants and perennial plants. The fruit-set ratios and fruits yield of all the four species are very high. 4) All the four species are self-compatibility. Although their pollen/ovule ratios are lower, pollen viability, percentage of pollen germination on stigma, pollen fertility are higher, and pollen longevity are longer. 5) The percentages of bracts in seeds package unit of four species are high. All the characteristics are important for these species to adapt to the extreme environment of Junggar desert and assure their reproductive success.