Responses Of Seed Germination And Seedling Growth Of Krascheninnikovia Arborescens To Environmental Factors

Krascheninnikovia arborescens is a high quality forage grass.It has rich in nutrition and has good palatability and high feeding value.K.arborescens is an important forage grass in desert and semi-desert areas and has high sand-fixation value.In addition,this species has some inherent excellent properties,such as the strong adaptability(cold and drought tolerance),long-time usage as forage grass and strong ability to resistance of grazing.It plays an extremely important role in the animal husbandry development in arid and semiarid regions.Although K.arborescens has a unique economic value and ecological benefits,it is gradually depressed after a long-term overgrazing and man-made destruction.This study mainly investigated the ecological processesduring the stages of seed germination and seedling growth of K.arborescens,including seed germination,seasonal dynamic of soil seed banks,seed storage conditions,and seedling growth.The results were as following:1.We tested the effects of temperature,light and osmotic stresses(Na Cl and PEG)on seed germination of K.arborescens to explain the adaption strategy in desert habitat.The results showed that,seed coat of K.arborescens was water-permeable and seed germination began after 2 hours of water absorption.Germination rate(GR),germination index(GI)and mean germination time(MGT)decreased significantly in low temperature conditions(e.g.5/15,5 oC)compared to other temperature regimes.Seed germination remained a high value(95%-100%)at other tested temperature regimes under both light and dark conditions.Therefore,K.arborescens was considered as a non-dormant species.Initial germination percentage decreased with the decrease of osmotic potential.Germination was not affected by osmotic potential(Na Cl and PEG)at concentrations higher than ﹣1.4 MPa,but germination index was significantly decreased with the increase of osmotic potential.Seed germination was decreased to 10%-14% when osmotic potential was lower than ﹣2.0 MPa.Germination percentage in high osmotic potentials(0~﹣2.0 MPa)had high recovery germination.But the seed mortality percentage under ﹣2.7 MPa Na Cl was higher(51%)than that under PEG with the same osmotic potential,which indicates that some seeds had lost their viability in high Na Cl solution.2.K.arborescens only has a transient soil seed bank.Soil seed bank mainly distributed in the range of 0-2 cm soil depth.In the wild,soil seed bank existed mainly after seed dispersal and before seed germination.With the increase of soil depth,consumption rate of soil seed bank was accelerated.Burial depth and time significantly affected seed germination rate and mortality rate both in the library and in the wild.3.K.arborescens had short-lived seeds.The viability of field stored seeds for a year dropped to 4%.High temperature and air relative humidity significantly influenced seed viability,and low temperature and humidity storage significantly extended the vitality of seeds.4.K.arborescens had strong drought resistance.Seed germination in 1% soil water content was 15%,that in 2% water content was 52%,and that in 4% ~ 20% water content was at a higher level.Seedling emergence had a strict requirement for soil water content.When soil moisture content was 1%,seed germinated but can’t emergence.Emergence percentage was only 2% in 2% water content,and seedlings ultimately died.Water content of 4%-20% was the suitable moisture content for seedling emergence.