The Fruit-set Patterns And Seed Germination Of Leymus Racemosus

Leymus racemoses (Lam.) Tzvel (Poaceae) is a perennial rhizomes herb, which mainly distributed indeserts of Gurbantunggut of Junggar Basin of Xinjiang, endangered and protected species. In this paper,fruit-set patterns, effect of different storage condition on seed germination, and effect of the lemma ondispersal, seed germination and seed viability of L. racemosus were studied manipulatively both in field,laboratory and the ecological adaptive strategies of this species in the harsh environment of Jungaer desertwere analyzed. The main results are as follows:(1)The fruit-set patterns: The fruit-set patterns of the different populations, different part of an ear andspikelets of desert plants L. racemosus was studied continually for2years. The results showed that:①Proportion of the Panicle length, spike width, total flowers, seed setting rate and large seeds of L.racemosus in all five populations in2011was higher than in2012; but the numbers of small seeds in2011was lower than in2012; Seed setting rate in the five populations was P2> P3> P1> P5> P4.②Thesequence of the panicle length, spike width, numbers of total flowers and seed setting rate of spikelets ondifferent part of ear were showed middle part> lower part> upper part.③The flowers and seeds on perspikelet were3.7±0.56and0.6±0.09, respectively. And the seed setting rate on the base part of spikeletreached the highest level. By combining two years observation of Climatic factors and differentpopulations’ environmental conditions in the period of duration, we found that the seed setting rate of L.racemosus is very sensitive to the interannual and environmental changes. That moisture and temperatureare the main factors that influence the fruit-set patterns of L. racemosus.(2)Effect of the storage condition on seed germination of L. racemosus：seed germination increasedinitially and then decreased slowly as increases the time of dry storage and buried in the soil surface,indicating that the seeds presence of after-ripening in this species. After2,7, and8months of burial, naturalgermination percentage of seeds buried at depth of5cm was5.15%,7.52%and94%, respectively. Thepercentage of ungerminated seeds (in natural condition) was>95%in laboratory. After2months of burial(in the natural habitat), did not observe germination of any seeds, and after8months of burial, which wasrising90%germination; Moisture content of seeds at different storage conditions was buried at depth of5cm> buried in the soil surface> dry storage in laboratory, and minimum moisture content of seeds was19.5%. In the natural habitat,12~90%(mean44.5%) of burial seeds were removed by animal, as a result,the number of seeds in soil had declined. It could be concluded that this specious form a transient seed bank, seeds after-ripening. Germination percentage of seeds of L. racemosus increased by darkness.(3)Effect of the lemma on dispersal, seed germination, seed viability and seed water absorption andwater loss of L. racemosus:the results showed that in still air, the landing speed of two kinds of disporesafter treatment was seeds without lemma> intact seeds; but the horizontal airflow at different wind speeds,the dispersal distance of two kinds of dispores was intact seeds> seeds without lemma; the lemma did notsignificantly effect on seed germination and seed viability, then no allelopathy to seeds; intact seeds wasslowly rised and decreased than seeds from without lemmas during the imbibition and dehydration. It canbe concluded that the intact seeds had enhanced the dispersal ability of fruit by wind, to better expand L.racemosus new living space, which indicating that lemma of intact seeds has batter keep-water ability onseed, to meet the conditions required for seed germination in arid environments.