Effects of wind speed,underlying surface,and seed morphological traits on the secondary seed dispersal in the Tengger Desert,China

The maintenance of sand-fixing vegetation is important for the stability of artificial sand-fixing systems in which seed dispersal plays a key role.Based on field wind tunnel experiments using 11 common plant species on the southeastern edge of the Tengger Desert,China,we studied the secondary seed dispersal in the fixed and semi-fixed sand dunes as well as in the mobile dunes in order to understand the limitations of vegetation regeneration and the maintenance of its stability.Our results indicated that there were significant variations among the selected 11 plant species in the threshold of wind speed(TWS).The TWS of Caragana korshinskii was the highest among the 11 plant species,whereas that of Echinops gmelinii was the lowest.Seed morphological traits and underlying surface could generally explain the TWS.During the secondary seed dispersal processes,the proportions of seeds that did not disperse(no dispersal)and only dispersed over short distance(short-distance dispersal within the wind tunnel test section)were significantly higher than those of seeds that were buried(including lost seeds)and dispersed over long distance(long-distance dispersal beyond the wind tunnel test section).Compared with other habitats,the mobile dunes were the most difficult places for secondary seed dispersal.Buried seeds were the easiest to be found in the semi-fixed sand dunes,whereas fixed sand dunes were the best sites for seeds that dispersed over long distance.The results of linear mixed models showed that after controlling the dispersal distance,smaller and rounder seeds dispersed farther.Shape index and wind speed were the two significant influencing factors on the burial of seeds.The explanatory power of wind speed,underlying surface,and seed morphological traits on the seeds that did not disperse and dispersed over short distance was far greater than that on the seeds that were buried and dispersed over long distance,implying that the processes and mechanisms of burial and long-distance dispersal are more complex.In summary,most seeds in the study area either did not move,were buried,or dispersed over short distance,promoting local vegetation regeneration.

Variability in the Content of 25α- and 25β-Steroidal Sapogenins among Thirty Morphologically Different Sudanese Seed Accessions of Fenugreek

Seeds of Fenugreek （Trigonellafoenum-graecum L.）, an international spice commodity, are much consumed in Sudan as a food, for flavoring and as a folk-remedy for several ailments, together with local beliefs in nutraceutical benefits. The authors have noted an immense variability in colour and other morphological characters of Fenugreek seeds offered in local Sudanese markets and wondered whether this variability is extended to their chemical composition. Steroidal sapogenins are important chemical constituents of Fenugreek seeds in view of their potential as precursors for the commercial synthesis of steroid drugs and their continually revealed beneficial biological activities. In this study, thirty Sudanese Fenugreek seed accessions collected from different geographical regions in Sudan were analyzed for their 25α-, 25β- and total sapogenin content using a simple and specific infra-red spectroscopic method. The seed accessions exhibited much morphological variability particularly in outer seed coat color and size. Preparative TLC followed by gravimetric analysis showed that steroidal sapogenins, mostly diosgenin and yamogenin, represented more than 70% of the steroids of Fenugreek seeds. Infra-red spectroscopic analysis showed that total 25α-sapogenins （calculated as diosgenin） varied from 0.65% to 1.68%. Total 25β-sapogenin （calculated as yamogenin） varied from 0.38% to 2.03%. The content of total sapogenins （α ＋ β epimeric forms） varied between 1.24% and 3.0% of the oven-dry weight of seeds. β-sapogenins （mostly yamogenin） were dominant over α-sapogenins （diosgenin） in most Sudanese Fenugreek seed accessions.

Seed Morphology and Seedling Variation of Four Ornamental Lupin Pedigrees

[Objective] This study was conducted to reveal seed characteristics, variation and their effects on seedling growth of ornamental lupins. [Method] The phenotypic characteristics and germination rate of the seeds of four excellent lupin pedigrees were measured, and then their correlations with seeding growth were analyzed. [Result] There were abundant variations among the four ornamental lupin pedigrees. Pink seeds had the largest volume and red seeds had the largest 1 000seed weight. The variation coefficients for the seed morphological traits among the four pedigrees ranged from 2.97% to 14.34%. Seed specific weight and 1 000-seed weight could be used as important indicators for selection in breeding because of their higher variability. Seed weight variation of ornamental lupin was mainly depen- dent on seed width variation. There was small variation in seed length. The seeds of the four ornamental lupin pedigrees started to germinate one day after sowing, and the germination period was 5 d. Germination rate coefficient and germination index of pink and red seeds were higher than those of blue seeds, but blue seeds had the largest germination rate. 1 000-seed weight shared significantly positive correlations with seed germination rate, germination potential and seedling retention rate. Round and large seeds had some advantages in germination. Full seeds had higher germination rate and speed, and seedling retention rate. There was a significant relationship between seed length-width ratio and the number of leaflets of seedlings. [Conclusion] The results provided references for the evaluation of seed phenotypic diversity and breeding research of ornamental lupins.

Which factors have stronger explanatory power for primary wind dispersal distance of winged diaspores:the case of Zygophyllum xanthoxylon(Zygophyllaceae)?

Aims How seed dispersal distance is related to various factors is a major challenge for seed ecologists.However,there are different answers as to which factor is most important in determining wind dispersal distance.This study is to quantitatively describe the relationship between various factors and primary wind dispersal distance of winged diaspores.Methods The dispersal distances of five morphologies of winged diaspores in Zygophyllum xanthoxylum(Zygophyllaceae)were measured under controlled conditions in a wind tunnel.The explanatory power of environmental factor(i.e.wind speed),plant trait(i.e.release height)and diaspore attributes(i.e.wing loading(the ratio of diaspore mass to projected area),settlement-velocity,shape index(the variance of diaspore length,width and thickness))to the variation in dispersal distance was assessed by releasing diaspores at varying wind speeds and release heights.Important Findings Wind speed and seed release height were the strongest explanatory factors to dispersal distance,contributing 41.1%and 24.8%(P<0.01)to total variation in dispersal distance,respectively.Wind speed accounted more for relatively light disc-shaped seeds than for relatively heavy spherical seeds.Wing loading,shape index and settlement-velocity explained 9.0%(P<0.01),1.4%(P<0.01)and 0.9%(not significant)of the variation in dispersal distance,respectively.From disc-shaped to four-winged diaspores,relative contributions of wing loading and shape index decreased but contribution of settlementvelocity increased.The relative contributions of various factors to wind seed dispersal distance may change with the change in seed morphology.

Kushan Period rice in the Amu Darya Basin:Evidence for prehistoric exchange along the southern Himalaya

The origins and prehistoric spread of rice agriculture between East and West Asia are hot topics in the current archaeological community.In this study,we present the results from a preliminary archaeobotanical study at the Khalchayan site in Uzbekistan,where we recovered the oldest securely dated rice thus far identified in Central Asia.We directly dated the rice grains to 1714–1756 cal yr BP(Kushan period),and morphologically compared them with other contemporaneous cultivated rice remains from China and India.The morphological results showed that the rice remains found at Khalchayan are more similar to cultivated japonica rice from southern China and northwestern India.Integrated archeological and chronological results from the surrounding area show that the rice remains found at Khalchayan likely spread along a southern Himalayan route from southwest China to northern India and finally reached the Amu Darya.The rice remains from Khalchayan are the first directly dated and well-reported rice remains found in Central Asia.By the Islamic period,rice was an important culinary aspect of the culture in Central Asia,but the cultural affinity towards rice only developed over the past two millennia.This study provides new information on the spread of rice agriculture globally,especially in arid-semiarid inland regions.