Alfalfa(Medicago sativa) is a typical perennial autotetraploid and outcrossing plant.The sexual reproduction of alfalfa is susceptible various factors,and its original genetic integrity is easy to lose.Vegetative propagation of alfalfa by stem cutting is extremly important to ensure the genetic stability of alfalfa resources and cultivars.In this research,taking male sterile mutant(ms1) identified in alfalfa as experimental material,the effects of different growth regulator treatments and culture mediums on its clonal propagation were studied.The results showed that,there were significant differences among treatments of three growth regulators on the clonal propagation(P0.05).The efficiency of ABT was the best for the regeneration,and then followed by NAA and IBA.The highest rooting rate reached under treatment of 150 mg·L-1 ABT.Under this treatment,the survival rate was up to 88.3%,which was 71.0% higher than that of the control(P0.05),and also exhibited the good performance of numbers of root(3.94),root length(8.96 cm),rooting effect(0.74) and numbers of leaf(10.46).The survival rate of all the cuttings was not significant different among the five culture mediums(P0.05),while significant differences in the numbers of root,root length,rooting effect and numbers of leaf were found(P0.05).The mixed culture medium was better than the single culture medium,which provided a good support for the growth of cloning plants,and the efficiency of M4(soil + vermiculite + perlite) and M5(soil + sand + perlite) were the best compared to the single garden soil.

Pollen is the foundation of plant reproduction,and successful release of pollen is essential for plant reproduction.Due to the complexity and the diversity of the process of pollen release in papilionaceous plants, the picture of the physiological and the mechanical mechanisms in pollen release is still incomplete.In this paper,the mechanism of pollen release in papilionceous plants is reviewed.The pollen release in papilionceous plants is a complex process,which includes a physiological process(internal release)and a mechanical(or physical)process(extrinsic release).The physiological process of pollen release includes anther formation and anther dehiscence.The formation of viable pollen depends on accurate execution of developmental programmes, and the tapetum cells are essential for the development of the pollen grain.In the case of anther dehiscence, four types of anther wall have been observed in papilionaceous plants including basic type,monocotyledonous type,dicotyledonous type and reduced type.The mechanical process of pollen release shows that there are four patterns in papilionaceous plants:the explosive model,piston model,brush model,and valvular model.Comparisons of pollination efficiency made between these models,showed that the piston and valvular models may be the two basic evolutionary branches of pollen release in papilionaceous plants.The spatial and temporal patterns of pollen release are still a hotspot of evolution in papilionaceous plants and are related to flower morphology,pollination biology and mating system.

紫花苜蓿(Medicago sativa L.)适应性强、生物质产量高,茎可用于生产酒精,叶片可用于家畜饲料,是最具开发潜力的能源植物之一.本文从紫花苜蓿生物能源利用角度出发,系统回顾了近年来紫花苜蓿作为能源植物在种质资源评价、细胞壁主要成分(纤维素、半纤维素、木质素)合成途径及其遗传调控以及栽培管理对酒精生产效率的影响等方面的研究进展,重点讨论了苜蓿细胞壁发育和木质素生物合成基因及其调控效应,并 对紫花苜蓿作为能源植物的研发前景进行了展望.

In the Hupfer method, the P fraction is classified as NH4Cl-P (loosely adsorbed P), BD-P (Fe-P), NaOH-P (Al-P), HCl-P (Ca-P) and residual-P. We extensively extracted the P fraction data from previous pub-lished papers and analyzed all the data together. The results show that total phosphorus (TP) was significantly correlated with NH4Cl-P, BD-P, NaOH-P, HCl-P and residual-P (P<0.001). Quadratic relationships were found between TP and NH4Cl-P, BD-P and HCl-P. There were significant linear relationships between TP and NaOH-P and residual-P. Furthermore, the native P content of sediments, external sources of P loading, resuspension of sediment particles and redox potentials were demonstrated as major factors influencing P distribution. This study provides a novel insight into the mutual correlation of each P composition and will help identify the hotspots of P release region by using fractionation and TP under favorable conditions.

Fifty four alfalfa cultivars were studied in a greenhouse with 2 cutting treatments.ANOVA and cluster analysis based on biomass,cell wall component(cellulose,hemicellulose and lignin) content,plant height, branches and stem/leaf showed the following results:1) there were significant differences for all biofuel traits such as biomass and cell wall compositions between 54 alfalfa cultivars(P<0.01),and the variations within varieties were higher than those among varieties;2) the variation coefficients of biomass and cell wall compositions analyzed in these 54 alfalfa cultivars showed that biomass(42.42%)>content of lignin(17.22%)>content of cellulose(12.74%)>content of hemicellulose(10.04%);3) The content of hemicellulose was significantly affected by cutting treatment,but not for biomass,content of cellulose and lignin;4) Cluster analysis based on biofuel traits divided 54 alfalfa cultivars into 5 groups,of which the groupⅡand the groupⅤhad the highest biomass production performance,and the latter group showed better regeneration.In this study,the comprehensive analysis based on yield production,contents of cellulose,hemicellulose and lignin showed that 8 cultivars-Gannong No.3, Huangyangzhen,WL903,Hetian,Sanditi,Pingliang,Dayushan and Italian alfalfa-could be potential materials for improving alfalfa as a biofuel feedstock in future breeding programs

Seed production of alfalfa (Medicago sativa L.) is important in determining the effective distribution of new cultivars to farmers. However, little is known about the biodiversity and their community function of native wild pollinators of alfalfa in agronomic systems. We investigated the biodiversity of insects which visited alfalfa flowers and their temporal foraging characters in Hexi Corridor, China. A high biodiversity of insect visitors was discovered, 20 insect taxa in all, including 13 species of Hymenoptera, 3 species of Coleoptera, 3 species of Lepidoptera and 1 species of Diptera. Three native bee species, Andrena squamata, Anthophora melanognatha and Megachile abluta,were validated as the principal pollinators. They showed significant variations in tripping mode and their diurnal distribution patterns. Our results indicated that the native wild bees are diverse and they complement each other. This means they have developed a more complex system for the pollination of alfalfa than has been previously found out.

Alfalfa (Medicago sativa L.) is one of the most important forage species worldwide. In order to discover the mechanism of low seed production, two cytological experiments were carried out to investigate ovule numbers per floret and ovule fertility among nine different alfalfa varieties. Results showed that there was significant difference in ovule numbers per floret among the nine alfalfa varieties (P<0.05), and the number of ovules per floret ranged from 7 to 13. The highest ovule number was Huangyangzhen while the lowest one was Ladak. Results also showed that there was significant difference in ovule fertility among different alfalfa varieties (P<0.05), and the average percentage of ovule sterility was 34.90%. The highest percentage of ovule sterility was observed in Russia with 49.07%, while the lowest percentage sterility was 25.20% in Zhungeer. Alfalfa seed set under artificial-pollination showed a significantly linear correlation with ovules per floret (P<0.05) but no significant correlation under self-pollination treatments. The results showed that the fertile ovules per pistil accounted for 51-75% with total ovules per pistil, but the percentages of actual seed yields with potential seed yields of the nine varieties were only 2.49-6.06%, which suggested that ovule sterility maybe just one of the limiting factors for alfalfa seed production. Our results indicated that female fertility of alfalfa was remained in the nature reproductive ability, which was probably due to the breeding selection program of alfalfa that was mainly focused on yield or quality, but seldom on seed production.

Although male sterility is important in obtaining heterosis, there is no widespread exploitation of male sterility in alfalfa breeding. Male sterile mutants could provide the basic materials for carrying out seed production in breeding programmes. In order to establish rapid screening methods from which it is feasible to obtain natural male sterile mutants in alfalfa, methods of pollen production and pollen viability were compared by analysing the genetic variance in 19 alfalfa varieties. Both pollen production and pollen viability varied significantly among varieties, and much higher variations existed within varieties than between varieties. It was determined that there was 87.87% variability within varieties for pollen production and 90.85% for pollen viability. No significant difference was observed between different reproductive branches (P=0.589). Screening by individual plant method, there were 58.48% plants with high pollen production, 33.33% with moderate pollen production, 7.36% with trace pollen production, and 0.83% with no pollen production. In total, 6 male sterile mutants were identified from varieties Graze401+z (ms1, M-fon1 and M-fon2), Longzhong (ms2) and Big west (ms3 and ms4), in which four mutants (ms1-ms4) were male sterile but female fertile mutants and two were multi-pistil male sterile mutants (M-fon1 and M-fon2). The mutants ms1-ms4 showed male sterility accompanied with abnormal anther development and pollen grains degeneration. M-fon1 and M-fon2 mutants developed flowers with multi-pistil, as well as no pollen, thereby displaying both male and female sterility.