Lucerne( Medicago sativa L.) is a plant of strict allogamy,and its pollination relies on bees mainly. Genetic variations of lucerne floral properties,including receptacle diameter,coronary length,number of flowers per raceme,number of racemes per twig,number of flowers per square metre,percentage of tripped flowers,nectar production,sugar concentration in nectar and contents of sucrose,fructose and glucose in nectar,have been studied with morphological markers,and floral properties of ten lucerne cultivars were also investigated to determine their role in number of visiting bees and to provide a basis for the evaluation of mutant flowers for visitation by bees. The results showed CV( coefficient of variation) of floral properties was from 0. 80% to 92. 30%,of which the content of glucose was the most significant one with variation from 0. 01 to 0. 53 μmol /L( P < 0. 05),and the sugar concentration was the most insignificant one( P > 0. 05). The significant order of floral properties affecting the number of visiting bees was that the nectar production per square metre( r = 0. 93,P < 0. 01) was in the first place,followed by the number of flowers per square metre( r = 0. 92,P < 0. 01),sucrose concentration of nectar sugar( r = 0. 82,P < 0. 05),coronary length( r = 0. 77,P < 0. 05) and nectar production per flower( r = 0. 71,P < 0. 05).
Soil pH is a main factor that affects the nodule formation and nitrogen fixation. The largely reduced nitrogen fixation effect caused by acid soil is the major limitation of alfalfa growth in the south of China. Thus selection of anti-acid nodule for inoculating on alfalfa is of great significance in practical production.Using nine candidate rhizobia( Rhizobium meliloti L.) as study objects,their colony diameters and the nodule number of each strain inoculated alfalfa variety were investigated at different pH conditions. The YNCY006 strain presented the strongest resistance to acid,while YNCY007 strain presented the weakest. For nodulation,GT13 R alfalfa inoculated with YNCY006 or YNCY008 strains was the best symbiosis system in the acidic soil.
