Effects Of Stamens Differentiations On Pollination Mechanism And Breeding System Of Two Glycyrrhiza Species

The Glycyrrhiza species has dimorphic stamens, namely long-and short-level stamens. The aims ofthis paper are (1) to describe the development of the stamens in Glycyrrhiza glabra L. and Glycyrrhizauralensis Fisch.(from the bud stage to full bloom) to determine what difference of stamen dimorphism inshape and variability of timing and position of stamen and (2) to determine the function role of long-andshort-level stamens in the pollination processes and its adaptive significance.The development of stamens (measurement of the filament, anther, and style lengths at fivedevelopment stages) and variability of timing and position of dimorphic stamens were observed underdissecting microscope. Pollen morphology was recoded with scanning electron microscopy. Also, thepollen vitality, quantity and chemical composition of pollen were counted and detected. In addition, thefruit set of different pollination treatments and the pollinator behavior of insects on different floralcomponents were also compared to examine to what extent the long-and short-level stamensdifferentiations.Glycyrrhiza glabra’s development characteristics consistent with Glycyrrhiza uralensis. Longerstamens anthers is ovate, shorter stamen anthers is kidney-shaped. In the early development stages longstamens filament length was significantly longer than the short stamens, anthers significantly greater thanthe short stamens. With the pollen mature and spread out in later development stage, the differencedecreases gradually. The pistil is always higher than the stamens, and the different developmental stagesectopic start with a small distance between the two large. The arrayal shape of stamens changed from tworows order in early time to inverted “V”-shaped arrangement at later stage. This change of timing andposition of stamens resulted in different quantity and vitality of pollen at different spaces, indicating thatthe flower of Glycyrrhiza glabra L. with the less male resources to obtain the most high pollinationefficiency and to improve the functionality of male.There were no differences in pollen grain morphology and size of two licorice’ dimorphic stamenswere observed by Pollen scanning electron microscope. Equatorial view of pollen grains in longer andshorter stamens are ellipsoidal or prolate spherical and polar view are3crack round with tricolporate.Glycyrrhiza glabra surface ornamentation of pollen with foveolate-fine reticulate, Glycyrrhiza uralensis isa fine mesh. The longer and shorter stamens’ pollen size of Glycyrrhiza glabra and Glycyrrhiza uralensiswere no significant difference between the dimorphic stamens. Histochemical of longer and shorter stamensin licorice plants pollen grains was no significant difference too. The number of Glycyrrhiza glabra longerstamen pollen grains about2times for the short stamens, there is a very significant difference (n=10; t=6.67, P <0.01). The number of Glycyrrhiza uralensis longer stamen pollen grains is about1.7times for theshort stamens, there are also a very significant difference (n=10; t=4.86, P <0.01). In addition, theviability of longer stamen pollen grains stronger than shorter stamen pollen in licorice plants.Differentiation may be due to the adjustment of the allocation of resources in the flower. Studies show that two liquorices flower-visiting frequency reduced when remove stamens in a singleday of the peak period of two flower-visitingthe. In this way Glycyrrhiza glabra seed setting rate isgenerally higher than the natural control. The results indicate that remove stamens to reduce theinterference between stamens and stigma and to improve the pollination rate. Glycyrrhiza uralensisemasculation process result in seed setting rate is generally lower than the control, indicating theGlycyrrhiza uralensis emasculation treatment’s ability to attract visitors reduce and eventually led todecline in seed rate, seed rate of treatment emasculate longer stamens were significant differences control.Two kinds of licorice plants seed rate differences may be due to the different species in the evolution of thelevel of inconsistency caused.Glycyrrhiza glabra and Glycyrrhiza uralensis’ long-and short–level stamens seed rate was nosignificant difference in artificial pollination selfing, geitonogamy, intraspecific outcrossing, interspecifichybridization. Glycyrrhiza glabra seed setting rate of descending order: mixed pollen interspecifichybridization, mixed pollen intraspecific outcrossing, natural control, a single type of pollen intraspecificoutcrossing, selfing of a single type of pollen; the Glycyrrhiza uralensis seed setting rate from high to low:mixed pollen interspecific hybridization, natural control, mixed pollen intraspecific outcrossing, pollenfrom a single type intraspecific outcrossing, selfing of a single type of pollen. Two licorices dimorphicstamen differentiation had no effect on the breeding system, mixed pollen more conducive to fructificationin Glycyrrhiza glabra and Glycyrrhiza uralensis.In summary, long-and short-level stamens of Glycyrrhiza glabra and Glycyrrhiza uralensis are"pollinating" stamens. Their dimorphic stamens does not exist functional differentiation.