Reproductive Structure And Seed Compositions Of Gnetum Parvifolium(Warb.) W.C. Cheng

Gnetum belongs to gymnosperm, which possess of some characteristics of angiosperm.Asone of the key groupsinvolved in the origin, it is of high researchvalue.The medicinal andeconomic values are also attractted people’s attention. Gnetum parvifolium(Warb.) W.C.Cheng,a rare and endangered species ofGnetum, has been listed in China Species Red List.However,there were no studies onthe reproductive structure and seed compositionsof G. parvifoliumyet,impeded the conservation and development of it. In the present experiments, by usingtheparaffin section,anatomic observation,Enzyme-Linked Immunosorbent Assay (ELISA) andHigh Performance Liquid Chromatography (HPLC), the reproductive structure, phenologicalperiod of reproductive growth, endogenous hormone in anthesis, seed germination andseedcompositions of G. parvifoliumwere investigated. This paper gave an primary discussiononphyletic evolution of G. parvifolium, laid the foundation forstudyingthe position of Gnetum onthe origin and evolvement of seed plants, additional provided embryological basis for resourcesconservation, introduction and development. The main conclusions were as follows (Theterminology we used in this paper were consistent with the Flora of China1999Edition):(1)Identification ofG. parvifoliumwhich under the field condition should be in floweringstage (from March to May) or fruiting stage (from August to September). The basis ofidentifications were:○1The numbers of male inflorescence involucral collarswere5~12, thenumbers of male flowersand“sterile ovules” in every involucral collar were40~80and8~15respectively;○2The numbers offemale inflorescence involucral collarswere8~12andthenumbers of ovulesin every involucral collar were5~8;○3Seeds sessile or nearly sessile.(2) The arrangements of female inflorescence were whorled and spiral, and the nucelluswere surrounded by three layers of envelopes.From outside to inside, the microstructures ofenvelopes were pseudoperianth (20~25layers of cells), outer integument (4~6layers of cells)and inner integument (3~5layers of cells). There were125~206free nuclei in the female gametophyte, which could exercise the function of egg nuclei. Before fertilization, there wereno indeed egg cellsdifferentiated from the free nuclei.Gnetummight be the most evolutivegroup in gymnosperm, which was in the excessive phase to angiosperms.(3) There were one round of “sterile ovule” and three or four rounds of male flowersinevery involucral collarof male inflorescence, two microsporangia in everymaleflower.Theinflorescence of G. parvifoliumwas compound structure,consisted of ovules andmale flowers which grew on the rachisdirectly. The inflorescence structure of G. parvifoliumwas similar to that of Pinus.(4) The developmental stages of G. parvifoliumfemale(male)inflorescenceincluded budstage, initial-flowering stage, full-flowering stage and bepollinatedstage(pollen-spreadingstage). The phenomenon that two kinds of inflorescence(femaleinflorescenceand “similar maleinflorescence”) could grow on the samefemale plant ofG. parvifolium was discovered for the first time. The ratio of “similar maleinflorescence”in budstage was77.33%, but it degenerated gradually with the development.The result of endogenoushormonesanalysisindicated that the maximum contents of Gibberellin A3(GA3)andZeatinriboside (ZR) were6.65ng·g-1FW and18.62ng·g-1FW, appeared at bud stage offemale inflorescence and were significantly higher than that in other stages; The maximumcontent of Indole-3-acetic acid (IAA)was103.06ng·g-1FW, appeared at bud stage of maleinflorescence. The decrease of GA3andZRcontents, andthe increase of IAAcontent might be thereason of the“similar maleinflorescence”degradation in female plant of G. parvifolium.G.parvifolium was not strictly dioecious plant, and the mechanism of sex differentiation wasoriginal, which made it closer to Pinus.(5) The embryo of G. parvifolium seed was post maturation. Seed germination requiredsix months and lastedfor two months, but the germination rate up to97%. Cold stratificationcould delaygermination for two months and removed the seed shell could expedite germinationfor two months. Seed morphology and nutritional contents were influenced by genetic factorsand growth environment.There were8essential amino acids in G. parvifoliumseed,39.10%ofthe total content. The flavone content was (15.07±0.88)%and italso riched instilbenes, such as Resveratrol (2231.0±1.65mg·kg-1), Isorhapontigenin(1471.7±0.72mg·kg-1) andGnetol(212.0±1.47mg·kg-1).Therefore, G. parvifolium seed has a high value in the aspect ofedible and health care.The size and nutritional contents(except fortotal fatcontent) ofG.parvifoliumseedsin DiaoLuoshan were significantly higher than that in other areas, indicatedthat this region might be more suitable as the introduced domesticated base of Gnetum.