Studies On The Reproductive Biology Of Bambusa Multiplex

In this paper, series of important stages in sexual reproduction of Bambusa multiplex wereinvestigated in details, including flowering morphology, pollen germination, microsporogenesisand male gametophyte development, megasporogenesis and female gametophyte developmentand the growth of pollen tube. In addition, the reason why Bambusa multiplex had lowseed-setting rate was analyzed. The results are as follows:(1) Flowering dynamic and pollen germination of Bambusa multiplex were observed anddetected through the field positioning observation. Some biological characteristics are asfollows: indefinite inflorescence, false spikelet clustered, continuous flowering type, flowerbuds differentiated in October of laster year while bloomed in April, palea and lemma openingwhen flowering, caryopsis and so on. Pollen grain was nearly spherical with a single germ pore.Both the germination rate and the storage rate of pollen grains were very low.(2) The order of the organogenesis of a flower is as follows: lemma, palea, lodicule,stamens and pistil. Stamens6, the order of occurrence of the anther primordium is as follows:the primordia near the rachillae, four primordial at the both sides and the primordia away fromthe rachillae.The anther wall was monocotyledonous type and tapetum was glandular type. Thecytokinensis was successive and the microspore tetrads were bilaterally. Mature pollen grainswere3-cell with one germinal aperture.(3) Some characteristics of pistil development are as follows:1-loculed ovary, parietals,one anatropous ovule with double layers, thick nucellus, megaspore mother cell developed froma female archesporial cell directly, linear megaspore tetrad, the functional megaspore developedfrom the chalazal megaspore and eight nuclear embryosac formed after three times mitosis ofthe functional megaspore. In addition, abnormal structures of the ovary often appeared duringthe pistil development process.(4) The path of pollen tube growth is as follows: The pollen grain began to germinate inthe stigma branch structure in30min after pollination, then pollen tube continued to elongate inthe gap of the branch structure in1-2h after pollination, then it growed into the top of ovary in2-3h after pollination and growed along the gap between the ovary wall and the outerintegument. At last, the pollen tube went into the embryo sac through the micropyle.(5) The reasons why Bambusa multiplex had low seed-setting rate lie in the abnormalstructure of the ovary, the low pollen germination rate and the poor pollination effectiveness.