| Leymus chinensis, a member of the family gramineae, is a perennial rhizome grass. Grasslands dominated by L. chinensis are widely distributed at the eastern end of the Eurasian steppe, the high palatability of L. chinensis and herbage production superior both in quality and quantity make the grasslands ideal for grazing and forage production. As it is an economically and ecologically important grass, this species has received considerable attention. One of the toughest problems faced for man-made propagation is its low sexual reproductivity, yet the causes of low fecundity of this species are uncertain. To better understand the causes of low fecundity, many aspects of the reproductive ecology in L. chinensis were studied. The main result are as follows.The flowers of I. chinensis are hermaphroditic and arranged in compound spikes Each flower has one pistil surrounded by 3 anthers. The mature pistil has two laterally feathery stigmas and a hairy ovary. Each anther has two microsporangia, each bearing two chambers. The ovary has one locule, containing one ovule. The ovule is anatropous, unitegmic and tenuinucellar. The ovary is superiorly positioned with basal placentation.Observed under the light microscope and laser scanning confocal microscopy, both of the megasporogenesis and female gametophyte are normal, and seldom abort. The archesporial cell originates from a single cell. It develops directly into megaspore mother cell. The dyad is formed after the first division, and meiosis II, resulting in a linear tetrad. Only the chalazal megaspore is functional and the upper three megaspores degenerate. The nucleus of the functioning megaspore divides to form nuclei. Subsequent divisions result in 4 and 8-nucleate stages, thus the development ofIVthe female gametophyte conforms to the Polygonum type. In a mature embryo sac, the egg apparatus consists of a egg cell with a vacuole and two synergids at the micropylar end. The two polar nuclei were at the lower middle part of the embryo. The number of nuclei in each antipodal cell increases up to tens before fertilization.Stained with TTC the pollen viability of L. chinensis was only 62.4%. Laser scanning confocal microscopy (LSCM) observations showed that, approximately 53.1% of the pollen germinated on the surface of the stigma, and the pollen tubes grew down the style all these readily visualized by staining callose in the pollen tubes with aniline blue. TTC tests showed that the pollen could survive about 3 h at room temperature.The pistil receptivity of L. chinensis lasted for about 3 h after anthesis. The number of pollen grains reaching the stigma (pollination success) gradually increased during the period of receptivity. There were approximately 86.7% of pistils were pollinated with an average of 16.5 pollen grains per pistil by the end of the period of receptivity. There was no further more significant increase thereafter. The low viability and short longevity of the pollen may lead to low fecundity of L. chinensis. The pollen-ovule ratio (P/O) was 79332/1. The flowers usually dehisce synchronously or basipetally within a spike between 14:00 h and 18:00 h on June 26 to June 30, and the highest density of pollen flow was occurred on June 28. High variability was found in pollen density among different times within an individual day and different positions within a spike. The climax of pollen dispersion occurred at 16:00 h to 17:00 h, during which 56.1% of the total pollen during the 4 h collection period were obtained. Among different positions in a spike, the highest pollen density was in the middle position.Much variation was observed in the fecundity in relation to different densities of pollen flow. In the whole period of pollination (June 26 to June 30), the variation of fecundity tended to be similar to that of pollen flow. Within an individual spike, the highest fecundity was found at the middle position. No seeds were produced if the spikes were wrapped with bags.The microgenesis and male gametophyte of L. chinensis are normal alth...
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