Abstract: Due to low seed yield of alfalfa in China,caused by thick sowing and dense plant growth,field experiments of pruning between plantg rows and spraying of growth regulators of paclobutrozol (PP333) and uniconazole (S3307) were conducted in Jiuquan,Ganzu Province,in 2001～2002 to observe the effect to the seed yield and germination.The result shows that compared to the unpruned alfalfa plants,the previous-autumn thinned out plants reduced their shoots per plant by 23.8% and their abortion seeds per pod by 55.6%,while their racemes per shoot increased by 28.1%.As the harvestable racemes per unit area had increased,the seed yield ascended from 563.8 kg/hm² to 763.3 kg/hm²,an increase of 35.4% (P<(0.05)).Pruning of the alfalfa plants the previous autumn and spraying of paclobutrozol and uniconazole in spring during the plant branching period,effectively dwarfed the plants.For this practice,the most effective way is using 0.15 or 0.20 kg/hm² uniconazole solution;for by the harvest time,the plant height,compared to the height of those not being sprayed with the solutions,descended by 19.4% and 17.8% respectively,yet the average pods per raceme increased by 16.5% and 25.3% (P<0.05) respectively.Compared to the 640.4 kg/hm² seed yield of alfalfa plants that hadnot been sprayed with the solutions,those being sprayed tended to gain higher seed yield.When the plants being sprayed with the solutions which contained 1.0 (kg/hm²) paclobutrozol,their seed yield increased by 39.1%,being the highest,with 0.15 or 0.20 kg/hm² uniconazole in the solution,the ratio of hard seed,in comparison to plants not being sprayed,decreased by 7% or 6% respectively.But plants sprayed with a solution containing 0.10 kg/hm² uniconazole had their hard seed ratio increased by 7% (P<0.05),in comparison.Thinning out between rows of close-planting alfalfa seed plots is a key measure to raise the seed proudction.Spraying growth regulator solution on the leaves along,but not pruning the plants,will not raise the seed yield much.

Key words: Grassland science, Alfalfa (Medicago sativa L), Thinning out (Pruning) between rows, Growth regulator

摘要： 针对紫花苜蓿种子生产中因播种量高、密度大、造成种子产量低的问题。2001～2002年,在甘肃酒泉进行行内疏枝与生长延缓剂(多效唑(PP333)和烯效唑(S3307))对种子产量影响的两个试验,并测定种子标准发芽率。结果表明,与未疏枝相比,秋季行内疏枝后,生殖枝密度和荚果的败育种子数降低23.8%和55.6%,生殖枝结荚花序数提高28.1%,种子产量由563.8提高到763.3kg/hm²,增产35.4%(P<0.05);秋季行内疏枝,翌年分枝期叶面喷施多效唑和烯效唑可以有效抑制植株生长,其中以烯效唑有效成分含量0.15和0.20kg/hm²的效果较为明显,收获期株高较对照分别降低19.4%和17.8%,而每个结荚花序的荚果数提高16.5%和25.3%(P<0.05)。与对照(640.4kg/hm²)相比,喷施多效唑和烯效唑后,种子呈增产趋势,其中多效唑(有效成分含量1.0kg/hm²)幅度最大,增产39.1%;烯效唑0.15和0.20kg/hm²处理,种子硬实率较对照分别降低7%和6%;烯效唑有效成分含量0.10kg/hm²处理,硬实率较对照提高7%(P<0.05);对于植株密度过大的种子田,行内疏枝是提高产量的关键,否则只用生长延缓剂控制株高,提高种子产量的幅度不大。

关键词: 草原学, 种子生产, 紫花苜蓿, 疏枝, 生长延缓剂