播期对夏谷幼穗分化及叶龄指数的影响

Effects of Sowing Dates on Panicle Differentiation and Leaf Number Index of Summer-Sowing Foxtail Millet [Setaria italica(L.) Beauv.]

【目的】研究不同播期条件下,夏谷品种幼穗分化进程及各分化阶段与叶龄指数之间的关联,为谷子生产调控和生长模拟提供依据。【方法】在山东省农业科学院作物研究所济南试验基地,以抗拿捕净除草剂夏谷品种济谷16和糯性新品种济谷18为材料,于2015年4月29日至7月8日设置8个播期处理,处理间隔为10 d。60万株/hm2大田生产条件下按播期顺序种植试验小区。在5叶期,每个小区内标记生长均匀一致的谷子植株120株,之后到抽穗每隔1—2 d选取有代表性的植株3—5株,在OLYMPUS SZX16数显体视显微镜下剥去样品苞叶至露出完整幼穗,进行系统观察与拍照,并详细记载不同播期条件下2个品种在各幼穗分化阶段的叶龄以及成熟期植株的总叶片数。【结果】播期和品种对夏谷幼穗分化的方式及形态特征没有影响,依据营养生长期、生长锥伸长期、枝梗分化期、小穗刚毛分化期和雌雄蕊分化期等5个幼穗分化阶段的特点,以济谷16的系列穗发育图片为例,清晰完整的描述了夏谷幼穗发育过程。播期对谷子生育期的影响主要是由于幼穗分化时期的起始时间和持续天数的变化引起。随着播期的推迟,幼穗分化时期的起始时间提前,由出苗后32 d变为22 d左右;幼穗分化过程的持续时间缩短,由28 d变为19 d左右;谷子生育期缩短,由109 d变为83 d左右。在不同的幼穗分化时期,叶龄和叶龄指数随播期的推迟变化趋势不同,而叶龄指数与幼穗分化时期在不同播期间保持着更为稳定的对应关系。2个品种在不同播期条件下,幼穗分化阶段与叶龄指数均符合直线回归关系,R2值在0.977—0.997,表现为极显著正相关,幼穗分化期Y依叶龄指数X的直线回归方程通式为:Y=b X+a,且不同品种在不同播期条件下对应的直线回归方程之间的差异达到极显著水平,济谷16、济谷18在不同播期条件下幼穗分化时期与叶龄指数的直线回归关系不可以用共用的直线回归方程来表示。【结论】2个夏谷品种幼穗分化发育形态基本一致,但播期对2品种幼穗分化的影响有所不同。播期造成的幼穗分化时间的差异是影响谷子生育期的主要原因。根据植株外部叶龄状态判断谷子幼穗分化时期是可行的。

【Objective】The panicle differentiation of summer-sowing foxtail millet and its relationship with leaf number index were investigated under different sowing times, so as to provide an application basis for millet production and growth simulation.【Method】Summer-sowing foxtail millet varieties Jigu 16 with sethoxydim resistance and Jigu 18 with waxy endosperm were used as materials, which were planted in plots in the order of sowing time in Jinan Experiment Station of Crop Research Institute, Shandong Academy of Agricultural Sciences. Eight sowing treatments were applied during April 29 to July 8, 2015 at the interval of 10 days. Plant density was set at 600 000/hm2. One hundred and twenty uniform seedlings at five-leaf stage were tagged in each plot for sampling. Thereafter, 3 to 5 plants were sampled at the interval of 1 to 2 days until heading. The young leaves were deliberately stripped till the young inflorescence fully presented under the OLYMPUS SXZ16 digital stereoscopic microscope to observe the morphological development of young inflorescence, and the leaf number and leaf number index were determined at different stages. The total leaf number was recorded at mature stage.【Result】The sowing date and varieties had no effect on the development pattern and morphological characteristics of the panicle differentiation in summer-sowing foxtail millet. Based on panicle differentiation characteristics of vegetative stage, elongation stage, panicle branch differentiation stage, spikelet and bristles protuberances stage and gynoecium and stamen formation stages, the young panicle development process was clearly and systematically characterized by referring series pictures of Jigu 16 panicle differentiation. The influence of sowing date on foxtail millet was predominantly incurred by the starting date and lasting time of young panicle differentiation. With sowing date delayed, the starting date of panicle differentiation was advanced from 32 days to 22 days after germination compared the earliest sowing treatment with the latest sowing treatment. The lasting time of panicle differentiation process was shortened from 28 days to 19 days. And the growth duration was from 109 days to 83 days. The changing tendency of leaf number and leaf number index showed a significant difference at each panicle differentiation stage, and the relationship of panicle differentiation stage with corresponding leaf number index was relatively stable in various sowing treatments. The regression analysis showed significant differences and positive linear correlation at 0.01 level between the panicle differentiation stage and leaf number index for each variety in different sowing treatments. The value of R2 was in the range of 0.977 to 0.997. The linear regression formula of young panicle differentiation stage（Y） to leaf number index（X） was as follows： Y= b X＋a, and the linear regression relationship of panicle differentiation stage with leaf number index could not be expressed by a same formula for Jigu 16 and Jigu 18 with different sowing times.【Conclusion】The development pattern of panicle differentiation of two summer-sowing foxtail millet varieties was basically similar, however, the influence of sowing dates on panicle differentiation was different. The time difference of panicle differentiation stages caused by sowing date primarily determined the growth duration. Panicle differentiation stages of foxtail millet could be forecasted according to leaf number indexes.