玉米种子定向种植对根系生长的影响

Effects of seed orientation planting on root growth in summer maize

为探究种子定向种植对根系生长的影响,本研究以夏玉米品种‘郑单958’为对象,于2020—2021年通过发芽纸试验、室外桶栽和田间试验研究了两种灌溉条件下(充分与干旱)尖端朝上(T-U)、尖端朝下(T-D,对照)、胚面朝上(E-U)和胚面朝下(E-D)4个种子定向对玉米根系和地上部分生长的影响。结果表明:在水分充足条件下,EU处理的玉米比其他处理的根系发达(深层根重密度平均高5%、平均根重密度平均高5%、深层根长密度平均高48%、平均根长密度平均高10%),且能够利用较多的土壤水分(18%);同时相比于其他处理,E-U处理的植株具有较宽的叶片生长方位角(35%)、较高的叶面积指数(7%)和地上生物量(3%),最终产量比其他处理平均高8%。相关分析表明,产量与地上部生物量、穗数和收获指数直接相关,与深层根重密度间接相关。干旱条件下,与其他处理相比,T-D处理的玉米种子根生长速率快(36%)、根角度窄(43%)、深层根重密度最高(19%)以及吸收较多的土壤水分(5%),导致即使在叶片生长方位角较窄的情况下仍能获得较高的地上生物量(6%)。总之,在水分充足条件下,玉米地上部与根系分布共同促进了胚面朝向种植处理的产量增长;而在干旱条件下,尖端朝下种植处理的干物质积累主要受根系分布的影响。本研究表明通过调整玉米种子播种方向既可以调控根系分布,又可以改善叶片生长方位角和冠层覆盖度,未来或许可以进一步提高玉米在干旱胁迫下的生物量和产量。

Seed orientation during planting significantly affects crop shoot growth;however,its effect on the root system remains unclear.To explore the effects of seed orientation on above-and below-ground growth,this study used cultivar of summer maize(Zea mays L.,Zhengdan 958)to conduct germination paper,soil pot,and field experiments,from 2020 to 2021.The experiments included two irrigation treatments(irrigation,and non-irrigation or drought)and four seed orientation plantings(tip pointed up,T-U;tip pointed down,T-D;embryo lying up,E-U;and embryo lying down,E-D).The root mass density,root length density,specific root length,soil water content,shoot biomass,and yield of maize were analyzed.The results showed that under irrigation treatment,the root systems of plants in the E-U group were the biggest(5%higher in deep root mass density and average root mass density,48%higher in deep root length density,and 10%higher in average root length density);thus,the soil water consumption was increased by 18%,from bell-mouthed to grain-filling.Additionally,plants in the E-U group had a wider leaf growth azimuth(35%),larger leaf area index(7%),and higher shoot biomass(3%);therefore,the grain yield was also higher(8%).Our correlation analysis showed that grain yield was directly correlated with shoot biomass,ear number,and harvest index;and indirectly correlated with deep root mass density.Under drought conditions,the maize roots under normal T-D treatment had a faster growth rate(36%)and narrower root angle(43%),resulting in the highest root mass density in the deep soil layer(19%),as well as higher soil water consumption(5%);as a result,plants also had higher shoot biomass(6%),even with a narrower leaf growth azimuth.In conclusion,under adequate water conditions,the distribution of the aboveground parts and root system together contributed to the increased grain yield under E-U treatment.Under drought conditions,dry matter production under the normal T-D treatment was mainly affected by root distribution.In the future,adjusting seed orientation when planting may facilitate a further increase in shoot biomass accumulation and yield formation by coinciding with root and shoot development under drought stress.