氮肥对紫花苜蓿根系形态发育的影响
摘要
紫花苜蓿(Medicago sativa L.)是各种家畜的优质饲草,其营养价值,经济价值均较高。随着我国农业产业结构的调整,南方农区奶牛业的兴起,当地的优质饲草缺口逐年加大。近年来,科研人员在南方农区冬闲田进行紫花苜蓿短期速生栽培的研究显示可获得较好的产量,并根据南方农区的生态条件和耕作制度设计出紫花苜蓿与粮经作物复种的季节性种植模式,配套相应的高产栽培技术。紫花苜蓿在南方农区具有非常大的种植潜力。但南方农区的生境条件与传统观念上紫花苜蓿的生长环境有着显著的差异。因此,明确适宜南方农区高产栽培的紫花苜蓿根系类型,及其在施用氮肥条件下紫花苜蓿根系形态发育和营养积累的变化,对当地推广种植紫花苜蓿具有重要意义。研究结果如下：
一、通过砂培试验对6个紫花苜蓿品种苗期的根系性状进行研究,明确不同品种间的根系差异。研究发现品种间在主根和根颈直径、侧根数、侧根密度、根系干重等方面具有显著差异。5叶期,赛迪10的根颈直径为1.41mm,二级侧根数为29.2个,显著大于其他供试品种；游客主根根颈下0-2cm段的一级侧根数达63%,较其他品种相同部位侧根密集。具有主根及根颈直径较大,侧根发生数目较多,一级侧根集中分布于主根根颈下0～2cm内的根系特征的紫花苜蓿品种,更适宜南方农区的生境条件。
二、以6个紫花苜蓿品种为试验材料,经过不同的施氮处理,通过盆栽及大田试验,在各生育期对其根系形态的差异,植株中营养成分的变化进行比较分析,从而明确氮肥对紫花苜蓿根系形态及营养成分积累的影响。试验结果显示,氮肥有效地促进了紫花苜蓿根系中主根及根颈膨大,第一侧根发生位置上移,根系干重增加,这些根系性状是促进地上部干重增加的有效因子。初花期施氮量为160 kgN·hm-2时,主根及根颈直径分别为7.74mm和9.28mm,较不施氮处理的膨大速度快22%和16%；第一侧根位于根颈下0.40cm,与不施氮处理相比上升0.06cm；单株根系干重为3.84g,较不施氮增加30%。施氮量为80 kgN·hm-2时也有相似表现。施氮肥后,紫花苜蓿植株中的氮含量呈显著上升趋势,施氮量为80 kgN·hm-2、160 kgN·hm-2时,植株体内的氮含量显著高于不施氮处理；紫花苜蓿根系中非结构性碳水化合物的含量先下降后上升,施氮量为80～160 kgN·hm-2时,根系中非结构性碳水化合物的积累量在初花期到盛花期高于不施氮处理。
综合以上研究结果,在南方农区进行紫花苜蓿的推广种植时,可将主根及根颈直径,侧根数目,一级侧根在主根根颈下0-2cm内的密集度作为目标性状进行筛选。氮肥对主根及根颈直径、侧根位置、根系干重具有显著地促进作用。施氮肥后,紫花苜蓿植株体内的氮含量显著上升,根系中的非结构性碳水化合物在初花期到盛花期也得到大量积累,尤其以施氮量为80～160 kgN·hm-2时表现较好。
Alfalfa (Medicago sativa L.) is the excellent forage for animals. Along with the adjustment of agricultural industrial structure and popularization of grain saving livestock husbandry in China, herbivorous livestock, especially dairy cows, is increasing significantly in southern agricultural regions. However, forage of high quality gap is increasing yearly. In recent years, researchers conducted lots of experiments on alfalfa short term cultivation on winter-fallow fields in southern agricultural regions. They proved that alfalfa could gain high yield. According to the ecological condition and planting system, alfalfa was planned as an after crop in paddy field with techniques of high yield cultivation. But there are certain differences between local environments and alfalfa growing conditions. So, it is of great significance to know that in southern agricultural regions, which kind of alfalfa root can grow better, and how the alfalfa root morphology and nutrients accumulations will change under nitrogen application. The research showed:
1. In order to clarify the differences of root morphology, the study on 6 alfalfa cultivars through sand culture experiment showed that, there were significant differences among taproot and root crown diameter, lateral root number and density and root dry matter yield. In 5th leaf age, the root crown diameter of Sidey 10 was 1.41mm. The second lateral root number of Sidey 10 was 29.2. The first lateral root number in 0-2cm of Eureka was up to 63%. The alfalfa cultivar, with special root type which was wide taproot and root crown diameter, plenty of lateral roots and lateral roots gathering below root crown 0～2cm, was superior to be popularized in southern agricultural regions.
2. The study was on 6 alfalfa cultivars through pots and winter-fallow field experiments. The purpose was to investigate root morphology changes and nutrients accumulations under different nitrogen application. The results indicated that nitrogen fertilizer could wide taproot diameter, root crown diameter, increase root dry matter yield, and move up first lateral root position significantly. These root traits were effectively correlated with shoot dry matter yield. Under the nitrogen application of 160 kgN·hm-2, taproot and root crown diameter were 7.74mm and 9.28mm, faster than the growth of non-nitrogen application by 22% and 16% at the early blooming stage. The first lateral root emerged below root crown 0.40cm, moving up by 0.06cm of non-nitrogen application. The root dry matter yield was 3.84g per plant, increasing by 30% of non-nitrogen application. There were similar performances under the nitrogen application of 80 kgN·hm-2. Meanwhile, nitrogen content in alfalfa plant was significantly increasing with the nitrogen application, especially at treatments of 80 kgN·hm-2 and 160 kgN·hm-2. The non-structure carbohydrate (NSC) in alfalfa root decreased firstly and increased then. From early blooming stage to full blooming stage, the NSC accumulation under 80～160 kgN·hm-2 was higher than that under non-nitrogen treatment.
All results above revealed that, such root traits, which were taproot and root crown diameter, lateral root number, the density of first lateral root below root crown 0～2cm, were important for alfalfa to be popularized in southern agricultural regions. Nitrogen fertilizer could significantly promote taproot and root crown diameter, first lateral root position and root dry matter yield. Also, under nitrogen application, nitrogen in alfalfa plant was increasing remarkably; the NSC in alfalfa root was accumulated heavily from early blooming stage to full blooming stage.
一、通过砂培试验对6个紫花苜蓿品种苗期的根系性状进行研究,明确不同品种间的根系差异。研究发现品种间在主根和根颈直径、侧根数、侧根密度、根系干重等方面具有显著差异。5叶期,赛迪10的根颈直径为1.41mm,二级侧根数为29.2个,显著大于其他供试品种；游客主根根颈下0-2cm段的一级侧根数达63%,较其他品种相同部位侧根密集。具有主根及根颈直径较大,侧根发生数目较多,一级侧根集中分布于主根根颈下0～2cm内的根系特征的紫花苜蓿品种,更适宜南方农区的生境条件。
二、以6个紫花苜蓿品种为试验材料,经过不同的施氮处理,通过盆栽及大田试验,在各生育期对其根系形态的差异,植株中营养成分的变化进行比较分析,从而明确氮肥对紫花苜蓿根系形态及营养成分积累的影响。试验结果显示,氮肥有效地促进了紫花苜蓿根系中主根及根颈膨大,第一侧根发生位置上移,根系干重增加,这些根系性状是促进地上部干重增加的有效因子。初花期施氮量为160 kgN·hm-2时,主根及根颈直径分别为7.74mm和9.28mm,较不施氮处理的膨大速度快22%和16%；第一侧根位于根颈下0.40cm,与不施氮处理相比上升0.06cm；单株根系干重为3.84g,较不施氮增加30%。施氮量为80 kgN·hm-2时也有相似表现。施氮肥后,紫花苜蓿植株中的氮含量呈显著上升趋势,施氮量为80 kgN·hm-2、160 kgN·hm-2时,植株体内的氮含量显著高于不施氮处理；紫花苜蓿根系中非结构性碳水化合物的含量先下降后上升,施氮量为80～160 kgN·hm-2时,根系中非结构性碳水化合物的积累量在初花期到盛花期高于不施氮处理。
综合以上研究结果,在南方农区进行紫花苜蓿的推广种植时,可将主根及根颈直径,侧根数目,一级侧根在主根根颈下0-2cm内的密集度作为目标性状进行筛选。氮肥对主根及根颈直径、侧根位置、根系干重具有显著地促进作用。施氮肥后,紫花苜蓿植株体内的氮含量显著上升,根系中的非结构性碳水化合物在初花期到盛花期也得到大量积累,尤其以施氮量为80～160 kgN·hm-2时表现较好。
Alfalfa (Medicago sativa L.) is the excellent forage for animals. Along with the adjustment of agricultural industrial structure and popularization of grain saving livestock husbandry in China, herbivorous livestock, especially dairy cows, is increasing significantly in southern agricultural regions. However, forage of high quality gap is increasing yearly. In recent years, researchers conducted lots of experiments on alfalfa short term cultivation on winter-fallow fields in southern agricultural regions. They proved that alfalfa could gain high yield. According to the ecological condition and planting system, alfalfa was planned as an after crop in paddy field with techniques of high yield cultivation. But there are certain differences between local environments and alfalfa growing conditions. So, it is of great significance to know that in southern agricultural regions, which kind of alfalfa root can grow better, and how the alfalfa root morphology and nutrients accumulations will change under nitrogen application. The research showed:
1. In order to clarify the differences of root morphology, the study on 6 alfalfa cultivars through sand culture experiment showed that, there were significant differences among taproot and root crown diameter, lateral root number and density and root dry matter yield. In 5th leaf age, the root crown diameter of Sidey 10 was 1.41mm. The second lateral root number of Sidey 10 was 29.2. The first lateral root number in 0-2cm of Eureka was up to 63%. The alfalfa cultivar, with special root type which was wide taproot and root crown diameter, plenty of lateral roots and lateral roots gathering below root crown 0～2cm, was superior to be popularized in southern agricultural regions.
2. The study was on 6 alfalfa cultivars through pots and winter-fallow field experiments. The purpose was to investigate root morphology changes and nutrients accumulations under different nitrogen application. The results indicated that nitrogen fertilizer could wide taproot diameter, root crown diameter, increase root dry matter yield, and move up first lateral root position significantly. These root traits were effectively correlated with shoot dry matter yield. Under the nitrogen application of 160 kgN·hm-2, taproot and root crown diameter were 7.74mm and 9.28mm, faster than the growth of non-nitrogen application by 22% and 16% at the early blooming stage. The first lateral root emerged below root crown 0.40cm, moving up by 0.06cm of non-nitrogen application. The root dry matter yield was 3.84g per plant, increasing by 30% of non-nitrogen application. There were similar performances under the nitrogen application of 80 kgN·hm-2. Meanwhile, nitrogen content in alfalfa plant was significantly increasing with the nitrogen application, especially at treatments of 80 kgN·hm-2 and 160 kgN·hm-2. The non-structure carbohydrate (NSC) in alfalfa root decreased firstly and increased then. From early blooming stage to full blooming stage, the NSC accumulation under 80～160 kgN·hm-2 was higher than that under non-nitrogen treatment.
All results above revealed that, such root traits, which were taproot and root crown diameter, lateral root number, the density of first lateral root below root crown 0～2cm, were important for alfalfa to be popularized in southern agricultural regions. Nitrogen fertilizer could significantly promote taproot and root crown diameter, first lateral root position and root dry matter yield. Also, under nitrogen application, nitrogen in alfalfa plant was increasing remarkably; the NSC in alfalfa root was accumulated heavily from early blooming stage to full blooming stage.
引文
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