玉米不同品种根系分布和干物质积累的动态变化研究

对四个不同类型的玉米品种的根系分布动态及其干物质积累进行了研究.结果表明:玉米的根系分布具有相似的规律,在土壤中的垂直分布:在0～40 cm耕层占总根量的50%～60%,41～70 cm占25%～30%,71 cm以下深层相对较少;在土壤中的水平分布:以株为中心由里向外逐渐减少,1/4行距处为40%～45%,1/2株距处为25%～30%,1/2行距处为20%～25%;但不同类型玉米品种也各有特点,掖单22的根系相对比较集中,可以减少行距和株距,增加密度;豫玉22根系分布比较分散,利于充分利用水肥条件,具有     

不同密度处理下玉米根系干重空间分布动态的研究

采用根钻挖掘法对不同密度处理下玉米根系干重在土壤中的空间分布特征进行了研究。结果表明:不同密度处理下,各取样点0～100cm土层内根系干重在整个生育期内均呈单峰曲线变化,峰值出现在灌浆期前后。在1/2行距处随着密度的增加,根系干重呈增加趋势变化;在1/2株距处,中密和高密处理差异较小,但显著大于低密。在1/4行距处,根系干重则随着密度的增加而逐渐减少。根系达到干重最大值后的下降过程均以高密处理的下降速度最快。不同取样点根系干重在土壤中的垂直分布情况为在大喇叭口期以前,根系干重最大值出现在10～20cm的土层内,而后随着土层深度的增加根系干重迅速下降;大喇叭口期以后根系干重在土壤中的垂直分布呈负指数曲线趋势变化。密度对不同取样点根系干重影响主要表现在0～40cm土层内1/2行距处拔节期各密度处理间无明显差异;小喇叭口期到灌浆期表现为高密>中密>低密;成熟期表现为中密>高密>低密。1/4行距处大喇叭口期以前各密度处理之间的差异不明显;从吐丝期到成熟期,中密和低密处理各土层的根重差异不明显,但均较高密处理的大。1/2株距处在大口期以前中密处理和高密处理各土层的根重无明显差异,但均较低密处理高,吐丝期以后各土层的根重则以中密处理最大,高密次之,低密最小。     

秸秆深层还田对玉米根系及产量的影响

针对辽西地区土壤耕层变浅和秸秆浅旋还田造成的土壤漏风跑墒等问题,实施秸秆机械化深层还田与常规耕作(CK)对比试验,测定玉米根系生长状况。结果表明,秸秆深层还田能够增强玉米扎根性能,扩展根系分布空间,扎根深度增加5～10 cm,根系分布空间扩大6000(初生节根)～154500(次生根)cm3;秸秆深层还田的次生根数目明显高于CK,且CK根系主要分布在10～20 cm土层深度,秸秆深松还田处理根系则集中分布在21～30 cm土层深度;秸秆深层还田处理与CK相比玉米产量提高18.16%,差异显著。     

深松条件下春玉米花后衰老过程中根系生物学变化特征

采用PVC管栽方法,研究模拟犁底层和深松处理下春玉米花后衰老过程中根系的生物学变化特征。结果表明,在玉米花后,相同根层节根数均表现为深松处理>模拟犁底层处理。犁底层影响根系在不同深度土壤空间分布,深松处理20～35 cm 土壤深度和36～75 cm 土壤深度玉米根系体积分别比犁底层处理增加176.33%和185.92%;在模拟犁底层处理下,90%以上的根系主要集中在0～20 cm土壤深度,深松处理90%以上的根系主要集中分布在0～35 cm深度土壤。深松增加下层土壤（30～75 cm）根系比重,根系空间分布更加合理。根系衰老进程,花后20 d开始犁底层处理下36～75 cm土壤深度玉米根系衰老速度加快,该深度根系重量开花期比深松处理低2.91%,花后50 d比深松处理低12.31%。犁底层的存在限制玉米根系的发育,深松有利于增加深层土壤的根系分布,能减缓后期根系衰老速度。     

不同土壤类型对玉米干物质积累动态及其分布的影响

研究结果表明:不同土壤类型对玉米干物质积累变化及分布影响较大。(1)砂姜黑土玉米干物质积累较多,且向雌穗、子粒中转运效率也高。(2)砂姜黑土玉米整个根系在土壤中分布较均,下扎较深,深层根量较多;而潮土玉米整个根系主要集中分布于0～20cm土层,下扎较浅,深层根量较少。(3)砂姜黑土玉米单产较高,较潮土玉米增产23.55%。     

不同密度玉米根系在大田土壤中的分布、重量的调节及与地上部分的关系

在早熟玉米新玉4号和中晚熟玉米Sc704单株根系最大重量出现的吐丝期与乳熟末期,采用双向切片法对不同种植密度的玉米挖根观察表明,玉米单株根重随密度增加而显著减少,呈密函数关系,冠根比却与密度呈显著的正相关关系。77％以上的根系集中分布在距植株0～20cm、深40cm的柱状土体内,但Sc704根系在土壤中的分布比新玉4号集中。玉米群体在根量上存在着一定的自动调节作用,且Sc704比新玉4号的调节能力强。吐丝期玉米单株根量达最大值,其同成熟期籽粒产量呈显著正相关。吐丝后上层根开始衰老,但深层根仍在不断增加。     

耕作方式对玉米根系构型及抗根倒伏能力的影响

通过云南典型的红壤坡耕地对土壤实施深松+旋耕 15 cm（SRT）、深松+免耕（SNT）、深松+翻耕 20 cm（SP1）、深松+翻耕30 cm（SP2）、旋耕15 cm（RT）、免耕（NT）、翻耕20 cm（P1）和翻耕30 cm（P2）8种耕作方式,研究对玉米的根系根条数、根直径、入土角度、根幅、生物量及根系抗拔力等的影响。结果表明,深松+翻耕20 cm处理能增加玉米根条数、根系入土角度和10 cm土层处根系生长幅度,增大根系生物量,尤其是深层土壤（20～30 cm）根系生物量,同时对玉米产量也具有提高作用。深松+翻耕30 cm处理能增大根系的垂直抗拔力。因此,土壤通过深耕处理能改善玉米根系构型和分布,进而增强玉米根系抗倒伏能力。     

玉米根系空间分布特性的数学模拟及应用

通过根箱试验获取玉米根系坐标数据,采用方程y=1/1/k+ae~-bx建立根系纵向和横向分布模型,利用模型分析田间氮肥运筹以及不同品种对玉米根系生长及分布的影响,研究玉米根系在土壤中的空间分布特性。结果表明,玉米在拔节期和灌浆盛期,分别约49.7%和20.7%的根系分布在20 cm深度土层内,34.6%和46.6%根系分布在20 cm横向范围内,其纵向和横向累积长度的变化均可用Logistic方程模拟。重基肥处理能够扩大拔节期的根系的空间分布。     

土壤温湿度对玉米根系的影响

采用方形整段标本法,对河北省保定市固城镇中国气象局农业试验基地玉米（屯玉46）不同生育期的根系进行监测,同时对土壤水分、地温进行分析,研究土壤湿度、温度对玉米根系生长发育的影响。结果表明,拔节期和完熟期的根长密度在10～20 cm土层最大,分别为0.49 cm/cm³和1.98 cm/cm³,分别占0～100 cm土层总根长密度的49%和28%;抽雄期和乳熟期则是0～10 cm土层最大,分别为0.45 cm/cm³和1.17 cm/cm³,分别占0～100 cm土层总根长密度的34%和22%。对于土壤水分,50 cm土层以上,不同时期基本保持较为平缓的变化趋势,拔节期和抽雄期40～50 cm土层的水分为整层最大,分别可达18.84%和17.83%;乳熟期和完熟期为50～60 cm土层的水分最大,分别可达22.7%和22.0%。50 cm土层以上,不同生育期玉米根长密度的垂直分布均为向下递减;50 cm土层以下,乳熟期和完熟期的根长密度与土壤水分具有较为一致的变化趋势,水分较多的层次对应的根长密度较大,根系量较多。在土壤剖面中,不同生育期玉米根长密度增长量变化的垂直分布与土壤水分变化的垂直分布较为一致,无偏相关系数分别为0.38、0.9和0.7。地温越高,玉米侧根越细,温度对根系生长发育和生理活性产生一定影响。     

海南中部典型槟榔-象草复合系统中根系空间分布及地下竞争

农林复合系统中，各组分根系的空间分布决定了其对系统内资源的竞争能力，是复合系统设计的重要依据。本文采用带状分层挖掘法，对槟榔–象草复合系统中二者的根系密度和空间分布进行研究，并用Levins提出的生态位重叠公式计算槟榔与象草的地下竞争指数。结果显示，槟榔根系的生物量密度(1343.88 g/m³)是象草(558.53 g/m³)的2.41倍。在水平方向上，槟榔细根(0～2 mm)、中根(2～5 mm)和粗根(>5 mm)的生物量密度、根长密度及竞争指数随根系距槟榔树干基部距离的增加呈下降趋势；象草的根系生物量密度、根长密度及竞争指数则随距离的增加呈上升趋势，且分布相对均匀。水平方向上，在距槟榔树干80 cm内时槟榔的整体根系生物量密度显著大于象草，120～140 cm处时象草的根系生物量密度显著大于槟榔，其余距离内二者之间的差异不显著；20～40 cm处槟榔的根长密度大于象草，但差异不显著，其余水平距离内象草根系的根长密度均显著大于槟榔；除距离树干20～60 cm处，其余区域内象草的竞争指数均大于槟榔。垂直方向上，0～20 cm土层内槟...     

花生根系在土壤中垂直分布特性的研究

花生根系干重在不同深度土层中的垂直分布里指数递减模式。根系干重有６２．６％－８５．５％分布在０—２０ｃｍ耕作层土壤中，１４．７％－２５．２％分布在２０—５０ｃｍ土层中。根系ＴＴＣ还原量、３２Ｐ吸收量随土层深度增加而逐渐降低．根系ＴＴＣ还原量有５０％－６０％分布在０—２０ｃｍ耕作层，３２Ｐ吸收量有４０％－５０％分布在０—２０ｃｍ耕作层。花生根系的吸收能力在深层土壤中占有较高的比例。     

根锚地力在小麦根系研究中的应用

为明确根锚地力在小麦生产和新品种选育中的应用价值,以黄淮麦区24个品种（系）为研究对象,测定和分析了小麦根锚地力并观察根-土复合体状态。结果表明,小麦锚地力相关性状存在较大变异,根锚地力参数受基因型和环境分别单独影响。小麦单茎锚地力、单茎根数、单根锚地力、单茎根干重的均值分别为19.77 N、12.51个、0.17 N和0.13 g,变化范围分别为16.07~24.30 N、9.50~14.8个、1.13~1.97 N和0.10~0.18 g,广义遗传力分别为46.3%、65.6%、11.5%和34.9%。单根锚地力与单茎锚地力呈极显著正相关,与单茎根数呈极显著负相关,相关系数分别为0.65和-0.55。单茎锚地力和单根锚地力与产量等农艺性状多呈显著正相关,而单茎根数和单茎根干重与产量等农艺性状多呈显著负相关。通过聚类分析将24个品种（系）分为4个亚类,其中第IV亚类综合性状优良,周麦22和周麦36为优秀代表品种。根据小麦根-土复合体状态的3种类型和锚地力参数反映的4个水平共划分出12种根系分布形态,L类型水平与垂直根系兼有,且根系发达、抗拉力强、根系活力强是最理想根分布形态。以上结果说明,可以将根锚地力作为小麦栽培及新品种选育的一个重要参数。     

Structure and Function of the Root Cap

The root cap (RC) is a multilayered dome of spindle-shaped parenchyma cells that overlies the growing root tip. It is present in the roots of almost all crop species. This paper briefly reviews some topics on the structure and function of the RC in the major crop species such as maize and rice. Special attention is placed on its contribution to the root system formation, that is, the elongation and growth direction of axile roots. The cells produced in the RC meristem are pushed forward as new cells form beneath them, and eventually the cells on the periphery of the RC fall off. The life cycle of RC cells of maize has been studied extensively and ranges from one to seven days. Approximately 4,000 to 21,000 cells are present in a complete maize RC, and 1,400 to 3,200 sloughed cells can be found in the rhizosphere soil per day per root. These cells, called root border cells (RBCs), mix with RC mucilage and play important roles for the root growth in soil. The RBC-mucilage complex effectively reduces the resistance roots experience during penetration into field soil, about 30–40% of the resistance being reduced by the presence of RC alone. The RC is also a tissue integral to gravitropism, and is known to determine the direction of root growth. The size of amyloplasts and coumellae in RCs has a strong influence on determining the growth angle of axile roots. The function of the individual regions of the RC and how the RC tissues and cells are formed should be studied further to advance our understanding regarding the critical roles of the RC in crop root growth.     

Rooting systems of oilseed and pulse crops. II: Vertical distribution patterns across the soil profile

Root distribution patterns in the soil profile are the important determinant of the ability of a crop to acquire water and nutrients for growth. This study was to determine the root distribution patterns of selected oilseeds and pulses that are widely adapted in semiarid northern Great Plains. We hypothesized that root distribution patterns differed between oilseed, pulse, and cereal crops, and that the magnitude of the difference was influenced by water availability. A field experiment was conducted in 2006 and 2007 near Swift Current (50°15′N, 107°44′W), Saskatchewan, Canada. Three oilseeds [canola (Brassica napus L.), flax (Linum usitatissimum L.), mustard (Brassica juncea L.)], three pulses [chickpea (Cicer arietinum L.), field pea (Pisum sativum L.), lentil (Lens culinaris)], and spring wheat (Triticum aestivum L.) were hand-planted in lysimeters of 15 cm in diameter and 100 cm in length which were pushed into soil with a hydraulic system. Crops were evaluated under low- (natural rainfall) and high- (rainfall + irrigation) water conditions. Vertical distribution of root systems was determined at the late-flowering stage. A large portion (>90%) of crop roots was mainly distributed in the 0-60 cm soil profile and the largest amount of crop rooting took place in the top 20 cm soil increment. Pulses had larger diameter roots across the entire soil profile than oilseeds and wheat. Canola had 28% greater root length and 110% more root tips in the top 10 cm soil and 101% larger root surface area in the 40 cm soil under high-water than under low-water conditions. In 2007, drier weather stimulated greater root growth for oilseeds in the 20-40 cm soil and for wheat in the 0-20 cm soil, but reduced root growth of pulses in the 0-50 cm soil profile. In semiarid environments, water availability did not affect the vertical distribution patterns of crop roots with a few exceptions. Pulses are excellent “digging” crops with a strong “tillage” function to the soil due to their larger diameter roots, whereas canola is more suitable to the environment with high availability of soil water that promotes canola root development.     

Genetic Opportunities to Improve Cereal Root Systems for Dryland Agriculture

Abstract

Understanding the major limitations to root growth is very important if we are to maximize water and nutrient use and increase yields. Limitations may be insufficient rooting depth, root diseases, nutrient deficiencies, toxicities and soil hardness. An understanding of these limitations will lead to more precisely identifying traits for which to select and breed. Examples of successfully overcoming limiting factors to improve crop performance by breeding and selection are given for cereal cyst nematodes in wheat, soil acidity and salinity. The importance of altered crop management practices to reduce limitations is also stressed. These have resulted in a more effective and healthier root system, which results in more water use and greater yields. Opportunities to genetically increase the size of the root system in dryland systems where water and nutrients are not all used by the crop are given.     

株行距配置对玉米根系性状及产量的影响

以郑单958为材料, 采用田间试验方法, 在50 025株/hm²、67 500株/hm²、100 050株/hm²密度下分别设两种株行距配置, 探讨增密条件下调控株行距配置对玉米根系性状及产量影响。结果表明, 3个种植密度下总体表现为小行距种植方式在0～60 cm土层内的根重密度、根长密度及根表面积密度均高于大行距处理。50 025株/hm²下吐丝期时0～60 cm土层内的根重密度和根长密度在两个株行距配置间差异显著(P<0.05), 两个株行距配置的根表面积密度在10叶展、吐丝期和吐丝后25 d差异显著(P<0.05);67 500株/hm²下不同时期两个株行距配置根重密度差异显著(P<0.05), 根长密度和根表面积密度在10叶展和吐丝后25 d差异显著(P<0.05);100 050株/hm²下, 两个株行距配置间根重密度和根长密度在10叶展和吐丝后25 d差异显著(P<0.05), 不同时期根表面积密度差异显著(P< 0.05)。同一密度下缩行增株后单株木质部伤流液体积增大, 根系供应能力增强, 产量增加, 50 025株/hm²、67 500株/hm²下产量分别提高了6.76%和4.89%。不同时期0～60 cm土层内根重密度、根长密度和根表面积密度与产量呈正相关, 其中10叶展时各根系性状均与产量呈显著正相关。     

Rooting systems of oilseed and pulse crops I: Temporal growth patterns across the plant developmental periods

Oilseed and pulse crops have been increasingly used to diversify cereal-based cropping systems in semiarid environments, but little is known about the root characteristics of these broadleaf crops. This study was to characterize the temporal growth patterns of the roots of selected oilseed and pulse crops, and determine the response of root growth patterns to water availability in semiarid environments. Canola (Brassica napus L.), flax (Linum usitatissimum L.), mustard (Brassica juncea L.), chickpea (Cicer arietinum L.), field pea (Pisum sativum L.), lentil (Lens culinaris), and spring wheat (Triticum aestivum L.) were tested under high- (rainfall + irrigation) and low- (rainfall only) water availability conditions in southwest Saskatchewan, in 2006 and 2007. Crops were hand-planted in lysimeters of 15 cm in diameter and 100 cm in length that were installed in the field prior to seeding. Roots were sampled at the crop stages of seedling, early-flower, late-flower, late-pod, and physiological maturity. On average, root length density, surface area, diameter, and the number of tips at the seedling stage were, respectively, 41, 25, 14, and 110% greater in the drier 2007 than the corresponding values in 2006. Root growth in all crops progressed rapidly from seedling, reached a maximum at late-flower or late-pod stages, and then declined to maturity; this pattern was consistent under both high- and low-water conditions. At the late-flower stage, root growth was most sensitive to water availability, and the magnitude of the response differed between crop species. Increased water availability increased canola root length density by 70%, root surface area by 67%, and root tips by 79% compared with canola grown under low-water conditions. Water availability had a marginal influence on the root growth of flax and mustard, and had no effect on pulse crops. Wheat and two Brassica oilseeds had greater root length density, surface area and root tips throughout the entire growth period than flax and three pulses, while pulse crops had thicker roots with larger diameters than the other species. Sampling roots at the late-flower stage will allow researchers to capture best information on root morphology in oilseed and pulse crops. The different root morphological characteristics of oilseeds, pulses, and wheat may serve as a science basis upon which diversified cropping systems are developed for semiarid environments.     

Root System Development Including Root Branching in Cuttings of Cassava with Reference to Shoot Growth and Tuber Bulking

Summary

In spite of the important role it plays for water and nutrient acquisition, information on the root system development in cassava (Manihot esculenta Grantz) is limited. To examine the root length and branching pattern with reference to shoot growth and tuber bulking, we grew cassava plants in containers under natural climatic conditions in the southern end of Sumatra Island, Indonesia. One 20-cm length cutting of cassava (cv. Ardira IV) was planted in either a plastic bucket or a wooden box. The containers, which were filled with heavy clay soil, had different sizes depending on the growing period. At 30, 60, 100, 140, 180, and 270 days after planting (DAP), both the shoot and roots were sampled for quantitative analysis. The dry weight of both shoot and roots increased rapidly with the leaf area. The axile root number, however, decreased from 60 to 140 DAP as a result of the abscission of roots emerging from the basal part of the cutting during tuber bulking. The total root length reached its maximum at 60 DAP and significantly decreased thereafter because of decay and decomposition during tuber bulking. On the other hand, the root branching either increased the branching order or retained it, as determined from a topological point of view. The root branching during the later growing period compensated for the decrease in total root length and contributed to maintain a sufficient root surface area. The surviving roots with a well-developed branching pattern could absorb water and nutrients essential for tuber bulking.