A simple Method for Selection of Potato Lines with a Higher Root/Total Ratio at an Early Stage in the Seedling Generation

Abstract

The growth directions and elongation rates of axile roots that compose the framework of an upland rice root system are quite varied. The objective of this study was to elucidate the direction of growth of the axile roots relative to their root diameter and the structural characteristics of their root caps. The relationships of photosynthate translocation to either the growth direction or the elongation rate of the axile roots were also examined using a stable isotope 13G. The growth direction of the axile roots significantly correlated with their diameter. The axile roots with a relatively large diameter tended to elongate vertically in the vegetative stage, though the regression coefficients varied according to phyllochrons. The roots that emerged at the reproductive stage elongated horizontally relative to the large diameter. In the roots that emerged at the same phyllochrons, the prophyll roots elongated more vertically than the proximal roots did. The axile roots that elongated vertically formed wide columellae and large amyloplasts in the cap cells. The highest ¹³C abundance in the axile root tip zone was found at 21 hrs after feeding ¹³CO₂. The length of the apical unbranched zone behind the axile root tip positively correlated with the ¹³C abundance in the root apical zones during the first 21 hrs after feeding, indicating that the roots that elongated fast would be superior in photosynthate intake in the apical zone. The axile roots that elongated vertically took in more photosynthate in their apical zones, however, the relationship was not particularly close.     

Variation of Germination Response to Temperature in Formosan Lily (Lilium formosanum Wall.) Collected from Different Latitudes and Elevations in Taiwan

Abstract

Deep penetration of an axile root is one of the important factors that allow crops to form deep root systems. In this study, the nodes from which the deepest penetrated roots had emerged were examined at the heading stage in upland rice and maize grown in large root boxes and in the field. Both experiments were designed to measure the direction, length, and rooting nodes of each root. In maize, the growth angles of axile roots increased with vertical elongation as rooting nodes acropetally advanced. The roots that emerged from the lower nodes, namely from coleoptilar to the second node, exhibited conspicuously horizontal elongation in the field, reaching 2.3 m in width at the maximum. The roots that emerged from higher than the fifth node were too short to penetrate deeply. Thus, these roots became the deepest root in less or no probability under field conditions. On the other hand, the fourth nodal root, which had an intermediate growth angle and length, had the highest probability. In upland rice, the deepest roots emerged from the nodes lower than the forth node on the main stem in the root boxes. In the field, however, the deepest roots emerged at later stages, that is, the roots from the middle nodes on the main stem and from the low nodes on the primary and secondary tillers were the deepest roots. Five out of nine of the deepest roots were from the prophyll nodes in three field-grown upland rice. The deepest roots from the same plant were estimated to have emerged and grown at approximately the same stage.     

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。     

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.     

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.     

不同耕作方式对辽西褐土物理性状及玉米根系分布的影响

通过连续3年大田试验，对旋耕、翻耕、深松3种耕作方式下的土壤物理性质、玉米根系分布和产量进行测定。结果表明，与翻耕和旋耕相比，深松显著增加了玉米田土壤耕层厚度和降低了犁底层厚度。在中下层土壤，深松还降低了土壤紧实度和容重，改善了土壤的孔隙状况，有利于玉米根系向下生长，使得中下层土壤的玉米根系不仅更丰富，而且占总根系量的比例也更高，最终提高了玉米产量。本研究表明，深松耕作有利于改善辽西褐土区土壤结构和促进玉米生长。     

生物炭对玉米根系特性及产量的影响

采用大田试验研究生物炭对郑单958产量和不同生育时期根系生长、形态特征及生理特性的影响,明确生物炭对玉米根系与产量的效应,探明生物炭在玉米生产上应用的潜力与价值。结果表明,土壤中施入生物炭能增加玉米根系的总根长、根体积和根干重,提高玉米根系总吸收面积和活跃吸收面积。在玉米生育后期,生物炭在一定程度上延缓了根系衰老,成熟期施生物炭处理根系活力分别比对照高48.12%和42.71%;同时维持了较为适宜的根冠比,根系生理功能增强;添加生物炭后郑单958最高产量达12 076.35 kg/hm2,比对照增产10.23%,具体表现为穗长、穗行数、行粒数和百粒重的提高。     

The Importance of Root Dynamics in Cropping Systems Research

SUMMARY

This paper examines the nature and importance of the dynamics of crop root growth, particularly root turnover, and the application to different cropping systems. Methods now available to investigate root dynamics are summarized, and information being obtained is presented. Effects of physical, chemical, and biological factors on root dynamics are discussed. Growth of new roots and death of older roots can change the initial distribution in soil, allowing roots to exploit zones that have a more favorable nutrient or water supply. In herbaceous crops, the lifespan of roots appears to range between 16 and 36 per cent of the annual growth cycle. However, there is a paucity of data with which results can be compared. Localized enrichment of the water and nutrient supply enhances root turnover, and plants growing in soil well supplied with nutrients tend to have shorter-lived roots than those from nutrient limiting conditions. Both drought and excess water can induce premature root death, as can the resupply of water after drought. Turnover of roots contributes to carbon deposition in soil through their death and decay, as well as from the release of exudates from those roots during their lifetime. Improved understanding of root turnover is important for the development of more sustainable cropping systems. In particular, it could be used to improve the exploitation of N released from green manure as well as capturing N that has been leached below the rooting zone of staple crops. It is stressed that root turnover has more importance for plants with longer life cycles than in short season annual crops.     

玉米‖花生间作系统作物产量及根系空间分布特征的影响

在农业部阜新农业环境与保育科学观测试验站分别设置2行玉米:4行花生间作(2M4P)、4行玉米:4行花生间作(4M4P)和玉米单作、花生单作4个种植模式,开展不同种植模式对作物产量及产量构成因素、生物量和根系特征的影响研究。结果表明,2个间作模式的土地当量比(LER)为1.16~1.24,具有一定的产量优势和较高的土地利用效率。间作中的玉米干物质积累量与单作接近,间作花生干物质积累量较单作明显下降。对根系研究发现,间作减少作物的细根生长,2M4P、4M4P处理的比根长(SRL)较单作玉米和花生分别下降了25%、23%和18%、12%,复合系统作物根表面积密度(RSAD)在0~40 cm土层中能够占到总土层的80%以上,间作作物的RSAD显著高于单作,表明作物根系在表层分布较为密集,间作影响了作物的根系生长与分布。     

No-Tillage Enhanced the Dependence on Surface Irrigation Water in Wheat and Soybean

Abstract

No-tillage often affects crop root development due to the higher mechanical impedance to root elongation, resulting in yield reduction under an unfavorable rainfall pattern, such as drought. In this study, we analyzed the changes in water source of wheat and soybean under drought stress in a continuous no-tillage field. Deuterium-labeled irrigation water was applied at different growth stages of crops to analyze their water uptake pattern. Mechanical impedance of the surface soil was 3.5 and 4.4 times higher in the no-tillage than in the conventional tillage under wet and drought conditions, respectively. Root length density and root branching index (the length of lateral roots per unit axile root length) of soybean in the surface soil layer were higher in the no-tillage field. This indicates that the increased branching by the higher mechanical impedance of undisturbed surface soil causes roots to accumulate in the surface soil layer. The deuterium concentration in the xylem sap of both crops was significantly higher in the no-tillage than in the tillage under a drought condition. This indicates that the crops in the no-tillage field depend highly on the newly supplied easily accessible water (irrigation water and/or rainfall) as compared with those in the conventional tillage field under a limited water supply. In conclusion, enhanced surface root growth in the no-tillage condition would result in higher dependence on surface supplied irrigation water than in the conventional tillage under drought.     

耕作方式对玉米生长发育、根分布及产量形成的影响

以郑单958为试验材料,大田条件下通过传统耕作（CK）、隔行深松（T1）和行行深松（T2）研究耕作方式对春玉米根系空间分布与地上部生长发育和产量的影响。与CK相比,T1、T2处理根总量较大,根系空间分布合理,利于根系吸收深层土壤的水分及养分;叶面积在前期T1、T2处理优势不明显,生长中后期叶面积指数均高于CK;深松处理（T1、T2）的单株干物质积累量增加,最大干物质积累速率加快,达到最大干物质积累速率的日期（T_max）推迟,干物质积累速率最大时的生长量（W_max）增大,生长活跃天数（p）延长,单株干物质积累潜力（Dwp）明显升高。深松处理明显增加玉米产量,T1、T2处理较CK产量分别提高4.72%和5.46%。深松增产的主要因素在于千粒重的提高,两个深松处理（T1、T2）之间产量未达到显著差异;相对于T2处理,T1处理节约动力、经济效益较高。     

模拟根层障碍条件下不同深度玉米根系与产量的关系研究

在池栽条件下采用模拟根层障碍的方法,研究不同深度根系与玉米生长和产量的关系。结果表明,根层阻隔显著降低玉米根系的生物量、总根长和根表面积,各处理光合生产能力和子粒产量显著低于无阻隔(对照);随着阻隔层的下移,根系和冠层各指标和产量受到的影响逐渐变小,0~20、21~40、41~60、61~80、80 cm以下各层根系对产量的相对贡献率分别为52%、11%、7%、12%、19%。20 cm耕层以下根系对产量的贡献达48%,其中60cm以下土层内根系对产量的贡献达31%,说明深层根系虽然生物量占总生物量比例很小,但其在花粒期对深层水肥的吸收利用对产量形成具有重要作用。     

球孢白僵菌不同施用方式对玉米促生作用的研究

采用土壤施用和叶面喷施2种方式将球孢白僵菌(Beauveria bassiana)菌株Bb202接种至玉米,研究不同接种方式及处理浓度对玉米生长的影响。结果表明,2种喷施方式对玉米苗均存在促生作用,且这种促生作用与孢子接种浓度密切相关。在叶面喷施处理中,白僵菌仅对玉米地上部分生长指标有促进作用,而对玉米苗的根长无显著影响;其中1.0×10~4孢子/m L处理组对玉米苗的促生效果最佳,其株高、叶长、叶宽、鲜重指标比蒸馏水对照组分别高出7.47%、15.42%、25.70%和16.85%。在土壤喷施处理中,白僵菌对玉米苗地上与地下部分均有显著促生作用;其中1.0×106孢子/m L和1.0×10~8孢子/m L处理组,玉米株高、叶长、根长、生物量指标较蒸馏水对照组分别提高了28.66%和29.59%、30.66%和37.85%、43.08%和33.60%、28.35%和32.55%。从对玉米苗的促生作用来看,用1.0×106孢子/m L的白僵菌悬浮液处理土壤,可以取得最经济、最显著的促生效果。     

玉米品种根系性状和产量不同年代的演替规律及其对深松响应研究

以1970～2010年10个玉米主栽品种为试材,在深松增密条件下,研究玉米品种演替过程中根系性状和产量的变化情况。结果表明,随着年代推进,玉米单株根系性状指标(根系干重、根长、根表面积以及根系平均直径)均呈先升后降的变化趋势,1980年各指标达到最大值。根系性状指标在20～50 cm土壤中根系所占比例随着品种更替而增加,根系不断向深层土壤延伸。深松增密措施更有利于玉米新品种形成横向紧缩、纵向延伸的根系构型,不仅通过改变根系空间分布实现结构性增产,而且通过改善耕层环境实现功能性增产。     

Dynamics of Root Border Cells in Rhizosphere Soil of Zea mays L.: Crushed Cells during Root Penetration,Survival in Soil,and Long Term Soil Compaction Effect

Abstract

Plant roots release mucilage and root border cells (RBCs) into rhizosphere, which function as a complex at the root–soil interface. The dynamics of RBCs in rhizosphere soil, however, remains unknown. In this study, the ratio of crushed root cap cells during root penetration into soil and survival of the RBCs after the release from the root cap were estimated in maize seminal root. In addition, the effects of long term soil compaction on RBCs release were investigated. During the root penetration into rhizosphere soil, 78, 56, and 45% of sloughed root cap cells were estimated to be crushed at the first, second, and third day after planting, respectively. The number of surviving RBCs decreased with time, but 6% of the RBCs in the rhizosphere still retained their cell walls at one month after planting. These cells were estimated to remain in the soil for at least 10 d after the release from lateral roots. Furthermore, RBCs release from newly emerged nodal root increased with aging of plants, and the cell release was significantly increased by soil compaction only at the seedling stage. In conclusion, significant number of RBCs were crushed during root penetration into soil, however many RBCs remained in the rhizosphere soil for a relatively longer period. Soil compaction significantly increased cell release only at the seedling stage.     

Deep rooting in winter wheat: rooting nodes of deep roots in two cultivars with deep and shallow root systems

Deep rooting of wheat has been suggested that it influences the tolerance to various environmental stresses. In this study, the nodes from which the deepest penetrated roots had emerged were examined in winter wheat. The wheat was grown in long tubes with or without mechanical stress and in large root boxes. The length and growth angle of each axile root were examined to analyze the difference in the vertical distribution of the roots between the two wheat cultivars, one with a deep and one with a shallow root system. In Shiroganekomugi, a Japanese winter wheat cultivar with a shallow root system, the rooting depths of the seminal and nodal roots decreased as the rooting nodes advanced acropetally. Six out of nine deepest roots were seminal root in the non-mechanical stress conditions. In Mutsubenkei, a Japanese winter wheat cultivar with a deep root system, grown in root boxes, not only the seminal roots but also the coleoptilar and the first nodal roots penetrated to a depth of more than 1.3 m in the root box, and became the deepest roots. In both cultivars, the seminal roots became the deepest roots under the mechanical stress conditions. There were no clear tendencies in the root growth angles among the rooting nodes in the wheat root system. This indicates that the length of the axile roots can explain the differences in the rooting depths among axile roots in a wheat root system. On the other hand, the axile roots of Mutsubenkei elongated significantly more vertically than those of Shiroganekomugi. This suggests that not only seminal but also nodal roots exhibit strong positive gravitropism and penetrate deeply in a cultivar with a deep root system. In wheat cultivars, it is likely that the extent of its Root Depth Index results partly from the gravitropic responses of both seminal and nodal roots.     

石灰抑制重金属铅影响玉米根系效应的研究

采用盆栽试验,研究了在施用石灰改良条件下,重金属铅污染对玉米根系生长的影响。结果表明,重金属铅通过破坏根尖细胞超微结构来抑制植物根系对养分的吸收。通过石灰处理的土壤提高了铅污染土壤的pH值,降低了铅的活动性,抑制了玉米根尖细胞对铅的吸收,降低了重金属铅对玉米根尖细胞的危害。     

几种水氮模式处理下冬小麦根系生长的差异

为了给冬小麦水氮管理提供理论依据,以京冬8号为试验材料,采用随机区组设计,研究了4种水氮模式(优化灌溉-传统施肥、传统水肥、秸秆还田-优化水肥、优化水肥、传统灌溉-优化施肥)处理下冬小麦根系生长的差异。结果表明,不同处理间冬小麦0~120 cm土层单位面积的根量有差异。与传统水肥相比,传统灌溉-优化施肥0~60 cm土层的根系长度有所减少,60~90和90~120 cm土层的根系长度分别增加14.62%和73.72%(P<0.05),总根量略增加;优化灌溉-传统施肥0~30 cm土层的根系长度明显增加(P<0.05),30~60、60~90和90~120 cm土层的根系长度分别减少3.52%、6.65%和18.21%,总根量增加;优化水肥和秸秆还田-优化水肥各土层的根量增加。与优化水肥相比,秸秆还田-优化水肥0~60 cm土层的根量有所增加,60~120 cm土层有所减少。各处理冬小麦根系密度随土层加深而递减的速度大小为优化灌溉-传统施肥>传统水肥>秸秆还田-优化水肥>优化水肥>传统灌溉-优化施肥。     

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。     

The Distribution of Wheat and Maize Roots as Influenced by Biopores in a Subsoil of the Kanto Loam Type

Abstract

Biopores are tubular soil macropores left by plant roots after their decay or burrowed by soil animals, which provide channels for deep rooting and improve crop access to water and nutrients. The density oi biopores, number of biopores per unit area, and proportion of biopores occupied by roots were measured on horizontal soil profiles at 30, 50, and 70 cm in depth in a fine-texture subsoil of Andosol (Light clay, a volcanic ash of the Kanto loam type) at the mature stage of wheat and maize. Images of 0,1 mm resolution from the pictures of cleaned profile surfaces were examined on a computer display. Dark spots with a circular and smooth boundary were regarded as biopores. The density of biopores larger than 1 mm in diameter ranged from 500 to 2,000 m^–2. The percentage of biopores occupied by roots was more than 30% of biopores larger than 1 mm and increased with depth. Roots were accumulated in biopores. The proportion of biopores (> 1 mm) with roots increased with depth. It was 28-35% in the wheat plot and 14-20% in the maize plot. This suggested that thinner wheat roots easily entered a biopore and remained in it. The possible influence of biopores on the spatial distribution of roots was discussed.