Effect of Soil Texture and the Clay Component on Migration of Meloidogyne incognita Second-stage Juveniles

The vertical migration of M. incognita juveniles introduced at 20 cm from the roots was studied in five natural soils, 100% silica sand, 95% silica sand with 5% clay, 90% silica sand with 10% clay, and 95% silica sand with 5% clay as a concentrated layer. In natural soils the percentage of juveniles capable of migrating 20 cm and penetrating the roots decreased when the percentage of clay and silt increased. No migration occurred in silica sand without clay particles; when 5 or 10% of clay were mixed to silica sand, 34 and 26%, respectively, of the juveniles were able to migrate 20 cm. Clay separated from silica sand in which tomatoes were grown was attractive for juveniles. It is suggested that clay particles aid in the migration of root-knot juveniles over long distances to plant roots by absorbing and holding root exudates or bacterial by-products which form a concentration gradient enabling nematodes to locate roots.     

Bacterial transport through porous solids: interactions betweenMicrococcus luteus cells and sand particles

Summary As part of an evaluation of microbial systems for potential application in enhanced oil recovery (EOR) in situ, the behaviour of bacteria within the labyrinths of porous structures was investigated. Sandpacks were utilised as models of reservoir formations. UsingMicrococcus luteus (NCIB 8553) cells under non-growing conditions, the interaction between the bacteria and sand particles was investigated by a simple shake flask system. The attachment of bacterial cells to sand was time-dependent and reversible. With increasing density of cell suspensions, competivive effects on binding to sand were observed, indicating a possible interaction between two subpopulations of cells. Similar effects occurred when suspensions ofM. luteus cells were pumped through sandpacks. Shake flask experiments indicated that the maximum binding of bacteria to sand was about 2×10⁹ cells · g^–1, representing a total coverage of approximately 20% of the surface of sand particles by bacterial cells.     

Observations on the Effects of Pressure Differences Between the Bathing Media and Exudates of Excised Maize Roots

Observation of the water fluxes from excised maize roots atvarious levels of suction showed significant differences betweencontrol roots and those which have been subjected to an evacuationpre-treatment. This involved placing excised lengths of rootin bathing medium in a flask which was evacuated (1 cmHg) for10 min; during this time air bubbles emerged from the cut ends. This pre-treatment has been shown to result in an increase inthe density of the root, which is ascribed to the replacementof air in the cortical intercellular spaces by bathing medium.The observed differences in the response to suction in the twogroups of roots is therefore explained as a decrease in theresistance to water flow of the cortex of the treated roots.     

Phosphorus sources and availability modify growth and distribution of root clusters and nodules of native Australian legumes

A variety of native Western Australian legumes produced root clusters in sand culture confirming field and published observations. In general, these legumes grew equally well when supplied with organic or inorganic sources of phosphorus. The nitrogen content of shoots and roots varied little among treatments for all species, however, phosphorus content was always greater in plants supplied with inositol‐P. The plasticity of root growth in response to localized placement of organic and inorganic sources of phosphorus was demonstrated using a simple ‘split root’ technique. Total root dry weight was, on average, more than doubled in P‐amended sand when compared with non‐amended sand. Root clusters tended to be produced in areas of relatively high phosphorus concentration and nodules in areas of low phosphorus concentration. Levels of phosphorus in lateral roots grown in P‐amended sand were significantly different from lateral roots grown in the corresponding non‐amended sand. Growth increases averaging 70% for white sand to over 100% for yellow sand indicated a large degree of ‘plasticity’ in roots under conditions of heterogeneous supply of phosphorus. Spatially exclusive development of organs for the acquisition of nutrients is discussed in relation to requirements for carbon in organ production and maintenance.     

Effects of sand burial depth on the root system of Salix cheilophila seedlings in Mu Us Sandy Land, Inner Mongolia, China

Salix cheilophila Schneid. is a naturally occurring Salix species in Mu Us Sandy Land, Inner Mongolia, China. We focused on the morphological adaptability of S. cheilophila to sand dune burial. For morphological measurements, 32 S. cheilophila seedlings were removed from a community which was in the process of being buried by a shifting sand dune. Each seedling collected included the entire root system. We measured the number, length, and biomass of the adventitious roots, primary lateral roots, and taproot, and compared the morphological characteristics of the root system, including adventitious roots, for seedlings buried to various levels in the sand. The growth range of adventitious roots increased as the length of the buried portion of the main shoot increased. In addition, the total dry weight of all current-year shoots tended to increase gradually with increasing total dry weight of the adventitious roots. These results suggest that S. cheilophila tends to make use of the sedimentary sand layer that accompanies shifting sand dunes. However, there was no correlation between biomass or number of adventitious roots and the length of the buried part of the main shoot. Thus, S. cheilophila does not grow adventitious roots proportional to the buried part. These morphological characteristics of the root system, including the adventitious roots, may indicate that S. cheilophila has poor morphological adaptability to sand dune burial.     

Medium optimization of transformed root cultures of Stizolobium hassjoo producing L-DOPA with response surface methodology

Medium optimization of B5 medium for hairy root cultures producing secondary metabolites was studied through statistical experimental design. Transformed root cultures of Stizolobium hassjoo producing L-DOPA were used as a model system. The serial dilution experiments facilitated logical choice of the upper and lower bounds on executing 2(11)(-)(6) fractional factorial design. Steepest ascent method as well as central composite design were sequentially employed to optimize the media of shake flask cultures. The modified B5 media of GM, PM, and GPM were obtained, indicating the optimum medium compositions for enhancing hairy root dry weight, L-DOPA content in hairy roots, and L-DOPA production, respectively. When cultivating S. hassjoo hairy roots in GM, PM and GPM for 16 days, the dry wt of hairy roots, L-DOPA content, and L-DOPA production obtained were ca. 530 mg per flask (10.6 g/L), 10.8% dry wt, and 806 mg/L, which were 1.8-, 2-, and 2.8-fold of basal B5 medium control runs, respectively.     

海滨沙地单叶蔓荆匍匐茎对沙埋适应的生长对策

单叶蔓荆(Vitex trifolia var.simplicifoli)是一种耐盐、耐旱固沙地被植物。依据海滨沙地自然沙埋特点对单叶蔓荆匍匐茎进行了不同厚度(半埋和全埋)和不同长度交叉沙埋处理,研究探讨了单叶蔓荆沙埋适应生长对策,为其开发利用、科学管理和海滨环境修复提供指导。结果表明,正常情况下,单叶蔓荆匍匐茎基部和中部生长缓慢,顶部生长快。轻度(沙埋匍匐茎基部)和中度(沙埋匍匐茎基部和中部)半埋和全埋使匍匐茎顶部生长加速,茎长增长量较对照高出1.5到3.1倍;但重度(沙埋整个匍匐茎)半埋和全埋使匍匐茎顶部净增长量减少12%和13%。在20d沙埋中,对照整个匍匐茎各段均无不定根长出,但不同程度半埋和全埋沙埋处理下沙下匍匐茎上均长出不定根,重度半埋使不定根生长受抑;同时匍匐茎上各段茎生物量上升,枝叶生物量下降,且随着沙埋程度的增加而增减幅度提高,在重度半埋和全埋达到最大。在轻度和中度半埋和全埋下,匍匐茎上未沙埋部位枝条生长加速。研究表明,在自然环境中,单叶蔓荆匍匐茎顶端是一个对环境变化反应敏感的部位,并与沙埋后单叶蔓荆茎延伸生长和植株能否生存密切相关。当匍匐茎顶部没被沙埋时,沙埋促进沙埋部位匍匐茎和枝叶中物质转移,加速匍匐茎顶部快速生长和物质积累以弥补沙埋带来的损伤维持物质和能量的代谢平衡。沙埋后,单叶蔓荆以茎顶端快速生长、形成不定根、枝条生长维持茎水分平衡和能量和物质代谢平衡,以快速生长摆脱沙埋影响的生长方式为其对沙埋环境的重要适应对策。因此,在海岸沙地单叶蔓荆种群管理和维护中,在强风移沙引起的重度沙埋后,及时剥离匍匐茎顶部沙子对维护单叶蔓荆种群的延续生存和扩散均有重要作用。     

Technical Factors of Artemisin Biosynthesis in Artemisia annua Hairy Root Culture

The optimum cultural conditions of growth and artemisinin accumulation of hairy roots in Artemisia annua L. were identified as follows: the initial pH 5.8 ~ 6.0; the rate of flask shaking, 130 ~ 150 r/min; the liquid medium volume per flask, 25%; light cycle, 16 h/d; temperature, 30 ℃. Under the above conditions, up to 233.3 mg/L of artemisinin could be obtained after 25 days of culture.     

摇瓶培养条件下雷公藤不定根生长及次生代谢产物含量的研究

以雷公藤(Tripterygium wilfordii Hook. f.)不定根为材料,研究摇瓶悬浮培养条件下接种密度、装液比例、逐级放大、消泡剂、大孔吸附树脂种类及浓度对雷公藤不定根增长量、不定根及培养基中雷公藤内酯醇、雷公藤吉碱、雷公藤次碱含量的影响。结果显示,接种密度在15 g/L (FW)时较适合不定根的继代培养和次生代谢产物的积累。250 m L摇瓶中装入100 m L培养基,即装液量为2/5时,培养基利用率最高。随着摇瓶体积的逐渐放大,不定根增长量和3种次生代谢产物含量略有下降,5 L摇瓶中不定根增长量为对照的91.6%,内酯醇、吉碱和次碱的含量分别为对照的91.8%、91.7%和96.9%。6种大孔吸附树脂中,XAD-7处理对不定根的生长有明显促进作用,培养结束时,3种次生代谢产物产量显著提高,当XAD-7浓度为0.5 g/瓶时不定根增长量为对照的1.2倍,内酯醇、吉碱和次碱产量最高,分别为对照的2.9、2.4和2.2倍。培养基中添加消泡剂后不定根增长量、3种次生代谢产物总产量均不同程度下降,其中,LX-603处理后,虽然不定根增长量为对照的85%,内酯醇、吉碱和次碱产量分别为对照的78%、64%和87%,但明显抑制了培养过程中泡沫的产生。研究结果表明筛选的摇瓶逐级放大培养雷公藤不定根的方法效果较好,可为雷公藤不定根生物反应器放大培养奠定基础。     

Scale-up production of puerarin from hairy roots of Pueraria phaseoloides in an airlift bioreactor

Hairy roots of the Chinese herb, Pueraria phaseoloides, obtained from leaf explants and transformed with the Agrobacterium rhizogenes, were cultured in 2.5 l airlift bioreactors for three weeks. Puerarin accumulated at 5,570 microg g(-1) dry wt, which is near 200 times as much as in 250 ml flask cultures. In addition, puearin was exuded into the nutrient medium at final concentrations higher than in the hairy roots themselves.     

不同培育方式对橡胶树实生苗生理指标、养分及长势的影响

橡胶树(Heveabrasiliensis)种子催芽生长一般使用沙床培育,沙子是不可再生资源,为了选择一种适合橡胶树种子培育方式来替代对沙子的依赖,该研究通过水培、悬空培育和传统的沙培比较橡胶树实生苗第1蓬叶稳定时,苗木的生长势、生理指标及养分含量。结果表明,水培实生苗地上部株高、茎粗、叶面积的长势最佳,壮苗指数和生物量的含量最高,但其根太长,根相对较细。水培的叶、茎、根的可溶性糖、丙二醛、游离脯氨酸、超氧化物歧化酶的含量均较低;水培和悬空培育的叶片和茎的叶绿素、类胡萝卜素及根系活力的含量没有显著性差异,均高于沙培。水培的叶、茎、根中的氮和磷含量最低,沙培的最高;而水培实生苗根和茎中钾的含量较高,叶片中含量与悬空培育、沙培均没有显著性差异;悬空培育在叶、茎、根中钾的含量最低。水培促进了苗木的生长,降低干旱胁迫,提高养分利用率,但后续还需调控根系,建设良好根团。悬空培育的苗木长势较弱,还需进一步完善方法。     

The allelopathic potential of alfalfa root medicagenic acid glycosides and their fate in soil environments

Summary The allelopathic effect of alfalfa (Medicago media Pers.) and red clover (Trifolium pratense L.) root saponins on winter wheat seedling growth and the fate of these chemicals in soil environments were studied. Seed germination, seedling and test fungus growth were suppressed by water and by alcohol extracts of alfalfa roots, and by crude saponins of alfalfa roots, indicating that medicagenic acid glycosides are the inhibitor. Powdered alfalfa roots inhibited wheat seedling growth when added to sand. At concentrations as low as 0.25% (w/w) the root system was completely destroyed whereas seedling shoots suffered little damage. Red clover roots caused some wheat growth inhibition when incorporated to sand, but their effect was much lower than in the alfalfa root treatment. Soil textures had a significant influence on the inhibitory effect of alfalfa roots. The inhibition of seedling growth was more pronounced on light than on heavy soils. This was attribted to the higher sorption of inhibitors by heavy soils. Incubation of alfalfa roots mixed into loose sand, coarse sand, loamy sand and clay loam for a period of 0–8 days resulted in decreased toxicity to bothT. viride and wheat seedlings. This decrease occurred more quickly in heavier soils than in loose sand, due to the hydrolysis of glycosides by soil microorganisms. Soil microbes were capable of detoxifying medicagenic acid glycosides by partial hydrolysis of sugar chain to aglycone. These findings illustrate the importance of medicagenic acid glycosides as an inhibitor of wheat seedling growth, and of their fate in different soil environments.     

Establishment of adventitious root culture of <Emphasis Type="Italic">Stevia rebaudiana</Emphasis> Bertoni in a roller bottle system

Cultures of adventitious roots of Stevia rebaudiana (Bert.) Bertoni were performed in a roller bottle system for the production of both primary and secondary metabolites. Adventitious roots were induced from 1-cm-long root tip explants derived from in vitro regenerated plantlets on solid Murashige and Skoog (MS 1962) media supplemented with 10.7 μM of α-naphthaleneacetic acid. These cultures were successfully maintained in the same medium for 6 months with regular subcultures after 4 weeks. Thereafter, the roots were cut into 1.0- to 1.5-cm-long segments and transferred to the roller bottle system containing a fresh root tissue culture on liquid MS medium supplemented with 10.7 μM NAA. The apparatus consisted of a flask rolling system adjusted to 4g, and 3° of flask inclination. The roots were allowed to grow in the absence of light for adaptation and adventitious root formation. The best conditions for cultivation were investigated, considering culture volume (25 ml), culture period (4 weeks), salt concentrations in the nutrient medium (33%) and optimal initial inoculum (0.2 g) of S. rebaudiana roots. These results could give important information on how to improve the development of adventitious roots of S. rebaudiana for the production of primary and secondary metabolites.     

海滨滨麦叶片和根对不同厚度沙埋的生理响应差异分析

以烟台海岸抗风沙植物滨麦为研究材料,通过对不同厚度沙埋下其叶片和根部抗氧化酶活力(超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT))、丙二醛(MDA)含量和渗透调节物含量变化的分析,探讨了叶片和根部对沙埋生理响应的差异。试验按滨麦成株株高(约40 cm)对其进行了轻度沙埋(在株高1/4处)、中度沙埋(2/4处)和重度沙埋(3/4处)。在沙埋第6天,分别测定了不同厚度沙埋处理下,植株各段叶片和根抗氧化酶活力、MDA和渗透调节物含量。结果表明,轻度和中度沙埋均加速植株生长。与对照相比,经轻度、中度沙埋处理6 d,叶片平均MDA含量增加,在重度沙埋下降低。不同厚度沙埋6 d,叶片平均SOD活力和脯氨酸含量增加,而CAT活力、可溶性糖和可溶性蛋白质含量下降。但不同厚度沙埋均使沙上叶片MDA、脯氨酸、可溶性蛋白质含量和SOD和CAT活力增加,尤其是叶片顶部增加最为明显,使沙下叶片MDA、可溶性糖、可溶性蛋白质含量和CAT活力下降,导致同株沙上和沙下叶片MDA、脯氨酸、可溶性糖、可溶性蛋白质含量和SOD和CAT活力差异显著(P0.05)。与叶片相比,根中MDA、可溶性蛋白质含量和SOD和CAT活力较低,而POD活力和可溶性糖含量较高并与叶片差异显著(P0.05)。不同厚度沙埋6 d,滨麦根中MDA和可溶性蛋白质含量变化较小,可溶性糖含量和CAT、POD、SOD活力略有降低。研究表明,滨麦根和叶片对不同厚度沙埋的生理响应不同。沙埋直接作用于叶片并诱发叶内氧自由基积累,但叶片通过快速激活的抗氧化酶保护系统(CAT、SOD)维持氧自由基代谢平衡,以及渗透调节物(脯氨酸、可溶性糖)的积累维护细胞水分代谢平衡,并满足能量的需求和快速生长。但在不同厚度沙埋下,由于根系不受沙埋直接影响而生理变化较小,并且还维持较低的膜脂过氧化水平,这可能是根能维持正常的吸水输水功能并在沙埋处理过程中和沙埋后地上叶片快速生长摆脱沙埋的重要物质基础。     

Inducer effect of Tween 20 permeabilization treatment used for release of stored tropane alkaloids inDatura innoxia Mill. hairy root cultures

Summary The effects of Tween 20 as permeabilizing agent on tropane alkaloids fromDatura innoxia Mill. hairy root cultures have been studied. The kinetics of the alkaloid release is detailed and shows three different stages: an initial rapid increase of the alkaloid level within the roots and in the culture medium, followed by a slower but higher increase of the alkaloid concentration in the medium. During this phase, the alkaloid concentration within the roots returned to a lower value. Finally, after a longer time, the quantity of hyoscyamine in the medium decreased significantly with a variable rate. According to the total alkaloid content per flask determinations under different conditions, it is clearly demonstrated that Tween treatment permeabilized the roots, but also acted as an inducer.     

Production of podophyllotoxin using cross-species coculture of Linum flavum hairy roots and Podophyllum hexandrum cell suspensions

Novel cross-species coculture systems using Linum flavum hairy roots and Podophyllum hexandrum cell suspensions were applied for in vitro production of podophyllotoxin. The hairy roots and suspensions were cocultured in Linsmaier and Skoog medium in dual shake flasks and dual bioreactors. In separate experiments, coniferin feeding was shown to be an effective strategy for increasing the accumulation of podophyllotoxin in P. hexandrum suspensions. Because roots of L. flavum are a natural source of coniferin, hairy roots of this species were used in coculture with P. hexandrum to provide an in situ supply of coniferin. Compared with P. hexandrum suspensions cultured alone in shake flasks or bioreactors, podophyllotoxin concentrations in cocultured P. hexandrum cells were increased by 240% and 72% in dual shake flask and dual bioreactor systems, respectively. The availability and stability of coniferin in the medium are the most likely factors limiting podophyllotoxin synthesis in coculture. Intensification of the coculture process is required to further improve total podophyllotoxin accumulation on a volumetric basis.     

Hairy roots of Brugmansia candida that grow without agitation: biotechnological implications

Hairy roots of Brugmansia candida that grew without agitation were obtained. Kinetics of growth and production of the tropane alkaloids scopolamine and hyoscyamine, with and without agitation, were studied. The exponential growth rate was higher in the roots that were exposed to shaking (0.13 d(-1)) than in the nonagitated ones (0.09 d(-1)). The specific production and the levels per flask of both alkaloids were enhanced without shaking. The use of these roots in large-scale productions could be economically advantageous. It remains to be seen if the data obtained in shake flasks can be extrapolated to large-scale bioreactors.     

Influence of sucrose concentration and phosphate source on biomass and metabolite accumulation in adventitious roots of Pseudostellaria heterophylla

In this study, we investigated the induction of Pseudostellaria heterophylla adventitious root and the effects of sucrose concentration and phosphate source on biomass increase and metabolites accumulation. These roots were initially cultured in Murashige and Skoog medium for 4 weeks. IBA 3.0 mg L^?1 proved to be the best auxin for inducing adventitious roots and the frequency of adventitious roots induced from roots (100 %) was higher than that from leaves (78 %) and stems (27 %). The medium with 4 % sucrose resulted in the optimum biomass i.e. 1.04 g/flask DW, and the content of saponin and polysaccharides reached the peak i.e. 0.676 and 24.4 %, respectively. With regards to phosphate source, 1.25 mM phosphate concentration was more favorable for biomass of roots (0.87 g/flask of DW), whereas the optimum saponin (0.74 %) and polysaccharides (22.09 %) were achieved with 2.5 mM phosphate. However, the saponin content at 2.5 mM phosphate did not show significant difference from the saponin content at 0.625 mM (0.69 %) or 3.75 mM phosphate (0.69 %).     

MOVEMENT OF EELWORMS

The optimum crumb sizes for movement of potato-root eelworm larvae in a sandy loam, a heavy clay and a peat soil were 150–250 and 250–400 μ. Mobility was very similar in clay and sandy loam, in both of which there was an optimum suction for movement. In the peat, however, mobility increased with suction and no optimum suction was established. Larvae may be able to move in peat at high suctions because friction between the larvae and the peat crumbs is less than between clay or sand crumbs. Larvae moved to the wet end of a moisture gradient in sand, the number increasing with the steepness of the gradient. The rate of spread of larvae in sand 150–250 μ diameter varied between 2 and 3 cm. a day, depending on suction. As pore size increases, any upward movement in a moisture gradient is opposed by falling under gravity. Larvae do not respond to a moisture gradient or fall under gravity in sand where the width of the pore approximates to the diameter of the larva. The presence of host roots also counteracted the response to a moisture gradient; the degree of orientation to the roots increased with the time the roots were in the sand. Direct observation on larvae, newly emerged from cysts, in the presence of host plant roots, suggests that larvae orientate themselves at a distance from the root and do not reach the root by random movement. Many of the movements of eelworms are explicable by considering the relationship between pore size, eelworm diameter and water distribution, and a diagram relates movement and various soil factors.