盐胁迫下褪黑素对小麦种子萌发和幼苗生理特性的影响

盐碱地会严重影响小麦种子的萌发和幼苗的生长。为了探究褪黑素对盐胁迫下小麦种子萌发和幼苗生长的影响,研究了NaCl（100 mmol·L^-1）胁迫下不同浓度的褪黑素（5、50、100、150、250 μmol·L^-1）对小麦种子萌发、幼苗生长、光化学活性、叶绿素含量以及根细胞活力的影响。结果发现,100 μmol·L^-1褪黑素能够显著缓解NaCl胁迫对小麦种子萌发的抑制作用;100~150 μmol·L^-1褪黑素可明显改进盐胁迫下小麦幼苗的生长状况,显著缓解盐胁迫对PS （光系统）Ⅱ光化学活性的抑制和小麦幼根细胞死亡的发生;150 μmol·L^-1褪黑素显著促进了小麦叶片叶绿素合成。综合分析表明,施用外源褪黑素可有效缓解盐胁迫对小麦造成的萌发率、光化学活性、叶绿素含量下降、生长迟缓、根细胞死亡等不利影响,以100~150 μmol·L^-1褪黑素的缓解效果最为明显。     

干旱胁迫下外源褪黑素对小麦生长和光系统活性的影响

为了从光系统活性探讨褪黑素对干旱胁迫下小麦生长的调节作用,通过石英砂盆栽试验,设置对照（CK）、5 μmol·L^-1褪黑素处理、25 μmol·L^-1褪黑素处理、100 μmol·L^-1褪黑素处理、干旱胁迫处理、5 μmol·L^-1褪黑素+干旱胁迫处理、25 μmol·L^-1褪黑素+干旱胁迫处理及100 μmol·L^-1褪黑素+干旱胁迫处理,分析了根施褪黑素对干旱胁迫下小麦叶片生理和光合作用的影响。结果表明,干旱胁迫显著降低了小麦叶片的相对含水量、地上部生物量及光合效率,抑制了植株的生长,而干旱胁迫下25 μmol·L^-1褪黑素处理最为显著地增加了小麦叶片相对含水量、地上部生物量及叶绿素含量,并显著提高了小麦叶片的净光合速率、气孔导度、光系统Ⅱ（PS Ⅱ）的最大荧光、PS Ⅱ最大光化学效率、远红光适应下的最大P700改变量、光系统I（PSⅠ）的实际光能转换效率及PSⅠ供体侧限制引起的非光化学能量耗散的量子产量。相反,CO₂浓度和PSⅠ受体侧限制引起的非光化学能量耗散的量子产量下降。蛋白免疫杂交分析表明,外源褪黑素处理可显著减少干旱胁迫下Lhca2蛋白含量的下降。由此表明,干旱胁迫下褪黑素可通过改变叶片的水分状况和提高叶片的光合能力来减轻干旱胁迫对小麦植株生长的抑制作用。     

LA浸种对小麦种子萌发和幼苗生理特性的影响

为了解拉肖皂苷元（LA）对植物生长的调控作用,以小麦品种小偃22为试验材料,研究了不同浓度LA浸种处理对小麦种子萌发和幼苗生理特性的影响。结果表明,0.001 m·L^-1 LA浸种处理下小麦种子的发芽率、发芽势和发芽指数最高,分别较对照提高了13.13%、214.81%和55.17%。0.005 mg·L^-1 LA浸种处理下小麦幼苗的根长和真叶长较对照分别提高了92.21%和46.75%。小麦幼苗的株高、鲜重和干重以0.001 mg·L^-1处理最高,分别比对照提高了26.53%、32.91%和122.22%。0.001 mg·L^-1LA浸种处理下,小麦叶片SOD、POD和CAT活性分别提高了39.43%、136.62%和60.42%,MDA含量降低60.49%。0.005 mg·L^-1 LA浸种处理下小麦幼苗的可溶性糖、可溶性蛋白以及游离脯氨酸的含量较对照提高了70.74%、32.12%和34.47%,差异显著。综上所述,适宜浓度LA浸种可显著促进小麦种子的萌发和幼苗的生长,提高小麦幼苗的抗氧化酶活性和渗透调节物质含量,对于小麦壮苗具有重要意义。     

纳米ZnO-Ag复合材料对小麦根腐病菌侵染下小麦幼苗生长的影响

为探讨纳米杀菌剂对小麦根腐病害的防控效果，以小麦京东8号为供试材料，通过盆栽试验，探究土壤接种麦根腐平脐孺孢（Bipolaris sorokiniana）情况下，自制纳米ZnO-Ag复合材料对B.sorokiniana的抑菌效果和小麦幼苗生长的影响。结果表明，纳米ZnO-Ag复合材料能显著抑制小麦根腐菌菌丝的生长，抑制作用随ZnO-Ag浓度的增加而增强；200 μg·mL^-1ZnO-Ag对病菌菌丝的抑制率高达91.17%，有效中浓度（EC₅₀）为34.15 μg·mL^-1；在土壤接菌情况下，经大于12.5 μg·g^-1ZnO-Ag复合材料处理，小麦种子的发芽势和发芽率、幼苗的根长、株高、地上部鲜重和干重、地下部鲜重和干重均显著高于对照组（未加纳米材料），小麦幼苗发病率显著低于对照组；浓度大于12.5 μg·g^-1ZnO-Ag处理组的小麦幼苗根长/株高和根冠比显著低于对照组。由此可得，纳米ZnO-Ag复合材料能够有效抑制土壤中小麦根腐病菌的生长，促进小麦种子萌发和幼苗生长，降低幼苗发病率。此结果为ZnO-Ag防控小麦根腐害提供了理论依据。     

氯化胆碱浸种处理对盐胁迫下小麦种子萌发以及幼苗生长的影响

为了明确氯化胆碱对盐害的缓解作用,以小麦品种周麦18为材料,采用不同浓度（0、200、400、600和800 mg·L^-1）的氯化胆碱溶液浸种处理,研究氯化胆碱浸种对NaCl（150 mmol·L^-1）胁迫下种子萌发以及幼苗生长的影响。结果表明,盐胁迫下小麦种子的萌发受到抑制,叶片叶绿素含量以及根系活力下降,叶片质膜透性增大,丙二醛和脯氨酸含量上升;而400 mg·L^-1氯化胆碱浸种处理能明显提高盐胁迫下小麦种子的萌发率,缓解幼苗叶绿素的降解,增加可溶性糖含量,提高根系活力,降低叶片质膜透性,减少丙二醛和脯氨酸的积累。由此说明,氯化胆碱浸种可以缓解盐胁迫引起的小麦幼苗的失水伤害以及膜脂过氧化,从而增强小麦幼苗的抗盐性。     

6-BA浸种对HgCl2胁迫下小麦种子萌发和幼苗生长的影响

为探讨6-苄基腺嘌呤（6-BA）浸种对HgCl₂胁迫下小麦种子萌发及其幼苗生长的缓解作用,以3个小麦品种为材料,研究了不同浓度6-BA浸种对200 mg·L^-1HgCl₂胁迫下小麦种子发芽、幼苗生长、抗氧化酶活性、可溶性蛋白和丙二醛含量的影响。结果表明,200 mg·L^-1HgCl₂处理后,3个小麦品种种子的发芽势、发芽率、根长、芽长和鲜重降低,幼苗的抗氧化酶活性和可溶性蛋白含量降低,丙二醛含量增加。一定浓度6-BA浸种可以缓解HgCl₂胁迫对小麦种子萌发的抑制作用,但对小麦的根长、芽长和鲜重的影响因小麦品种而不同。HgCl₂胁迫下,3个小麦品种幼苗的SOD、POD活性和可溶性蛋白含量随着6-BA浓度的增加均基本呈先升高后降低的趋势,最佳6-BA浓度因品种而不同;3个小麦品种的MDA含量均呈先降低后升高的趋势,以6-BA浓度为15 mg·L^-1时MDA含量最低。说明一定浓度6-BA浸种能够缓解HgCl₂胁迫对小麦种子萌发和幼苗生长的毒害作用,但最佳6-BA浓度因小麦品种的不同而不同。     

外源NO对盐胁迫下小麦幼苗叶片丙二醛、叶绿素及氧化酶的影响

为了给小麦抗盐育种和盐渍土小麦丰产栽培提供理论依据,本试验以SNP为外源NO供体,分析不同浓度外源NO浸种对盐胁迫（100 mmol·L^-1 NaCl）下小麦幼苗叶片MDA含量、叶绿素含量、SOD活性和CAT活性的影响。结果表明,不同浓度NO可以显著降低盐胁迫后叶片中MDA含量,显著提升叶绿素a和叶绿素b含量,显著增强SOD和CAT活性（P<0.05）,其中以0.06 mmol·L^-1 SNP浸种处理效果最好。因此,外源NO对盐胁迫小麦幼苗的生长有一定的缓解作用。     

外源甜菜碱和脯氨酸对盐胁迫下大麦种子萌发及幼苗生长的影响

为探讨盐胁迫条件下外源甜菜碱（GB）和脯氨酸（Pro）对不同大麦品种种子萌发及幼苗的效应，以课题组前期筛选到的耐盐品种中川大麦和盐敏感品种ZY218为材料，在萌发期和苗期以200 mmol·L^-1NaCl为胁迫条件，分别施加浓度为0、0.5、1.0、5.0、10.0 mmol·L^-1的外源GB和浓度为0、5.0、15.0、30.0、45.0 mmol·L^-1的外源Pro进行处理，测定并分析了不同处理下大麦萌发及幼苗相关指标。结果表明，与不添加外源物质的对照相比，施加外源GB和Pro均可有效缓解盐胁迫对大麦种子萌发及地上部分生长的抑制作用；提高叶片过氧化物酶（POD）、超氧化物歧化酶（SOD）和过氧化氢酶（CAT）活性及叶绿素含量；外源Pro可以显著增加幼苗的总根长、总根体积和总根表面积，有效缓解盐胁迫对大麦幼苗根系生长的抑制作用，且对盐敏感品种效应更大。因此，施加外源GB或Pro可有效缓解盐胁迫对大麦种子萌发和幼苗生长的抑制作用。     

喷施硒肥对黑小麦籽粒产量及硒含量的影响

为探究叶面喷施硒肥对黑小麦籽粒产量和硒含量的效应,以临黑131和冬黑1206两个黑小麦品种为材料,分别在拔节期（4月17日）、孕穗期（4月28日）和灌浆期（5月14日）3个时期喷施0、10、20、30 mg·L^-14个浓度的亚硒酸钠溶液,分析叶面喷施不同浓度硒对黑小麦籽粒产量及硒含量的影响。结果表明,拔节期和孕穗期喷施硒肥对黑小麦有增产效果,而灌浆期喷施硒肥增产效果不明显;孕穗期和灌浆期喷施硒肥浓度为10 mg·L^-1至20 mg·L^-1时,黑小麦籽粒可达到富硒标准（0.15～0.30 mg·kg^-1）。综上所述,在黑小麦孕穗期叶面喷施浓度介于10 mg·L^-1至20 mg·L^-1之间的Na₂Se0₃溶液,在不减少产量的前提下,可显著提高黑小麦籽粒中的硒含量,使黑小麦籽粒达到富硒水平,增加黑小麦的营养价值。     

外源NO对镧胁迫下燕麦幼苗叶片抗坏血酸-谷胱甘肽循环的影响

为探讨外源一氧化氮(NO)对稀土元素镧(La)胁迫下植物抗氧化系统的调节机制,采用水培方法,研究了NO供体硝普钠(SNP)对200 μmol·L^-1 La³⁺胁迫下燕麦幼苗生长、La含量及叶片抗坏血酸-谷胱甘肽循环的影响。结果表明,施用100 μmol·L^-1 SNP显著缓解了La³⁺胁迫对燕麦幼苗根长、株高和植株干重的抑制,使叶片过氧化氢和丙二醛含量增幅下降;地上部La含量显著降低,并有效逆转了La³⁺胁迫诱导的还原型抗坏血酸(AsA)、氧化型抗坏血酸(DHA)、还原型谷胱甘肽(GSH)和氧化型谷胱甘肽(GSSG)含量的升高,提高了AsA/DHA和GSH/GSSG比值及单脱氢抗坏血酸还原酶(MDHAR)、脱氢抗坏血酸还原酶(DHAR)、抗坏血酸过氧化物酶(APX)和谷胱甘肽还原酶(GR)活性。表明La胁迫下外源NO可抑制La从根系向地上部的转运,并通过提高抗坏血酸-谷胱甘肽循环相关酶活性及AsA/DHA和GSH/GSSG比值,减轻La胁迫诱导的H₂O₂对燕麦幼苗的伤害。     

Genotypic Variations in Response of Lateral Root Development to Fluctuating Soil Moisture in Rice

Abstract

Developmental plasticity in lateral roots may be one of the key traits for the growth of rice plants under soil moisture fluctuations. We aimed to examine responses in seminal root system development to changing soil moisture for diverse rice cultivars. Special attention was paid to the two different types of lateral roots ; the generally long, thick L type capable of branching into higher orders, and the non-branching S type. Plants were grown in half-split polyvinyl chloride tubes fixed with transparent acrylic plate for root observation under glasshouse conditions. When plants were grown first under drought conditions, then rewatered, the seminal root system development in terms of dry weight and total length was promoted as compared with plants grown under continuously well-watered conditions in IR AT 109 and Dular, drought tolerant cultivars. Promoted production of L type lateral roots mainly contributed to the development of the longer seminal root system. Plants exposed to soil submergence before they were grown under drought conditions did not show such promoted responses in these two cultivars. However, in KDML 105, a drought tolerant cultivar, the production of especially L type laterals was substantially promoted under drought and rewatered conditions. Honenwase was characterized by the shallow root system and great reduction in root system length when soil moisture becomes limited. These facts show that genotypic variations exist in the plastic response of rice seminal root system and that the L type lateral root plays a key role in manifestation of this plasticity.     

Simple Bioassay for PAMP-Triggered Immunity in Rice Seedlings Based on Lateral Root Growth Inhibition

Pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) is an essential layer of plant disease resistance. Robust bioassays for PTI are pre-required to dissect its molecular mechanism. In this study, we established that lateral root growth inhibition as a simple and robust measurement of PTI in rice seedlings. Specifically, flg22, a well-characterized PAMP from bacterial flagellin, was used to induce PTI in rice seedlings. While flg22 treatment induced PR gene expression and mitogen-activated protein kinase activation in the roots of rice seedlings to support the PTI triggered, this treatment substantially repressed lateral root growth, but it did not alter primary root growth. Moreover, treatments with chitin (i.e., a fungal PAMP) and oligogalacturonides (i.e., classical damage-associated molecular pattern) clearly inhibited the lateral root growth, although a priming step involving ulvan was required for the chitin treatment. The bioassay developed was applicable to various rice cultivars and wild species. Thus, lateral root growth inhibition represents a simple and reliable assay for studying PTI in rice plants.     

Effects of Low Root Temperature on Dry Matter Production and Root Water Uptake in Rice Plants

Abstract

Chilling is a major constraint in rice production in cool climates. In rice (Oryza sativa L.) plants, both the air temperature and the water (soil) temperature affect various growth processes independently, and low root zone temperature (thus, root temperature) can inhibit rice growth and yield. In this study, we investigated the effect of low root temperature on rice growth in relation to dry matter production and root water uptake. Plants were grown in hydroponic solutions at two temperatures, one equivalent to air temperature and the other 14ºC for 15 d starting 11 d after germination. Low temperature of the solution (low root temperature) inhibited dry matter production of rice plants by decreasing leaf area rather than photosynthetic rate. The response of leaf area was affected by changes in plant water status, that is relative water content (RWC) of stem was decreased by low root temperature resulting in reduced leaf area. The decrease in RWC caused by low root temperature was related to that in root hydraulic conductance (K_r). The responses of transpiration (E) and K_r to the low root temperature depended more on root surface area than on changes in hydraulic conductance per unit root surface area (Lp_r). These results suggest that dry matter production under the low root temperature condition is controlled mainly by quantitative growth parameters such as leaf area and root surface area.     

Genotypic Variations in Responses of Lateral Root Development to Transient Moisture Stresses in Rice Cultivars

Abstract

Soil water regimes under field conditions inevitably tend to fluctuate ranging from drought to waterlogging. Genotypes that adapt better to such changing hydrologic conditions are assumed to have the ability to maintain root system development under such conditions. This study aimed to evaluate the responses of root system development based on lateral root production to transient moisture stresses, and the contribution of the elongation of seminal and nodal root axes and their lateral, root branching, and aerenchyma development in the seminal root axis, to root system development. The seedlings of two aerobic genotypes (UPLRi7 and NSICRc9) and one irrigated-lowland genotype (PSBRc82), and two parental genotypes (Nipponbare and Kasalath) of chromosome segment substitution lines (CSSLs) were grown by hydroponics. The seedlings were exposed to a drought condition by adding polyethylene glycol to the solution for 7 days and then to an O₂-deficient stagnant condition for 7 days (drought-to-stagnant condition), or to reverse successive conditions (stagnant-to-drought condition). Under both conditions, the aerobic genotypes showed greater ability to produce lateral roots than the irrigated-lowland genotype. Under the transient stagnant-to-drought condition, the root traits that contributed to greater lateral root production in the aerobic genotypes were faster seminal root elongation that was closely associated with branching of lateral roots, and greater nodal root production. Under transient drought to stagnant condition; these were faster seminal root elongation mediated by higher aerenchyma formation, and greater nodal root production. Kasalath showed much greater ability to produce lateral roots under both transient moisture stress conditions than Nipponbare. This indicates the potential utility of the CSSLs for precise identification of desirable root traits with less genetic confounding.     

不同类型水稻的根系分布特征比较

对不同类型水稻的根系分布进行了比较,研究发现籼型水稻和粳型水稻的根系垂直分布有比较明显的差异,在20 cm以下的根系干物重占总根重的百分比籼型水稻一般在10%以下,而粳型水稻一般高于15%。根深指数对比结果同样表明了这一趋势,粳型水稻的根深指数一般在10以上,而籼型水稻的根深指数一般低于10。上述两个指标均表明,与籼型水稻相比,粳型水稻具有明显的深扎根性。亚种间杂交水稻的根系分布更接近粳型水稻。     

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.     

Root growth,soil water variation,and grain yield response of winter wheat to supplemental irrigation

Water shortage threatens agricultural sustainability in the Huang-Huai-Hai Plain of China. Thus, we investigated the effect of supplemental irrigation (SI) on the root growth, soil water variation, and grain yield of winter wheat in this region by measuring the moisture content in different soil layers. Prior to SI, the soil water content (SWC) at given soil depths was monitored to calculate amount of irritation water that can rehydrate the soil to target SWC. The SWC before SI was monitored to depths of 20, 40, and 60 cm in treatments of W20, W40, and W60, respectively. Rainfed treatment with no irrigation as the control (W0). The mean root weight density (RWD), triphenyl tetrazolium chloride reduction activity (TTC reduction activity), soluble protein (SP) concentrations as well as catalase (CAT), and superoxide dismutase (SOD) activities in W40 and W60 treatments were significantly higher than those in W20. The RWD in 60–100 cm soil layers and the root activity, SP concentrations, CAT and SOD activities in 40–60 cm soil layers in W40 treatment were significantly higher than those in W20 and W60. W40 treatment is characterized by higher SWC in the upper soil layers but lower SWC in the 60–100-cm soil layers during grain filling. The soil water consumption (SWU) in the 60–100 cm soil layers from anthesis after SI to maturity was the highest in W40. The grain yield, water use efficiency (WUE), and irrigation water productivity were the highest in W40, with corresponding mean values of 9169 kg ha^?1, 20.8 kg ha^?1 mm^?1, and 35.5 kg ha^?1 mm^?1. The RWD, root activities, SP concentrations, CAT and SOD activities, and SWU were strongly positively correlated with grain yield and WUE. Therefore, the optimum soil layer for SI of winter wheat after jointing is 0–40 cm.     

两个亚种间杂交稻组合的根系生理活性

以亚种间杂交组合Ⅱ优2070及恢复系2070、Ⅱ优419及恢复系中419为材料,分析测定了在不同生育期水稻的根系生长、伤流液量及根源细胞分裂素含量的变化情况,结果表明亚种间杂交组合具有根系生长优势和较强的伤流强度,根系伤流液中玉米素及细胞分裂素总量高于恢复系,杂交组合根系活力强,与玉米素及细胞分裂素总量下降缓慢有关。     

木薯新品种华南8号的选育

木薯新品种华南8号(Manihot esculenta Crantz.cv.M.SC8)是由中国热带农业科学院热带作物品种资源研究所通过CIAT从泰国引进的CMR38-120的自然杂交种F1无性系后代中选育而成的。该品种具有良好的丰产性和广泛的适应性,并有很强的抗风能力和出苗率。其鲜薯产量约36.79t/hm2,比现大面积种植的当家品种华南20(5SC205)增产40.90%,其块根干物率和淀粉含量分别为质量分数40.86%和32.69%,分别比SC205高2.70个百分点和2.16个百分点。因此,华南8号是一个高产、优质的饲用和工业应用型木薯新品种。为了保护新品种及便于产权鉴定,对新品种华南8号建立分子指纹。     

大豆断根发根的解剖学研究

通过大豆断根处理后发根的解剖学观察,结果表明:大豆根的初生木质部为4原型,侧根发生于对着木质束的中柱鞘细胞;根茎转位区侧生根发生部位和过程与侧根相似;茎的不定根由射线薄壁细胞分化而成。断根处理与对照发根规律基本一致,不同断根处理根系形成有明显差异,适宜的断根处理可改善根系生长状态与吸收条件。