基于盐胁迫条件下施用氮钾肥对面包果养分吸收及渗透物质积累的影响

为探究不同氮钾配比影响盐胁迫下面包果生长的营养生理机制,以面包果[Artocarpus altilis (Parkinson) Fosberg]为材料,研究不同氮钾配比对盐胁迫下面包果养分吸收及渗透物质的影响。结果表明：与阴性对照（N₀K₀+W）相比,单盐胁迫（N₀K₀+S）对面包果生长指标有一定抑制作用,对根系生长指标有一定促进作用,其中N₁K₁+S处理的面包果地下部干重较单盐胁迫处理呈增加趋势,根系生长指标呈下降趋势。所有盐胁迫处理均显著增加根茎叶中的Na⁺含量和Na⁺/K⁺。与阳性对照（N₀K₀+S）相比,N₁K₁+S处理显著增加根茎叶中K⁺含量,减少叶中Na⁺含量和Na⁺/K⁺。N₁K₂+S处理较N₁K₁+S处理显著减少根茎中的Na⁺含量,N₂K₂+S处理较N₂K₁+S处理显著增加根中的N、P、K⁺、Na⁺含量和Na⁺/K⁺,茎中的N和K⁺含量以及叶片中的Na⁺含量、Na⁺/K⁺和叶片可溶性糖含量。N₂K₁+S处理较N₁K₁+S处理显著减少根、茎中K⁺含量,增加叶片N、Na⁺含量和Na⁺/K⁺,降低叶片可溶性糖含量,增加脯氨酸含量。N₂K₂+S处理较N₁K₂+S处理显著增加根、茎、叶中的Na⁺含量和Na⁺/K⁺。综上所述,适量增施氮钾肥通过调节K⁺、Na⁺向各器官的运输缓解盐胁迫对面包果生长及养分吸收的抑制效应,可为盐碱地的面包果施肥提供参考。     

耐盐性不同水稻品种对盐胁迫的响应及其生理机制

【目的】阐明耐盐性不同水稻品种对盐胁迫的响应差异及其生理机制。【方法】耐盐水稻品种连鉴5号、盐稻16Z38和盐敏感水稻品种华粳5号、连粳17号生长于盆钵，盆栽土设置2个不同盐浓度处理：0 g/kg (对照)；3 g/kg(盐胁迫)。【结果】与对照相比，在盐胁迫下两类品种均有不同程度的减产，耐盐品种减产的幅度明显小于盐敏感品种。耐盐水稻品种具有较高的产量主要在于较高的颖花量和结实率。与盐敏感品种相比，耐盐水稻品种在分蘖中期、拔节期、抽穗期和灌浆中期叶片中超氧化物歧化酶等抗氧化酶活性较高，拔节期和抽穗期具有较高根系脯氨酸含量、脯氨酸合成酶活性和较高的K⁺/Na⁺值，分蘖至拔节以及抽穗至成熟期具有较高的作物生长率，抽穗期具有较高的叶面积指数和叶片SPAD值，抽穗至灌浆中期具有较高的根系氧化力。【结论】在盐胁迫下耐盐水稻品种较高的总颖花量、较强的抗氧化和渗透调节能力、较高的根系氧化力和K⁺/Na⁺值是其获得较高产量的重要原因。在盐胁迫下叶片超氧化物歧化酶活性较强和根系氧化力较高可作为评定水稻品种耐盐性的重要...     

盐胁迫对热带水稻生长、生理生化特性及产量构成的影响

我国土壤盐渍化问题日趋严重，水稻是盐渍化土地改良的首选粮食作物，而盐胁迫是影响水稻生长和产量的主要非生物胁迫之一。为全面深入了解盐胁迫对水稻的影响，以31份不同耐盐性的热带水稻品种(系)为试验材料，采用幼苗期培养箱水培法和全生育期盆栽土培法开展试验，研究0 NaCl(CK)、0.3%NaCl和0.6%NaCl对热带水稻生长、生理生化特性及产量构成的影响。结果表明：(1)盐胁迫抑制了热带水稻幼苗和根系的生长。其中苗高和根数随NaCl浓度的升高而显著降低；0.3%NaCl和0.6%NaCl处理的根长显著低于CK处理；0.6%NaCl处理的苗鲜重显著低于CK和0.3%NaCl处理。(2)盐胁迫使热带水稻叶片的叶绿素积累降低，0.3%NaCl和0.6%NaCl处理的叶绿素a、叶绿素b及类胡萝卜素含量均显著低于CK处理；脯氨酸(Pro)、丙二醛(MDA)及Na⁺积累增加，0.6%NaCl处理的Pro含量、MDA含量及Na⁺含量均显著高于CK和0.3%NaCl处理；K⁺积累下降，0.3%NaCl和0.6%NaCl处理的K^+...     

不同水稻品种对NaCl胁迫的生理响应及耐盐性评价

土壤盐渍化是限制作物生长的重要因素之一，培育水稻耐盐新品种，对扩大水稻种植面积具有重要意义。为探究不同品种水稻幼苗的生长及生理的变化趋势，明确不同水稻品种苗期耐盐性强弱，以 5 个水稻品种为试验材料，采用水培方式研究不同浓度 NaCl(0、70、140 mmol/L)处理对水稻苗期生长及相关生理指标的影响，并利用主成分分析及隶属函数法进行综合评价其耐盐性。结果表明，盐胁迫下，盐分对各水稻品种的根长、根表面积、根体积、根尖数及根平均直径总体上起抑制作用，其中‘HH11’和‘日本晴’的根系生长指标值变化较小，‘9311’和‘JX99’的根长、根体积、根表面积、根尖数均受到显著抑制，‘HD961’平均根尖数最多。随着 NaCl 浓度增大，各品种株高、根系活力总体呈逐渐下降趋势，叶绿素总含量、相对电导率、丙二醛含量、脯氨酸含量、根系 Na⁺/K⁺总体呈上升趋势，而根系 Na⁺、K⁺含量呈先升高后减少的趋势。其中，盐胁迫下‘9311’和‘JX99’相对电导率、脯氨酸含量增幅最大，‘日本晴’和‘HH11’的丙二...     

不同氮素形态、pH对茶树元素吸收及有机酸含量影响

以茶树龙井43为材料,利用营养液水培试验研究了不同氮素形态、pH对茶树体内阴阳离子和有机酸的影响,初步明确茶树养分吸收与氮素形态及pH的关系。结果表明,与NO_3^--N处理相比,NH_4^+-N处理提高-的含量以及根中N、SO_4^2-含量,但是NH_4^+-N处理降低了茶树对Ca、Mg、B、Mn、Zn的吸收,也减少了成熟叶中SO_4^2-、根中H_2PO_4^-的累积量。与其他处理相比,NO_3^--N处理提高了成熟叶中苹果酸、草酸、柠檬酸浓度。茶树对养分的吸收、积累也与介质pH有关,尤其是pH与氮素互作时。在NO_3^--N处理下,pH 6.0显著提高了茶树对B、Mn、Zn的吸收和根中K、Ca、Mg浓度。茶树中有机酸含量受pH影响较大,与pH 4.0和pH 5.0相比,pH 6.0提高了茶树成熟叶中苹果酸、柠檬酸、草酸浓度以及根中草酸浓度。茶树对养分的吸收、积累与自身体内有机酸浓度有较好的相关性,茶树中全氮含量与柠檬酸、草酸浓度具有显著负相关性,而阳离子Zn²⁺、Ca²⁺、Mg²⁺、Mn²⁺含量与柠檬酸、草酸浓度具有显著正相关性。     

亚精胺对盐胁迫下黄华占水稻幼苗根系抗氧化酶活性及Na+稳态的影响

以黄华占种子为材料，研究盐胁迫条件下，外源亚精胺(Spd)对水稻幼苗根系的生长、抗氧化酶活性、活性氧(ROS)代谢、丙二醛(MDA)以及Na⁺稳态的影响。结果表明，经100 mmol/L NaCl溶液处理水稻幼苗根系的ROS、·O₂^-、H₂O₂、Na⁺和MDA含量显著升高，过氧化物酶(POD)和过氧化氢酶(CAT)活性显著降低；在盐胁迫条件下，施用0.1 mmol/L Spd显著提高水稻幼苗根系的CAT和POD活性，显著降低ROS、·O₂^-、H₂O₂、Na⁺和MDA含量，从而减轻Na⁺毒害和过氧化造成的膜损伤，保护生物膜系统的稳定，维持细胞的稳态。     

钙离子对绿茶浸提茶汤理化与感官品质的影响

研究了含不同质量浓度钙离子（0~100mg/L）的水对绿茶浸提茶汤的理化成分及感官品质的影响。研究结果表明,随着钙离子质量浓度的升高,浸提茶汤浊度增加,pH值下降;总固形物和氨基酸含量呈增加趋势,茶多酚和蛋白质含量呈下降趋势,而咖啡碱和黄酮化合物含量差异不显著;儿茶素EGC含量呈增加趋势,C、EGCG、GCG、ECG及CG含量都呈下降趋势,EC含量差异不显著;Al³⁺、Cu²⁺、Na⁺、Zn²⁺含量呈下降趋势,而K⁺、Mg²⁺、Mn²⁺含量呈增加趋势;茶汤感官品质下降,逐渐变浑浊,熟闷味加重,苦涩味增加。钙离子主要通过参与冷后浑形成、诱导儿茶素组分异构化及氧化分解反应等作用影响茶汤品质。     

活性腐殖酸肥对花生叶片光合特性及产量的影响

为明确活性腐殖酸肥对花生叶片光合特性及产量的影响，促进花生肥料高效利用及绿色可持续发展，选用山花9号花生品种为试验材料，设活性腐植酸肥750 kg/hm²(FS100)、活性腐植酸肥600 kg/hm²(FS80)、活性腐植酸肥525 kg/hm²(FS70)、普通三元复合肥750 kg/hm²(PS100)、不施肥(CK)5个处理，在花生饱果成熟期测定叶绿素含量、叶面积指数、净光合速率等光合相关指标及产量。结果表明：活性腐殖酸肥显著提高了花生叶片的光合能力，与普通三元复合肥处理相比，活性腐殖酸肥处理显著提高了花生的叶面积指数、叶绿素含量和净光合速率，其中，2021年FS80处理的叶面积指数、叶绿素含量、净光合速率分别提高了8.3%、18.6%、18.0%,2022年分别提高了6.2%、7.5%、12.2%。FS100和FS80处理两年的生物产量均显著提高；单株结果数两年分别提高20.8%、13.4%和17.6%、10.1%,平均单果质量分别提高5.9%、5.3%和5.2%、4.9%。荚果产量两年分...     

外源钙及其抑制剂对蝴蝶兰幼苗耐热性的影响

为探讨Ca²⁺信号参与调节蝴蝶兰耐热性形成的生理机制,采用适宜浓度的外源Ca²⁺（CaCl₂）、胞外Ca²⁺螯合剂（EGTA）和质膜Ca²⁺通道抑制剂（LaCl₃）溶液喷施蝴蝶兰幼苗植株,以喷施蒸馏水为对照,测定高温胁迫下蝴蝶兰幼苗植株的抗氧化酶活性、丙二醛、渗透调节物质和光合色素含量的变化。结果表明,与对照相比,CaCl₂处理能显著增强超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性,增加脯氨酸、可溶性蛋白、可溶性糖、叶绿素和类胡萝卜素含量,显著降低丙二醛含量,减轻了蝴蝶兰幼苗的高温伤害,而LaCl₃和EGTA处理不同程度地降低SOD、POD和CAT活性,降低脯氨酸、可溶性蛋白、可溶性糖、叶绿素和类胡萝卜素含量,显著增加丙二醛含量,使蝴蝶兰幼苗受害加重。由此认为,Ca²⁺信号可通过参与抗氧化酶活性、脯氨酸和光合色素的代谢过程来调控蝴蝶兰幼苗耐热性的形成。     

茶树Na+/H+逆向转运蛋白基因CsNHX1、CsNHX2的克隆及表达分析

Na⁺/H⁺逆向转运蛋白（Na⁺/H⁺ antiporter,NHX）在植物生长发育与逆境响应过程中扮演着重要角色。本研究以龙井长叶茶树品种为材料,克隆获得了茶树CsNHX1和CsNHX2基因cDNA全长序列,GeneBank登录号分别为：MG722977和MG515211。生物信息学分析结果显示,CsNHX1和CsNHX2的cDNA全长分别为1β691βbp和1β757βbp,均包含1个1β626βbp的开放阅读框,编码541个氨基酸,预测分子量为59.5βkD和59.7βkD,理论等电点为7.07和8.79;蛋白序列分析结果显示,CsNHX1和CsNHX2属于典型的跨膜蛋白,均含有保守的Na⁺/H⁺ Exchanger结构域;进化树分析显示,CsNHX1和CsNHX2均为IC类中定位于液泡膜上的Class I成员。qRT-PCR结果显示,干旱、低温和盐胁迫能够显著诱导CsNHX1和CsNHX2上调表达;外源ABA处理下,CsNHX1和CsNHX2表达水平整体变化趋势不显著;高温胁迫处理下,茶树CsNHX1表达水平显著降低,而CsNHX2表达水平逐渐增加,表明茶树CsNHX1和CsNHX2参与了茶树对多种环境胁迫的响应过程,但对于不同逆境胁迫的应答模式存在一定差异。     

不同秸秆还田方式对棕壤磷素及玉米吸磷量的影响

通过田间试验,研究玉米秸秆直接还田、腐熟还田与化肥配施等处理对棕壤磷素、玉米吸磷量、玉米产量、磷肥利用率的影响。结果表明,除秸秆直接还田处理外,其他施肥处理均能显著提高土壤有效磷含量,且彼此间差异显著,以腐熟秸秆配施化肥处理最明显。各施肥处理均显著提高玉米吸磷量和玉米产量,以未腐熟秸秆配施化肥处理增产最明显。各处理的磷肥利用率从高到低依次为秸秆直接还田配施化肥处理秸秆腐熟还田配施化肥处理单施化肥处理。秸秆还田配施化肥提高了玉米产量,玉米吸磷量和磷肥利用率直接还田好于腐熟还田。     

盐胁迫下钾吸收途径的抑制对小麦叶片K~+、Na~+含量的影响

为研究盐胁迫下小麦维持钾、钠平衡的生理机制,以耐盐小麦沧麦6005和盐敏感小麦矮抗58为材料,利用TEA、NEM、Ba(NO_3)_2三种药物分别抑制钾离子通道、钾载体及非选择性阳离子通道,测定正常及盐胁迫下小麦叶片K~+、Na~+含量,比较耐盐性不同的小麦品种在K~+、Na~+吸收中的差异。结果显示,盐胁迫下,沧麦6005和矮抗58叶片K~+含量下降,Na~+含量增加;沧麦6005叶片Na~+含量低于矮抗58,K~+/Na~+比值高于矮抗58。正常条件下,NEM、TEA处理均可降低沧麦6005和矮抗58叶片K~+含量,NEM处理较TEA处理效果更为明显;TEA处理显著降低了盐胁迫下矮抗58叶片K~+含量,而NEM处理则明显降低了盐胁迫下沧麦6005的叶片K~+含量;TEA、NEM、Ba(NO_3)_2处理降低了盐胁迫下矮抗58叶片Na~+含量,仅NEM处理降低了沧麦6005叶片Na~+含量。综上所述,正常条件下,钾载体是小麦K~+吸收的主要方式;盐胁迫下,耐盐品种和盐敏感品种K~+吸收途径不同,耐盐品种的NSCCs和钾离子通道具有更强的"拒钠"能力。     

磷对NaCl胁迫下玉米幼苗渗透调节能力的影响

研究不同供磷水平对NaCl胁迫下玉米幼苗有机渗透调节物质和离子含量的影响。结果表明,盐胁迫下低磷处理玉米幼苗叶片中可溶性糖和游离氨基酸增加,根系中显著降低;增加供磷水平,叶片中可溶性糖和游离氨基酸含量下降,根系中含量上升,同时叶片和根系中可溶性蛋白含量增加。磷可降低盐胁迫下玉米幼苗各器官中的Na~+含量,同时增加各器官的K~+、Ca~(2+)和Mg~(2+)含量,降低Na~+/K~+与Na~+/Ca~(2+)比值。磷有助于维持植株的碳氮代谢平衡,促进有机渗透调节物质的运输与分配,改善各器官的离子平衡,增强植株的渗透调节能力,从而缓解盐胁迫带来的伤害。     

Comparative effects of salt and alkali stresses on organic acid accumulation and ionic balance of seabuckthorn (Hippophae rhamnoides L.)

Seabuckthorn (Hippophae rhamnoides L.) is uniquely capable of growing well under various extreme environmental conditions, such as water deficit, salt stress, low temperature, and high altitude. It is of economic value and its berries are used in cosmetics and pharmaceutical products. In this study, we compared the effects of salt stresses (9:1 molar ratio of NaCl to Na₂SO₄, pH 6.48–6.65) and alkali stresses (9:1 molar ratio of NaHCO₃ to Na₂CO₃, pH 8.70–8.88) on the levels of inorganic ions and organic acids in H. rhamnoides L. to elucidate the physiological mechanism by which it tolerates salt or alkali stress (high pH). The results showed that, in leaves and stems under alkali stress, the Na⁺ content increased to a much greater extent than under salt stress. Neither salt nor alkali stress decreased the K⁺ content in leaves and stems; however, in roots, the K⁺ content decreased sharply with increasing alkali stress, whereas it remained relatively unchanged with increasing salt stress. This revealed a specific mechanism of absorption or transport for Na⁺ and K⁺ that was affected strongly by alkali stress. The results indicated that accumulation of organic acid (OA) was a central adaptive mechanism by which H. rhamnoides maintained intracellular ionic balance under alkali stress. OA may play different roles in different organs during adaptation to alkali stress, and its percentage contribution to total negative charge was higher in leaf than in stem. H. rhamnoides accumulated mainly malate, oxalate, and citrate in leaves and stems; however, in roots, less malate and citrate was accumulated, and acetate accumulation was enhanced significantly, which indicated that roots and shoots use different mechanisms to modulate OA metabolism.     

不同秸秆还田方式对黑土土壤氮素和物理性状的影响

通过大田试验对不同秸秆还田方式下黑土农田生态系统土壤氮素和物理性状进行研究。结果表明,不同秸秆还田处理土壤容重降低0.09～0.19 g/cm3;土壤比重增加19.82%～29.49%;土壤总孔隙度增加18.23%～22.26%。过腹还田处理增加土壤全氮含量;秸秆直接还田处理和腐解还田处理土壤全氮含量低于常规栽培方式(对照)和无秸秆处理;不同秸秆还田处理增加了土壤铵态氮和微生物量氮含量;过腹还田处理降低了土壤硝态氮含量,提高了土壤可溶性有机氮含量;秸秆直接还田处理和腐解还田处理增加了土壤硝态氮含量,降低了土壤可溶性有机氮含量。因此,不同秸秆还田方式配施微生物菌剂,结合先进的栽培方式是增加土壤有效氮素的有效途径,有利于退化黑土的可持续利用。     

Evaluation of salt-tolerant genotypes of durum wheat derived from in vitro and field experiments

The performance of selected salt-tolerant genotypes of durum wheat [Triticum turgidum L. subsp. durum (Desf.) Husn.], derived from field and in vitro assessment methods, was evaluated under greenhouse and field conditions. Eight durum wheat genotypes comprising three salt-tolerant genotypes and one salt-sensitive genotype selected from each of the methods were used. This study was conducted under both saline and non-saline field conditions as well as under greenhouse condition with salinized solution culture at 0 mM (control), 75 and 150 mM NaCl (concentrations) using supplemental Ca²⁺. Days to heading, days to maturity, plant height, number of grains per spike, grain weight per spike, 1000 grain weight, number of spikes per m², grain yield and harvest index were recorded in the field experiments. Plant dry weight, Na⁺, K⁺ and Ca²⁺ accumulated in the hydroponically grown seedlings were measured 20 days after salinity treatments. In spite of the smaller range of genotypes used by the in vitro screening method, tolerant genotypes screened by the in vitro method (ITGs) performed comparably with those of the field-derived tolerant genotypes (FTGs) for grain yield under saline field conditions. Field salinity significantly reduced (P < 0.01) means of all traits averaged on eight tested genotypes. In vitro salt-tolerant genotypes Dipper-6 and Prion-1 produced the highest dry weight and K⁺/Na⁺ ratio under salt stress conditions (150 mM NaCl) in the greenhouse. Although dry matter correlated with the grain yield (R² = 0.37), the regression coefficient was higher for shoot K⁺/Na⁺ ratio (R² = 0.44). Dipper-6 (ITG) and Prion-1 (ITG) genotypes have been ranked superior while Massara-1 (ISG) was inferior for salt tolerance in the regression analysis. However, based on grain yield reduction Ajaia/Hora/Jro/3/Gan (FTG) and PI40100 (ITG) were the most tolerant having 58% and 60% reduction, respectively.     

利用隶属函数值法对玉米成熟期抗旱性的综合评价

以10个不同基因型玉米为试验材料,在宁夏中部干旱带,通过测定不同品种成熟期的K~+/Na~+、光合气体交换参数、农艺性状及产量性状等指标进行抗旱性鉴定,并利用主成分分析和隶属函数法对其抗旱性强弱进行综合评价。结果表明,干旱胁迫地和对照田中,各参试品种的光合特征参数、K~+/Na~+及形态性状等均有明显差异,且干旱胁迫条件下的净光合速率(P_n)、株高、产量均显著低于对照(P0.05)。同一品种不同器官的K~+/Na~+值表现为茎基茎叶根,表明植株体内的离子吸收和运输具有选择性,茎基具有贮存K~+的作用,根具有贮存Na~+的功能。不同基因型玉米品种的抗旱能力根据综合评价值(D值)大小,综合评价其抗旱性强弱顺序为A111-3/H242HoViY1北21/A58A3/A18高WY2宁3/1522H237/A18桂青贮1号H237/1506A3/A18。     

秸秆还田条件下不同有机肥对土壤养分和冬小麦养分积累的影响

为了解秸秆还田条件下不同类型有机肥在麦田的施用效果,采用田间试验,设置T1(6 000kg·hm~(-2)玉米秸秆粉碎深翻还田)、T2(6 000kg·hm~(-2)玉米秸秆粉碎+有机肥A 1 500kg·hm~(-2)深翻还田)、T3(6 000kg·hm~(-2)玉米秸秆粉碎+有机肥B 1 500kg·hm~(-2)深翻还田)3个处理,研究了秸秆还田条件下不同类型有机肥对冬小麦越冬期、孕穗期和成熟期土壤微生物量碳(MBC)、氮(MBN)、土壤速效养分含量、冬小麦植株养分积累量以及冬小麦产量和当季经济效益的影响。结果表明,与T1处理相比,T2处理冬小麦各生育时期土壤微生物量碳、氮、土壤矿质态氮和土壤速效钾含量、植株氮和钾的积累量、冬小麦孕穗期和成熟期土壤速效磷含量、植株磷的积累量均显著提高;冬小麦实际产量和当季相对净收益亦均显著增加,分别提高了17.5%和22.0%。T3处理冬小麦越冬期土壤微生物量碳、越冬期和孕穗期土壤微生物量氮、各生育期土壤矿质态氮和越冬期土壤速效钾、各生育期植株氮和钾的积累量、孕穗期和成熟期植株磷的积累量亦均显著提高;冬小麦实际产量提高10.3%,达显著水平,但其当季经济效益并未显著提高。本试验条件下,综合施用两种有机肥对不同指标的影响,以T2处理效果更佳。     

A rapid quantification method for tissue Na+ and K+ concentrations in salt-tolerant and susceptible accessions in Vigna vexillata (L.) A. Rich.

A rapid quantification method for leaf sodium (Na⁺) and potassium (K⁺) concentrations was developed using a compact ion meter. Leaf ion concentrations were evaluated for species of Vigna vexillata (L.) A. Rich. after two weeks of treatment with 0–200 mM of sodium chloride. To compare the ion extraction efficiency, extraction solutions of distilled water and ammonium acetate were tested. The ion concentrations of extracts obtained by both solutions were measured using an ion meter, and the values were validated using ion chromatography. For both extraction solutions, the ion meter values were highly correlated with those of the ion chromatograph. However, correlations between ion meter and chromatograph values were largely different for Na⁺ and K⁺. The rapid quantification of ion concentrations using an ion meter developed in this study was successfully utilized for evaluating differences in leaf Na⁺ concentrations, K⁺ concentrations, and K⁺/Na⁺ ratio in species of V. vexillata.     

Differential Sensitivity of Rice Cultivars to Salinity and Its Relation to Ion Accumulation and Root Tip Structure

Abstract

Effects of NaCl on the growth, ion content, root cap structure and Casparian band development were examined in four rice (Oryza sativa L.) cultivars with different salt resistance (salt-sensitive indica-type IR 24 and japonica-type Nipponbare and salt-resistant indica-type Nona Bokra and Pokkali). Experiments were conducted to find the differences in salinity resistance during early seedling and developed seedling stages among the cultivars. For salinity treatment, sodium chloride (NaCl) was added to nutrient solution at concentrations of 0, 25 and 50 mM for 7 days from germination to the 7th day (early seedling stage) or from the 7th day to 14th day (developed seedling stage). Growth inhibition by salinity was more prominent in the early seedling stage than in the developed seedling stage. Based on the growth, the order of the sensitivity was IR24 > Nipponbare > Nona Bokra > Pokkali. The growth of NaCl-treated rice cultivars relative to control was significantly and negatively correlated with the Na⁺ content and Na⁺/K⁺ ratio in roots and shoots in both stages. Scanning electron microscopic observation revealed that the root cap tissues proliferated and extended to the basal part of the root tip by salinity. The length of root cap was, however, reduced by 50 mM NaCl in sensitive cultivars due to peeling off. An endodermal Casparian band was formed in the basal region of the root tip. Development of the Casparian band was more prominent in sensitive cultivars than in tolerant cultivars. Root cap proliferation might be related to NaCl resistance in rice seedlings, but the Casparian band may not function efficiently in Na⁺ exclusion. Essentially the present results suggest that exclusion of Na⁺ from roots plays a critical role in expression of Na⁺ resistance in rice seedlings and the root cap is important for Na⁺ exclusion.