干旱胁迫对滞绿大豆种子萌发的影响及芽期抗旱性评价

为研究干旱胁迫对滞绿大豆种子萌发性状的影响,以滞绿和非滞绿常规大豆品种(系)为供试材料,通过PEG模拟干旱胁迫,对不同基因型大豆种子萌发性状进行了对比分析,并对其抗旱性进行了综合评价.结果表明:滞绿大豆品种在干旱胁迫中后期能维持较高的吸水率,失水时间较常规品种晋大74延迟6～12 h.PEG胁迫显著降低了大豆种子的发芽率、发芽势、培根长、下胚轴长、胚根干(鲜)重及贮藏物质转运率.滞绿突变体stg在胁迫过程中吸水率最大,但发芽能力较弱.stg诱变后代品系M9种子相对发芽势、相对发芽率和萌发抗旱系数均大于其它品种(系).常规品种晋大74根系的伸长受PEG胁迫的影响最大,相对下胚轴长和相对胚根长显著小于晋大滞绿1号和stg诱变后代品系.晋大滞绿1号相对胚根长和胚根/下胚轴指数分别为0.85和2.38,显著大于其它品种(系),表明其在PEG胁迫下会优先促进胚根的伸长.通过隶属函数值对不同大豆品种(系)进行芽期抗旱性综合评价,结果表明晋大滞绿1号为强抗旱类型,其杂交母本晋大74为中等抗旱品种.     

北方杂草稻中胚轴伸长特性的初步研究

以在北方稻区收集的93份杂草稻材料和16个栽培稻品种为试验材料,研究了中胚轴伸长特性。结果表明,杂草稻和栽培稻的中胚轴在光照条件下不伸长,而在黑暗条件下都有伸长,但不同材料伸长的能力不同,杂草稻的中胚轴伸长能力强于栽培稻。在栽培稻中,籼稻的中胚轴伸长能力又强于粳稻。以中胚轴长度为指标的UPGMA聚类分析结果显示,参试的109份材料可以分为长中胚轴类型、短中胚轴类型和中间类型三种。57％的杂草稻材料属于长中胚轴类型和中间类型。除籼稻品种IR70外,其它栽培稻品种均属于短中胚轴类型。     

小麦品种抗旱性与深根性和深层根系活性的关系

为明确小麦根系垂直生长与抗旱能力的关系,以不同抗旱类型品种洛旱6号、西农979和郑麦366为材料,在柱栽条件下研究了不同生育时期最大根深、根干重垂直分布、根系活性垂直变化等性状。结果表明,本试验条件下,小麦根深在挑旗期达最大值,越冬至挑旗期间根系生长速度快。挑旗期和抽穗期不同抗旱类型品种间根深差异显著,其中抗旱性强的品种最大根深较大;与抗旱性弱的品种相比,抗旱性强的品种总根干重和深层根干重小,根系生理活性强。籽粒灌浆期表现为抗旱性越强,深层根系生理活性越强。据此认为,抗旱性强的小麦品种未必具有较大的根干重或深层根干重,但其根系下扎深且深层根系生理活性较强,尤其是生育后期的根系生理活性强。     

花生茎节茸毛及其与抗旱性关系的研究

在不同水分条件下,对花生茎节茸毛的密度和长度及其与抗旱性关系进行初步研究。结果表明,在不同水分条件下,17个品种中,茸毛密度只有6个品种变化不规律;基部节位茸毛密度易发生变化,中上部节位茸毛密度级别较平稳,且与抗旱性有关,在密度各级别中都有抗旱性强的品种,但在抗旱性差的品种中未发现有密度大的。茸毛长度的变化,在水分胁迫条件下比在田间条件下茸毛变短,且呈显著的正相关,但茸毛长度与抗旱性、密度均无明显关系。     

渗透胁迫对小麦萌发生长及其某些生理生化特性的影响

采用乙二醇（ＰＥＧ６０００）渗透胁迫的方法,研究了两个不同抗旱性小麦品种对渗透胁迫的反应。结果表明,在渗透胁迫下,随水势的降低,小麦咱子萌发发生长减弱,表现为发芽率降低;芽长、根长和根数减少;根系活力和活跃的根比表面积下降;细胞膜伤害程序和叶片脯氨酸含量影响。抗旱性不同的品种相比,抗旱性强的品种受渗透胁迫影响较小,而抗旱性弱的相对较大     

干旱胁迫下不同苎麻品种的形态解剖特征研究

抗旱性强的苎麻品种,在正常水分条件下叶面茸毛多、叶着生角度小、比叶重大,而在干旱胁迫下叶片衰老慢,根冠比大、根活跃吸收面积大、萝卜根数量多且直径大,纤维细胞直径和胞壁厚度降低幅度小。抗旱性强的苎麻品种正常水分及干旱条件下叶片气孔密度以及茎导管和根系维管束均较大。     

向日葵不定根的研究——向日葵不定根的形态结构

向日葵除了由种子的胚根长成的主根及其侧根外,还能够自胚轴处再长出不定根。到开花期不定根总量已超过自主根上发出的侧根的重量,以后还在继续增加。向日葵的主根及其侧根的初生结构为典型的4原型,导管发育较迟,而不定根则为6原型,主要是受到胚轴结构的影响,根与胚轴的结构很协调。从不定根的结构特点导致吸收功能等较主根侧根强盛,表现出结构与功能的一致性。     

干旱协迫下不同苎麻品种的形态解剖特征研究

抗旱性强的苎麻品种,在正常水分条件下叶面茸毛多、叶着生角度小、比叶重大,而在干旱胁迫下叶片衰老慢,根冠比大、根活跃吸收面积大、萝卜根数量多且直径大,纤维细胞直径和胞壁厚度降低幅度小。抗旱性强的苎麻品种正常水分及干旱条件下叶片气孔密谋以及茎这和根系维管束均较大。     

干旱胁迫下两个甘蔗新品种(系)的抗旱生理

测定了3个不同甘蔗品种在干旱胁迫及旱后复水条件下的相对质膜透性、丙二醛含量、叶片相对含水量,对其抗旱性进行综合评判。结果表明:云蔗05-596的抗旱性表现最好,云蔗05-704其次,两者的抗旱性综合指标优于抗旱性强的对照品种ROC22。     

渗透胁迫对小麦萌发生长及某些生理生化特性的影响

采用乙二醇 (PEG6 0 0 0 )渗透胁迫的方法 ,研究了两个不同抗旱性小麦品种对渗透胁迫的反应。结果表明 ,在渗透胁迫下 ,随水势的降低 ,小麦种子萌发生长减弱 ,表现为发芽率降低 ;芽长、根长和根数减少 ;根系活力和活跃的根比表面积下降 ;细胞膜伤害程度和叶片脯氨酸含量增加。抗旱性不同的品种相比 ,抗旱性强的品种受渗透胁迫影响较小 ,而抗旱性弱的相对较大。     

Development and Distribution of Root System in Two GrainSorghum Cultivars Originated from Sudan under Drought Stress

Abstract

The difference in rooting pattern between two grain sorghum cultivars differing in drought tolerance was investigated under drought stress. The cultivars, Gadambalia (drought-tolerant) and Tabat (droughtsusceptible), were grown in bottomless wooden or acrylic root boxes to examine root parameters. Gadambalia consistently exhibited higher dry matter production and leaf water potential than Tabat under drought stress in both root boxes. In the experiment with wooden root boxes, under a drought condition, Gadambalia extracted more water from deep soil layers (1.1-1.5 m), which was estimated from the reduction in soil water content, than Tabat. This was because Gadambalia had a significantly higher root length density in these soil layers. The high root length density was due to enhanced lateral root development in Gadambalia. In the other experiment with acrylic root boxes, though total root length in the upper soil layer (0-0.5 m) was declined by limited irrigation in both cultivars, the reduction in Gadambalia was moderate compared with that in Tabat owing to the maintenance of fine root growth. Unlike Tabat, Gadambalia had an ability to produce the nodal roots from higher internodes even under drought, which resulted in the high nodal root length of Gadambalia. The growth angle of nodal roots was significantly correlated with root diameter, and the nodal roots from the higher internodes had large diameters and penetrated into the soil more vertically. These results indicate that the responses of roots (i.e. branching and/or growth of lateral root, and nodal root emergence from higher internodes) to soil dryness could be associated with the drought tolerance of Gadambalia.     

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.     

大豆品种苗期根系性状的遗传变异及其与耐逆境胁迫的关系

从301份黄淮海和长江中下游地区代表性大豆地方品种和育成品种(系)中按根系类型选取62份,用以研究不同生态区大豆苗期根系性状的遗传特点、与地上部性状的相关以及与逆境胁迫的关系.大豆苗期一级侧根数、主根长、根干重、总根长和根体积等性状,在品种间、各苗龄间均存在显著遗传变异.不同生态区间生长进度不同,长江中下游晚熟品种的根干重、总根长、根体积发育速度较快,而北方早熟品种的根系发育较慢.根系性状与整株干重呈高度相关;根干重、根总长和根体积的相对值与耐旱平均隶属函数值,一级侧根数、主根长、总根长、根体积、根干重的相对值与耐铝毒平均隶属函数值呈极显著相关,且根系性状的相对值在品种间存在显著变异,可用做耐逆性选择的根系指标.黄淮海区品种的耐旱相关根系性状值高于长江中下游区品种,表明耐旱种质的相关根系性状具有生态适应性.     

大豆苗期耐旱性与根系性状的鉴定和分析

2003年对63份大豆品种在盆栽自然干旱和盆栽水分控制两种条件下进行苗期耐旱性鉴定,两者鉴定结果间的关联分析表明两者呈极显著相关,两者间的鉴定分级结果比较一致,筛选出一批苗期耐旱型品种.综合分析2001～2003年的大豆苗期耐旱性鉴定结果,筛选出稳定耐旱型(1级)品种4份(晋豆14、汉中八月黄、科丰1号和因黑豆)和稳定干旱敏感型(5级)品种1份(宁海晚黄豆).苗期耐旱隶属函数值与根系性状间的相关分析表明,比根长、比根干重、比根表面积和比根体积等根系性状相对值与耐旱隶属函数值呈极显著相关,根总长、侧根总长、侧根数等根系性状绝对值与耐旱隶属函数值间的相关不显著,说明利用根系性状绝对值进行苗期耐旱性的评价较为牵强,而利用根系性状相对值进行耐旱品种的鉴定筛选比较可靠.     

Utilizing Chromosome Segment Substitution Lines (CSSLs) for Evaluation of Root Responses to Transient Moisture Stresses in Rice

Abstract

Drought and waterlogging that occur sequentially under field conditions are important abiotic stresses affecting plant growth and development. The ability to maintain the root system development during the contrasting moisture stresses may be one of the key traits for plant adaptation. This study aimed to identify the key root traits that contributed to the above ability by comparatively examining the effects of the two moisture stresses in succession on root system development. The chromosome segment substitution lines (CSSLs) from the crosses between the japonica rice cultivar Nipponbare and indica rice cultivar Kasalath were used for precise comparison of root system development. The rice seedlings were grown by hydroponics under a continuously well-aerated condition for 14 days (non-stressed), a drought condition for 7 days followed by an oxygen (O₂)-deficient (stagnant) condition for 7 days (drought-to-stagnant, D-S), or a stagnant condition for 7 days followed by drought condition for 7 days (stagnant-to-drought, S-D). CSSL43 and 47 did not show any significant differences in growth from Nipponbare under the non-stressed condition, but exhibited greater lateral root production under the stresses. Lateral root production was most closely related to faster seminal root elongation mediated by higher aerenchyma formation in the D-S condition, and to more branching of lateral roots on the seminal root axis in the S-D condition. The D-S condition severely affected lateral root production due to reduced seminal root elongation and aerenchyma formation. These results confirmed the fact that those root traits previously identified using different cultivars greatly contribute to plant adaptation. Oxygen deficiency preceded by drought (D-S) was more stressful to roots than drought preceded by O₂ deficiency (S-D), because drought reduced root aerenchyma formation during the subsequent stagnant condition.     

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.     

Progressive drought alters architectural and anatomical traits of rice roots

Background

Root architectural and anatomical phenotypes are important for adaptation to drought. Many rice-growing regions face increasing water scarcity. This study describes drought responses of 11 Egyptian rice cultivars with emphasis on plastic root responses that may enhance drought adaptation.

Results

Eleven Egyptian rice cultivars were phenotyped for root architectural and anatomical traits after 6 weeks growth in soil mesocosms under well-watered conditions. Four of these cultivars were more intensively phenotyped under progressive drought stress in mesocosms, using a system where more moisture was available at depth than near the surface. In response to drought stress, all cultivars significantly reduced nodal root number while increasing large lateral root branching density and total lateral root length in the deepest portions of the mesocosm, where moisture was available. Nodal root cross-sectional area, but not stele area, was reduced by drought stress, especially in the basal segments of the root, and the number of late metaxylem vessels was reduced in only one cultivar. Alterations in deposition of lignin were detected by UV illumination from laser ablation tomography, enhanced by digital staining, and confirmed with standard histochemical methods. In well-watered plants, the sclerenchyma and endodermis were heavily lignified, and lignin was also visible throughout the epidermis and cortex. Under drought stress, very little lignin was detected in the outer cell layers and none in the cortex of nodal roots, but lignin deposition was enhanced in the stele. Root anatomical phenes, including cross-section area and metaxylem vessel number and lignin deposition varied dramatically along large lateral root axes under drought stress, with increasing diameter and less lignification of the stele in successive samples taken from the base to the root apex.

Conclusions

Root architectural and anatomical traits varied significantly among a set of Egyptian cultivars. Most traits were plastic, i.e. changed significantly with drought treatment, and, in many cases, plasticity was cultivar-dependent. These phenotypic alterations may function to enhance water uptake efficiency. Increased large lateral root branching in the deep soil should maintain water acquisition, while water transport during drought should be secured with a more extensively lignified stele.

     

PEG模拟干旱胁迫下甘蓝型油菜的根系特性与抗旱性

采用砂培法,利用14%（m/V）聚乙二醇（PEG-6000）模拟干旱胁迫,研究39份甘蓝型油菜发芽期根系性状的变化及其与抗旱性的关系。结果表明,干旱胁迫对油菜根鲜重和侧根数有明显的抑制作用,而对根长和根冠比的影响较小。相关分析表明,相对侧根数与活力指数之间以及根长与活力指数之间均呈显著正相关,可作为抗旱性鉴定的辅助指标。杂交种和常规种在根系性状上差别不显著,表明其抗旱能力相当。对油菜的抗旱性进行综合评价和聚类分析发现,在欧式距离为60时39份材料可分为5个类群,其中A类抗旱性最强,平均相对侧根数77.9%,相对根长98.9%;E类抗旱性最差,平均相对侧根数69.3%,相对根长84.5%。筛选出发芽期抗旱性较强的3份材料：OR918、OR805和OR2025。       

不同降雨条件对不同耐旱型大豆根系的影响

为了明确耐旱型大豆根构型的特异性,田间条件下,以不同耐旱型大豆为研究对象,探讨不同降雨条件对大豆根系特性的影响。结果表明:干旱胁迫降低了各时期大豆植株的根和地上部生物量;同一地点,R2和R4期取样,辽豆14的根和地上部生物量高于辽豆21。随着生育进程的推进,根冠比值逐渐增大;一般而言,V4~R4期,干旱胁迫提高了植株的根冠比。苗期干旱胁迫显著提高了大豆根长,但结荚期和鼓粒期干旱胁迫均降低了大豆根长、根表面积。大豆根长占比以细根为主,平均根直径≤2.5 mm的根长比例均在90%以上。根表面积占比也主要以细根为主,但大豆根体积分配比例较高的却主要是根系直径2.5 mm的粗根。研究结果进一步丰富了耐旱基因型大豆根器官应答干旱胁迫的理论知识,对大豆抗旱生产栽培具有重要的理论价值和实践意义。