铵态氮和硝态氮营养对水、旱稻根系形态及水分吸收的影响

为研究不同形态氮素营养对水稻和旱稻根系生长及水分吸收的影响,采用水培供应不同形态氮素(铵态氮、硝态氮、铵态氮和硝态氮混合)的方法培养水稻和旱稻,并对水稻和旱稻的根系形态进行了扫描分析;同时,通过测定根系伤流液和采用HgCl2抑制水通道蛋白活性的方法,比较了水稻和旱稻根系对不同氮素形态响应的差异。 铵态氮营养水稻（或旱稻）的根干质量明显低于硝态氮营养水稻（或旱稻）,但单位根表面积的水分吸收与根系伤流液量比硝态氮营养高;3种形态氮素营养水稻（或旱稻）运输水分的主要方式均是水通道蛋白的跨膜运输途径,但铵态氮营养水稻（或旱稻）的根系通过水通道蛋白跨膜运输途径运输水分的能力明显高于硝态氮营养水稻（或旱稻）;与水稻相比,旱稻对硝态氮营养具有较强的适应性。     

Water supply from pearl millet by hydraulic lift can mitigate drought stress and improve productivity of rice by the close mixed planting

The authors have proposed the close mixed planting technique using mixed seedlings of two different crop species that results in close tangling of their root systems. Especially, the combination of drought-adaptive upland crops (e.g. pearl millet or sorghum) and flood-adaptive lowland crop of rice would be beneficial to overcome the drought and flood conditions and to reduce the risks of crop failure. In our previous studies, we found that upland crop yield losses by flood stress was mitigated by mix-cropped rice, owing to the oxygen gas released from the rice roots into the aqueous rhizosphere. In the present study, we conducted two experiments to assess whether mixed cropping a drought-resistant cereal, pearl millet, would improve the performance of co-growing drought-susceptible crop, rice under drought conditions. In the field experiment, some grains were obtained from the rice plants mix-cropped with pearl millet under drought condition. However, no rice matured in the single cropping system. In the model experiment using deuterium analysis, it was confirmed that water absorbed by pearl millet roots from deep soil layer was utilized by rice, suggesting that mix-cropped rice could withstand drought stress and complete grain filling using water released into the upper soil layer by hydraulic lift.     

水陆稻杂交组合叶片相对含水量的遗传研究

以3个水陆稻组合(旱稻277/春江016、巴西陆稻/春江016、旱稻502/郑稻6号）的亲本、F[sub]1[/sub]、B1、B2和F[sub]2[/sub]为试验材料,在人工控制条件下经干旱协迫处理,研究叶片相对含水量的遗传规律。叶片相对含水量表现为数量性状遗传特征,主要受加性效应控制,同时还受到显性效应的影响,其广义遗传率和狭义遗传率均较高。还对栽培稻品种的抗旱性改良方法以及陆稻种质资源在水、陆杂交稻中的利用进行了探讨。     

水分胁迫对节水抗旱稻产量形成和根系形态生理特性的影响

目的 探究节水抗旱稻组合旱优73在不同灌溉条件下产量形成特点及其根系形态生理的变化情况。方法 以节水抗旱稻旱优73和高产水稻H优518为材料,通过根管试验设置三种水分处理(常规灌溉、轻度水分胁迫、重度水分胁迫),调查株高、分蘖、根系形态特征和生理特性以及产量构成因素,分析性状之间的关系,探究不同程度水分胁迫对旱优73和H优518产量形成和根系形态生理的影响及其差异。结果 两年的重复试验结果表明,与常规灌溉相比,在轻度水分胁迫下,旱优73的产量及其构成因素无显著变化,H优518的产量在两年内平均减少了25.6%,每穗粒数、结实率、千粒重也显著降低;在重度水分胁迫下,两品种产量及其构成因素均显著降低,其中,旱优73的产量两年内平均减少了28.8%,H优518产量减少了46.1%。与常     

水稻在不同土壤水分状况下脯氨酸的累积与抗旱性的关系

 以6个中熟水、陆稻品种为材料，研究了在不同土壤水分状况下水稻叶片中游离脯氨酸的累积及其与抗旱性的关系。在低土壤水分处理下，抗旱性水稻品种叶片中游离脯氨酸累积开始较早，持续时间长，抗旱性较差的品种则开始较迟，持续时间短；脯氨酸开始累积的叶水势阈值，抗旱性品种为－0.62～－0.66 MPa，抗旱性较差的品种为－0.70～－0.82 MPa；土壤水势为－0.04 MPa时，处理10 d后叶片的相对脯氨酸含量（处理／对照×100%）与品种的抗旱系数呈极显著正相关（r＝－0.9712）；保持土壤水势为－0.04 MPa和－0.06 MPa，处理后30 d和40 d叶片的相对脯氨酸含量与减产率呈极显著的负相关（r＝－0.9342、－0.9581）。建议把在低土壤水分条件下脯氨酸累积较早、持续时间长这一生理特性作为评价水稻品种抗旱性的一个指标。     

Variation in root system architecture and drought response in rice (Oryza sativa): Phenotyping of the OryzaSNP panel in rainfed lowland fields

Root growth at soil depths below 30 cm may provide access to critical soil water reserves during drought in rainfed lowland rice. In this study, the OryzaSNP panel, a set of 20 lines representing genetic diversity in rice used for the discovery of DNA sequence polymorphisms, was evaluated for root characteristics in the field over three seasons varying in drought severity. Root length density (RLD) at a depth of 30–45 cm varied up to 74–92% among genotypes under drought stress (2008–2009 dry seasons), ranging from 0.024 to 0.23 cm cm⁻³ in 2008 and from 0.19 to 0.81 cm cm⁻³ in 2009. Real-time monitoring of soil moisture profiles revealed significant differences among genotypes, and these differences were correlated with RLD at those soil depths. Among the lines evaluated, the Aus isozyme group, particularly the genotype Dular, showed greater drought resistance associated with deep root growth and the highest drought response index (less reduction in yield by drought stress). Since the set of genotypes used in this study has been completely sequenced for SNP markers, the phenotypic information on root growth and drought avoidance responses presented here could be used in initial analysis of the genetic basis of dehydration avoidance traits and in facilitating improvement in drought resistance in rice.     

Growth and Yield of Six Rice Cultivars under Three Water-saving Cultivations

Abstract

We evaluated the genotypic differences in growth, grain yield, and water productivity of six rice (Oryza sativa L.) cultivars from different agricultural ecotypes under four cultivation conditions: continuously flooded paddy (CF), alternate wetting and drying system (AWD) in paddy field, and aerobic rice systems in which irrigation water was applied when soil moisture tension at 15 cm depth reached ?15 kPa (A15) and ?30 kPa (A30). In three of the sixcultivars, we also measured bleeding rate and predawn leaf water potential (LWP) to determine root activity and plant water status. Soil water potential (SWP) in the root zone averaged ?1.3 kPa at 15 cm in AWD, -5.5 and -6.6 kPa at 15 and 35 cm, respectively, in A15, and ?9.1 and ?7.6 kPa at 15 and 35 cm, respectively, in A30. The improved lowland cultivar, Nipponbare gave the highest yield in CF and AWD. The improved upland cultivar, UPLRi-7, and the traditional upland cultivar, Sensho gave the highest yield in A15 and A30, respectively. The yields of traditional upland cultivars,Sensho and Beodien in A30 were not lower than the yields in CF. However, the yields of the improved lowland cultivars, Koshihikari and Nipponbare, were markedly lower in A15 and A30. Total water input was 2145 mm in CF, 1706 mm in AWD, 804 mm in A15, and 627 mm in A30. The water productivity of upland rice cultivars in aerobic plots was 2.2 to 3.6 times higher than that in CF, while those of lowland cultivars in aerobic plots were lower than those in CF. The bleeding rate of Koshihikari was lower in A15 and A30 than in CF and AWD, and its LWP was significantly lower in A15 and A30 than in CF and AWD, but Sensho and Beodien showed no differences among the four cultivation conditions. We conclude that aerobic rice systems are promising technologies for farmers who lack access to enough water to grow flooded lowland rice. However, lowland cultivars showed severe growth and yield reductions under aerobic soil conditions. This might result from poor root systems and poor root function, which limits water absorption and thus decreases LWP. More research on the morphological and physiological traits under aerobic rice systems is needed.     

水分胁迫下稻作幼苗酯酶等同工酶的 分析

利用电泳技术对稻作异养期幼苗在水分胁迫下的茎叶、根进行酯酶等同工酶的分析,以探讨稻作抗旱性和生化基础。研究结果表明：（１）水分胁迫后,水旱稻一些品种茎叶的ＳＯＤ（超氧化岐化酶）和过氧化物酶的若干同工酶酶带活性增强,但在根系中酶带活性均出现不同程度的减弱。（２）水分胁迫后,水旱稻茎叶中的酯酶同工酶出现一条新的酶带Ａ３。（３）水分胁迫后,早稻根系的酯酶同工酶Ａ１酶带活性减弱程度明显轻于水稻。水旱稻杂种     

Genotypic Variation in Response of Rainfed Lowland Rice to Prolonged Drought and Rewatering

Abstract

Duration of the drought period is important for plant response during drought and after rewatering. We hypothesized that, if drought duration is extended, (1) high seedling vigor and rapid development of a deep root system will not be advantageous, and (2) osmotic adjustment will be more important. Six diverse rice (Oryza sativa L.) genotypes were selected from rainfed lowland germplasms to examine the development of a deep root system and osmotic adjustment, and their relationship with biomass production during drought and after rewatering, under two different drought durations (shorter and prolonged) in the greenhouse. NSG19 and KDML105 had greater seedling vigor (larger seedling biomass), developed a deep root system earlier in response to drought, extracted soil water more quickly, and their pre-dawn leaf water potential declined more rapidly during the prolonged drought period. These two genotypes showed superior drought recovery even after a prolonged drought period in which they suffered a greater reduction in transpiration, water use efficiency, and biomass production. The superior recovery ability was associated with larger plant size by the end of the drought period rather than with plant water status during drought, such as osmotic adjustment or leaf water potential. Osmotic adjustment was greater during prolonged drought periods (ca. 0.7 MPa) than during shorter drought periods (ca. 0.5 MPa), and lower osmotic adjustment was mostly associated with a higher leaf water potential. Genotypic variation in osmotic adjustment was observed, but there was no clear relationship between osmotic adjustment and biomass production during drought periods. These patterns of response of rice seedlings to drought and rewatering in the greenhouse should help to explain the patterns of adaptation of rainfed lowland rice in the field. Selection for drought recovery ability should be an advantageous strategy for early season drought.     

植物生长物质冠菌素诱导旱稻、水稻幼苗抗旱性的效应及生理机制

以旱稻 297 和水稻越富幼苗为材料,在 20% PEG 模拟干旱条件下,研究了植物生长物质冠菌素处理对叶片水分状况、质膜透性、渗透调节物质（脯氨酸、可溶性糖和可溶性蛋白）及内源激素（ABA、IAA 和GA3）含量的影响。干旱胁迫下,冠菌素处理可以维持旱稻 297（0.01 μmol/L）和越富（0.1 μmol/L）较高的叶片相对含水量,促进幼苗叶片中脯氨酸、可溶性糖和可溶性蛋白的积累,降低质膜透性,维持细胞质膜的完整性;同时,冠菌素（0.01 和0.1 μmol/L）处理明显促进旱稻 297 和越富幼苗叶片中ABA的积累,并改变了 IAA 和GA3 的浓度及比例。冠菌素处理能改善旱稻和水稻幼苗耐干旱胁迫的能力,最适浓度分别为0.01 μmol/L和0.1 μmol/L。     

Breeding for drought tolerance: Direct selection for yield, response to selection and use of drought-tolerant donors in upland and lowland-adapted populations

Drought is the most important constraint reducing rice yield in rainfed areas. Earlier efforts to improve rice yield under drought mainly focused on improving secondary traits because the broad-sense heritability (H) of grain yield under drought stress was assumed to be low, however gains in yield by selecting for secondary traits have not been clearly demonstrated in rice. In present study, the effectiveness of direct selection for grain yield was assessed under lowland reproductive stage stress at Raipur in eastern India and under upland reproductive stage drought stress at IRRI. The selection under severe stress (in both upland and lowland trials) resulted in greater gains under similar stress levels (yield reduction of 65% or greater under stress) in evaluation experiments than did selection under non-stress conditions, with no yield reduction under non-stress conditions. We observed similar H of grain yield under stress and non-stress conditions, indicating direct selection for yield under drought will be effective under both lowland and upland drought stresses. None of the secondary traits (panicle exsertion, harvest index, leaf rolling, leaf drying) included in our study showed a higher estimate for H than grain yield under stress. Secondary traits as well as indirect selection for grain yield under non-stress situation were predicted to be less effective in improving yield under drought in both lowland and upland ecosystem than direct selection for grain yield under the respective stress situations. The low, but positive values observed for genetic correlation (r_G) between yield under stress and non-stress indicated that it is possible to combine drought tolerance with high-yield potential but low values also indicated that selection for grain yield needs to be carried under stress environments. The study also indicated that under lowland drought stress, the use of highly drought-tolerant donors, as parents in crosses to high yielding but susceptible varieties resulted in a much higher frequency of genotypes combining high-yield potential with tolerance than did crosses among elite lines with high-yield potential but poor tolerance. Breeding strategies that use drought-tolerant donors and that combine screening for yield under managed drought stress with screening for yield potential are likely to result in the development of improved cultivars for drought-prone rainfed rice producing areas.     

Matching the Expression of Root Plasticity with Soil Moisture Availability Maximizes Production of Rice Plants Grown in an Experimental Sloping Bed having Soil Moisture Gradients

Abstract

Soil moisture distributions in rainfed lowland rice environments are largely determined by the position in the toposequence. In this study, we developed an experimental sloping bed that can simulate the soil hydrological conditions in sloping rainfed lowland rice environments to examine if the expression of promoted root system development in relation to soil moisture availability along the soil profile may maximize water uptake and dry matter production under drought. The gradient of available water along both the surface soil layer and the vertical soil profile was successfully created by manipulating ground water levels in the experimental sloping bed indicating the practical effectiveness of this experimental system. Then, two contrasting genotypes, IRAT109 (upland rice adapted japonica) and KDML105 (lowland adapted indica) were grown for plasticity evaluation. Dry matter production was maintained even at a higher position in the toposequence in IRAT109, but decreased in KDML105. Such maintenance of dry matter production in IRAT109 was attributed to its greater ability to increase root length density in a deeper soil layer, where more soil moisture is available. In contrast, KDML105 maintained root length density in the upper soil layer, and could not utilize the soil moisture available in the deeper soil layer. These results imply that the genotype that expressed root plasticity with root system developing in the soil portion where more soil moisture was available showed greater dry matter production than the genotype that showed root plasticity in the soil layer where soil moisture was less available.     

不同渗漏条件下尿素用量对水稻生长和氮肥利用率的影响（英文）

 利用¹⁵N示踪技术在温室中研究了无渗漏(长期淹水)和渗漏条件下氮肥施用量对水稻生长和氮肥利用率的影响。氮肥对水稻地上部和根的生长起重要作用。水稻不同生育阶段各器官干物质积累随施肥量增加而提高。土壤的渗漏状况也强烈影响水稻各部分生长及氮肥利用率。长期淹水条件下，水稻的根系生长受到抑制，地上部积累量下降，氮肥利用率为18.66%～35.67%；在渗漏条件下，水稻的生长状况相对较好，氮肥利用率达42.0%～65.8%。水稻对氮肥的利用率随氮肥用量的增加而减少，作为基肥施用¹⁵N回收率比追施低。长期淹水条件下氮肥的激发效应为18%，高于渗漏条件下的5.1%。0～80 cm土壤剖面中残留的肥料氮低于总施用量的10%。     

Genetic Diversity of Rice Landraces from Lowland and Upland Accessions of China

Genetic diversity of rice landraces from lowland and upland accessions of China was investigated using 66 polymorphic simple sequence repeat (SSR) markers.The total number of alleles detected from all 324 tested accessions was 555 with an average allele number (Na) of 8.409 per locus,the average effective number of alleles (Ne) of 3.574 and the average Shannon’s information index (I) of 1.378.The genetic diversity was higher for the indica landraces compared to the japonica landraces,and the upland landraces were more genetically diverse than the lowland landraces.The SSR markers,RM72,RM232,RM219,RM241,RM224 and RM3 showed the highest rates of polymorphism and these SSR markers were suitable to assess the genetic diversity of rice germplasm resources.A dendrogram of 324 accessions of lowland and upland landraces showed that all rice accessions were mainly subdivided into two groups,japonica and indica,with some being intermediate.The distribution of lowland and upland landraces among the japonica and indica rice groups was distinct,with obvious differentiation between the lowland and upland landraces in japonica rice,but no such clear distinction in indica rice.     

Yield response of rice (Oryza sativa L.) genotypes to drought under rainfed lowlands: 2. Selection of drought resistant genotypes

Drought frequently reduces grain yield of rainfed lowland rice. A series of experiments were conducted in drought-prone northeast Thailand to study the magnitude and consistency of yield responses of diverse, rainfed lowland rice genotypes to drought stress environments and to examine ways to identify genotypes that confer drought resistance. One hundred and twenty-eight genotypes were grown under non-stress and four different types of drought stress conditions. The relationship of genotypic variation in yield under drought conditions to genetic yield potential, flowering time and flowering delay, and to a drought response index (DRI) that removed the effect of potential yield and flowering time on yield under stress was examined.Drought stress that developed prior to flowering generally delayed the time of flowering of genotypes, and the delay in flowering was negatively associated with grain yield, fertile panicle percentage and filled grain percentage. Genotypes with a longer delay in flowering time had extracted more water during the early drought period, and as a consequence, had higher water deficits. They were consistently associated with a larger yield reduction under drought and in one experiment with a smaller DRI. Genotypes, however, responded differently to the different drought stress conditions and there was no consistency in the DRI estimates for the different genotypes across the drought stress experiments. The results indicate that with the use of irrigated-control and drought test environments, genotypes with drought resistance can be identified by using DRI or delay in flowering. However, selections will differ depending on the type of drought condition. The inconsistency of the estimates in DRI and flowering delay across different drought conditions reflects the nature of the large genotype-by-environment interactions observed for grain yield under various types of drought in rainfed lowland conditions.     

不同形态氮素营养和水分条件对苗期水稻生长及渗透调节能力的影响

 为比较不同形态氮素营养下籼稻与粳稻对水分胁迫的响应,采用室内营养液培养,通过供应不同形态氮素及100 g/L PEG6000模拟水分胁迫的方法,对4种不同基因型水稻的生长状况及渗透调节能力进行了分析。结果表明：1）与铵态氮营养相比,水分胁迫明显抑制了硝态氮营养籼稻和粳稻的地上部生长,降低了叶片净光合速率,且对粳稻的抑制效果更加显著;2）水分胁迫条件下,铵态氮营养籼稻和粳稻植株内的游离氨基酸和K+可以更有效地积累、转运和穿梭,以致伤流液和韧皮部汁液拥有更强的渗透调节能力;3）铵态氮营养籼稻和粳稻在通过渗透调节降低叶片渗透势的同时,能够提高或维持叶片含水量。由此可见,铵态氮营养下,籼稻和粳稻均可通过渗透调节促使叶片在渗透势下降和维持含水量之间达到合理的平衡,保证叶片在水分胁迫下维持正常的光合速率,提高了水稻的抗旱能力。     

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。     

Developmental Plasticity of Rice Root System Grown under Mild Drought Stress Condition with Shallow Soil Depth; Comparison between Nodal and Lateral roots

The plasticity in root system development (RSD) is a key trait for the adaptation of rice to mild drought. However, the enhanced RSD due to the plasticity may not be always a sole function of promoted lateral root (LR) production, but also of the integrated responses of nodal root (NR) development. In this study, we aimed to evaluate the effects of mild drought intensities on the development of the NR and LR, and their contribution to the entire RSD. We used six genotypes including KDML105 (indica, lowland adapted), a high lateral rooting ability genotype. The plants were grown up to heading or maturity stage for two years under soil with limited soil depth (20 cm) assuming the presence of the hardpan and at different moisture gradients generated by the line source sprinkler system. The effects of drought intensities generally differed between the development of NR and LR. In both years, all genotypes showed highest LR development under mild drought stress intensities. However, in some genotypes including KDML105, NR development was maintained in a limited soil moisture range only, which was narrower and wetter than that in which LR plasticity was expressed. Furthermore, the entire RSD was maintained only when both the NR and LR were simultaneously promoted or maintained. These results suggest that the NR have less plasticity than the LR in response to drought and the contribution of the plasticity in LR development to the entire RSD is dependent on both the soil moisture and nodal rooting ability.     

水稻胚芽鞘长度与抗旱性的关系及QTL定位

对由水稻品种珍汕97B和旱稻品种IRAT109构建的重组自交系195个株系的胚芽鞘长度及抗旱系数的研究表明,水分胁迫下水稻重组自交系群体的胚芽鞘长度与抗旱系数的相关系数为0.2206**。应用由213个SSR标记构建的遗传连锁图对控制胚芽鞘长度和抗旱系数的QTL进行了定位。检测到胚芽鞘长度和抗旱系数的主效QTL各为13个和5个,单个QTL对表型的贡献率为2.28%～22.65%;在第9染色体上两者的QTL出现在相同的分子标记区间（RM160-RM215）。检测到胚芽鞘长度和抗旱系数的互作位点分别为17对和3对,影响胚芽鞘长度的互作位点联合贡献率为5835%;影响抗旱系数的互作位点联合贡献率为11.93%。控制胚芽鞘长度和抗旱系数的QTL分别与其他研究中控制根系性状（深根干质量、根深、根长、根数等）的QTL位于相同的标记区间。     

Effect of Soil Compaction on Dry Matter Production and Water Use of Rice (Oryza sativa L.) under Water Deficit Stress during the Reproductive Stage

Abstract

The effect of a long term of soil compaction on dry matter production (DMP) and water use in rice cultivated under limited water supply during the reproductive stage is unknown. Our objectives were to determine which of the transpiration (Tr) or water use efficiency (WUE) is dominant in determining DMP under compacted and desiccated soil conditions. When irrigation in the period around the reproductive stage was terminated in artificially compacted and non-compacted fields, the rate of suppression of DMP by soil compaction was similar in the three rice cultivars, but DMP was higher in drought resistant cultivars having deep root density at the heading stage. Six cultivars were grown in pots of 1.0 m in depth containing the soils of three levels of soil bulk density (SBD). Water supply was restricted by keeping the water table in the pot deep without irrigation during the reproductive stage. DMP and Tr in all cultivars decreased with increasing SBD, and a close relationship was seen between DMP and Tr. WUE was thus a fairly stable factor for all cultivars examined. Tr was positively correlated with root length density and was relatively maintained at a high SBD in drought-resistant cultivars having a higher root length density. We concluded that water shortage under compacted soil conditions during reproductive stage suppressed the DMP, and DMP suppression accompanied a reduction of Tr due to poor root development rather than the reduction of WUE. In the drought-resistant cultivars reduction of DMP was relatively small due to their highly developed root systems that allowed high water absorption from the deep layers in the compacted soil.