Effects of AG1 and AG2 QTLs on Nonstructural Carbohydrate and Seed Management Options for Rice Seedling Growth and Establishment under Flooding Stress

Rice (Oryza sativa) plants acquired excess photosynthates in the form of nonstructural carbohydrates (NSCs) in their stems and grain. Despite keen interest in rice NSC, the dynamics of NSC accumulation, translocation and re-accumulation have not yet been well investigated. AG1 and AG2 QTLs associated with flooding tolerance through catalyzing starch into soluble sugar in germinating seeds. Here we conducted three experiments, greenhouse and field to lay the groundwork for large-scale diversity studies on grain NSC and some agronomic traits under direct-seeded rice (DSR) system, using elite lines incorporating AG1, AG2 and AG1-AG2 QTLs into the popular varieties PSB Rc82 and Ciherang-Sub1 along with the donors Kho Hlan On (AG1) and Ma-Zhan Red (AG2). In germinating seedlings, soluble sugars increased, while starch concentration decreased gradually especially in the tolerant checks and AG1-AG2 introgression lines under flooded soil. Soluble sugar accumulation in stem started to increase from the vegetative stage and peaked at the panicle initiation stage then gradually decreased towards the maturity stage. But Sub1-AG lines had higher sugar and starch concentrations at different growth stages than other genotypes in wet season 2016 and dry season 2017. Plant survival rate was positively correlated with the stem NSC at the early vegetative stage (21 days after sowing), and stem NSC was positively associated with plant height at different growth stages. Among the tested seeding rate, the most suitable seeding rate, 4 g/m² with shallow burial depth (0.5 cm), resulted in better seedling establishment, relatively higher seedling vigor index and higher leaf area index under flooding in DSR system. Introgression of AG1-AG2 QTLs had no any negative impact on nonstructural carbohydrate, germination rate, and growth and biomass production.     

淹水条件下改良剂对苏打盐化草甸土的洗盐效应

为明确改良剂在苏打盐化草甸土不同深度土层的改良效果,采用室内淋溶土柱的试验方法,设置S0、S1、S2、S3、S4和S5(每个土柱横截面积0.0113 m~2)分别施用改良剂0.00、0.01、0.05、0.10、0.50 g和1.00 g,折合成公顷用量分别为0.0、8.9、44.3、88.5、442.5 kg·hm~(-2)和885.1 kg·hm~(-2))6个处理,分析淹水条件下不同改良剂用量对苏打盐化草甸土的洗盐效应。结果表明,与未施改良剂处理(S0)相比,S3、S4和S5处理显著降低不同土层(0～30cm)土壤容重(降幅3.88%～8.87%)、增加土壤孔隙度(增幅3.82%～9.38%)、降低土壤pH值(降幅2.36%～8.05%);S2、S3、S4和S5处理显著提高20～40 cm土壤水分入渗量,增幅55.9%～294.6%(P0.05);施用改良剂处理交换性Na~+含量在0～10 cm和10～20 cm土层显著降低,降幅4.84%～56.5%(P0.05),20～30 cm和30～40 cm土层中增幅1.09%～17.1%;S3、S4和S5处理0～10 cm土层电导率显著降低,降幅49.0%～60.4%(P0.05),20～40 cm土层显著增加,增幅3.68%～19.8%(P0.05);S2、S3、S4、S5处理10～20 cm土层碳酸根含量显著降低,降幅5.98%～23.4%(P0.05),S3、S4、S5处理0～30 cm土层碳酸氢根含量降幅1.49%～18.0%;S2、S3、S4和S5处理显著提高0～30 cm≥0.25 mm水稳性团聚体,增幅达16.4%～161.7%(P0.05);S3、S4和S5处理0～30 cm土层MWD显著增加,增幅达5.78%～161.7%(P0.05)。针对本次供试土壤盐渍化程度,综合改良效果及改良剂施用量,改良剂适宜用量为每个土柱0.10 g(88.5 kg·hm~(-2))(S3处理),可达到最优淋洗效果。     

Impact of waterlogging and temperature on autumn growth,hardening and freezing tolerance of timothy (Phleum pratense)

Precipitation has generally increased in Norway during the last century, and climate projections indicate a further increase. The growing season has also become longer with higher temperatures, particularly in autumn. Previous studies have shown negative effects of high temperatures and, depending upon temperature conditions, contrasting effects of waterlogging on hardening capacity of timothy. We studied effects of waterlogging on seedlings of timothy (Phleum pratense, cv. Noreng) under three pre-acclimation temperatures: 3°C, 7°C, 12°C, and in autumn natural light in a phytotron at Holt, Tromsø (69°N). After temperature treatments, all plants were cold acclimated at 2°C for three weeks under continued waterlogging treatments. Freezing tolerance was determined by intact plants being frozen in pots at incremental temperature decreases in a programmable freezer. Waterlogging resulted in a higher probability of death after freezing, and a significantly reduced regrowth after three weeks at 18°C, 24 hrs light in a greenhouse. Increasing pre-acclimation temperatures also had a clear negative effect on freezing tolerance, but there was no interaction between temperatures and waterlogging. The results indicate that waterlogging may have negative implications for hardening of timothy and may contribute to reduced winter survival under the projected increase in autumn temperatures and precipitation.     

沼液淹没土壤抑制根结线虫及对土壤线虫群落的影响

为探索沼液抑制根结线虫的效果,本研究通过盆栽试验,以番茄为试供作物,对比了种植前沼液淹没土壤(BSS)、种植期间浇灌沼液(BS)和加热(HE)3种方法对根结线虫的防控效果。结果表明,与不采取任何措施的对照(CK)处理相比, BSS处理抑制根结线虫效果最为明显,防效高达97.1%,根结指数分别比HE和BS处理降低96.9%和92.9%。HE处理尽管在处理土壤后显著降低了根结线虫数量,但在最后破坏性取样时(结束试验)出现反弹,根结线虫数量甚至高于CK处理。对于土壤线虫群落,CK处理中以植食性线虫为主(81.8%);两个沼液处理中食细菌线虫占优势(平均78.3%),且其中的杂食捕食性线虫在土壤前处理后消失,在试验结束时又重新出现,但所占比例依然非常低。沼液淹水方式的高效防控效果揭示了利用沼液防控根结线虫的关键期在于线虫入侵到植物根部之前的幼虫期。然而,在盆栽系统中,沼液淹水的方式也对作物生长表现出了一定的抑制趋势。高量沼液施用防控病害的同时引发的植物毒害作用以及环境污染风险,需要进一步开展田间研究。     

狗牙根与空心莲对水库消落带土壤氮磷释放影响的模拟

通过水库水位涨落室内模拟试验,探究丹江口库区消落带优势物种狗牙根和空心莲2种草本植物对土壤氮磷释放过程影响。结果表明:(1)水淹结束后(32天),空心莲子草土壤TN、TP分别降低11.75%,25.28%,狗牙根分别降低3.62%,25.77%。(2)干湿交替环境主要影响土壤中NH_4~+-N、NO_3~--N和AP的含量的变化,对土壤中的TN、TP含量的影响较小。(3)狗牙根的死亡增加土壤TN、NH_4~+-N、TP量,即不耐淹植被过滤带虽然能净化径流中N、P等污染物,但截留的污染物和植物吸收的养分随着植物体的分解再次进入水体或土壤,无法达到有效防控农业面源污染的目的。该研究为丹江口水库利用植被缓冲带防控水体富营养化提供一定理论依据。     

Effect of Lime and Flooding on Phosphorus Availability and Rice Growth on Two Acidic Lowland Soils

Abstract

Loss of soil‐water saturation may impair growth of rainfed lowland rice by restricting nutrient uptake, including the uptake of added phosphorus (P). For acidic soils, reappearance of soluble aluminum (Al) following loss of soil‐water saturation may also restrict P uptake. The aim of this study was to determine whether liming, flooding, and P additions could ameliorate the effects of loss of soil‐water saturation on P uptake and growth of rice. In the first pot experiment, two acid lowland soils from Cambodia [Kandic Plinthaqult (black clay soil) and Plinthustalf (sandy soil)] were treated with P (45 mg P kg^?1 soil) either before or after flooding for 4 weeks to investigate the effect of flooding on effectiveness of P fertilizer for rice growth. After 4 weeks, soils were air dried and crushed and then wet to field capacity and upland rice was grown in them for an additional 6 weeks. Addition of P fertilizer before rather than after flooding depressed the growth of the subsequently planted upland rice. During flooding, there was an increase in both acetate‐extractable Fe and the phosphate sorption capacity of soils, and a close relationship between them (r²=0.96–0.98). When P was added before flooding, Olsen and Bray 1‐extractable P, shoot dry matter, and shoot P concentrations were depressed, indicating that flooding decreased availability of fertilizer P. A second pot experiment was conducted with three levels of lime as CaCO₃ [to establish pH (CaCl₂) in the oxidized soils at 4, 5, and 6] and four levels of P (0, 13, 26, and 52 mg P kg^?1 soil) added to the same two acid lowland rice soils under flooded and nonflooded conditions. Under continuously flooded conditions, pH increased to over 5.6 regardless of lime treatment, and there was no response of rice dry matter to liming after 6 weeks' growth, but the addition of P increased rice dry matter substantially in both soils. In nonflooded soils, when P was not applied, shoot dry matter was depressed by up to one‐half of that in plants grown under continuously flooded conditions. Under the nonflooded conditions, rice dry matter and leaf P increased with the addition of P, but less so than in flooded soils. Leaf P concentrations and shoot dry matter responded strongly to the addition of lime. The increase in shoot dry matter of rice with lime and P application in nonflooded soil was associated with a significant decline in soluble Al in the soil and an increase in plant P uptake. The current experiments show that the loss of soil‐water saturation may be associated with the inhibition of P absorption by excess soluble Al. By contrast, flooding decreased exchangeable Al to levels below the threshold for toxicity in rice. In addition, the decreased P availability with loss of soil‐water saturation may have been associated with a greater phosphate sorption capacity of the soils during flooding and after reoxidation due to occlusion of P within ferric oxyhydroxides formed.     

水分调控和钝化剂处理对水稻土镉的钝化效应及其机理

采用盆栽试验,研究了水分管理和钝化剂处理对红壤性水稻土重金属镉的钝化效应及其作用机理。结果表明,在土壤镉含量为0．75mg·kg。下,添加海泡石复配磷肥可以显著提高土壤pH值,长期淹水、常规管理水分条件下,土壤交换态cd分别降低了20．4％和15．7％,碳酸盐结合态cd分别下降了15．5％和14．1％,糙米cd分别降低了52．3％和46．O％。未添加钝化剂条件下,长期淹水处理的根表Fe（Ⅱ）含量比常规处理增加了1．2倍,根表cd含量则是常规处理的82．6％。土壤经钝化处理后,长期淹水和常规管理水分条件下,根表Fe（Ⅱ）分别增加了40．1％和70．0％,而根表cd分别降低了35．3％和42．4％。糙米cd含量与根表Fe（Ⅱ）含量呈显著负相关,与根表cd含量呈显著正相关。土壤Fe“和cd“对水稻根表吸附点位的竞争以及土壤镉较低的生物有效性是钝化处理组糙米镉含量下降的主要原因。     

棉花不同生育期淹水历时对其生长状况和产量构成的影响

通过桶栽土培试验,分别在苗期(S)、蕾期(B)、花铃期(F)和吐絮期(T)进行淹水2、4、6、8、10 d的处理,淹水深度均为5 cm,并以全生育期不淹水为对照(CK),探索了黄淮地区夏季棉花不同生育期淹水历时对其生长状况和产量构成的影响。结果表明,在棉花苗期、蕾期和花铃期淹水6 d后,株高和叶面积开始显著小于CK(P0.05)。不同生育期淹水处理均会导致棉花株高、叶面积、果枝数、节数、铃数和单铃质量的下降,且淹水历时越长,下降幅度越大。淹水导致棉花减产最为严重的生育期为花铃期,其余依次为蕾期、苗期和吐絮期,4个生育期在淹水2~10 d条件下的平均减产率分别为28.0%、12.9%、7.3%和2.9%。在棉花苗期,当淹水不超过6 d时,如果排涝及时,其形态指标及产量构成均能在吐絮期恢复至与CK无显著差异水平。在棉花蕾期淹水关键期为4 d,而在花铃期即使淹水2 d也可导致其形态发育停滞,产量无法恢复至CK水平。     

厄尔尼诺和大气环流异常与1998年洞庭湖区洪涝的关系

分析了厄尔尼诺与湖南洞庭硝区洪涝的统计相关和西太平洋副热带高压（简称副高）与１９９８年洞庭湖区洪涝的关系。结果表明,在厄尔尼诺次年洞庭湖区域出现洪涝的频率较大,副高 形成１９９８年洞庭湖区洪涝的重要原因。     

环境因素和作物生长对稻田CH_4和N_2O排放的影响

采用大田试验方法,研究了常规灌溉和持续淹水条件以及不同水平有机质(小麦秸秆)投放量(0、2.25、4.5t@hm-2)条件下各环境因素(包括土壤温度、灌溉水层深度和土壤Eh)对CH4和N2O排放的影响以及水稻生长与CH4排放的关系.结果表明,在2种水分管理下,CH4的累积排放量均与水稻冠层高度呈显著正相关(P<0.001).连续淹水条件下,无论有无外源有机质投放,稻田CH4排放的季节性变化均与土壤温度呈指数相关(P<0.001),而N2O排放的季节性变化则仅取决于土壤水分条件.