Effects of Different Potassium (K) Fertilizer Rates on Yield Formation and Lodging of Rice

As one of the most important nutrients for plants, potassium (K) has substantial effects on growth and development of crops. Present study was conducted in three different sites in South China in late season in 2019 with the objective to study the effects of different applied amounts of K fertilizer on yield formation and lodging of rice. Four K fertilizer treatments, K₀: 0 kg potassium oxide (K₂O) ha⁻¹ (control); K₁: 64.20 kg K₂O ha⁻¹ ; K₂: 128.55 kg K₂O ha⁻¹ and K₃ 153.90 kg K₂O ha⁻¹ were applied in the field experiment. The results showed that K₂ and K₃ treatments significantly increased panicle number per unit area, grain number per panicle, seed-setting rate and the grain yield of rice compared with K₀ treatment. Higher net photosynthetic rates were recorded in K₂ and K₃ treatments than K₀ treatment at tillering stage, heading stage and maturity stage. K fertilizer treatments also increased the chlorophyll content and dry matter accumulation by 6.16–23.52% and 21.32–64.59% compared with K₀ treatment, respectively. Moreover, the total N and K accumulation in the aboveground tissues of rice significantly increased under K₂ and K₃ treatments compared with K₀ treatment. Furthermore, compared with K₀ treatment, K fertilizer treatments significantly enhanced the breaking-resistant strength by 40.94–144.24% and reduced the lodging index of rice by 13.14–36.72%.     

会仙岩溶湿地4种覆被下土壤酶活性和微生物生物量

研究湿地系统中的稻田被撂荒以后土壤酶活性和微生物生物量的变化可以为湿地的保护提供参考依据。以桂林会仙岩溶湿地为研究样地,采集芦苇湿地、华科拉莎草湿地、稻田撂荒地（以双穗雀稗和莲子草为优势植被）和稻田的耕层土壤样品,采用比色法和氯仿熏蒸法分别检测土壤酶活性和微生物生物量。结果表明,稻田撂荒地的土壤微生物生物量碳（MBC）为（345.20±30.06） mg/kg,显著低于其它三种覆被下的土壤;微生物生物量氮（MBN）、微生物DNA、蔗糖酶活性和碱性磷酸酶活性分别为（48.03±18.48） mg/kg、（5.65±1.48）μg/kg、（19.16±1.43） mg g^-1（24h）^-1和（2.20±0.94） mg g^-1（24h）^-1,均显著低于稻田,而与两种天然湿地没有显著差异。主成分分析表明,稻田撂荒地能与稻田明显分开,而与其它两种覆被土壤有所交叉。统计分析表明,MBC和碱性磷酸酶活性均与pH呈显著正相关关系（P<0.05）;MBN、蔗糖酶活性和碱性磷酸酶活性均与土壤总有机碳（SOC）呈显著的正相关关系（P<0.05）;土壤微生物DNA与SOC、总氮（TN）和碱解氮（AN）均呈显著正相关关系（P<0.01）,与Mg²⁺呈显著正相关关系（P<0.05）。以上研究结果表明,会仙湿地中的稻田在撂荒以后,土壤微生物生物量和两种土壤酶活性显著降低,影响微生物生物量和土壤酶活性变化的主要因素是pH、SOC、TN、AN和Mg²⁺。因此,建议在稻田撂荒地上重新种植水稻,以加快会仙岩溶湿地的恢复过程。     

Performance of Sclerodermus brevicornis,a parasitoid of invasive longhorn beetles,when reared on rice moth larvae

Biological control efficiency can be improved by developing effective mass‐rearing systems to produce large numbers of high‐quality parasitoids. This study explored an alternative host for rearing Sclerodermus brevicornis (Kieffer) (Hymenoptera: Bethylidae), a potential biocontrol agent for the suppression of exotic and invasive wood‐boring longhorn beetle (Coleoptera: Cerambycidae) populations in the European agroforestry ecosystems. We tested larvae of the rice moth, Corcyra cephalonica Stainton (Lepidoptera: Pyralidae), as host for the parasitoid. We quantified the probability and timing of host attack and parasitism as well as reproductive success, offspring production, and the characteristics of adult offspring. As S. brevicornis is a quasi‐social species (multiple females, communally produced offspring broods), we also explored the effects of varying the number of females to which individual hosts were presented, with the aim of determining the optimal female‐to‐host ratio. As time to host attack can be a limiting factor in S. brevicornis rearing protocols, we tested the use of adult females of another bethylid species, Goniozus legneri Gordh, to paralyse C. cephalonica larvae prior to presentation. We identified the conditions within our experiment that maximized offspring production per host and offspring production per adult female parasitoid. We found that C. cephalonica is suitable as a factitious host and, as it is considerably more straightforward for laboratory rearing than cerambycid species, it is a good candidate for adoption by future S. brevicornis mass‐rearing and release programmes.     

Preface to the Special Issue “Presynaptic Dysfunction and Disease”

The synapse is formed between a presynapse (which releases neurotransmitter) and the postsynapse (which transduces this chemical signal). Over the past decade, presynaptic dysfunction has emerged as a key mediator of a series of neurodevelopmental and neurodegenerative disorders. This special issue will highlight some of the important presynaptic molecules and mechanisms that are disrupted in these conditions and reveal potential routes for therapy.     

翻压山黧豆绿肥与氮肥减施对水稻生长及其养分吸收与产量的影响

为探明种植翻压山黧豆绿肥与减施氮肥下的水稻生产潜力,通过3年田间定位试验,设置冬闲+不施肥(NF)、山黧豆绿肥(GM)、冬闲+常规氮肥(100%N,CK)、山黧豆绿肥+80%常规氮肥(GM+80%N)、山黧豆绿肥+70%常规氮肥(GM+70%N)、山黧豆绿肥+60%常规氮肥(GM+60%N)6个处理,研究不同处理对水稻生长、养分吸收及产量的影响。结果表明：(1)与CK相比,翻压山黧豆绿肥并减施氮肥处理均能够显著提升水稻株高、增加水稻分蘖数、提高水稻干物质积累量,其中以GM+70%N施肥处理提升效果最为明显。(2)GM+70%N施肥处理下,不同生育时期水稻株高、有效分蘖数分别较对照常规施肥(100%N)提升了13.32%~ 15.73%和33.98%~59.47%,水稻干物质积累量提高了23.19%~144.18%,且随着生育时期的推进增加速率依次降低。(3)种植翻压山黧豆绿肥并减施氮肥处理下水稻产量均有所提高,其中GM+70%N和GM+80%N处理显著提高,增产分别达13.84%,7.25%,且GM+70%N处理下水稻植株和籽粒养分吸收更为全面。研究发现,种植翻压山黧豆并适量减施氮肥能有效促进水稻生长和养分的吸收积累,显著提高水稻产量,说明翻压山黧豆绿肥可替代稻田30%~40%的氮肥施入量,并可在避免水稻旺长的同时实现水稻高产,是四川水稻种植较好的耕作措施。     

生物炭调控盐胁迫下水稻幼苗耐盐性能

土壤盐渍化降低土壤生产力。探索生物炭对盐胁迫下水稻幼苗耐盐性能的影响,对调控盐渍区水稻生产潜力具有重要意义。本研究通过生物炭介入盐胁迫稻田土壤的盆栽试验,调查了生物炭对盐胁迫下土壤环境和水稻幼苗耐盐性能的影响。盐胁迫设置4个水平,分别为0 g NaCl·kg^-1土(S0),1 g NaCl·kg^-1土(S1),2 g NaCl·kg^-1土(S2),3 g NaCl·kg^-1土(S3)。生物炭设置2个水平,分别为0 g生物炭·kg^-1土(C0),3 g生物炭·kg^-1土(C1)。结果表明:生物炭介入盐胁迫土壤,显著提高了水稻幼苗地上部干物重,有效改善了水稻幼苗农艺性状,显著提高了水稻幼苗茎秆中全钾含量,显著提高水稻幼苗钾钠比79.61%,提高了水稻幼苗耐盐性。生物炭介入也对水稻幼苗抗氧化性能有改善作用,显著降低了水稻幼苗中丙二醛含量,平均显著降低14.25%,抑制膜脂过氧化作用,提高抗氧化能力,减轻盐胁迫对水稻幼苗的伤害。水稻幼苗收获后土壤中水溶性氯离子和水溶性钠离子含量在生物炭介入条件下分别显著降低9.13%、17.77%。因此,添加适量生物炭能有效降低土壤水溶性盐含量,改善土壤盐胁迫环境,提升水稻对盐渍土壤的适应能力。     

水稻长日照开花因子Lfm1的图位克隆

开花期是水稻最重要的农艺性状之一,水稻的花期决定着水稻的地区适应性和最终产量。人工选择使水稻从短日照向长日照、低纬度向高纬度扩张,因此水稻已逐渐进化出适应长日照条件下的开花调控机制。目前,虽然鉴定了一些影响水稻长日照的开花基因如SDG724、RFT1、EHD4、DTH2,但是挖掘水稻长日照开花基因还十分有限。本研究通过筛选水稻突变体库,获得一批在长日照下花期有显著差异的突变体材料,其中一份突变体lfm1(late-flowering mutant1),在长日照条件下开花延迟,在短日照条件下开花时间正常。通过图位克隆,将Lfm1基因初定位至第8染色体端粒附近。进一步的精细定位将Lfm1基因定位于分子标记8-0.269和与8-0.283之间,范围为12 kb,该区域包括3个候选基因。经测序分析发现,在突变体lfm1中,LOC_Os08g01420基因的第六外显子2800处缺失9个碱基,突变体lfm1等位于已报道的突变体ehd3。在适度(中日照条件下,~12 h/12 h)的光照条件下,突变体lfm1表现为穗粒数增多,生育期略延长,具有应用于生产的潜力。Lfm1基因的克隆为培育适应不同生态区域的水稻材料提供了重要的基因资源。     

硅素对水稻幼苗镉积累及抗胁迫应答的调节效应

施硅(Si)可以显著缓解镉(Cd)胁迫对水稻生长发育的毒害效应。本研究通过水培分根试验,研究了Si对水稻幼苗Cd积累及胁迫应答的调节效应。结果表明: Cd胁迫下水稻幼苗的生物量显著降低,加Si可以显著缓解Cd对水稻幼苗生长的抑制效应。水稻幼苗对Cd的吸收、转运和积累明显受到Si的影响,单侧根系Cd胁迫下加Si(Si-Cd+Si,Si-Cd)使根系对Cd的滞留系数达83.3%～83.6%,限制了Cd从根向地上部转移。单侧根系Cd胁迫下非胁迫侧加Si(Si-Cd)处理的植株对Cd的吸收和累积明显增加,尤其是根中Cd的积累量较单侧根系Cd胁迫下无Si(CK-Cd)处理增加了48.2%;而单侧根系Cd胁迫下双侧加Si(Si-Cd+Si)处理则显著降低了根和地上部对Cd的吸收,较CK-Cd处理分别降低了36.7%和54.9%。双侧Cd胁迫下单侧加Si(Cd-Cd+Si)则使根和地上部对Cd的吸收量显著减少,较双侧根Cd胁迫(Cd-Cd)处理分别降低了57.8%和46.5%。Cd胁迫下水稻幼苗根中含较高浓度的Si,加Si则使Cd胁迫下根和地上部积累更多的Si。加Si也影响了水稻幼苗对其他金属元素如钙(Ca)、镁(Mg)、锰(Mn)的吸收,Cd-Cd+Si处理显著增加了根系和地上部的Ca、Mg浓度,但Mn浓度的变化则因Cd胁迫程度而表现不同。加Si对Cd胁迫下根系超氧化物歧化酶(SOD)和过氧化物酶(POD)活性有一定的影响,尤其是Si-Cd处理的胁迫侧POD和非胁迫侧SOD活性显著上升,有利于清除Cd胁迫产生的氧自由基。总之,Si对Cd胁迫下水稻幼苗生长、Cd和Si等的吸收及根系的抗氧化反应有一定的调节效应,植株体内较高的Si浓度有利于增强植株对Cd的耐受性。     

三氟苯嘧啶不同种子处理方式对稻飞虱的控制效应

为探明三氟苯嘧啶不同种子处理方式对稻飞虱的田间防治效果、防治时长以及对稻田蜘蛛和水稻的安全性,为该药剂种子处理防治稻飞虱提供科学依据,本研究设置10％三氟苯嘧啶悬浮剂按不同浓度(0.375、0.75、1.125和1.5 g a.i./kg种子)对水稻种子分别以干种子拌种(干拌)、清水浸种后拌种(湿拌)和药剂浸种3种方式,清水处理作为空白对照.结果表明,3种处理方式下的水稻发芽率和出苗率均与空白对照间无显著差异,播种后100 d,各浓度对稻飞虱的防治效果均在90％以上;当药剂浓度相同时,干拌与湿拌防治时长要优于药剂浸种;不同浓度三氟苯嘧啶药剂处理在3种方式下稻田蜘蛛种群数量均略低于空白对照田蜘蛛数量.因此,水稻生产中使用三氟苯嘧啶0.375～1.5 g a.i./kg种子干拌或湿拌处理,可有效降低田间稻飞虱种群数量,对天敌蜘蛛影响较小,对水稻种子发芽、出苗安全,可在水稻生产中推广使用.