不同生育阶段洪涝淹没时长对水稻生长发育及产量构成的影响

夏季小流域洪涝常常导致南方稻田受淹并成灾。为探究小流域洪涝淹没时长对水稻生长发育及产量的影响,于2015—2016年在广西象州县选用丝香1号和百香139进行双季稻淹水试验,分别设分蘖期、孕穗期和开花期淹没0(对照CK)、2、4、6、8、10 d处理,测定淹没前后的茎蘖数变化、抽穗期及收获后的每穗粒数、结实率、千粒质量和每盆稻谷产量,并对产量构成因素进行相关分析和通径分析。结果表明:与对照组相比,同一生育期内淹没时间越长茎蘖死亡率越高、植株恢复生长越慢,但不同的淹没时期影响程度和主要影响对象存在差异。分蘖期淹没超过6d则死苗率大于80%,且不能完全恢复生长,收获时水稻茎蘖数显著低于对照组;孕穗期淹没超过6d则死苗率大于50%,而淹没小于4 d的处理水稻能恢复生长,收获时水稻茎蘖高于对照组;开花期淹没10 d死苗率不足50%,收获时茎蘖数与对照组差异不显著。分蘖期淹没小于4 d水稻始穗期及抽穗持续时间均无显著变化,大于8 d则水稻始穗期显著推迟,抽穗持续时间增加;孕穗期受淹没则会使水稻始穗期推迟,抽穗持续时间显著增加,甚至收割时也未能达到齐穗期标准。分蘖期淹没小于4 d,单株产量无显著下降,淹没6 d及以上则减产率大于80%;孕穗期及开花期淹没超过2 d则减产率大于50%。不同生育期淹没处理下产量的主要因素不同,分蘖期主要受有效穗数和结实率影响,孕穗期受结实率及每穗粒数影响,开花期受结实率和有效穗数影响。研究可为建立西南地区双季稻洪涝灾害指标体系和提出减灾管理措施提供依据。     

两步进气法和水蒸气对竹材下吸式固定床气化性能的影响

以毛竹加工剩余物为研究对象,采用自制的两步进气下吸式固定床气化炉,在当量比(ER)一定的情况下,研究进气比例(AR,0%和60%)和水蒸气/生物质质量比(ms/mb,0,0.045,0.112,0.153,0.211,0.245和0.305)对气化炉性能(炉内温度分布、原料消耗率和气化强度)和可燃气指标(温度、成分、热值和焦油含量)的影响。结果表明:1)与一步进气法相比,两步进气法(AR为60%时)可显著提高气化炉炉温,并且分别在2个进气位置出现2个温度峰,分别为热解区的606℃和氧化区的856℃,可燃气的温度也增加至377℃; 2)两步进气法可显著提高可燃气的可燃组分含量和热值,降低焦油含量,CO含量、H_2含量和低位热值的最大值分别为17.47%、14.67%和4.54 MJ/Nm^3,焦油含量最低值为55.4 mg/Nm^3; 3)随着m_s/m_b从0.045增加至0.305,气化炉内各反应区的温度逐渐降低,与空气气化剂相比,虽然热值并未增加,但是可燃气中H_2和CO的含量发生变化,导致V(H_2)/V(CO)比例逐渐增加至1.01,有助于应用于合成气的研究。本研究为竹材废弃物的能源化利用提供了新的途径和基础数据。     

Effects of defoliation on whole‐plant maize characteristics as forage and energy crop

Hail affects yield and quality of maize crops, and consequences also depend on the growth stage at which the injury occurred. Whole‐plant maize (WPM) silage is often used within the same farm for cattle feeding and biogas production. The present study aimed to verify the effects of hail damage, simulated by artificial defoliation, on yield and chemical and nutritional features, as well as on biochemical methane potential (BMP) of maize forage. In a randomized block design with three replicates, four defoliation levels (0%, 33%, 66% and 100% of leaf area removal respectively) have been applied at either the V12 (12th leaf), R1 (silking) or R3 (milk) stages for two consecutive years. WPM yield, chemical and nutritional features, and BMP were measured. Dry‐matter (DM) yield per hectare was progressively reduced (p < 0.001) with increasing levels of defoliation and with application at V12 in comparison with R1 or R3 (1.26 vs. 1.39 and 1.46 kg ha^?1 for V12 vs. R1 and R3; p < 0.003). Nutritive value and BMP per unit of product were less altered than dry‐matter yield per hectare by defoliation. Anticipating defoliation reduced net energy for lactation (5.26 vs. 5.46 MJ kg^?1 DM for V12 and R3 respectively; p = 0.02). Total defoliation resulted in an accumulation of nitrates (NO₃) compared to the other treatments (3.98 vs. 1.53 g NO₃ kg^?1 DM; p < 0.001). BMP was mainly reduced by early and complete defoliation. Equations were developed to estimate the effects of defoliation on yield, composition, and nutritive and energetic values of WPM.     

Stem elongation in Pennisetum purpureum results from a fixed pattern of vegetative development potentially enhanced by the initiation of flowering

The characterization of stem elongation is of fundamental importance in C4 tropical grasses as it affects forage quality and determines optimal management practices. The objectives of this study were to analyse the determinants of stem elongation and leaf area production in shoots of Pennisetum purpureum cv. Napier (elephant grass) using unstressed isolated plants. Three experiments were conducted in Brazil during the spring, summer and autumn seasons. Regular measurements of leaf and pseudostem length were performed on the main and primary axes. Ten destructive measurements were also performed during each experiment to monitor apical meristem height, internode length and the number of initiated leaves. The onset of stem elongation occurred at the same vegetative stage (i.e., appearance of leaf 13) irrespective of the seasons and experiments. The first internode to elongate belonged to phytomer 8, and a constant lag of five phyllochrons was systematically observed between internode production and its rapid elongation period. Higher stem and internode elongation rates were observed during the reproductive phase (autumn) versus the vegetative phase (summer and spring group). Maximal internode length reached 8–10 cm in summer and spring and 20 cm in autumn, at approximately phytomers 12–13. A similar pattern was reported for all primary axes irrespective of the experiments, the position of the first internode to elongate descending regularly down the main axis. These results provide key elements to predict the onset of stem elongation in the field from simple measurements. They could contribute to improving crop models for perennial tropical C4 grasses.     

不同品种、成熟期鲜莲中淀粉的结构特性研究

莲子淀粉的结构特性对带壳莲子加工品质和食用品质影响显著。为提高带壳莲子调理食品的品质,本文采用场发射扫描电镜、直链淀粉全自动分析仪、X-射线衍射仪、马尔文激光粒度仪等仪器对4个莲子品种蜡熟期和完熟期莲子淀粉的结构特性进行研究。结果表明,同一品种不同成熟度莲子淀粉中的直链淀粉、抗性淀粉含量和淀粉颗粒粒径随成熟度的增大而增大,而同一品种不同成熟度莲子淀粉的结晶度随鲜莲成熟度的增大而减小（除京广1号外）。在4个品种中,建选17号和建选35号鲜莲中的淀粉含量在蜡熟期和完熟期都较高,而直链淀粉含量最低,对于延缓淀粉老化具有一定效果。     

基于主成分分析的玉米萌发期抗旱性综合评定

试验在人工气候室内利用称重法精确控制75%和35%土壤相对含水量(RWC),通过分析播种后7 d不同玉米品种的发芽率、根系生长、干物质转化等对干旱胁迫的响应差异,对10个玉米品种进行萌发期抗旱性综合评定。结果表明,干旱胁迫降低了玉米的发芽势、发芽率、发芽指数、种子萌发抗旱指数、地上部与地下根物质积累和贮藏物质转运率,增大了根冠比。利用主成分分析与热图分析得出,玉米萌发期抗旱鉴定的四级指标分别为干物质积累量、发芽指数和种子萌发抗旱指数;根长、根冠比和根干重等;根体积和贮藏物质转运率;发芽势。将指标按照对抗旱性影响的差异分为4类,发芽率、发芽指数、种子萌发抗旱指数;根体积、贮藏物质转运率;根冠比;根长和芽长。依据综合值对10个玉米品种萌发期抗旱性评价,其抗旱性强弱依次为浚单29、蠡玉35、五谷704、吉祥1号、先玉335、博优989、郑单958、伟科702、农玉2号、登海605。     

甬优12抽穗动态调查及稻曲病预防适期研究

稻曲病已由次要病害上升为主要病害,对水稻生产危害严重,不但影响产量还降低其品质。稻曲病发生后(出现稻曲球)就很难防治,只能预防不能治疗。适时打药是高效预防稻曲病的关键。本研究结果表明,对籼粳杂交稻甬优12而言,在破口前10～13 d用专化杀菌剂预防1次、破口期再预防1次的处理防治效果最好,穗防效和病情指数防效分别为94.59%和98.33%;仅在破口前10 d或13 d喷1次药预防的处理,穗防效分别为86.95%和87.36%,病情指数防效分别为94.98%和95.99%。鉴于在实际生产中很难准确确定具体哪一天是破口前的第10 d或第13 d,本研究采用水稻生理学性状"叶枕平"(剑叶叶枕与倒数第2叶叶枕持平,或叶枕距为零)界定为最佳打药期,即稻田中1/3～1/2水稻植株处于叶枕平为第1次打药预防稻曲病的适期,第2次打药适期为破口前。     

甘蓝型油菜苗期抗旱性鉴定及综合抗旱指标筛选

为系统评价甘蓝型油菜（Brassica napus L.）苗期的抗旱性,筛选出合理的油菜抗旱指标,为区域栽培提供材料和理论依据,对10种甘蓝型油菜品种和材料采取持续干旱（控水15d）和正常浇水两种处理,针对温室控水试验结果,分析干旱胁迫对油菜生理生化、生长发育、根系形态等34个指标的影响,结合综合抗旱系数、因子分析和隶属函数进行综合评价;在此基础上,运用聚类分析和灰色关联度分析筛选抗旱性评价指标和划分抗旱类型。结果表明,CDC值（综合抗旱系数）和加权抗旱系数均与相对产量呈显著正相关。根据CDC值,材料抗旱性由强到弱为：145027 > 绵油11 >万油27 > 渝油28 > 汉油8号>中双11号>德杂油5号>万油25 >GH06 > GH04/GH02。对CDC值聚类分析,可将10种参试材料抗旱性聚为3级,其中145027为Ⅰ级,绵油11、万油27、渝油28、汉油8号、中双11号 为Ⅱ级,德杂油5号、万油25、GH06、GH04/GH02为Ⅲ级。关联度分析结果表明,光合参数指标、含水量指标、植株 形态和根系性状指标与油菜苗期的抗旱性关系密切。      

Physiological Responses of Contrasting Rice Genotypes to Salt Stress at Reproductive Stage

Salinity is a major abiotic stress affecting plant growth and productivity. Considerable genetic variation is present in rice in response to salt stress, with higher sensitivity during early seedling and reproductive stage. In this study, physiological changes in leaves and developing panicles of rice genotypes(IR686, Sadri, Rc222, CSR28, IR670 and Pokkali) contrasting in salt tolerance at the reproductive stage were evaluated in greenhouse experiment under salt stress. The results showed that IR670 and the tolerant-check Pokkali maintained lower Na~+/K~+ ratio, less reduction in chlorophyll concentration, lower malondialdehyde(MDA) production, higher concentrations of reduced ascorbate(reduced AsA), higher proline accumulation and lower percentage reduction in pollen viability than the salt-sensitive genotypes under salt stress. The higher concentration of reduced AsA suggests an efficient ROS-scavenging system. Physiological measurements and pollen viability analysis revealed that Sadri(moderately tolerant at the seedling stage) is sensitive to salt stress at the flowering stage. The findings will be useful in breeding salt tolerant varieties at both seedling and reproductive stages by selecting appropriate genotypes and phenotypes.