棉铃发育不同时期的质量变化研究

为探索棉铃发育过程中重量及品质的变化情况,通过挂牌选取不同时期棉铃进行测定分析。结果发现：在常规种植方式下,棉花上部（7台以上）、中部（4~6台）和下部（1~3台）果枝铃重有所差异,中部铃重最高,下部次之,上部最低,最大差值可达1.6 g;棉铃发育上,花后40~50天籽棉、铃壳、皮棉重量增加最快,且均在花后70天最重,而衣分则在花后55天最高;纤维品质指标中除了短纤维率呈不断下降趋势,花后45~55天下降最大,其余指标整体呈随生育进程增加而增加趋势,但长度、整齐度、断裂伸长率分别在花后65、70、60天出现最高值并有下降趋势。综上所述,棉铃发育并不是越长越好,花后超过70天,棉花重量、衣分、长度、强度、整齐度等多项指标都会降低,不利于棉花质量提升。     

Uptake and Accumulation Characteristics of Arsenic and Iron Plaque in Rice at Different Growth Stages

Arsenic (As) uptake by rice plants and its toxicity to human beings have caused worldwide concerns. Investigating the characteristics of As accumulation in rice in relation to root surface iron plaque during the whole growth of rice would provide important information for devising measures to mitigate rice As uptake in As-polluted areas. Uptake and accumulation characteristics of As in rice at different growth stages as well as iron plaque on rice root surfaces were investigated in a pot culture experiment in a greenhouse. The results showed that As concentrations in roots, stems, and leaves increased with rice growth, while As concentration in spikelets decreased with grain development: 53.63% of As content in leaves, 61.51% in spikelets, and 82.09% in stems were found at both the jointing and booting stages, which suggested that the two stages were the key stages of As uptake. Root surface iron plaque at different growth stages was extracted by DCB (dithionite-citrate-bicarbonate). DCB-extractable iron (Fe) and DCB-extractable As were significantly increased with rice growth (P < 0.001), and there was a significant positive correlation between DCB-extractable Fe and As (P < 0.001), indicating that iron plaque was very important to sequester As on rice root surfaces.     

Effects of nitrogen deposition on soil organic carbon fractions in the subtropical forest ecosystems of S China

Experiments were conducted between 2003 and 2008 to examine how N additions influence soil organic C (SOC) and its fractions in forests at different succession stages in the subtropical China. The succession stages included pine forest, pine and broadleaf mixed forest, and old‐growth monsoon evergreen broadleaf forest. Three levels of N (NH₄NO₃)‐addition treatments comprising control, low‐N (50 kg N ha^–1 y^–1), and medium‐N (100 kg N ha^–1 y^–1) were established. An additional treatment of high‐N (150 kg N ha^–1 y^–1) was established in the broadleaf mixed forest. Soil samples were obtained in July 2008 for analysis. Total organic C (TOC), particulate organic C (POC, > 53 μm), readily oxidizable organic C (ROC), nonreadily oxidizable organic C (NROC), microbial biomass C (MBC), and soil properties were analyzed. Nitrogen addition affected the TOC and its fractions significantly. Labile organic‐C fractions (POC and ROC) in the topsoil (0–10 cm) increased in all the three forests in response to the N‐addition treatments. NROC within the topsoil was higher in the medium‐N and high‐N treatments than in the controls. In the topsoil profiles of the broadleaf forest, N addition decreased MBC and increased TOC, while no significant effect on MBC and TOC occurred in the pine and mixed forests. Overall, elevated N deposition increased the availability of labile organic C (POC and ROC) and the accumulation of NROC within the topsoil irrespective of the forest succession stage, and might enhance the C‐storage capacity of the forest soils.     

草地贪夜蛾对不同生育期玉米产量的影响及防治指标

为明确草地贪夜蛾Spodoptera frugiperda对我国玉米产量造成的损失,并制订相应的防治指标,在玉米不同生育期分别接入不同数量的草地贪夜蛾3龄幼虫,研究其为害玉米后对产量和其他相关指标造成的影响,建立不同生育期产量损失与不同为害率之间的回归方程。结果显示,大喇叭口期接虫对玉米成株期株高有显著影响,玉米各生长时期接入不同数量草地贪夜蛾后对产量损失均有显著影响。根据防治成本及玉米产量等指标计算出国内玉米的经济危害允许水平为5.56%。利用回归方程计算出玉米小喇叭口期、大喇叭口期以及吐丝期的防治指标分别是为害率达8.72%、7.99%和6.17%。     

黄瓜留种株光合特性的研究

以津研4号为试材,研究了黄瓜种株光合速率及其日变化。结果表明,在不同生育期内,黄瓜光合作用日变化类型不同,在黄瓜种株生长前期,叶片光合速率日变化呈双峰曲线型,有明显的"午休"现象,而在果实生理成熟期叶片光合作用日变化呈单峰曲线型,无"午休"现象;黄瓜叶腋负载果实对光合速率有明显的促进作用。     

棉花单铃干物质积累分配的分期动态模拟及检验

 【目的】通过分期模拟不同开花期棉铃干物质在铃壳、籽棉、纤维、种子上的积累和分配，建立比棉铃干物质积累与分配的单一综合模型更实用、预测效果更好的分期模拟模型。【方法】在系统分析不同基因型、不同施肥量、不同开花期棉铃干物质积累与分配动态规律的基础上，以每日生理热效应为驱动变量，在综合考虑了氮素营养、水分胁迫、同化物供需比等对棉铃的生长发育主要影响因子的前提下，建立基于每日生理热效应的棉花单铃干物质积累与分配的分期动态模型。【结果】模拟检验结果显示，棉花四桃（伏前桃、伏桃、早秋桃、晚秋桃）单铃、籽棉、纤维干物质积累的模拟值与观察值之间的均方差根（RMSE）分别为0.1767～0.5659、0.0725～0.5279、0.0613～0.2634 g，而单一综合模拟模型的RMSE值超过或接近分期模拟模型相对应的RMSE值的上限。【结论】分期模拟棉铃干物质的积累与分配比单一综合模拟模型预测效果要准确、可靠。     

棉花杂种优势利用的研究进展与发展思路

概述了棉花杂种优势利用的研究现状及发展趋势,同时指出了在杂种优势利用中存在的若干问题,总结了几种简化制种的方法,并对未来杂种优势利用的研究发展趋势进行了初步的探讨。     

美国黄松个体高生长过程研究

运用SAS软件,建立美国黄松树高生长量与树龄的间的回归方程。生长模型分析表明：14龄前美国黄松高生长缓慢;14～18龄,高生长最快;18龄后高生长速率变慢,据此,可将美国黄松的生长过程划分为“慢—快—慢”3个生长阶段,在此3阶段中,树高平均生长速度分别为0．31m／a,0．75m／a和0．56m／a,对应于不同的生长阶段,应采取相应的经营措施。     

陆地棉F_2单株结铃数的发育遗传研究

根据数量性状遗传分析的加性-显性发育遗传模型,以6个陆地棉亲本及其按完全双列杂交法配制的15个正交组合F2不同发育阶段的单株结铃数的两年观察值为研究素材,采用MINQUE(1)方法分析了F2单株结铃数在不同发育阶段的遗传动态及其对最终结铃数的影响。试验结果表明,陆地棉F2单株结铃数在结铃早中期具有较大的显性遗传效应,具有较大的杂种优势利用潜力,而在中后期加性遗传效应较强,进行遗传选择效果较好。     

不同施氮水平对麦茬复种饲料油菜生长性状的影响

通过田间小区试验，研究了不同施氮水平对麦茬复种饲料油菜不同生育期株高、鲜重、干重、叶面积指数、相对生长率、净同化率和作物生长率的动态变化规律，为该种植模式推广提供理论支撑。结果表明，麦茬复种油菜不同生育期地上生物产量的累积规律为幼苗期缓慢，蕾薹期最快，开花后减缓，基本符合“S”型生长曲线。增施氮肥能极显著提高复种油菜地上部干重、鲜重及其日生长量，以1000kg／hm^2施氮处理为最优产量施肥设计，干重、鲜重与其日生长量的累积规律呈极显著性正相关关系（r=0．967）。增施氮肥能明显提高或改善复种油菜株高、叶面积指数、相对生长率以及群体同化率和生长率，高氮肥水平更有利于油菜干物质积累和群体形态结构建成，达到适时丰产。