不同生育期滇重楼光合日变化及光响应特征1）

于2013年6月（花期）、8月（果实膨大期）和9月（果实成熟期）份对3年生幼龄期滇重楼和8年生成熟期滇重楼光合生理指标日变化和光响应参数进行了测定。结果表明：幼龄期和成熟期滇重楼叶片净光合速率（ Pn ）变化日进程在6月份出现严重午休,仅在10：00出现一个峰值;而在8、9月份上午和下午各出现一个峰值,在中午出现“午休”现象。空气温度（Ta）偏高引起气孔关闭是导致滇重楼“午休”的主要因素。成熟期滇重楼叶片在不同生长季节日均Pn和最大净光合速率（Pnmax）均高于幼龄期叶片,而幼龄期滇重楼初始量子效率较高,且光补偿点和光饱和点均低于成熟期滇重楼,对弱光的利用率更高。幼龄期和成熟期滇重楼叶片日均Pn 在8月下旬最大,其次是6月下旬,9月下旬最低,且在当年的生育后期,光饱和点有增大的趋势,由大到小的顺序为9月份、8月份、6月份。成熟期滇重楼花萼具有同叶片类似的同化功能,日均Pn 为叶片的779．％～104．0％,但其Pnmax和光饱和点均低于成熟期和幼龄期叶片的,对弱光的利用效率高于叶片。     

小流域降水径流沟渠中氮磷的流失特征与生态拦截效应

为研究降水径流过程中非点源污染物氮、磷浓度的变化特征,分析降水作用下长沙县金井河小流域农业源头沟渠水中氮、磷的流失特征与生态拦截效应。结果表明:在降水初期非点源污染物氮、磷浓度与降水径流量的变化均呈逐渐递增趋势,雨后均呈递减变化;降水作用下沟渠系统总氮输出的最大值为4.67 mg/L,总磷输出的最大值为0.38 mg/L,其氮素输出的主要形态为氨态氮和硝态氮;雨后各断面氮、磷的输出随着时间的增加呈先增加后降低的趋势,其中总氮与总磷含量分别在雨后第3天和第2天达到最高;菖蒲–茭白段的生态拦截效果明显高于自然段的自然净化效果,表明植物拦截和吸收是植被段氮、磷去除的重要途径,菖蒲、茭白在6月吸收氮、磷分别达26.90、2.34 g/m~2。     

玉米群体生长与光截获的动态模拟及应用

【目的】群体光截获对玉米生长发育及产量形成均有重要的影响,合理的群体结构直接决定着玉米产量的增加与稳定。群体结构的测量较为繁琐,费时费力,且不能与当地太阳辐射情况充分结合,从而无法对群体结构和功能做出整体的评价。因此,有必要构建合理、简便的玉米群体光截获动态模型,结合群体不同生育期的形态指标与光辐射情况,对群体结构做出快速而精准的评价,为不同区域玉米品种选择、播种密度确定、以及后期管理等提供参考意见。【方法】将玉米群体结构模型与光分布模型相结合,建立简易可靠的群体光截获动态模型。该模型可模拟玉米整个生育期群体光截获的动态变化,并对不同生育期群体结构做出相应的评价。同时,在中国农业大学吴桥实验站开展了两个田间试验,对模型的准确性和应用功能进行了验证。试验均为三因素,分别为品种、密度和氮肥处理,其中试验一:设置2个品种(郑单958,丹玉405),3个密度(4.5×10~4,6.0×10~4,7.5×10~4株/hm~2)和3个氮肥处理(不施氮;施氮180 kg·hm~(-2),于播前、大喇叭口期和吐丝期以1:4:1的比例施入;施氮270 kg·hm~(-2),于播前、大喇叭口期和吐丝期以4:4:1的比例施入);试验二:设置1个品种(郑单958)、1个密度(8.25×10~4株/hm~2)和6个播期(4月20日,5月5日与20日,6月4日与18日,7月3日)。在两个试验中,对玉米不同生育期的群体形态指标、干物重、及产量均进行了测定。【结果】吐丝期和灌浆中期的群体光截获率模拟值与测量值的相关系数分别为0.91和0.85,均达到显著相关。运用该模型对两个田间试验数据的模拟结果显示,光截获率(量)随灌浆期的推进呈先增后减的趋势,吐丝后50 d光截获衰减加速。在试验地区,密度超过6×104株/hm~2时,光截获随密度变化不大;播期为6月中上旬时形成的玉米群体具有较为理想的光截获能力,结构功能潜力较大。产量与灌浆期有效光辐射呈正相关,但相关性随生育期推进逐渐减弱,表明灌浆后期产量的增加对群体光截获的需求减弱。在玉米生长发育后期物质转移对产量的贡献可能发挥着更加重要的作用。产量与群体光截获相关性的动态变化与品种有关,紧凑株型优于平展型。【结论】选择株型紧凑且生育后期群体结构维持较好的玉米品种,通过增加密度可进一步增加夏玉米产量。调整播期增强灌浆初期光合效率也是有效的增产方法之一。     

连续光照及光质对水培生菜生长及营养品质的影响

以罗马生菜为材料,研究在不同LED光质下采前连续光照24、48、72 h对生物量和营养品质的影响。结果表明,连续光照24 h后,生菜叶片中硝酸盐含量大幅下降,随着连续光照时间的增加,硝酸盐含量趋于稳定。地上鲜重、可溶性糖、VC含量在连续光照48 h后增幅最大,之后趋于稳定。可溶性蛋白含量随连续光照时间的增长而轻微下降。R/B=4、连续光照48 h对生菜生物量及营养品质的提高效果最好。     

Characterization of mobile LiDAR data collected with multiple echoes per pulse from crowns during foliation

Abstract

As a state-of-the-art technology for fine-scale forest investigation, mobile terrestrial light detection and ranging (LiDAR), also referred to as mobile laser scanning (MLS), recently has been increasingly exploited to improve its performance on this task. One potential solution is to apply special MLS systems with the capability of collecting multiple echoes per pulse (multi-echoes, for short) from canopies. The methodologies of this rationale turned out to perform better but still insufficiently for canopy properties retrieval, owing to their common defective premise. That is, the knowledge of the characteristics of MLS scan data comprising multi-echoes, so far, is in shortage, especially when regarding the dynamic process of tree foliation. As a pioneering work for this challenge, this study attempted to comprehensively analyze the characteristics of MLS multi-echoes collected from tree crowns during foliation. Specifically, new stable multi-echoes-related features were deduced under the schematic frame of relative quantification, in both spatial and temporal sense. “Relative” here briefly means the division operation deployed on the attributes of multi-echoes, individually in terms of the number of echoes, echo width and crown volume integrity, between their different return orders. Then, the “relative” schematic was primarily validated for more stably representing crown properties during foliation, based on the real data that was collected by the Sensei MLS system with a maximum of three echoes per pulse. Further, a case of tree species classification was examined using a linear discriminant classifier, and it was testified that the resultant temporal statistical rules of multi-echoes as the reverse clues can enhance the performance of MLS in applications.     

Comparative Performance of Rice with System of Rice Intensification (SRI) and Conventional Management using Different Plant Spacings

The System of Rice Intensification (SRI) reportedly enhances the yields of rice (Oryza sativa L.) through synergy among several agronomic management practices. This study was conducted to investigate the effects on rice plant characteristics and yield by comparing the plants grown with different methods of cultivation – SRI vs. recommended management practices (RMP) focusing on the impact of different plant spacings. Performance of individual hills was significantly improved with wider spacing compared with closer‐spaced hills in terms of root growth and xylem exudation rates, leaf number and leaf sizes, canopy angle, tiller and panicle number, panicle length and grain number per panicle, grain filling and 1000‐grain weight and straw weight, irrespective of whether SRI or RMP was employed. Both sets of practices gave their highest grain yield with the spacing of 20 × 20 cm; however, SRI yielded 40 % more than the recommended practice. At this spacing, canopies also had the highest leaf area index (LAI) and light interception during flowering stage. The lowest yield was recorded at 30 × 30 cm spacing under both the practices, as a result of less plant population (11 m^?2), despite improved hill performance. During the ripening stage, hills with wider spacing had larger root dry weight, produced greater xylem exudates, and transported these towards shoot at faster rates. These features contributed to the maintenance of higher chlorophyll levels, enhanced fluorescence and photosynthesis rates of leaves and supported more favourable yield attributes and grain yield in individual hills than in closely‐spaced plants. Moreover, these parameters further improved in SRI, apart from the enhanced percentage of effective tillers and showed substantial and positive impacts on grain yield (17 %) compared with recommended practice. In conclusion, wide spacing beyond optimum plant density, however, does not give higher grain yield on an area basis and for achieving this, a combination of improved hills with optimum plant population must be worked out for SRI.     

Cost-efficient light control for production of two campanula species

A cost-efficient light control system based on weather forecasts, electricity prices and daily photosynthesis integral (DPI) was evaluated for application in the commercial production of the long-day (LD) plant Campanula portenschlagiana ‘Blue Get Mee’ and C. cochlearifolia ‘Blue Wonder’. Experiments were conducted under both autumn and spring conditions and included four treatments. Three treatments were controlled by the software system DynaLight Desktop which automatically defined the most cost-efficient use of supplemental light, -based on a predefined set point of DPI, forecasted solar irradiance and the market price on electricity. The set points of DPI in the three treatments were 300, 450 and 600 mmol CO₂ m⁻² leaf d⁻¹ and the treatments were compared with a traditional LD 19-h treatment. The DPI-based light control strategy resulted in very irregular light patterns including daily periods of solar irradiance combined with supplemental light in low light periods and a night period interrupted by irregular light breaks (NB-lighting). Both campanula species flowered in the DPI-based treatments during spring, but the flowering percentage was low and non-uniform during autumn. This was caused by a combination of the irregular light, low natural light intensities and a decrease in daily light integral (DLI), and could be restored by maintaining a continuous 19 h photoperiod with incandescent lamps (<5 μmol m⁻² s⁻¹), illustrating that photoperiod was an important factor for flowering in LD species grown under low light intensities. Growth in terms of carbon gain was marginally affected by the irregular light and a 25% reduction in electricity costs was achieved without major reductions in plant quality in spring. Our results illustrate that plant production of LD species can be maintained in a cost-efficient light control system where the use of supplemental light is based on weather forecasts and electricity prices.     

不同光质对豇豆幼苗光合特性和若干生理生化指标的影响

在南方设施栽培环境条件下,以矮生豇豆为试材,研究不同光质(红光、蓝光、绿光、白光)对叶片光合特性及生理生化指标的影响.结果表明,红光处理有利于叶绿素含量、光合速率、蒸腾速率、可溶性糖含量的提高,而蓝光处理则有利于类胡萝卜素含量、可溶性蛋白质含量的提高.不同光质处理豇豆叶片的超氧化物歧化酶、过氧化物酶、过氧化氢酶活性均呈...     

Crown projection area of young Pinus sylvestris: A model and its test

In this study we applied a theoretical model for determining the projection area of a Scots pine (Pinus sylvestris L.) crown in different directions. The model is based on the assumption that the foliage elements (shoots) are randomly distributed within a symmetrical crown envelope. The model was tested using photographically measured data for three young Scots pine crowns. The compatibility between calculated and measured values was satisfactory.     

水分胁迫对常见绿化植物苗木光响应特性的影响

采用盆栽试验研究正常供水(黎明前小枝水势ψ-0.8MPa)和中度水分胁迫(-2.5MPaψ-3.5MPa)条件下,3种生活型绿化植物苗木光响应特性。结果表明:3种生活型苗木光响应曲线均与非直角双曲线接近;在正常供水条件下,乔木、灌木和攀援植物苗木的最大光合速率(Pnmax)分别为10.44、11.17、16.40μmol·m-2·s-1,表观光合量子效率(AQ,Y)分别为0.066、0.045、0.037,暗呼吸速率(Rd)分别为0.56、1.47、1.51μmol·m-2·s-1,光补偿点(LC,P)分别为17、33、46μmol·m-2·s-1,光饱和点(LS,P)分别为336、358、612μmol·m-2·s-1;土壤水分胁迫能显著降低乔木、灌木和攀援植物苗木的Pnmax、AQ,Y,而对Rd无显著影响,LS,P和LC,P的变化因种类而不同。在土壤水分胁迫条件下,灌木表现出较高的光合活性,其Pnmax、AQ,Y和Rd值均比乔木和攀援植物高,表明灌木苗木对土壤水分的生态适应能力较强。