Shading effects on spatial growth and biomass partitioning of Cynodon dactylon

Cynodon dactylon is a low-growing C4 weed that is highly sensitive to shading. This species shows severe biomass reductions and highly plastic morphological changes in response to resource availability. The objective of this study was to analyse the effect of shading on the spatial and biomass growth of C. dactylon . Two experiments were carried out exploring different environmental conditions. Six treatments were applied on C. dactylon patches. Daylight and 18%, 41%, 48%, 69% and 85% shading of daylight photosynthetic active radiation (PAR) were imposed in Expt 1 and 0%, 22%, 44%, 50%, 74% and 87% shading of daylight PAR in Expt 2. Patches were slightly elliptical in shape and grew 3.2 and 1.5 cm d⁻¹ with 0% shading, on average, during the whole studied periods in Expts 1 and 2 respectively. Biomass was significantly reduced from 41% shading onwards in Expt 1 and from 50% shading in Expt 2. However, patch extension rate was only significantly reduced from 85% and 74% shading in Expts 1 and 2 respectively. Biomass partitioning was modified by shading in both experiments. A functional analysis of C. dactylon patches showed that the patch extension rate diminished linearly when patch biomass growth rate was lower than 1.66 g d⁻¹; above this value, the extension rate remained constant.     

Restoration of tuber production by exposure to unshaded daylight in Eleocharis kuroguwai Ohwi shaded during the early tuber formation period

The loss of final tuber weight of Eleocharis kuroguwai Ohwi by shading during the early tuber formation period (TFP) is overcome by exposure to unshaded daylight thereafter (late TFP). In the present study, the growth parameters that contribute to the dry matter increase (DMI) per day of tubers in the late TFP were examined. DMI of the tuber during the late TFP was determined by that of the whole plant and the ratio of the DMI of the tuber to that of the whole plant during this period. The ratio of the DMI of the tuber to that of the whole plant during the late TFP was significantly correlated with the DMI of the whole plant during the first 14 days of the late TFP. During the late TFP after the exposure to unshaded daylight, DMI of the whole plant correlated with the surface area of the stem (SAS) and net assimilation ratio (NAR), and the SAS correlated with the stem dry weight (DW) and specific stem-surface area (SSA). SSA negatively influenced NAR, but NAR was increased by unshading. During the late TFP after shading, the effect of the decrease of the stem DW due to shading on the DMI of the whole plant was mitigated by the large SAS and high NAR. These results indicate that the growth parameters that contribute to the DMI of tuber during the late TFP after exposure to unshaded daylight are SAS and NAR just after unshading, and SSA during this period.     

The effect of non-inversion tillage and light availability on dispersal and spatial growth of Cynodon dactylon

The invasive ability of Cynodon dactylon is dependent on self dispersal and on cultivation practices. Tillage can seriously change patch biomass and spatial structure, spreading vegetative propagules of the weed. The objectives of this study were: (i) to quantify the effect on non‐inversion tillage on dispersal, establishment and colonization of C. dactylon and (ii) to propose a simple model considering soil cultivation effects and light availability on spatial growth of weed patches. Two experiments were carried out, exploring different soils and environmental conditions. Spatial distribution of vegetative units differed when tillage was conducted with different non‐inversion implements and could be described by simple functions. A minimum patch biomass seems necessary before vegetative structures are vulnerable to movement by cultivation. Only a small proportion of the biomass dispersed from original patches was able to establish. However, simulation showed that the area colonized by C. dactylon mostly increased by means of tillage dispersal, both with and without crop competition, in one growing cycle. It appears sensible to consider changing cultivation practices to reduce weed dispersal and to use crop competition for light to create unsuitable habitats limiting weed colonization.     

增施氮肥、硼肥对花期遮阴条件下玉米籽粒产量的影响

遮阴已成为影响夏玉米产量的重要因子,提高玉米耐阴性可为高产、抗逆栽培提供理论依据。以‘苏玉29’为试验材料,系统研究了小喇叭口期增施氮肥、硼肥缓解花期遮阴胁迫对夏玉米形态建成、物质积累和产量的影响。结果表明：遮阴处理降低了株高、茎粗、单株叶面积和干物质积累量,并延长了散粉吐丝间隔期。与遮阴处理比,小喇叭口期增施硼肥、氮肥不同程度提高了株高、茎粗、单株叶面积和干物质积累量,且同时增施硼肥、氮肥增幅最大。遮阴处理显著增加了秃尖长,降低了穗粒数和粒重,增施硼肥氮肥缓解了遮阴对突尖长、穗粒数和粒重的影响。增施硼肥、氮肥和同时增施硼肥、氮肥处理产量分别较遮阴处理提高36.7%、8.0%和43.1%。遮阴处理降低叶面积影响干物质积累,产量的降低与突尖增长、穗粒数较少和粒重降低有关。小喇叭口期增施硼肥和氮肥是缓解花期遮阴对产量不利影响的有效措施。 关键词：玉米;遮阴;氮肥;硼肥;产量;农艺性状     

遮阴对冀中南优质强筋小麦形态和品质的影响

选用4个适于冀中南种植的优质强筋小麦进行花后遮阴处理,测定了株高和旗叶形态特征、千粒重以及品质性状,研究不同遮阴条件下这些主要形态特征和品质性状的变化。结果表明：与对照(S0)相比,25%遮阴(S1)增加小麦株高,50%遮阴(S2)株高增幅低于S1,藳优2018甚至低于S0;不同品种旗叶对遮阴处理响应不同,师栾02-1和石优20通过增加叶片长度增加旗叶叶面积,藳优5766叶片厚度降低,藳优2018无显著变化;遮阴造成千粒重降低,蛋白含量、沉降值和湿面筋含量品质指标增加,但是面筋指数下降;遮阴对面团流变学特性影响在品种间存在较大差异,遮阴提高石优20和藳优5766的面团形成时间、稳定时间、拉伸能量和最大拉伸阻力,但是降低师栾02-1的面团形成时间、稳定时间、拉伸面积和最大拉伸阻力,降低藳优2018面团形成时间、稳定时间和最大拉伸阻力,却增加拉伸面积。优质强筋小麦品质对遮阴的响应有共同点,但也存在品种间差异, 可能是遮阴降低小麦光合速率导致光合产物合成和运输受阻,蛋白含量的相对提高使得不同小麦在遮阴处理中有共性的反应,例如4个小麦品种的蛋白含量和湿面筋含量都增加,同时品种间籽粒的蛋白组成不同,可能是导致粉质参数和拉伸参数存在差异的重要原因。     

Comparative performance of the highly invasive Mimosa invisa and its less invasive subspecies under different nutrient and light conditions

Invasive plants may be more plastic than non‐invasive plants and maintain high fitness under various environmental conditions. Previous studies mainly focused on the comparisons between invasive and native plants, and comparisons between highly invasive and less invasive exotic species are still relatively rare, especially for comparisons at the subspecies level. This study examined the effects of nutrient addition and shading on the performance of the highly invasive Mimosa invisa and its less invasive subspecies M. invisa var. inermis under either isolated or competitive conditions. Nutrient addition increased biomass and plant height and decreased root‐to‐shoot ratio (R/S). Shading decreased biomass and R/S and increased plant height. Under isolated conditions, the two invaders did not differ in R/S, plant height and plasticity of these traits in response to nutrient addition or shading, and the two invaders also did not differ in biomass production under each of the nutrient and light treatments. When the two invaders competed with each other, M. invisa outcompeted M. invisa var. inermis under high soil nutrient conditions, and the two invaders did not differ in performance under other growth conditions. Thus, only considering competition may we find out the difference between highly invasive species and their closely related, less invasive subspecies. Management of M. invisa should focus on habitats with high soil nutrient availability, in which M. invisa is more likely to dominate.     

基于多体接触碰撞的松软地面车轮沉陷仿真

提出了一种大规模多体系统接触碰撞理论与车辆地面力学理论相结合的仿真方法,并基于多体动力学仿真平台开发了车轮土壤相互作用仿真模块。基于该方法建立的土壤动力学模型和车轮土壤接触碰撞模型,进行了车轮沉陷的仿真。根据记录,在普通配置台式计算机上模拟土槽系统30 s的运动,仅需20 min。在相同实验条件下,仿真结果与土槽实验结果趋势一致,仿真曲线与土槽实验曲线吻合良好。由此表明该仿真算法能够满足越野行驶仿真的需要。     

抽穗后遮荫对龙粳31产量及籽粒灌浆的影响

对水稻龙粳31抽穗后进行遮光处理,研究遮荫处理与未遮荫处理(CK)在产量及其构成、功能叶片的SPAD值和灌浆特性等方面的差异。结果表明:龙粳31抽穗后进行遮荫,主要影响千粒重和结实率两个产量因素,产量降低达到极显著水平;胁迫功能叶片SPAD值升高;遮光处理的强、弱势粒籽粒最大灌浆速率GR_(max)和平均灌浆速率GR_(mean)均低于对照。     

水稻耐光氧化和耐阴特性的鉴定及其生理基础

水稻耐光氧化和耐阴特性的鉴定及其生理基础焦德茂，高亮之，金之庆，季本华，严建民（江苏省农业科学院，南京２１００１４；南通师范专科学校，南通２２６００７）关键词：光氧化；耐阴；光合特性ＩｄｅｎｔｉｆｉｃａｔｉｏｎａｎｄＰｈｙｓｉｏｌｏｇｉｃａｌＢａｓｉ...     

不同坡位植被生长状况与土壤养分空间分布特征

地形和土壤是影响植被群落的重要因素,植被生长状况与土壤养分含量随地形而变化。以吴起县枣庄沟小流域为研究区,采用样方法对不同坡位草地植被群落进行了植被调查,采集0—20cm的表层土壤测定土壤有机质、全氮、全磷含量,研究不同坡位上植被群落与土壤养分变化关系,以期了解黄土高原丘陵沟壑区地形对植被恢复的影响机制,为当地生态恢复提供科学依据与指导。结果表明:不同坡位上草地植被群落物种多样性、丰富度及地上生物量虽无显著差异,但各项指标均表现出坡下>坡中>坡上的趋势,这与土壤养分含量变化趋势相同。其中坡下位置各项土壤养分含量均为最大,植被生长状况最好;而沟坡位置土壤有机质含量、全氮含量、物种丰富度指数与地上生物量均为最低。植被生长状况与土壤养分在不同地形上变化趋势基本一致,具有一定相关性。