杨农间作田的光强和土壤水分状况及其对农作物的影响

试验选择株行距３ｍ×２８ｍ,１０￣１１ａ的杨农间作田,研究其光强和土壤水分空间分布与农作物生长发育的关系。结果表明,间作田林冠下和林冠外的光强分别为全日照的３６．４％和７４．８％;行中为８０．２％,林冠下和林冠外的土壤含水率分别为行中的６２．６３％￣６７．７１％和８８．８８％￣７３．７３％,由于光照不足和水分胁迫,降低了作物的株高和叶面积,使花生和小麦的平均产量比对照田分别降低２２．３％和１９．９     

The effects of density, light and shelter on the growth and survival of African catfish (Clarias gariepinus Burchell, 1822) fingerlings

The effects of stocking density, light and shelter on the growth and survival of Clarias gariepinus fingerings was evaluated. In this experiment African catfish with initial individual mean weight 0.79±0.1 g were reared at two different stocking densities—5 fish l⁻¹ and 10 fish l⁻¹ in either sheltered or unsheltered tanks with reduced and normal light condition. In all conditions growth rate was significantly affected by stocking density. The growth rate was significantly higher at low densities and in reduced light conditions where shelter was provided. Survival rate was in excess of 79% in all treatments and was not affected by treatment.     

Higher density swards have a higher load bearing capacity

Increasing the water table is an important pathway to reduce greenhouse gas emissions from peaty soils. In order to continue utilizing grasslands on these soils, methods to increase load bearing capacity at a higher water table are sought. The objective of this study was to assess the effect of sward density on load bearing capacity, measured as both penetration resistance and the newly developed method measuring load bearing capacity through impact depth. Simultaneously, a new method to measure load bearing capacity through impact depth was developed. The study was conducted between 2018 and 2020 on 14 different farms in the western peat meadow district in the Netherlands, where the sward density measured with the point quadrat method ranged from 24% to 92%. Swards with a higher sward density showed a higher load bearing capacity than swards with a lower density. In a modelling approach an increase from 30% sward density to 90% sward density could result in a lengthening of the grazing season between three (11%) and six weeks (22%), depending on the soil moisture conditions. Load bearing capacity was also highly correlated with gravimetric soil moisture content as wetter conditions lowered load bearing capacity. In order to capture load bearing capacity more accurately a new measurement device was constructed which represents treading cattle. Both output (impact depth) and method (resembles cow hoof) are close to practice, which makes it a very suitable method allowing for easy interpretation by farmers.     

不同光质及胁迫处理对鼠尾藻及附生藻类光合生理的影响

利用鼠尾藻(Sargassun thumbergii)、菱形藻(Nitzschia)、石莼(Ulue pertusa)和绢丝藻(Callithamnion corymbosum)作为研究对象,通过白光、蓝光、红光照射,1%硝酸铵、1%柠檬酸、3%硫酸铵处理不同时间,淡水浸泡不同时间3种杂藻清除方法,系统研究光质、药物和淡水处理对鼠尾藻及杂藻光合生理的影响。结果显示,对于相对生长速率(RGR)、表观光合速率(Pn)及表观光合速率与呼吸耗氧速率(R)的比(Pn/R),鼠尾藻幼孢子体在蓝光下均明显大于在白光和红光下,而菱形藻则在红光下较大,且鼠尾藻幼孢子体与菱形藻在蓝光下的Pn比明显大于其在白光和红光下的Pn比。结果显示,鼠尾藻幼孢子体若与菱形藻进行竞争,在蓝光下相对于在白光和红光下更有优势。硝酸铵、硫酸铵、柠檬酸药物处理对鼠尾藻幼孢子体的生理状态有一定的影响,且这种伤害具有不可逆性;对鼠尾藻嫩芽的伤害较小,且可恢复正常;对石莼的清除效果不明显,对绢丝藻有伤害。淡水处理对鼠尾藻幼孢子体有伤害,对鼠尾藻嫩芽伤害较小,对石莼影响不大,对绢丝藻有伤害。研究表明,在鼠尾藻幼苗早期培育过程中,可增大蓝光的照射或减少红光的照射,在一定程度上能促进鼠尾藻的生长且抑制菱形藻的生长;在鼠尾藻早期幼苗的杂藻清除中,应避免使用1%硝酸铵、1%柠檬酸和3%硫酸铵处理,会对鼠尾藻幼孢子体产生伤害;鼠尾藻育苗早期不宜使用淡水浸泡除去杂藻,鼠尾藻嫩芽每次淡水浸泡30 min,可清除杂藻,且对藻体无伤害。     

灯光诱饵技术对深水网箱养殖鱼类品质的影响

为评估太阳能灯光诱饵技术在深水网箱养殖鱼类品质改善方面的应用效果,本研究在青岛金沙滩海域的深水网箱中设计并安装太阳能灯光诱饵设备,通过“灯光诱饵”吸引活体饵料聚集于网箱内,从而为实验大黄鱼(Pseudosciaena crocea)、鲈鱼(Lateolabrax japonicus)和真鲷(Pagrus major)提供天然饵料,全程无人工投饵,使其在自然状态下,拟半野生化养殖至上市。大黄鱼、鲈鱼和真鲷经过5个月的实验网箱及传统网箱养殖后,通过测定其脂肪、脂肪酸和氨基酸含量判断其品质。结果显示,在安装灯光诱饵设备的影响下,网箱养殖大黄鱼、鲈鱼和真鲷的感官性状显著好于传统网箱养殖鱼类,11月3种鱼体肥满度比6月均显著下降(P<0.05)。灯光诱饵网箱养殖大黄鱼和真鲷肌肉内粗脂肪含量分别比传统网箱养殖低75.24%和46.81%,差异极显著(P<0.01),鲈鱼差异不显著(P>0.05)。灯光诱饵网箱养殖大黄鱼、鲈鱼和真鲷肌肉内DHA含量高于传统网箱养殖鱼类,差异极显著(P<0.01);总脂肪酸含量、棕榈酸含量低于传统网箱养殖鱼类,差异极显著(P<0.01)。灯光诱饵网箱养殖的3种鱼的肌肉内的呈味氨基酸、呈鲜味氨基酸、呈甘味氨基酸、总氨基酸和非必需氨基酸含量均升高,其中大黄鱼变化最显著,实验组比对照组的呈味氨基酸、呈鲜味氨基酸和呈甘味氨基酸含量分别高11.78%、9.17%和19.57%,差异显著(P<0.05)。研究表明,太阳能灯光诱饵深水网箱养鱼技术虽然降低了养殖鱼类的生长速度,但可以改善养殖鱼类品质,且养殖投入明显降低,养殖收入显著提高,该方法可显著提升产出效益,因此,可作为一种绿色健康养殖模式进行推广应用。     

光照对短须裂腹鱼生长及生理影响研究

光照是影响鱼类活动、摄食和生长的主要环境因子之一。本文分别以野生和养殖短须裂腹鱼(Schizothorax wangchiachi)为研究对象,研究了短须裂腹鱼对光谱、光强选择趋向性及光谱对短须裂腹鱼生长、生理的影响。结果显示,黄光、红光和绿光都对短须裂腹鱼起到吸引作用;利用黄光进行光照强度选择性研究发现,在低光照强度范围(22.6~64.7 lx),短须裂腹鱼对光强的趋向性没有显著差异(P>0.05);为期56 d的养殖实验发现,不同的光照颜色显著影响短须裂腹鱼的生长率和存活率(P<0.05),黄光和自然光处理组的养殖效果无显著性差异;无论在生长率和应激水平,均优于蓝光环境,蓝光提升了短须裂腹鱼的应激水平,导致存活率下降。研究结果可为水利工程建设过鱼设施诱鱼光源的选择提供科学依据。     

浅谈寓辩证唯物主义观点教育于物理教学之中

介绍了如何结合物理学科的教学内容,来培养学生辩证唯物主义观点的教育意义、基本要求和基本途径,进而达到培养学生科学的思维和研究方法.     

果袋透光性对宁海白枇杷果实品质及抗氧化能力的影响

以白沙枇杷品种宁海白为试材,分析了白色单层、黄色单层、外浅黄内白双层、黄色双层和外灰内黑双层等5种不同透光率纸袋套袋对枇杷果实品质以及抗氧化能力的影响。结果表明,套袋能提高果实表面的明亮度。套袋后果实的总糖含量较对照下降,下降程度随果袋透光率性的下降而增强,其中外灰内黑纸袋与对照相比差异达到显著水平。套袋还降低了果实的总酚含量、类黄酮含量和果实的抗氧化能力,其中以透光性低的外灰内黑双层纸袋下降最大;但对类胡萝卜素含量影响较少。套袋后果实的抗氧化能力下降,与总酚和类黄酮含量降低呈显著正相关。     

主干形桃树对光截获能力和果实产量品质的影响

以6a生八月脆桃为试材,在果实成熟期观测分析了2种树形(主干形和开心形)对光截获能力和果实产量及品质的影响。结果表明,2种树形同一层次的平均单果质量、着色指数、光洁度差异不显著;果实硬度和可溶性固形物有显著差异,果实硬度表现为主干形﹥开心形,可溶性固形物则表现为开心形﹥主干形。对光截获能力的影响表现为主干形>开心形;叶面积指数、果实产量指标均表现为主干形高于开心形;果实产量是开心形的2.11倍。桃树主干形是高光效、高产树形。     

不同光质对延迟栽培‘巨峰’葡萄新梢生长及生理特性的影响

为研究不同光质对延迟栽培‘巨峰’葡萄新梢形态特征和叶绿素含量、叶片光合特性的影响,从‘巨峰’葡萄新梢开始生长前进行不同光质的早晚补光,以不补光为对照。结果表明,不同光质补光均促进新梢生长,缩短了新梢节间长度;不同光质补光下叶绿素含量大小顺序为黄光、红光、白光、蓝光、红＋蓝光、对照：不同光质对叶片的净光合速率影响很大,以补红光处理的最强,补黄光的次之,补红光＋蓝光的最低．