土壤水分对湿地松幼苗光合特征的影响

通过设置常规供水(CK)、轻度干旱(T1)、水饱和(T2)、水淹(T3)4个处理组,研究湿地松当年实生幼苗在不同土壤水分条件下的光合生理响应及叶绿素荧光特性。结果表明:不同水分处理对湿地松幼苗的叶片气体交换参数、水分利用效率(WUE)、光合色素、叶绿素荧光参数等指标有不同的影响;其中,T3的光合色素含量最低;T2、T3组的湿地松幼苗表现出较低的净光合速率(Pn)、电子传递速率(ETR)和PSⅡ光化学的量子效应(ΦPSⅡ),但与其他耐水淹植物相比,T3条件下的湿地松幼苗仍具有较高的Pn,说明湿地松幼苗具有较强的耐水淹能力;在T1条件下,湿地松幼苗具有较高的WUE和较低的蒸腾速率(Tr)、气孔导度(Gs)以对抗干旱的逆境,其Pn、PSⅡ最大光化学效率(Fv/Fm)、ETR和ΦPSII均有所下降,但仍能维持在相对正常的水平。研究证明,湿地松幼苗具有一定的耐淹耐旱特性,可运用于三峡库区消落带的植被重建。     

2个种源栓皮栎对干旱及复水的光合生理响应

为了探究干旱复水对2个种源栓皮栎幼苗光合生理特性的影响,测定了不同水分处理(正常供水、轻度干旱、中度干旱和重度干旱)及复水处理下盆栽栓皮栎幼苗生长、叶片气体交换及叶绿素荧光参数。结果表明:随着干旱胁迫程度的加重,幼苗生长受到的抑制程度增加;气体交换参数净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和水分利用效率(WUE)均呈下降的趋势,而气孔限制值(Ls)呈上升趋势,在重度干旱胁迫下气体交换参数变化幅度最大;叶片非光化学猝灭系数(NPQ)呈现先上升后下降的趋势,PSII潜在活性(Fv/Fo)、最大光化学效率(Fv/Fm)、电子传递速率(ETR)和实际光量子效率(ΦPSⅡ)均呈下降趋势。主要叶绿素荧光参数对干旱胁迫的响应与气体交换参数一致,即重度胁迫对光合电子传递造成了最严重的损伤。干旱后复水,导致栓皮栎光合生理参数不同程度的恢复。就种源地而言,老君山种源的幼苗在干旱胁迫下主要参数的变化程度大于北坡山种源的幼苗,且在复水后老君山种源幼苗恢复程度低于北坡山种源,表明北坡山种源的栓皮栎抗旱力和恢复力均强于老君山种源。     

杂交马褂木叶片发育过程中资源利用效率的变化格局

对一年生杂交马褂木( Liriodendron chinense Sarg.× L. tulipifera L.)叶片展开过程中光能转换效率、水分利用效率和光合碳同化的变化规律及栽植密度对中下部叶片资源利用效率的影响进行了研究,结果表明(1) 叶片展开过程中,净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(E)、气孔限制值(Ls)、总光合速率(Pm)、净光合比率(Pn/Pm)、PSⅡ的原初光能转化效率(Fv/Fm)和PSⅡ的光量子产率(φPSⅡ) 、羧化效率(CE) 和水分利用效率(WUE)显著上升,而胞间CO2浓度(Ci)和呼吸速率(R)显著下降;(2) 叶片展开过程中,光合碳同化"暗系统"的完善远远慢于能量转换的"光系统";(3) 叶片展开过程中,影响净光合速率增长的主导因素不是气孔导度,而是"暗系统"完善程度, "光系统"的影响远小于"暗系统"的影响; (4) 郁闭的高密度群体中,中下部叶片的Pn、Gs、E、Ls、Pm、Fv/Fm、φPSⅡ、CE和WUE显著低于上部完全展开叶,Ci显著高于上部完全展开叶,Pn/Pm和上部完全展开叶没有显著差异,而未郁闭的低密度群体中,中下部叶片的上述所有参数与上部完全展开叶无显著差异;(5) 导致高密度群体叶片Pn大幅度下降的主导因素是CE的大幅下降,而不是"光系统"和气孔导度;(6) 密度过大加速了中下部叶片光合功能的下降.     

土壤干旱胁迫对沙棘叶片光合作用和抗氧化酶活性的影响

在半干旱黄土丘陵区,采用盆栽控水试验,通过测定3年生沙棘苗木在8个土壤水分梯度下的光合速率、叶绿素荧光、抗氧化酶活性等光合生理生化指标,探讨沙棘叶片光合作用在土壤干旱逐渐加重过程中的变化过程、机制及其与土壤水分的定量关系.结果表明:(1)土壤相对含水量(RWC)在38.9％-70.5％范围内,随干旱胁迫加重,沙棘的净光合速率(Pn)、气孔导度(Gs)和胞间CO2浓度(Ci)明显下降,而气孔限制值(Ls)显著上升,即Pn下降主要是由气孔限制造成的;当RWC＜38.9％时,干旱胁迫继续加剧,Pn和Ls都降低,而Ci显著上升,即Pn下降的主要原因已经转变为非气孔因素的限制.(2)土壤适度水分胁迫能够提高沙棘叶片的水分利用效率(WUE),维持沙棘Pn和WUE处于较高水平的RWC范围为58.6％-82.9％和48.3％-70.5％.(3)土壤干旱加重过程中,沙棘的最大荧光(Fm)、PSⅡ最大光化学效率(Fv/Fm)、PSⅡ实际光化学效率ΦPSⅡ,光化学猝灭(qP)均表现出逐渐降低的趋势,而初始荧光(Fo)显著升高,非光化学猝灭(NPQ)则表现出先上升后下降的趋势;RWC在38.9％-70.5％的范围内,热耗散是沙棘重要光保护机制;RWC＜38.9％时,PSⅡ受到损伤,电子传递受阻.(4)土壤干旱加重过程中,沙棘叶片的超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性表现出先升高后降低的趋势,丙二醛(MDA)含量则表现出逐级递增趋势;土壤干旱程度在RWC为48.3％-70.5％时,对沙棘叶片的抗氧化酶系统活性有诱导作用;而土壤干旱到严重胁迫(RWC＜38.9％)时,沙棘叶片的抗氧化酶系统损伤,抗氧化酶活性下降,细胞膜遭到破坏.土壤干旱程度在RWC为48.3％-70.5％时,沙棘叶片可以通过热耗散和酶活性调节协同作用,稳定光合机构的正常功能,Pn下降的主要原因是气孔限制;而干旱到严重胁迫(RWC＜38.9％)时,PSⅡ系统和抗氧化酶系统损伤,是光合作用发生非气孔限制的主要原因.在半干旱黄土丘陵区,沙棘生长所允许的最大土壤水分亏缺在RWC为38.9％,维持沙棘具有较高WUE和Pn的土壤水分阈值为RWC在58.6％-70.5％之间.     

五节芒不同种群对Cd污染胁迫的光合生理响应

通过盆栽模拟试验,以分别来自粤北大宝山矿区和惠州博罗非矿区的两个五节芒种群为试验材料,比较研究了两个种群在Cd胁迫下的气体交换参数、叶绿素荧光特性、光合色素含量和叶绿体超微结构变化的差异。结果表明:(1)Cd胁迫下五节芒两种群叶片净光合速率(Pn)、蒸腾速率(E)、气孔导度(Gs)、胞间二氧化碳浓度(Ci)、叶绿素含量(Chl)都有不同幅度的下降;叶绿体超微结构遭到破坏。矿区种群随Cd胁迫程度的加深,净光合速率下降较慢,叶绿体的外形及基粒结构受到的影响较小。(2)轻度Cd胁迫下气孔限制是五节芒非矿区种群Pn降低的主要因素,中度和重度Cd胁迫下非气孔限制是Pn降低的主要因素。(3)Cd胁迫下五节芒两种群PSⅡ反应中心最大光化学效率(Fv/Fm)、PSⅡ潜在活性(Fv/Fo)、PSⅡ有效光化学效率Fv′/Fm′均有所下降。总体上矿区种群降幅较小,PSⅡ利用光能的能力及PSⅡ的潜在活性均较强。PSⅡ光化学猝灭系数(qP)、非光化学猝灭系数(NPQ)的变化表现为Cd胁迫下两种群qP值降低、NPQ值升高,总体上抗性强的矿区种群qP降低的幅度低且NPQ升高幅度大。随着Cd胁迫浓度增加,矿区种群实际光化学反应效率(ΦPSⅡ)和电子传递速率(ETR)变化幅度不大,而非矿区种群显著下降,表明矿区种群PSⅡ反应中心电子传递活性受到的影响小,光合机构的损伤程度低。研究表明,五节芒矿区种群对重金属Cd有较强的耐受能力,适合作为金属矿区植被恢复建设的禾本科先锋物种。     

硅对低温胁迫后檀香紫檀苗木生长和光合生理的影响

为探究硅(Si)对檀香紫檀(Pterocarpus santalinus)抗寒性的影响,对1年生苗木施Si后经(–3±0.5)℃胁迫24 h恢复栽培90 d的生长、叶片光合参数和4种碳同化关键酶活性进行了研究。结果表明,施Si的檀香紫檀苗木发育健壮,抗寒性提高,显著促进低温胁迫后的生长恢复;施Si显著抑制低温胁迫导致的檀香紫檀苗木叶绿素含量降低和叶绿素a/b减小,促进表观光合电子传递速率(ETR)、实际光量子效率Y(Ⅱ)和PSⅡ调节性能量耗散Y(NPQ),降低PSII非调节性能量耗散Y(NO)和非光化学荧光淬灭(NPQ);施Si提高受低温胁迫檀香紫檀苗木的光合速率(Pn)、气孔导度(Gs)和水分利用效率(WUE);施Si的檀香紫檀苗木在低温胁迫后,核酮糖-1,5-二磷酸羧化酶(Rubisco)、果糖-1,6-二磷酸酶(FBP)、果糖-1,6-二磷酸醛缩酶(Ald)、磷酸烯醇式丙酮酸羧化酶(PEPC)活性显著提高。适量施Si有利于保持低温胁迫下苗木光合膜结构的完整性和生理功能的稳定性,是提高檀香紫檀苗木抗寒性、有效应对低温胁迫的营养管理措施。     

干旱胁迫对金花茶幼苗光合生理特性的影响

以金花茶一年生实生苗为材料,采用盆栽控水试验,研究不同水分处理(CK、T1、T2、T3,土壤含水量分别为田间持水量的85%~90%、65%~70%、50%~55%、35%~40%)对金花茶幼苗光合生理指标的影响。结果显示:(1)在重度干旱胁迫(T3处理)下,金花茶植株都因干旱而死亡,表明金花茶幼苗对干旱胁迫的耐受极限为田间持水量的50%~55%(土壤含水量为15.04%~16.54%)。(2)随着干旱胁迫程度的加剧,金花茶幼苗叶片净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、气孔限制值(Ls)和PSⅡ实际光化学量子效率(ΦPSⅡ)均显著降低,胞间CO2浓度(Ci)和水分利用效率(WUE)无显著变化,干旱胁迫下金花茶光合速率降低的主要原因是由非气孔因素所致。(3)与CK相比,T1处理下叶片初始荧光(F0)、最大荧光(Fm)、PSⅡ最大光化学效率(Fv/Fm)和丙二醛(MDA)含量均无显著变化,而T2处理下F0、MDA含量显著升高,Fm、Fv/Fm显著降低;T1处理下金花茶的PSⅡ反应中心还未受到伤害,而T2处理下其光合机构发生了不可逆的破坏。(4)叶片叶绿素总量(Chl)、叶绿素a(Chl a)、叶绿素b(Chl b)、类胡萝卜素(Car)含量、Chl a/Chl b、Car/Chl、叶片相对含水量(RWC)均随干旱胁迫的增强而降低,脯氨酸(Pro)含量随干旱胁迫的加剧呈现出先升高后降低的趋势。研究表明,金花茶对干旱胁迫极为敏感,水分稍有亏缺,便会明显抑制其光合作用;金花茶不耐干旱的生理特性可能是限制其种群扩散的一个重要原因。     

高温对水稻黄叶突变体剑叶光合特性和叶绿体超微结构的影响

以水稻黄叶突变体为材料,进行高温胁迫处理(9:30～17:30,40℃;其它时间段与自然温度相同),研究高温胁迫对其剑叶光合特性和叶绿体超微结构的影响。结果表明:高温胁迫使水稻黄叶突变体剑叶净光合速率(Pn)、PSⅡ原初光化学效率(Fv/Fm)、PSⅡ光量子效率(фPSⅡ)和非循环光合电子传递速率(ETR)显著降低,初始荧光(F0)显著增加,同时使剑叶叶绿素、可溶性蛋白质含量显著降低,细胞膜透性显著增加,叶片的叶绿体内基粒和基质片层模糊、疏松,结构紊乱。研究发现,40℃高温胁迫致使水稻黄叶突变体剑叶叶绿体超微结构破坏,引起PSⅡ反应中心的光化学效率降低,最终造成叶片光合能力减弱。     

土壤极端干旱对金银花光合生理生化特性的影响

为探索金银花(Lonicera japonica Thunb.)光合作用对土壤逐渐干旱的响应过程及其与土壤水分的定量关系,以沂蒙山区3年生金银花苗木为试验材料,测定分析其叶片光合作用、叶绿素荧光及抗氧化酶活性等对土壤水分的响应特征,为进一步研究金银花光合效率响应"极端干旱水分阈值-阈值持续-复水恢复"的机制提供依据。结果显示:(1)当29.7%≤土壤相对含水量(RSWC)≤79.6%时,随着RSWC的降低,叶片的净光合速率(Pn)和蒸腾速率(Tr)降低,胞间CO2浓度(Ci)逐渐减小,Pn降低的主要原因是气孔限制;而其非光化学猝灭(NPQ)及抗氧化酶活性逐渐增大,表明金银花叶片主要通过热耗散消除掉PSⅡ过多激发能,同时抗氧化酶活性提高,清除了细胞内过多的活性氧。(2)当11.4%≤RSWC≤29.7%时,金银花叶片Pn降低伴随着Ci增大和Ls减小,Pn降低的主要限制因素转变为非气孔因素,同时其PSⅡ最大光化学效率(Fv/Fm)、PSⅡ实际光化学效率(ΦPSⅡ)、电子传递效率(ETR)、光化学猝灭(qP)及NPQ显著降低,初始荧光(Fo)显著增大,表明此水分范围内PSⅡ遭到破坏,光合电子传递受到抑制;且叶片抗氧化酶活性显著降低,而丙二醛含量显著增大,导致活性氧过量积累,膜系统受到严重破坏。(3)当RSWC为11.4%时,叶片Pn接近0,植物发生萎蔫,光合机构受损伤程度最大。研究表明,金银花光合作用由气孔因素限制向非气孔因素限制转折的水分点(RSWCSL-NSL)、Pn≈0的水分点(RSWCPn≈0)以及植物叶片萎蔫水分点(RSWCwilting)分别为29.7%、11.4%和11.4%。     

水分胁迫下大丽花光合及叶绿素荧光的日变化特性

以大丽花品种‘粉西施’为试验材料,采用盆栽方法,研究了不同土壤含水量处理对‘粉西施’叶片光合及荧光特性日变化的影响。结果表明:随着水分胁迫程度的加深,大丽花叶片的Pn、Tr和Gs日平均值均降低,Ci日平均值在轻度和中度胁迫下降低,在重度胁迫下升高;在轻度和中度水分胁迫下大丽花Pn降低的主要原因是气孔限制,而重度水分胁迫下是非气孔因素;Pn在水分胁迫下的日变化曲线由单峰型变成双峰型,出现"午休"现象,且Tr和Gs在水分胁迫下的日变化曲线和Pn一致,但Ci日变化较平稳,与Pn相反。随着水分胁迫程度的加深,大丽花叶片的初始荧光(F0)日平均值升高,日变化曲线呈倒"V"型,PSⅡ反应中心可能破坏或可逆失活;Fm、Fv/Fm和ΦPSⅡ日平均值均降低,日变化曲线呈"V"型。水分胁迫使大丽花光抑制程度加深,抑制了PSⅡ的光化学活性,致使用于光化学反应的光能及实际光化学效率降低。研究结果发现,大丽花品种‘粉西施’在不同水分胁迫下都产生了光合作用的光抑制而使净光合速率降低;光合机构可适应轻度和中度水分胁迫而发生可逆失活,没有受到不可恢复的伤害,而重度水分胁迫降低了叶片的光合机构活性,加剧了光抑制程度,严重限制了光合作用;适宜大丽花生长的土壤含水量应为田间最大持水量的30%以上。     

濒危种四合木与其近缘种霸王水分关系参数和光合特性的比较

运用压力室-容积技术(P-V技术)对西鄂尔多斯地区特有的濒危植物四合木(Tetraena mongolica Maxim.)和生长于同一生境的近缘种霸王(Zygophyllum xanthoxylon (Bunge) Maxim.)的7个水分关系参数饱和含水量时最大渗透势(Ψ_s^sat) 、初始质壁分离时的渗透势(Ψ_s^tlp) 、初始质壁分离时渗透水相对含量(ROWC^tlp) 、初始质壁分离时的相对含水量(RWC^tlp) 、质外体水的相对含量(AWC) 、束缚水与自由水的比值(V_a / V₀),以及细胞最大弹性模量(ε^max)进行了测定,同时利用Li-6400光合作用测定系统测定了二者叶片气体交换参数的日变化,从生理生态学角度探讨了二者生存力、适应力的差异。结果表明:1)四合木的ε^max、ROWC^tlp值和RWC^tlp值均显著低于霸王,而Ψ_s^sat值Ψ_s^tlp值、AWC和V_a / V₀高于霸王。二者保持膨压的能力和方式不同,四合木表现为较小的细胞体积和较强的持水能力,主要以高的组织弹性来保持膨压,而霸王主要以增加细胞质浓度的渗透调节来维持膨压,弹性调节较弱。且四合木保持最大膨压的能力和维持最低膨压的极限渗透势低于霸王,耐旱性弱于霸王。2)自然条件下,四合木和霸王叶片的光合速率(Pn)、蒸腾速率(Tr)日进程均呈"双峰"曲线,主峰出现在11:00时,次峰出现在15:00时左右,光合作用的午间降低是由气孔导度(Gs)降低造成的。二者相比,四合木光合速率和水分利用效率(WUE)低于霸王,光合能力和对干旱环境适应能力弱于霸王。研究表明四合木在生理生态学方面的生存力、适应力弱于霸王。     

Rainfall triggered dynamics of Aedes mosquito aggressiveness

Inspired by Davidson method of estimating daily survivals of a structureless population of mosquitoes, we present a model which describes the behavior of floodwater mosquitoes in terms of emergence functions following a rainfall event, blood feeding frequency and parous stages, and survival at various stages. As a generalization of the Davidson formula, we have developed an approach for dealing with the dynamics of structured population of mosquitoes, and derived various formulas allowing assessment of demographic parameters like durations of gonotrophic cycles and (apparent) daily survivals. The method was subsequently applied to field data of floodwater mosquitoes Aedes vexans arabiensis, potential vectors of Rift Valley fever in West Africa, collected during the 2003 rainy season in Barkedji, Senegal. We found that mosquitoes emerged about 3 to 4 days following an efficient rainfall, and mosquito emergences, described by a bell shaped function, lasted for about 2 days. The mean duration of the gonotrophic cycle was 3 days and the apparent daily survival about 0.87.     

中华白海豚雄性生殖系统组织学初步研究

采用组织学和形态学方法研究了中华白海豚(Sousa chinensis)的雄性生殖系统。以睾丸和附睾中是否存在精母细胞及精子细胞等作为判断雄性中华白海豚性成熟的标准,通过比较不同个体睾丸和附睾的组织结构特征,发现成熟个体的生精小管和附睾的组织学结构与未成熟个体间存在显著差异。通过测量样本睾丸的2个形态参数:生精小管直径和生精小管的相对面积,得到性成熟个体的生精小管直径为(118.3±12.8)μm,生精小管相对面积为0.52;未成熟个体的生精小管直径(47.4±3.5)～(60.3±6.0)μm,生精小管相对面积为0.27～0.40。     

Seasonal variation in Emiliania huxleyi coccolith morphology and calcification in the Aegean Sea (Eastern Mediterranean)

A seasonal morphological variability is observed in Emiliania huxleyi var. huxleyi specimens, collected from discrete water samples in the Aegean Sea. Biometric analyses reveal a consistent pattern of increase in the size of coccoliths and coccospheres, including the thickness of the inner tube elements (INT), in winter/spring time low sea surface temperature and moderate productivity samples when compared with summer time high temperature-low productivity samples. The small range of salinity change in the Aegean Sea and the absence of seasonal pattern in nutrient content do not support any association with the observed increase in E. huxleyi coccolith size. A relatively increased [HCO₃^-] content is observed during spring-time interval related with the increase in the coccolith size, however it remains unclear which parameter of the carbonate system causes the observed effects.     

Pyrolysis characteristics and kinetics of Arundo donax using thermogravimetric analysis

The increase of the price of fossil means, as well as their programmed disappearing, contributed to increase among appliances based on biomass and energy crops. The thermal behavior of Arundo donax by thermogravimetric analysis was studied under inert atmosphere at heating rates ranging from 5 to 20 °C min⁻¹ from room temperature to 750 °C. Gaseous emissions as CO₂, CO and volatile organic compounds (VOC) were measured and global kinetic parameters were determined during pyrolysis with the study of the influence of the heating rate. The thermal process describes two main phases. The first phase named active zone, characterizes the degradation of hemicellulose and cellulose polymers. It started at low temperature (200 °C) comparatively to wood samples and was finished at 350 °C. The pyrolysis of the lignin polymer occurred during the second phase from 350 to 750 °C, named passive zone. Carbon oxides are emitted during the active zone whereas VOC are mainly formed during the passive zone. Mass losses, mass loss rates and emission factors were strongly affected by the variation of the heating rate in the active zone. It was found that the global pyrolysis of A. donax can be satisfactorily described using global independent reactions model for hemicellulose and cellulose in the active zone. The activation energy for hemicellulose was not affected by a variation of the heating rate with a value close to 110 kJ mol⁻¹ and presented a reaction order close to 0.5. An increase of the heating rate decreased the activation energy of the cellulose. However, a first reaction order was observed for cellulose decomposition. The experimental results and kinetic parameters may provide useful data for the design of pyrolytic processing system using A. donax as feedstock.     

昆仑山北坡不同海拔塔里木沙拐枣的光合生理生态特性

在2008年7月25日-8月6日的连续晴天中,选择昆仑山北坡塔里木沙拐枣自然分布区3个海拔高度(2100,2300,2500m),利用便携式光合测定仪LI-6400测定塔里木沙拐枣的光合生理生态特性。结果表明:2100m处塔里木沙拐枣的光补偿点(LCP)和光饱和点(LSP)与2300m,2500m处差异分别达到显著,而3者间的最大净光合速率(P_max)差异均达显著。表观量子效率(AQY)在3个海拔之间差异均不显著,但在2100m处的羧化效率(CE)分别与2300m和2500m处的差异显著。相同海拔下塔里木沙拐枣的暗呼吸速率值(R_day)要高于光呼吸速率值(R_p),且2500m处的暗呼吸速率分别与2100m和2300m处的有显著的差异,2100m处的光呼吸速率分别与2300m和2500m差异显著。3个海拔塔里木沙拐枣的净光合速率(P_n)、蒸腾速率(T_r)和气孔导度(G_s)的日变化均为单峰曲线。随着海拔的升高,塔里木沙拐枣P_n,T_r,G_s和L_s的日均值降低,但光能利用率(LUE)和水分利用效率(WUE)却显著增加。塔里木沙拐枣的P_n与叶温(T_l)、大气温度(T_a)和光照强度(PPFD)具有极显著的正相关关系,与海拔呈显著负相关,与空气相对湿度(RH)和大气CO₂浓度(C_a)之间均不具有显著相关性。T_r与T_a,T_l和PPFD具有极显著的正相关性,与RH之间存在显著的负相关。G_s只与C_a之间呈极显著的负相关。P_n与T_r,L_s,G_s,WUE和V_pdl分别具有极显著的正相关性,与C_i呈极显著的负相关。通过对不同海拔高度塔里木沙拐枣光合生理参数与光、温等生态因子关系的对比分析表明:塔里木沙拐枣对山地荒漠草地自然环境变化的温度和光照有很好的生态适应性。     

Parasitization of fifth instar tasar silkworm, Antheraea mylitta, by the uzi fly, Blepharipa zebina; a host-parasitoid interaction and its effect on host's nutritional parameters and parasitoid development

The uzi fly, Blepharipa zebina, is a well-known larval endoparasitoid of the tropical tasar silkworm, Antheraea mylitta. The present study dealt with the effect of the number of maggots developing per host on host nutritional parameters, parasitoid development and reproduction. Nutritional indices for ingestion, digestion, approximate digestibility, relative consumption rate, relative growth rate, and gain in body weight declined significantly with the increase in parasitoid burden, but the efficiency of conversion of digested food recorded a significant increase. The efficiency of conversion of ingested food remained little affected. The developmental period was significantly extended in larvae parasitized with 5 and 10 maggots per larva (mpl). Cocoon shell weight decreased by 27-63.5% in parasitized groups (1, 2, and 5 mpl) while larvae parasitized with 10 mpl could not spin cocoons. The maggot development period, recovery percentage, and fecundity of the uzi fly declined significantly with the increase in number of maggots developing per host.     

低氧对甘肃鼢鼠体内ACTH及血液生理指标的影响

为研究低氧对甘肃鼢鼠(Myospalax cansus)血清促肾上腺皮质激素(ACTH)及血液生理指标的影响,采用KX-21N全自动血液分析仪对甘肃鼢鼠低氧处理前后血液中红细胞数(RBC)﹑血红蛋白浓度(HGB)﹑红细胞压积(HCT)、平均红细胞体积(MCV)、平均血红蛋白含量(MCH)及平均血红蛋白浓度(MCHC)进行测定,并采用SN-695A型智能放免r测量仪测定血清中ACTH浓度。结果表明,氧浓度分别为14.1%、10.5%和6.5%条件下,甘肃鼢鼠RBC、HGB和HCT均显著升高,MCV变化不明显,MCH和MCHC下降,血清ACTH含量显著升高;腹腔注射ACTH后甘肃鼢鼠RBC、HGB、HCT均显著升高。说明低氧激活了甘肃鼢鼠下丘脑-垂体-肾上腺皮质轴(HPA),导致ACTH分泌增加,刺激皮质酮分泌,致RBC、HGB、HCT含量增加,从而提高血液中红细胞的携氧能力以适应低氧生活环境。     

A short-term divergent selection for resistance to Teladorsagia circumcincta in Romanov sheep using natural or artificial challenge

This experiment was conducted to assess the efficiency of selection on the basis of response to artificial challenges in order to breed sheep resistant to natural infection. A short-term divergent selection process was designed to estimate the genetic parameters of these two traits. Two flocks, including 100 Romanov ram lambs each, were challenged in 1990 when they were 6 months old. One flock received three artificial infections with 20 000 third-stage Teladorsagia circumcincta larvae, at intervals of 7 weeks. Faecal egg counts (FEC) were performed on Days 22, 25 and 28 post infection (p.i.) and the animals were drenched on Day 28 p.i. The other flock was grazed for 5 months on a pasture contaminated with the same species. Faecal samples were taken from the lambs at similar ages. About 5 rams with the lowest FEC and 5 with the highest FEC were selected in each flock and mated with unselected ewes. Their offspring (200 animals) were challenged in 1992, half in the same way as their sires, and the other half by the other method. Because of a drought in the summer of 1990, it was necessary to repeat part of the experiment, and in 1992 the 5 and 8 rams with the lowest and highest FEC, respectively, were selected from the offspring challenged on the pasture in 1992 and were mated with unselected ewes. Their progeny (about 80 animals) were challenged in 1994, half by natural infection, half by artificial infection. The mean FEC of the flock increased from the first to the third artificial infection. The natural infection was highly variable in different years, reflecting the difficulty of assessing resistance using this mode of challenge. Genetic parameters were estimated using animal models and REML solutions. The repeatabilities of the FEC following artificial and natural infection were 0.49 and 0.70 respectively within a period of one week, and 0.22 and 0.41 respectively for periods separated by intervals of 7 weeks; the heritabilities of the single egg count were 0.22 and 0.38 respectively. The genetic correlation was 0.87: the FEC recorded under natural or artificial infection appear to depend on the same genetic potential.