水分胁迫对牛心朴子光合生理特性影响的研究

采用PVC管种植模拟土壤干旱的方法,研究了牛心朴子(Cynanchum komarovii)在水分胁迫下光合速率(Pn)、气孔导度(Gs)、胞间CO2浓度(Ci)、叶绿素荧光的变化规律及不同生育期适应性表现。结果表明：土壤水分胁迫对牛心朴子叶片光合生理的影响与其胁迫时间及其胁迫程度都有关系,胁迫前中期Pn下降的原因主要是气孔限制,而到后期则以非气孔因素限制为主。中度土壤水分胁迫在短期内对牛心朴子叶片光合作用具有促进作用,而且有利于WUE的提高。而重度胁迫对牛心朴子Pn的影响较显著,而且非气孔因素的出现早于中度胁迫的处理。牛心朴子的光合生理对土壤水分胁迫具有一定的适应时期和适应范围。     

水分胁迫对牛心朴子、甘草叶片色素、可溶性糖、淀粉含量及碳氮比的影响

在宁夏灵洲区牛心朴子、甘草自然生境条件下,采用土壤控水措施,研究了土壤水分胁迫对两种优势旱生植物牛心朴子(Cynanchumkomarovii)和甘草(Glycyrrhizauralensis)叶片中的叶绿素;根、茎、叶中的可溶性糖、淀粉含量和C/N比值的影响。结果表明:1土壤水分长期胁迫,导致了这两种旱生植物叶绿素a(Chla)、叶绿素b(Chlb)、类胡萝卜素(Car)含量及Chla/Chlb、Car/Chl比值等的显著变化(P<0.01);2甘草Chla的含量和Chla/Chlb的比值始终大于牛心朴子,相反牛心朴子Chlb、Car的含量和Car/Chl比值却又始终大于甘草;3土壤水分长期胁迫引起了两种植物根、茎、叶可溶性糖含量的升高和淀粉含量的降低;4土壤水分长期胁迫引起了两种植物根、茎、叶C/N比值的降低,但牛心朴子C/N比值在处理的各个时期均大于甘草;5土壤水分长期胁迫引起牛心朴子和甘草Chla、Chlb、Car含量及Chla/Chlb、Car/Chl的比值、可溶性糖、淀粉和C/N比值的增加或减少的程度不同。     

毛乌素沙地油蒿和牛心朴子生理生态学研究

 作为毛乌素沙地植被主要建群种的油蒿(Artemisia ordosica)在一些地方出现了不同程度的退化,而萝摩科的一种多年生草本植物牛心朴子(Cynanchum komarovii)却出现了繁茂的生长。它们之间存在着一定的演替关系。本文通过对油蒿和牛心朴子的生理生态学特性和生殖生物学特性的研究及对其生境各要素的分析,说明了油蒿具有变水植物的特点,牛心朴子具有恒水植物的特点。在不同立地条件下,两种植物的光合、蒸腾及气孔行为都不相同。即便是在相同立地条件下,牛心朴子的水分利用效率亦显著高于油蒿;并且,牛心朴子只受轻微水分胁迫或不受水分胁迫,而油蒿则始终处于水分胁迫之下,说明牛心朴子在竞争中比油蒿占有相对的优势。在生态诸因子中,土壤水分状况是演替的外因,两种植物的水分生理生态特性和生殖生物学特征的差异是演替的内因。     

毛乌素沙地牛心朴子叶片的光合特征研究

对毛乌素沙地主要建群植物牛心朴子（Cynanchum komarovii Al.Iljinski)的光合特征进行了动态研究。结果表明,牛心朴子整个生育期间光合作用日变化呈双峰曲线,第一峰出现在上午11：00左右,第二峰出现在下午16：00左右,第一峰值明显高于第二峰值;蒸腾速率日保持恒定且维持较低的水平,但不同时期差别明显;不同叶位光合作用存在明显差别,以上部展开第3叶为最高;牛心朴子气孔对环境条件变化不敏感;叶绿素荧光猝灭日变化分析显示,牛心朴子叶绿体PSⅡ的原初光化学效率（Fv/Fm)以及通过PSⅡ非环式电子流的量子效率在上午10：00左右较高,中午下降,下午15：00左右又呈回升的现象。     

宁夏荒漠草原优势植物生长及生物量分配对放牧干扰的响应

于2011年植物生长旺季(8月)在围封禁牧(NG)、轻度放牧(LG)、中度放牧(MG)和重度放牧(HG)区分别随机选取荒漠草原优势植物甘草(Glycyrrhiza uralensis)和牛心朴子(Cynanchum komarovii)各15株为研究对象,对比分析其生长特征、各植物构件生物量及生物量资源分配差异对不同放牧强度的响应机制,为退化草原的恢复演替提供依据。结果表明:(1)甘草株高和地径、牛心朴子株高均随放牧强度的增加呈先升高后下降的趋势,而且均在轻度放牧条件下最高,重度放牧时则显著降低。(2)甘草和牛心朴子的总生物量、茎生物量和叶生物量随着放牧强度的增加呈先升高后降低的趋势,且不同放牧强度间差异显著;甘草和牛心朴子根系生物量随放牧强度的加强变化趋势不同。(3)甘草和牛心朴子生物量分配的总体格局为:根叶茎;随着放牧强度的增加,甘草根生物量比呈先升高后降低趋势,茎生物量比呈下降的趋势,叶生物量比呈上升趋势,而牛心朴子根生物量比呈先下降后升高的趋势,茎生物量和叶生物量呈先增加后下降的趋势。研究认为,不同放牧强度下两种植物形态可塑性和生物量分配格局的差异反映出植物生态适应策略的不同。     

放牧干扰对荒漠草原植物叶性状及其相互关系的影响

以宁夏退化荒漠草原优势植物牛心朴子、乳浆大戟、甘草和牛枝子为对象,分析放牧干扰对植物的比叶面积(specific leaf area, SLA)、叶干物质含量(leaf dry matter content, LDMC)、叶面积和叶干质量等叶性状的影响,探讨荒漠草原生态系统中不同物种对环境改变的响应和适应对策.结果表明: 随着放牧强度的降低,牛心朴子、乳浆大戟、甘草和牛枝子的SLA总体呈显著降低的趋势;SLA在不同放牧强度间差异显著,而LDMC则无显著差异.不同植物的叶性状相关性存在差异,牛心朴子和甘草的SLA和LDMC呈显著负相关,而乳浆大戟和牛枝子的SLA和LDMC呈正相关.牛心朴子、甘草、乳浆大戟和牛枝子的SLA对生存环境改变的反应比LDMC更敏感.植物的SLA可以作为荒漠草原植物资源利用对策的指示指标.     

水分胁迫对牛心朴子植株生长及渗透调节物质积累的影响

采用PVC管种植模拟土壤干旱的方法,研究了牛心朴子(Cymanchum komarovii)在水分胁迫下植株生长及渗透调节物质的积累情况。结果表明：牛心朴子植株地上部对土壤水分比较敏感,随水分胁迫程度的加强和胁迫时间的延长,植株生长显著变缓,直至停止生长,而根／冠比值则有所加大;可溶性糖是牛心朴子根系主要的渗透调节物质,随着土壤水分胁迫程度的加重,根系中的可溶性糖呈明显的增加趋势,叶中的可溶性糖则随胁迫的加重而呈下降趋势,说明在干旱胁迫下牛心朴子的同化产物大部分分配于根系之中;Pro在牛心朴子叶、茎、根的渗透调节中也起着重要作用,随土壤水分胁迫的加重,其在根、茎、叶中的积累明显增加;而无机离子在牛心朴子渗透调节过程中的作用很小。     

水分胁迫对牛心朴子叶片光合色素及叶绿素荧光的影响

研究了水分胁迫对牛心朴子叶片光合色素及叶绿素荧光动力学参数的影响。结果表明,在长期的水分胁迫中,牛心朴子叶片的叶绿素a(Chl a)、叶绿素b(Chl b)和类胡萝卜素(Car)含量没有下降或下降不明显。直到处理末期才显著下降;叶片叶绿素荧光动力学参数Fo、Fm、Fv、Fv／Fm变化不大,在处理末期各处理Fo降低,轻度、重度水分胁迫的Fm、Fv、Fv／Fm升高。说明K期水分胁迫后牛心朴子的光合功能受到影响,但牛心朴子仍表现出较强的适应干旱的能力。     

鄂尔多斯草地退化过程中个体分布格局与土壤元素异质性

应用复合个体-距离法分析了鄂尔多斯草地退化过程中多种群和优势种个体分布格局,应用统计方法分析了土壤有机碳和氮元素的异质化过程。结果表明：在鄂尔多斯草地退化过程中,多种群和优势种个体分布格局大多表现出不同尺度下的随机分布和聚集分布,但多种群的个体分布格局在本氏针茅(Stipa bungeana) 油蒿(Artemisia ordosica)群落中出现均匀分布;优势种油蒿和牛心朴子(Cymanchum komarovii)在油蒿 牛心朴子群落中均出现了均匀分布。土壤元素在单一优势种群落中存在不同程度的异质性,油蒿群落中异质化程度最强;在共优势种本氏针茅 油蒿群落中,出现了土壤元素相对均质化,油蒿 牛心朴子群落中,异质化程度相对减弱。由于对土壤水分和养分的竞争,使共优势种群落出现植物的均匀分布,土壤元素相对均质化。土壤元素先后异质化过程首先表现为土壤有机质的异质化过程,然后才表现为土壤氮的异质化过程。土壤元素先后异质化过程表明异质化过程首先表现为植被异质化,植被的异质化导致土壤某些元素的异质化。     

鄂尔多斯草地退化过程中植被地上生物量空间分布的异质性

应用地统计学方法分析研究了鄂尔多斯草地荒漠化过程中植被地上生物量空间分布的异质性。发现从本氏针茅(Stipa bungeana)、本氏针茅 油蒿(Artemisia ordosicn)、油蒿、油蒿 牛心朴子(cynanchum komarovii)、牛心朴子群落的5个退化系列群落中,植被地上生物量空间格局异质化程度及其相关范围变化非常明显。变异函数的基台值(C0 C)在5个退化群落中的变化表明,在本氏针茅群落中,植被地上生物量空间分布异质性较低(0．48),本氏针茅 油蒿群落增强(19．47),油蒿群落显著增强(1522),油蒿 牛心朴子群落减弱(171．6),牛心朴子群落显著减弱(4．164)。变异函数的相关范围(A0)表明,在本氏针茅群落空间相关范围较小(53．9cm),本氏针茅 油蒿群落增加(77．8cm),油蒿群落减小(51．7cm),油蒿 牛心朴子群落增加(62．9cm),牛心朴子群落增加(94．6cm)。空间变异比分析表明,由空间自相关因素引起的空间异质性占主要部分(74．2％～80．7％)。空间分布格局图(Kriging map)分析进一步显示,退化群落中植被地上生物量格局变化显著。从本氏针茅群落退化到油蒿群落的中度荒漠化过程中,植被地上生物量空间分布的异质性的增强。由油蒿群落退化到牛心朴子群落的严重荒漠化过程中,植被地上生物量空间分布的异质性减弱。     

On-station comparative analysis of reproductive and survival performance between Red Maasai,Dorper, and Merino sheep breeds

The reproductive performance of ewes and the survivability of lambs to weaning have a critical economic impact on sheep farming worldwide. Further, knowledge of major mortality causes allows an opportunity for improved flock management to evade financial losses. The maximum likelihood estimates for generalised linear mixed models and chi-square test methods were used to examine 971 mating records, 839 and 763 lambs born and weaned (singles or twins) from the Naivasha Sheep and Goats station in Kenya for the years 2011 to 2020 consisting of Dorper, Red Maasai (RedM), and Merino breeds. The RedM (P < 0.05) outperformed Dorper and Merino in weaning rate, whereas reproductive performance between the three breeds was not significantly different (P > 0.05) in litter size and multiple lambings per ewe lambing. On the one hand, Dorper significantly (P < 0.05) outperformed the other two breeds only in weaning weight per lamb born. In addition, among all the major causes of death, pneumonia appeared to be the one to which Dorper breeds were most susceptible (chi-square test, P < 0.05). According to the findings of this study, neither the Dorper nor the Merino sheep breeds were reproductively superior to the RedM in an extensive semi-arid production environment. In addition, Dorper's susceptibility to the leading causes of mortality, particularly pneumonia and sheep pox, were relatively high compared to other breeds and could be a precursor to massive economic losses for Dorper sheep producers. In contrast to the indigenous RedM breed, imported sheep breeds appeared to be more susceptible to major mortality-related under an extensive production system. Therefore, regardless of weaning weight, RedM breed production appears to be a more viable investment for small-scale farmers, particularly in semi-arid regions.     

Time dependency of molecular rate estimates and systematic overestimation of recent divergence times

Studies of molecular evolutionary rates have yielded a wide range of rate estimates for various genes and taxa. Recent studies based on population-level and pedigree data have produced remarkably high estimates of mutation rate, which strongly contrast with substitution rates inferred in phylogenetic (species-level) studies. Using Bayesian analysis with a relaxed-clock model, we estimated rates for three groups of mitochondrial data: avian protein-coding genes, primate protein-coding genes, and primate d-loop sequences. In all three cases, we found a measurable transition between the high, short-term (< 1-2 Myr) mutation rate and the low, long-term substitution rate. The relationship between the age of the calibration and the rate of change can be described by a vertically translated exponential decay curve, which may be used for correcting molecular date estimates. The phylogenetic substitution rates in mitochondria are approximately 0.5% per million years for avian protein-coding sequences and 1.5% per million years for primate protein-coding and d-loop sequences. Further analyses showed that purifying selection offers the most convincing explanation for the observed relationship between the estimated rate and the depth of the calibration. We rule out the possibility that it is a spurious result arising from sequence errors, and find it unlikely that the apparent decline in rates over time is caused by mutational saturation. Using a rate curve estimated from the d-loop data, several dates for last common ancestors were calculated: modern humans and Neandertals (354 ka; 222-705 ka), Neandertals (108 ka; 70-156 ka), and modern humans (76 ka; 47-110 ka). If the rate curve for a particular taxonomic group can be accurately estimated, it can be a useful tool for correcting divergence date estimates by taking the rate decay into account. Our results show that it is invalid to extrapolate molecular rates of change across different evolutionary timescales, which has important consequences for studies of populations, domestication, conservation genetics, and human evolution.     

Predation rate and numerical response of Aphidoletes aphidimyza feeding on different densities of Aphis craccivora

Predation rate and numerical response are basic to any investigation of predator–prey relationships and key components in the selection of predators for biological control. The density-dependent predation rate and numerical response of Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) to varying densities (5, 10, 20, 40, 60 and 80) of third-instar Aphis craccivora (Koch) (Hemiptera: Aphididae), were studied in laboratory conditions [23±1°C, 70 ± 5% relative humidity (RH), and a photoperiod of 16:8 h L:D. Predation rate data were analysed using the age-stage, two-sex consumption rate software. Net consumption rate (C₀) increased by increasing prey density. The lowest and highest net consumption rates were 20.75 and 190.8 prey nymphs at densities of 5 and 80 A. craccivora. The transformation rate from prey population to predator offspring (Q_p) increased by increasing prey density. The reproductive numerical response, in terms of eggs laid, increased curvilinearly with increasing prey density. Females laid 121.375 ± 4.301 eggs when exposed to the highest prey density (80) and 52.5 ± 1.544 eggs at lowest prey density (5). It can be concluded that different densities of A. craccivora influenced the reproductive performance of A. aphidimyza in terms of predation rate and numerical response.     

光周期和温度对虎斑蝶卵、幼虫及蛹存活的影响

通过在人工气候箱内设定不同光周期和温度梯度单虫饲养观察个体发育史,研究了光周期和温度对虎斑蝶Danaus genutia幼期存活的影响,研究结果可为该高观赏价值蝶种的规模化养殖提供依据。结果表明,在长光照(L∶D=15∶9)条件下,17.5、20.0、22.5、25.0、27.5、30.0℃时虎斑蝶卵的孵化率分别为63.72%、71.67%、65.75%、75.00%、67.12%、59.56%,幼虫的存活率分别为85.67%、85.96%、91.19%、89.20%、80.86%、68.78%,蛹的存活率分别为82.76%、100.00%、96.00%、97.06%、100.00%、100.00%;在短光照(L∶D=9∶15)条件下,17.5、20.0、25.0、30.0℃时虎斑蝶卵的孵化率分别为86.36%、67.06%、75.00%、77.50%,幼虫的存活率分别为85.05%、84.59%、85.74%、80.78%,蛹的存活率分别为93.30%、94.12%、100.00%、100.00%。结果表明,17.5℃和30.0℃均不利于虎斑蝶幼期的存活,20.0～27.5℃是其幼期生长发育适宜的温度范围。长光照利于幼虫的存活,短光照利于卵的孵化和蛹的羽化;在17.5～30.0℃内,较高的温度利于蛹的羽化,而较低的温度利于卵的孵化和幼虫的存活;温度对虎斑蝶卵的孵化、幼虫的存活及蛹的羽化影响大于光周期;在养殖生产上,建议将幼期养殖温度控制在20.0～27.5℃,幼虫期饲养在长光照下为宜,卵和蛹期置于短光照下为宜。     

光合单位的周转率与叶片光合速率的关系

利用闪光技术,测得若干高等植物叶片的光合单位为 1450～2050 Chl/CO_2。在含O_2 2％及CO_2浓度和光通量密度都饱和的条件下,测得叶片的连续光合速率为25～70μmol CO_2 m~(-2) s~(-1)。从上述数据及叶片叶绿素含量计算,得叶片光合单位的周转率已达80～160次/s。这样的周转速率与Emerson当初用改变闪光间暗间隔而测到的光合单位周转时间相似(即<10 ms/次,或>100次/s),从而证实了光合单位的周转与光合速率直接有关。这样的速率可称之为叶片光合的理论速率。     

沙埋对两种一年生藜科植物存活及光合生理的影响

为了解沙埋对沙生植物存活的影响及其光合生理响应特征,比较不同藜科沙生植物耐沙埋能力及其光合响应,在内蒙古科尔沁沙地研究了沙米(Agriophyllum squarrosum)和大果虫实(Corispermum marocarpum)在不同沙埋深度下第5、10、15天的净光合速率、气孔导度、蒸腾速率、水分利用效率的变化,并于植物生长末期对存活率进行了测定。结果表明:沙米较大果虫实具有较强的耐沙埋能力,其中沙米幼苗最大耐沙埋深度超过苗高10 cm,大果虫实在埋深等于其苗高时全部死亡;随沙埋深度增加,沙米和大果虫实的存活率均显著下降,但沙米的下降幅度明显小于大果虫实;沙埋后,2种植物的气孔关闭或开放程度减小,通过降低蒸腾速率和提高水分利用效率来适应沙埋胁迫;随着沙埋胁迫的加剧,2种植物的净光合速率下降,表明沙埋胁迫对植物的光合作用破坏较大;相比于大果虫实,沙米对于沙埋胁迫有着更好的光合适应,随着胁迫的时间增加,其净光合速率有所恢复。     

Nutrient requirements and stress response of Populus simonii and Paulownia tomentosa

The aim of this investigation was to estimate the optimum nutrient requirements and responses to low relative nutrient addition rates of seedlings of two important broadleaf tree species in China, Populus simonii Carr. and Paulownia tomentosa (Thunb.) Steud. In preliminary experiments the optimum nutrient proportions were estimated under high concentration conditions. The nutrients consumed were replaced by means of daily additions determined by pH and conductivity titrations without changing the nutrient solutions. A relatively high K level was needed in relation to nitrogen; higher than in birch or grey alder seedlings. To obtain a high relative growth rate, suitable proportions by weight were 100 N:70 K:14 P:7 Ca:7 Mg for the Populus seedlings and 100 N:75 K:20 P:8 Ca:9 Mg for the Paulownia seedlings.
In studies of nutrient stress responses the relative nutrient addition rate was used as the treatment variable under low conductivity conditions. The responses and relationships were similar to those described for birch, grey alder and Salix . The relative addition rate, and there was also a strong linear regression between relative growth rate and nitrogen status. Relative growth rates were high and the maximum weight increase was about 19% day⁻¹ in Populus and over 25% day⁻¹ in Paulownia . The nitrogen productivity of Paulownia was very high, 0.26 g dry weight (g N)⁻¹ h⁻¹, and for Populus it was 0.16 g dry weight (g N)⁻¹ h⁻¹.     

新疆野生郁金香与栽培品种的杂交性状

为研制具有自主知识产权的郁金香（Tulipa gesneriana）新种质,本实验选择6种栽培郁金香品种为母本,5种野生郁金香为父本进行杂交试验。结果显示,平均受精率为（84．8±3．5）％,母本受精率最高的是克斯奈丽斯,平均为（94．0±2．3）％,受精率最低的是蒙特卡罗,平均为（71．0±3．8）％。果实发育1个月最高坐果率为100．0％,平均为（75．2±4．1）％,2个月最高坐果率为（90．0±3．6）％,平均为（47．0±3．4）％;杂交种子平均结实率为24．3％。研究结果表明,母本与杂交组合对受精率、坐果率和结实率有显著影响,父本则没有显著影响：杂交组合小黑人×伊犁郁金香、小黑人×柔毛郁金香及小黑人X天山郁金香亲合性较好,其杂交种子结实率分别为78．2％、68．4％和57．5％。     

Growth and social interactions of wild and sea-ranched brown trout and their hybrids

A laboratory study of the social behaviour and growth performance of juvenile brown trout Salmo trutta of wild and sea-ranched origin and their crosses, indicated that the social behaviour of wild and sea-ranched fish differed. Male and female parents seemed to have a different impact on the juveniles. The category having wild mother and sea-ranched father were less aggressive, less active in general, but active in feeding, and therefore had higher growth rates. This pattern arose despite that the feeding rate and the motivation to first get a food item when food was provided did not differ between the groups of fish. Wild fish tended to be most aggressive. If sea-ranched and wild fish have different intrinsic (genetically based) 'life styles', the crosses between wild and sea-ranched fish indicate that there is likelihood for an introgression of genes adapted to hatchery environment into the genetics of wild conspecifics. This is particularly serious when hatchery-reared fish invades wild populations over many years.     

Altitudinal and seasonal effects on aerobic metabolism of deer mice

Summary I compared the maximal aerobic metabolic rates ( ), field metabolic rates (FMR), aerobic reserves ( -FMR), and basal metabolic rates (BMR) of wild and recently captured deer mice from low (440 m) and high (3800 m) altitudes. To separate the effects of the thermal environment from other altitudinal effects, I examined mice from different altitudes, but similar thermal environments (i.e., summer mice from high altitude and winter mice from low altitude). When the thermal environment was similar, , FMR, and aerobic reserve of low and high altitude mice did not differ, but BMR was significantly higher at high altitude. Thus, in the absence of thermal differences, altitude had only minor effects on the aerobic metabolism of wild or recently captured deer mice.At low altitude, there was significant seasonal variation in , FMR, and aerobic reserve, but not BMR. BMR was correlated with , but not with FMR. The significant positive correlation of BMR with indicates a cost of high , because higher BMR increases food requirements and energy use during periods of thermoneutral conditions.Abbreviations BMR basal metabolic rate - FMR field metabolic rate - partial pressure of oxygen - T _a ambient temperature - T _b body temperature - T _e operative temperature - maximal aerobic metabolic rate