4种针叶幼树的光合生理特性与大气湿度关系的研究

应用２２５ＭＫ３ＩＲＧＡ在室内控制的环境条件下测定研究了侧柏,樟子松,油松和杆等４种针叶幼树的净光合速率,暗呼吸强度,光补偿点与大气湿度的关系,研究结果证明,各种幼树的净光合速率均随大气湿度的降低而减弱,二者之间的关系可用ｙ＝ａ＋ｂｌｎｘ方程表达。其变化速率（ｂ）在树种间有明显差异,它可以反映出不同树种对大气干旱忍耐力即抗旱性的差异“ｂ＂值小的树种表明其抗旱性强。依此排列出的上述４种幼树的抗旱性强     

干旱对苗木萌芽期水分状况、ABA含量及萌芽特性的影响

 采用4种常见造林树种沙棘（Hippophae rhamnoides L.）、油松（Pinus tabulaeformis）、刺槐（Robinia pseudoacacia L.）和杨树(Populus simonii),研究水分胁迫下苗木移栽后萌芽过程中体内水分状况与ABA累积关系,探讨干旱使苗木致死的生理学机制。结果表明,土壤干旱导致苗木组织含水量、芽体生长速率、萌芽率及成活率显著下降;各树种在萌芽过程中其芽体和韧皮部中的脱落酸（ABA）含量随土壤干旱程度的加重而升高,并与苗体组织含水量、萌芽率及成活率呈显著负相关;抗旱性强的沙棘和油松芽体和韧皮组织中ABA绝对含量比杨树和刺槐高5～10倍左右;经统计分析发现,4种苗木的萌芽速度、萌芽率以及移栽成活率均与韧皮部的组织含水量显著相关。     

刺槐,国槐根际土壤生化成分及其对伴生杨树营养的影响

分析了杨树、刺槐和国槐的根面与根际土壤中的游离氨基酸及植物生长素ＩＡＡ,测定了不同处理小区中杨树叶片的营养状况（Ｎ、Ｐ、Ｋ和叶绿素含量）以及净光合速率和气孔阻力．结果表明,刺槐、国愧和杨树根面氨基酸组成和数量有很大差别;３个树种根际土壤中氨基酸含量显著低于根面．３个树种根面和根际土壤中ＩＡＡ含量为刺槐＞国槐＞杨树．混交豆科树种后,杨树叶片营养状况有所改善,净光合速率明显提高,气孔阻力有所降低．     

水稻抗旱性与叶片抗脱水能力、脯氨酸及糖的关系

在人控土壤干旱（含水量１７．５％左右）条件下,研究了水稻抽穗灌浆期抗旱性与抗脱水能力、抗衰老能力、叶片中游离脯氨酸及可溶性糖的关系,结果表明：抗旱性强的品种,抗脱水与抗衰老能力也强,且叶片中游离脯氨酸与干旱前期（１０天内）可溶性糖含量增加,反之亦然．     

高温和低湿对干热河谷7个植被恢复树种光合参数的影响

采用人工气候室控制环境条件,研究了高温（30℃和40℃）对印楝（Azadirachta indica A．Juss．）、木豆[Cajanus cajan（Linn．）Huth]、赤桉（Eucalyptus camaldulensis Dehn．）、蓝桉（E．globulus Labillardiere）、柠檬桉（E．citriodoraHook．）、大叶相思（Acacia auriculiformis A．Cunn．）和麻风树（Jatropha curcas Linn．）7个干热河谷植被恢复树种幼苗叶片光合参数的影响,以及低湿条件对麻风树幼苗叶片光合参数的影响,并对高温及低湿条件下各树种叶片光合参数与叶片含水量的关系进行了探讨。结果表明：在高温条件下,供试树种叶片的净光合速率（Pn）和Fv／Fm值均随叶片含水量的提高逐渐增加,但在40℃条件下各树种的Pn以及刚nn值均明显降低,表明叶片含水量高有利于各树种叶片Pn和n／Fm的提高,而40℃高温则对其Pn和Fv／Frn有明显抑制作用。在非干旱条件下,高温对各树种幼苗的Pn、气孔导度（Gs）、胞间c0：浓度（ci）和蒸腾速率（Tr）均有不同程度影响。在40℃条件下,供试树种中印楝和赤桉幼苗的Pn降幅最小;大叶相思、蓝桉和木豆幼苗的Gs明显增加;各树种幼苗的ci均明显提高;除印楝外,其他6个树种幼苗的Tr明显加剧且叶片水分利用效率降低。在叶片含水量较高的状况下,供试7个树种中印楝和赤桉幼苗的FV／Fm值受高温的影响较小。在空气相对湿度20％的条件下,麻风树幼苗的Pn、Cs、ci及Tr均明显降低,且均随叶片含水量的提高而增加,表明叶片含水量下降是麻风树幼苗光合作用减弱的重要影响因素。研究结果表明：干热河谷地区的高温引起的植物光合限制以非气孔因素为主导;在供试的7个树种中,印楝和赤桉对干热河谷高温干旱生境的适应或忍耐能力较强。     

安西荒漠植物群落和优势种的分布与环境的关系

应用排序（ＤＣＡ）和回归分析方法对安西砾石戈壁荒漠植物群落及优势种的分布与环境的关系进行了研究。结果表明,该区群落的盖度（Ｃ）和密度（Ｄ）均与年降水量（Ｒ）有密切关系,而群落的种类丰富度（Ｎ）则与土壤含盐量（Ｓ）相关,其回归关系式为：Ｃ＝０．０５１９６８１６３ｅ０．０４０７８６８２１Ｒ（Ｒ＝０．９５,Ｐ＜０．０１）,Ｄ＝０．２７１４７９１３ｅ０．０５２７４１８２９Ｒ（Ｒ＝０．９６,Ｐ＜０．０１）,Ｎ＝１３．７７４８－６．４７７３０３ｌｇ１０００Ｓ（Ｒ＝０．８３,Ｐ＜０．０１）。即：年降水量是决定戈壁荒漠植物群落盖度和密度的主要因素,土壤含盐量则与群落种类丰富度的关系尤为突出。优势种的抗旱性顺序是：红砂（Ｒｅａｕｍｕｒｉａｓｏｎｇｏｒｉｃａ（（Ｐａｌ．）Ｍａｘｉｍ．）＞泡泡刺（ＮｉｔｒａｒｉａｓｐｈａｅｒｏｃａｒｐａＭａｘｉｍ．）＞黑柴（ＳｙｍｐｅｇｍａｒｅｇｅｌｉＢｇｅ．）＞珍珠（ＳａｌｓｏｌａｐａｓｅｒｉｎａＢｇｅ．）＞膜果麻黄（ＥｐｈｅｄｒａｐｒｚｅｗａｌｓｋｉＳｔａｐｆ．）,而耐盐性顺序是：珍珠＞红砂＞黑柴＞泡泡刺＞膜果麻黄     

滨海盐碱地刺槐(Robinia pseudoacacia)混交林土壤水盐动态

以固氮树种刺槐与绒毛白蜡、榆树、臭椿三树种的混交林及其纯林为研究对象,研究了刺槐与不同树种混交对土壤水分、盐分年动态变化的影响。研究结果表明：（1）刺槐与3个树种混交,刺槐臭椿混交林生长最好,均高于各自纯林。（2）混交林一定程度改善了土壤含水量及层次分布,土壤含水量整体趋势均表现出0～60 cm表层土中含水量高于各自纯林,而深层土壤含水量低的特点,只有8月份纯林和混交林的土壤含水量没有显著差别。不同树种在具体层次上略有差异;（3）混交林降低了土壤含盐量,改变了土壤盐分层次分布和年变化规律。不同月份间土壤含盐量随土壤深度、混交树种的变化而变化。深层土壤含盐量高,表层土壤含盐量低,混交林含盐量低于纯林且存在树种差异。混交林与纯林含盐量均雨季低,旱季高;但在某一具体月份各层次含盐量差别不大;不同土层含水量、含盐量与天然降水之间有明显的相关性,天然降水是混交林及纯林土壤水分的主要来源。     

土壤干旱条件下保水剂对多年生黑麦草光合特性的影响

以多年生黑麦草（Lolium perenne Linn．）为研究对象,对土壤干旱条件下（土壤含水量12．6％、10．5％、8．4％和6．3％）使用保水剂后叶片光合特性的动态变化进行了分析。结果显示：随土壤含水量的降低和胁迫时间（12d）的延长,多年生黑麦草叶片的净光合速率（Pn）、气孔导度（Gs）、蒸腾速率（Tr）和光能利用效率（LUE）呈逐渐下降的趋势;随土壤含水量的降低,胞间CO2浓度（Ci）逐渐升高、瞬时水分利用效率（WUE）逐渐降低,但随胁迫时间的延长Ci和WUE则呈现不同的变化趋势;总体上,在土壤含水量不同的条件下及不同的胁迫时间各指标均有显著差异（P〈0．05）。与未添加保水剂的各处理组相比,添加质量分数2％保水剂后多年生黑麦草叶片的Pn、Gs、WUE和LUE值均增大,而Ci和Tr值则降低,差异达显著水平（P〈0．05）。研究结果表明：合理使用保水剂能提高多年生黑麦草叶片的光合能力以及土壤的保水能力,增强多年生黑麦草对干旱环境的适应性。     

散孔材和环孔材树种叶水分传输能力及其与抗旱性的关系

选取树龄相同的3种散孔材(杨树、梧桐和樱花)和3种环孔材(刺槐、合欢和白蜡)树种,用3种不同方法(解剖法、加压法和水容法)研究了其叶水力导度的差异及与抗旱性(PV曲线参数)的关系.结果显示:解剖法估算的最大叶水力导度高于加压法和水容法,加压法和水容法在6个树种中的5个上测定值完全一致,3种散孔材与环孔材树种的叶最大水力导度无显著差异.3种散孔材树种的饱和渗透势和膨压损失点渗透势与3种环孔材相比差异不大,但膨压损失点的相对含水量则低于环孔材树种,质外体含水量高于环孔材树种,导致其综合抗旱性指数也高于3种环孔材树种.研究表明,散孔材和环孔材树种的叶最大水力导度与其抗旱性之间并无显著相关关系.     

植物的水容特征与其耐旱性的关系

在自然风晾条件下,研究了不同植物器官的相对含水量、水势及比水容之间的相互关系。结果表明：植物叶片阻止体内蒸腾失水的能力大小顺序依次为：花生（Arrachishypogaea）＞甘薯（Ipomoeabatatas）＞大豆（Glycinemax）＞玉米（Zeamays）,各植物茎的保水能力相差不大;甘薯的茎、叶在风晾4h后仍未永久凋萎,其他植物的茎、叶在风晾1～3h就出现永久凋萎;花生、甘薯、大豆和玉米叶片风晚3～4h后,其水势的下降幅度分别为：1．00,1．30,1．80和2．70mPa,花生、甘薯、大豆茎的水势下降幅度分别为：1．95,1.40和1．30mPa;植物茎、叶的水势与其相对含水量具有较好的对数关系;植株茎、叶的比水客值范围在0．0258～0．6835mPa-1之间,叶片的比水容大于茎的比水容。因此,植物的水容特征表明不同植物茎、叶的保水、释水能力不同,因而其耐旱、抗旱性不同。玉米和大豆的耐旱性小于花生、甘薯的耐旱性。     

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.     

The molecular clock ticks regularly in muroid rodents and hamsters

Summary Extensive DNA sequence data are used to compare the rates of nucleotide substitution in the mouse, rat, and hamster lineages. A relative rate test using hamster sequences as references shows that the rates of synonymous and nonsynonymous substitution in the mouse and rat lineages are nearly equal and a test using human sequences as references shows that the rates in the mouse, rat, and hamster lineages are also nearly equal. Under the assumptions that the guinea pig lineage and the myomorph (mouse, rat, and hamster) lineage diverged 70–100 million years (Myr) ago and that the rate of nucleotide substitution has been constant in all these lineages since their divergence, the date of the mouse-rat split is estimated to be between 20 and 29 Myr ago, which is considerably older than the date ( 12 Myr) suggested by available rodent fossils and considerably younger than the date ( 35 Myr) suggested by Wilson and colleagues. The murid-hamster split is estimated to be 1.6 times older than the mouse-rat split.     

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。     

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.     

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     

Growth, protein-turnover rates and nucleic-acid concentrations in the white muscle of rainbow trout during development

We have studied the growth rate, nucleic-acid concentration, protein-accumulation rate (K_G), and several other parameters relating to protein turnover, such as the protein-synthesis (K_S), and protein-degradation rates (K_D), protein-synthesis capacity (C_S), protein-synthesis efficiency (K_RNA), protein-synthesis rate per DNA unit (K_DNA) and protein-retention efficiency (PRE), in the white muscle of rainbow trout during development. Both growth rate and relative food intake decreased significantly with age and weight, as did the food-efficiency ratio (FER) and protein-efficiency ratio (PER). Although absolute RNA and DNA contents increased with age, their relative concentrations decreased. The RNA/DNA ratio increased sharply from 14 to 28 weeks but afterwards decreased towards initial values. Hypertrophy increased rapidly to the 28-week stage but thenceforth increased much more slowly. Hyperplasia, on the other hand, continued to increase linearly, resulting in a significant four- to fivefold predominance in this type of growth at the end of the 96-week experimental period. K_G decreased significantly with age, as did K_S, and C_S, whereas at the 14-week stage, K_D was significantly lower than at other ages. K_RNA increased until 28 weeks. K_DNA increased significantly in juvenile fish compared to both fingerlings and adults, where it showed similar lower values. PRE remained high at all ages.     

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。