Habitat and Population Effects on the Germination and Early Survival of the Invasive Weed, Lythrum salicaria L. (purple loosestrife)

In this study, we examined how environmental factors and differences among populations of Lythrum salicaria L. (Lythraceae; purple loosestrife) influenced the establishment of this species into both its preferred wetland habitat and secondary upland habitat. Seeds and seedlings from five parents from each of the three populations were planted in each wetland and upland of two sites in both disturbed and undisturbed plots. More seeds germinated in wetland than in upland sites (31% as compared to 11%) and, although a disturbance resulted in greater germination (23% as compared to 17% in undisturbed plots), there was no interaction with habitats. The results of a simultaneous greenhouse germination study in which seeds were planted under saturated and drained conditions suggest that the higher germination observed in wetland sites was due to the higher moisture present at such sites (79% vs. 45% in saturated and drained conditions, respectively). Disturbance enhanced both germination and growth of L. salicaria and this was especially so for seedlings. Dry weights of seedlings from disturbed plots were five times greater than those from undisturbed plots ( =9.2 vs. 1.8g in disturbed and undisturbed conditions, respectively). In addition to environmental factors, population differences are likely to play an important role in the spread of L. salicaria as we found differences between the populations in both life stages examined. One of the populations germinated equally well in both moisture treatments. In our seedling establishment experiment, one of the populations produced both the smallest plants and the most and earliest flowers, suggesting superior reproduction.     

The Effects of Exotic Grasses on Litter Decomposition in a Hawaiian Woodland: The Importance of Indirect Effects

Exotic grasses and grass-fueled fires have altered plant species composition in the seasonal submontane woodlands of Hawaii Volcanoes National Park. These changes have altered both structural and functional aspects of the plant community, which could, in turn, have consequences for litter decomposition and nitrogen (N) dynamics. In grass-invaded unburned woodland, grass removal plots within the woodland, and woodland converted to grassland by fire, we compared whole-system fluxes and the contributions of individual species to annual aboveground fine litterfall and litterfall N, and litter mass and net N loss. We assessed the direct contribution of grass biomass to decomposition and N dynamics, and we determined how grasses affected decomposition processes indirectly via effects on native species and alteration of the litter layer microenvironment. Grasses contributed 35% of the total annual aboveground fine litterfall in the invaded woodland. However, total litterfall mass and N were not different between the invaded woodland and the grass removal treatment because of compensation by the native tree Metrosideros polymorpha, which increased litter production by 37% ± 5% when grasses were removed. The 0.3 g N m^–2/y^–1 contained in this production increase was equal to the N contained in grass litter. Litter production and litterfall N was lowest in the grassland due to the loss of native litter inputs. Decomposition of litterfall on an area basis was highest in the grass-invaded woodland. We attributed this effect to increased inherent decomposability of native litter in the presence of grasses because (a) the microenvironment of the three vegetation treatments had little effect on decomposition of common litter types and (b) M. polymorpha litter produced in the invaded woodland decomposed faster than that produced in the grass removal plots due to higher lignin concentrations in the latter than in the former. Area-weighted decomposition was lowest in the grassland due to the absence of native litter inputs. Across all treatments, most litter types immobilized N throughout the incubation, and litter net N loss on an area basis was not different among treatments. Our results support the idea that the effects of a plant species or growth form on decomposition cannot be determined in isolation from the rest of the community or from the direct effects of litter quality and quantity alone. In this dry woodland, exotic grasses significantly altered decomposition processes through indirect effects on the quantity and quality of litter produced by native species.     

侧柏不同器官水提取物对油松种子萌发和幼苗生长的他感效应

研究了侧柏（Platycladus orientalis）根、枝、叶、果实不同浓度水提取物及枝叶挥发油对油松种子萌发和幼苗生长的他感效应。结果表明：侧柏各器官及挥发油都含有化感物质,均对油松种子萌发及幼苗生长表现出“高抑低促”效应,而且低浓度时的促进作用明显强于高浓度时的抑制作用。与对照相比,在浓度为2 mg·mL^-1时,侧柏根水提取物对油松幼苗根长和鲜重的促进能力最强,其根长和鲜重分别比对照提高了79.78%和376.60%;侧柏叶水提取物对油松幼苗苗高促进能力最强,比对照提高了102.41%;侧柏枝水提取物对油松种子发芽的促进能力最强,发芽率比对照提高了65.63%。而在浓度为30 mg·mL^-1时,除了侧柏根和枝水提取物对油松种子萌发（87.50%）和鲜重（85.11%）表现出明显的抑制作用外,其它提取物对油松幼苗根长和苗高生长的抑制作用均不明显。侧柏枝叶挥发油对油松种子萌发,幼苗生长均表现为促进作用,特别对油松种子萌发具有显著的促进作用,其促进率达70.37%。说明侧柏和油松混交,可能有利于油松树木生长及生产力的提高。     

光合微生态菌剂对种子萌芽及幼苗生长的影响

种子萌芽及幼苗生长试验结果表明,光合微生态菌剂可提高种子萌芽率,促进幼苗根系发育和生长,对苗期病害具有较好的防治效果,稀释50倍的菌剂可有效控制蔬菜苗期立枯病和恶苗病的发病率,防治效果达到70%以上。     

The Effects of Invasive Ants on Prospective Ant Mutualists

Ants are recognized for their abilities both to engage in mutualistic interactions with diverse taxa, and to invade and dominate habitats outside their native geographic range. Here, we review the effects of invasive ants on three guilds of mutualists: ant-dispersed plants, ant-tended arthropods, and ant-tended plants. We contrast how those three guilds are affected by invasions, how invasive ants differ from native ants in their interactions with those guilds, and how the seven most invasive ant species differ amongst themselves in those interactions. Ant-dispersed plants typically suffer from interactions with invasive ants, a result we attribute to the small size of those ants relative to native seed-dispersing ants. Effects on the ant-tended arthropods and plants were more frequently positive or non-significant, although it is unclear how often these interactions are reciprocally beneficial. For example, invasive ants frequently attack the natural enemies of these prospective mutualists even in the absence of rewards, and may attack those prospective mutualists. Many studies address whether invasive ants provide some benefit to the partner, but few have asked how invasives rank within a hierarchy of prospective mutualists that includes other ant species. Because ant invasions typically result in the extirpation of native ants, this distinction is highly relevant to predicting and managing the effects of such invasions. Interspecific comparisons suggest that invasive ants are poorer partners of ant-dispersed plants than are most other ants, equally effective partners of ant-tended arthropods, and perhaps better partners of ant-tended plants. Last, we note that the invasive ant taxa differ amongst themselves in how they affect these three mutualist guilds, and in how frequently their interactions with prospective mutualists have been studied. The red imported fire ant, Solenopsis invicta, appears particularly likely to disrupt all three mutualistic interactions, relative to the other six invasive species included in this review.     

影响翅果油树种子萌发及幼苗生长的几种因素的比较研究

通过对翅果油树种子进行了适温处理、变温处理、激光处理、超声波处理、H₂O₂处理、PEG处理,对发芽实验进行研究,然后测定发芽率、发芽势、萌发指数、根长、芽长、株高、茎粗以及叶绿素含量。萌发实验的结果表明, 变温预处理和PEG预处理能最有效地解除抑制物对种子萌发的影响,对种子进行变温处理和PEG处理是解除种子休眠和提高萌发率的有效途径。本实验为促进濒危植物翅果油树的种群繁衍以及对翅果油树的可持续利用提供一定的科学依据。     

FecB基因在9个绵羊品种中的多态性及其与产羔数和羔羊生长发育的相关性

以绵羊BMPR-IB基因为候选基因,应用PCR-RFLP方法通过分析湖羊、夏洛来、陶赛特、萨福克、罗米丽、中国美利奴羊、中国美利奴肉用多胎品系以及陶赛特×中国美利奴羊和萨福克×中国美利奴羊杂交后代共615只个体的FecB基因多态性,以及BMPR-IB基因多态性对产羔数、体尺和体重的影响.结果表明,BMPR-IB基因在不同品种(系)绵羊中共有3种基因型(BB、B+和++),但基因型频率分布在各品种(系)间差异极显著(P<0.01).在湖羊中仅有BB基因型;在中国美利奴肉用多胎品系中BB、B+和++基因型频率分别为51%、30%和19%;而其他品种(系)羊中则仅有++基因型.对中国美利奴羊肉用多胎品系研究,发现BB和B+基因型群体平均产羔数分别为2.8和2.3,显著高于++基因型群体(1.2,P<0.01).在90日龄时,BB和B+基因型群体的体重分别为18.6±3.70 kg和18.0±3.31 kg,显著高于++基因型群体(15.6±2.22kg,P<0.05);此外,90日龄时,BB和B+基因型群体比++基因型群体胸围、胸宽较大(P<0.05);但这些差异在120日龄时消失.另外,我们还发现不同地区群体的第一胎产羔数存在明显差别.这些结果表明,BMPR-IB基因为影响绵羊产羔数的主效基因,并首次证明该基因对后代羔羊出生后生长发育具有加性效应.     

磁化水对小麦种子萌发、幼苗生长和生理特性的生物学效应

为研究磁化水对作物的生物学效应,本文详细分析了磁化水处理对小麦种子萌发、幼苗生长和生理特性的影响。研究结果显示：磁化水处理小麦的种子发芽参数与对照相比无显著差异;磁化水处理对小麦的株高、根长、地上部和根部鲜重等生长参数也无显著影响;同样,磁化水处理在叶片色素含量、可溶性糖、可溶性蛋白质含量、含水量、细胞汁液渗透势等重要生理特征参数方面也未显示出显著差异。此外,磁化水并未显著影响小麦叶片的光合作用。综上所述,磁化水处理对小麦种子萌发和幼苗生长无明显的生物学效应。     

盐穗木miRNA417的克隆及对种子萌发和幼苗成活率的影响

MicroRNA (miRNA)是植物重要的基因表达调控因子,miR417的表达受盐胁迫的调节,高盐胁迫时,拟南芥miR417的表达能够抑制种子的萌发和幼苗成活。本研究通过分析miRbase数据库中已知植物miRNA417的序列,利用PCR技术成功克隆获得了盐生植物盐穗木的miR417（HcmiR417）的前体序列,将其构建至植物表达载体pCAMBIA1301上,通过花絮浸染法对拟南芥进行遗传转化。结果表明,在150 mmol·L^-1 NaCl的胁迫下,分别过表达HcmiR417和过表达拟南芥miRNA417（AtmiR417）的转基因拟南芥种子的萌发率和幼苗存活率均较野生型低,但两种转基因拟南芥株系之间没有差异。初步验证了盐生植物HcmiR417在种子萌发和幼苗成活率方面也具有负调控作用,盐生植物盐穗木和拟南芥植物miRNA在功能没有显示出差异。     

外源一氧化氮供体对几种植物种子的萌发和幼苗生长的影响

以0、0.1、0.3、0.5、0.7、0.9mmol·L-1共6种浓度的外源一氧化氮(NO)供体硝普钠(SNP)处理豌豆、黄瓜、玉米和刺槐种子及其砂培幼苗后的结果表明:0.1～0.3mmol·L-1SNP对种子发芽势、发芽率及幼苗的根长、叶绿素含量和生物量有明显的促进作用;随着SNP浓度的增加,种子萌发和幼苗生长明显受抑制,不同植物受抑制程度的差异明显.     

Contrasting Effects of Substrate and Fertilizer Nitrogen on the Early Stages of Litter Decomposition

Commonly observed positive correlations between litter nitrogen (N) concentrations and decomposition rates suggest that N frequently limits decomposition in its early stages. However, numerous studies have found little, if any, effect of N fertilization on decomposition. I directly compared internal substrate N and externally supplied inorganic N effects on decomposition in sites varying in soil N availability. I decomposed eight substrates (with initial %N from 0–2.5) in control and N-fertilized plots at eight grassland and forest sites in central Minnesota. N fertilization increased decomposition at only two of eight sites, even though decomposition was positively related to litter N at all sites and to soil N availability across sites. The effect of externally supplied N on decomposition was independent of litter N concentration, but was greater at sites with low N availability. The inconsistent effects of substrate and externally supplied N may have arisen because decomposers use organic N preferentially as an N source; because inorganic N availability across sites or with fertilization induced changes in microbial community attributes (for example, lower C:N or greater efficiency) that reduced the response of decomposition to increased inorganic N supply; or because the positive correlation between litter N or site N availability with decomposition was spurious, caused by tight correlations between litter or site N and some other factor that truly limited decomposition. These inconsistent effects of substrate N and external N supply on decomposition suggest that the oft-observed relationship between litter N and decomposition may not indicate N limitation of decomposition.     

西双版纳外来植物的物种多样性、用途和生态危害的初步研究

在西双版纳282科近5000种高等植物中,有外来植物153科1127种,其中药用、花卉和可食用种类分别占39．0％、33．9％和20．3％。外来植物集中分布在植物园和当地居民的庭院中,并沿道路向外扩散。外来植物丰富了西双版纳的物种多样性,促进了地方经济发展,但少数杂草类入侵物种的生态危害很明显。     

光温互作和培养基中的附加成分对香蕉试管苗生长的影响

光照强度和温度对香蕉试管苗的长根数、总根数、苗高和青叶数影响极显著。光照强度为10μmol·m-2·s-1时,总根数和长根数最多;光照强度为25μmol·m-2·s-1时,青叶数最多,苗高随其升高而降低。温度为28℃时,总根数和长根数最多;26℃时,苗最高;32℃时,青叶数最多。培养基中添加85mg·L-1磷酸二氢钾后,试管苗的鲜重、干重、苗高、茎径、叶长、叶宽和青叶数增加;添加5mg·L-1腺嘌呤后,鲜重、茎径和叶长增加;添加4.8mg·L-1多效唑的发根数、最长根长、叶鲜重和茎径显著增加,苗高降低。     

化学药剂对水稻种子萌发和幼苗生长的影响

以早丰 11号水稻种子为材料 ,用KNO3、KH2 PO4 、Na2 HPO4 等不同药液浸种 .结果显示 ,早丰 11号种子在适当浓度的KNO3、KH2 PO4 、Na2 HPO4 浸种后 ,发芽势、发芽率比对照有所提高 ,幼苗生长加快 ,表现在根长、发根数、苗高、鲜重比对照生长好 ,并且对水稻秧苗表现有抵抗低温的作用 .     

Effects of drying regime on microbial colonization and shredder preference in seasonal woodland wetlands

1. Energy budgets of wetlands in temperate deciduous forests are dominated by terrestrially derived leaf litter that decays under different drying conditions depending on autumn precipitation. We compared decay rates and microbial colonization of maple leaves under different inundation schedules in a field experiment, and then conducted a laboratory study on shredder preference. In the field, litter bags either remained submerged (permanent), were moved to a dried part of the basin once and then returned (semi-permanent), or were alternated between wet and dry conditions for 8 weeks (temporary).
2. There was no difference in decay rates among treatments, but leaves incubated under permanent and semi-permanent conditions had higher fungal and bacterial biomass, and lower C : N ratios than those incubated under alternating drying and wetting conditions.
3. To determine the effects of these differences in litter nutritional quality on shredder preference, we conducted a laboratory preference test with larvae of leaf-shredding caddisflies that inhabit the wetland. Caddisflies spent twice as much time foraging on permanent and semi-permanent litter than on litter incubated under temporary conditions.
4. There is considerable variation among previous studies in how basin drying affects litter breakdown in wetlands, and no previous information on shredder preference. We found that frequent drying in a shallow wetland reduces the nutritional quality of leaf litter (lower microbial biomass and nitrogen content), and therefore preference by invertebrate shredders. These results suggest that inter-annual shifts in drying regime should alter detritus processing rates, and hence the mobilization of the energy and nutrients in leaf litter to the wetland food web.     

Effects of Amendments on Growth and Uptake of Cd and Zn by Wetland Plants,Typha angustifolia and Colocasia esculenta from Contaminated Sediments

A pot study was conducted to compare the effects of amendments (CaHPO₄ and cow manure) on growth and uptake of Cd and Zn from contaminated sediments by two wetland plant species, Typha angustifolia and Colocasia esculenta. Contaminated sediments (Cd 33.2 mg kg^–1 and Zn 363 mg kg^–1) were collected from Mae Tao basin, Mae Sot district, Tak province, Thailand. The experiment consisted of 4 treatments: control (uncontaminated sediment), Cd/Zn, Cd/Zn + 5% CaHPO₄, and Cd/Zn + 10% cow manure. Plants were grown for 3 months in the greenhouse. The addition of CaHPO₄ resulted in the highest relative growth rate (RGR) and highest Cd accumulation in both T. angustifolia and C. esculenta while the lowest RGR was found in C. esculenta grown in the cow manure treatment. Both plant species had higher concentrations of metals (Cd, Zn) in their belowground parts. None of the amendments affected Zn accumulation. C. esculenta exhibited the highest uptake of both Cd and Zn. The results clearly demonstrated the phytoremediation potential of C. esculenta and the enhancement of this potential by CaHPO₄ amendment.     

Polymorphism of FecB Gene in Nine Sheep Breeds or Strains and Its Effects on Litter Size, Lamb Growth and Development

Nine sheep breeds or strains, including 615 individuals were screened with forced PCR RFLP method for the FecB gene to study the polymorphism and its effects on litter size, body weight and body size. Results showed that the polymorphism frequencies of FecB gene were significantly imbalanced in these breeds or strains. The Hu sheep were all homozygous carriers of FecB gene(BB). In the Chinese Merino prolific meat strain, the genotype frequencies of BB, B+ and ++ were 51%, 30% and 19%, respectively, whereas all the other flocks had only the wild-type (++) genotype. Results within the Chinese Merino prolific meat strain showed that the mean litter size of ewes with genotype BB and B+ were 2.8 (±0.74) and 2.3 (±0.63) (P<0.05). whereas ++ genotype ewes had a litter size of only 1.2 (±0.68) (P<0.01). At day 90 after birth, the body weights of BB/B+ genotype lambs were higher than that of ++ genotype lambs (18.6±3.70 kg. 18.0±3.71 kg vs 15.6±2.22 kg, P<0.05). In addition, the heart girth and chest width of BB/B+ genotype lambs were significantly longer than those of the ++ lambs (P<0.05). No significant differences were observed in either body weight or body size at day 120. Litter size at first lambing from Hu at Natural Source Conservative Region was found to be significantly higher than that from the other two regions sampled (P<0.05). In addition to the additive effect on litter size, these findings showed for the first time that the FecB gene had a positive effect on early postnatal body growth.     

凋落物对土壤酸化的缓冲及其对根系生长的影响

凋落物层是森林生态系统中一个十分活跃的界面,一方面环境因素影响凋落物的积累和分解,另一方面凋落物的动态反过来又影响到系统内的水热收支平衡、土壤的理化特性以至森林生产力。值得注意的是,在高度工业化的现代社会,大气污染作为一种新生的环境因子不同程度地作用于森林生态系统,凋落物层则是大气污染物(如酸雨)作用于森林土壤亚系     

烯效唑浸种对玉米幼苗生长和内源激素含量的影响

烯效唑浸种对玉米苗期叶片和叶鞘伸长生长有抑制作用,且抑制效应随烯效唑浓度的增大而增强,但植株粗壮,叶宽和茎基宽增加,根系增多,根长增加.烯效唑浸种的玉米幼苗中LAA和GA3含量下降,叶鞘中尤为明显;ZT含量则是地上部提高,根中下降,ABA含量提高,植株各器官中(IAA GA3)/ABA比值均下降,IAA/GA3比值均升高,IAA/ZT和GA3/ZT比值则是地上部降低,根中升高.