水体泥沙对苦草生长发育和叶片光合生理特性的影响

用粒径小于100μm的泥沙分别配置浊度为30、60、90NTU和120NTU的浑浊水体,将苦草(Vallisneria asiatica)幼苗分别种植于上述水体中,水深约60cm,定期统计植株的叶长、叶宽、叶片数和株数,利用水下饱和脉冲荧光仪(DIVING～PAM)测定泥沙附着苦草叶片在光化光下的荧光参数,并测定其超氧化物歧化酶和过氧化物酶活性.结果表明,随着水体中泥沙含量的增加苦草植株的叶宽、叶片数和植株数呈显著的降低趋势,在浊度30NTU的水体中,植株叶长增长速度显著大于对照;随着实验时间的延长,在泥沙含量较高的水体(浊度≥60NTU)中,植株逐渐死亡,而在浊度30NTU的水体中,幼苗能进行正常的生长发育.秋季植株开花时,叶片上的泥沙附着量逐渐增大,在30NTU水体中泥沙附着叶片的实际光化学效率、光化学荧光淬灭系数和电子传递速率均显著高于对照,而且附着叶片的超氧化物歧化酶和过氧化物酶活性与对照的差异不显著.表明在低浓度泥沙水体中泥沙附着有利于苦草叶片PSⅡ免受秋季高光照的伤害,从而减缓苦草叶片光合功能的衰减.因此,在泥沙含量较低的浅水体(浊度≤30 NTU)中可以适当引种苦草幼苗(最好由冬芽和根状茎萌发得到),植株能正常生长发育和繁殖.     

水体浊度对苦草光合荧光特性的影响

用粒径小于100μm的泥沙分别配置浊度为30、60、90 NTU(nephelometric turbidity units)的混浊水体,将苦草(Vallisneria natans)成株分别种植于上述水体中,利用水下饱和脉冲荧光仪(DIVING-PAM)测定植株最长叶片水下10 cm处ΔFv/Fm的光合日变化及快速光响应曲线(RLC)。结果表明,1个月后,水体浊度对苦草成体植株Fv/Fm和光合系统Ⅱ(PSⅡ)无显著影响,叶片ΔFv/F’m的日变化曲线呈“V”形;泥沙浊度≥60 NTU时,ΔFv/F’m降低幅度较小,光强降低时恢复较快,植株受光抑制的程度变小。快速光响应曲线结果显示,实验期间苦草开始衰老,光响应能力下降;随水体混浊度的升高,叶片光响应能力下降减慢。表明在浅(水深1.0 m)而浑浊的水体中,短时间内混浊水体对苦草成株叶片PSⅡ的影响较小。     

悬浮泥沙溶液对金鱼藻快速光响应曲线的影响

用粒径小于100μm的泥沙分别配置浊度为30、60、90 NTU的混浊溶液,将金鱼藻(Ceratophyllum dem er-sum)种植于该溶液中,1个月后测定植株叶片的快速光响应曲线,研究悬浮泥沙对金鱼藻光合荧光特性的影响。结果表明,在60、90 NTU的悬浮泥沙溶液中金鱼藻叶片的荧光产量(Ft)、光适应最大荧光产量(Fm′)和有效荧光产量(ΔFv/Fm)都显著低于对照和30 NTU的植株。与对照相比较,在混浊溶液中植株叶片的光化学淬灭(qP)和非光化学淬灭(qN)随光照强度的增加显著降低,光合能力和热耗散能力显著降低。混浊溶液中,随溶液浊度的增加植株最小饱和光强(Ek)和最大相对电子传递效率(rETRm ax)也显著低于对照植株,光合作用受到显著影响。因而,金鱼藻不适于在高浊度的悬浮泥沙溶液中生长。     

水体泥沙对菖蒲和石菖蒲生长发育的影响

三峡库区消落带植物恢复不仅面临长期淹水逆境,还面临高水位落差、反季节消落等环境因素的胁迫。菖蒲和石菖蒲是库区常见的两种湿生植物,探讨它们在泥沙水体中的生长发育,有利于为三峡库区消落带植被恢复的物种选择提供科学依据。用粒径小于100μm的泥沙分别配置浊度为30、60和90NTU的浑浊水体,8月将菖蒲(Acorus calamus L.)和石菖蒲(Acorus tatarinowii S.)植株分别种植于上述水体中,翌年4月统计植株的萌发数、叶长、叶宽、叶片数,利用水下饱和脉冲荧光仪(DIVING-PAM)测定叶片的快速光响应曲线。结果表明,各浊度组植株的萌发率与对照组相同,30NTU组石菖蒲和菖蒲的植株数显著多于对照组,且石菖蒲的植株数随水体浊度增加呈增多趋势,而菖蒲的植株数呈相反趋势。石菖蒲和菖蒲30NTU组植株的叶长、叶宽以及总叶片数、总叶长均显著大于对照组;石菖蒲60NTU组和90NTU组植株的叶长、叶宽和总叶长显著小于对照组(P<0.05),而菖蒲60NTU组的叶长、叶宽和叶片数显著大于对照组(P<0.01),90NTU组植株的叶长、叶宽和叶片数与对照组无显著差异(P>0.05),且菖蒲60NTU组和90NTU组植株的总叶片数和总叶长均显著低于对照组(P<0.01)。由快速光响应曲线可知,在较高光强照射下各浊度组植株的光化学荧光淬灭系数(qP)、非光化学淬灭系数(qN)和相对电子传递速率(rETR)均显著降低,但在低光下各浊度组植株的qP、qN和rETR均显著高于对照组,且菖蒲对低光的耐受范围大于石菖蒲。因而,菖蒲和石菖蒲均能长期生长于浅(0.9m)的悬浮泥沙水体中,具有一定的耐淹能力。     

水体悬浮泥沙对黑藻生长和叶绿素荧光特性的影响

利用粒径小于100 μm的泥沙调制水体浊度分别维持在30、60和90 NTU,将黑藻幼苗种植于上述水体中,定期测定植株的分枝长、分枝数和鲜质量,利用水下饱和脉冲荧光仪（DIVING-PAM）测定叶片在光化光下的荧光参数.结果表明：随着泥沙含量的增加,植株分枝数受到明显抑制,生物量逐渐降低,而分枝长则呈显著增加趋势;随着试验时间的延长,浑浊水体中光化学最大量子产量（F_v/F_m）值呈明显〖JP2〗降低趋势,但显著高于对照.在17 μmol·m^-2·s^-1光化光照射下,与第30天相比,第60天时30、60和90 NTU组植株叶片的有效荧光产量（△F_v′/F_m ′）分别增加了48.9%、36.8%和17.2%（P<0.01）,相对光合电子传递速率（rETR）分别增加了56.7%、42.2%和21.4%（P<0.01）;而在104 μmol·m^-2·s^-1光化光照射下,第60天时植株的△F_v′/F_m′、光化学淬灭系数（q_P）和rETR显著降低,且热耗散能力（q_N）也显著降低,表明黑藻植株适应低光环境, 且在高光强条件下黑藻叶片易受到光伤害.可引种黑藻幼苗于混浊的浅水水体中.     

水体浊度对菹草(Potamogeton cripus)幼苗生长发育的影响

用粒径小于100μm的泥沙配置浊度为30、60、90、120、150NTU和180NTU的混浊水体,将菹草（Potamogeton cipus）幼苗分别移栽于上述水体中,观测菹草幼苗在各浊度水体中的生长发育状况,并用水下饱和脉冲叶绿素荧光仪（DIVING-PAM）测定菹草幼苗光合作用PSⅡ最大量子产量（Fv/Fm）、有效荧光产量（Yield）、光化学荧光淬灭系数（qP）、非光化学荧光淬灭系数（qN）等指标。结果表明,菹草幼苗对混浊水体有较强的耐受能力,在30、60NTU和90NTU的混浊水体中,水体浊度对菹草幼苗的存活、生长发育及光合结构PSⅡ影响不显著（P〉0．05）。当水体浊度≥120NTU时,在短期（〈10d）胁迫下,水体浊度对于菹草幼苗的存活、生长发育无显著影响（P〉0．05）,但是,随着胁迫时间的延长（〉10d）,菹草幼苗虽能成活但生长发育明显受到抑制,幼苗叶片受光胁迫时,能通过增加热耗散（qN）保护其光合结构PSⅡ免受伤害;而更长时间的胁迫（80d）,在高浊度（120、150NTU和180NTU）水体中的菹草幼苗开始大量死亡,其Fv/Fm、Yield、qP值均显著低于对照（P〈0．05）,qN值的急剧下降,说明光合结构PSⅡ开始受到破坏。     

水体浊度对菹草(Potamogeton cripus)幼苗生长发育的影响

用粒径小于100 μm的泥沙配置浊度为30、60、90、120、150 NTU和180 NTU的混浊水体,将菹草（Potamogeton cripus）幼苗分别移栽于上述水体中,观测菹草幼苗在各浊度水体中的生长发育状况,并用水下饱和脉冲叶绿素荧光仪（DIVING-PAM）测定菹草幼苗光合作用PSII最大量子产量 （Fv/Fm）、有效荧光产量（Yield）、光化学荧光淬灭系数（qP）、非光化学荧光淬灭系数（qN）等指标。结果表明,菹草幼苗对混浊水体有较强的耐受能力,在30、60NTU和90NTU的混浊水体中,水体浊度对菹草幼苗的存活、生长发育及光合结构PSII影响不显著（p>0.05）。当水体浊度≥120NTU时,在短期（<10d）胁迫下,水体浊度对于菹草幼苗的存活、生长发育无显著影响（p>0.05）,但是,随着胁迫时间的延长(>10d),菹草幼苗虽能成活但生长发育明显受到抑制,幼苗叶片受光胁迫时,能通过增加热耗散（qN）保护其光合结构PSII免受伤害;而更长时间的胁迫（80d）,在高浊度（120、150 NTU和180 NTU）水体中的菹草幼苗开始大量死亡,其Fv/Fm、Yield、qP值均显著低于对照（p<0.05）, qN值的急剧下降,说明光合结构PSII开始受到破坏。     

悬浮泥沙对亚洲苦草幼苗生长发育的影响

将亚洲苦草（Vallisneria asiatica Miki L.）幼苗植株种植于浊度分别为30NTU、60NTU和90NTU的悬浮泥沙水体中,统计各处理苦草幼苗的生长发育状况,并使用水下饱和脉冲叶绿素荧光仪（DIVING-PAM）测定PSⅡ最大量子产量（FV/Fm）、实际光化学效率（Yield）、光化学荧光淬灭系数（qP）、非光化学荧光淬灭系数（qN）、表观电子传递效率（ETR）以及快速光响应曲线。结果表明,实验第5天,悬浮泥沙对于苦草幼苗的存活、生长发育及光合作用影响不显著（p〉0.05）,苦草幼苗在低光胁迫下通过增加热耗散以保护PSⅡ。30d后,悬浮泥沙对于苦草幼苗的存活、生长发育及光合作用影响显著（p〈0.05）,30NTU组苦草幼苗生长发育虽明显受到抑制,但仍能保持一定的存活率;而泥沙浊度为60NTU和90NTU时则完全不利于苦草幼苗存活。30NTU、60NTU、90NTU组的Fv/Fm值、Yield值、qP值、最大ETR均显著低于对照（p〈0.05）,30NTU组最小饱和光强为176μmol quanta/m^2.s,而60NTU、90NTU组则只有17μmolquanta/m^2.s,远低于对照组的248μmol quanta/m^2.s。     

水体浊度对菹草萌发及萌发苗光合荧光特性的影响

用粒径小于100μm的泥沙分别配置浊度为30、60NTU和90NTU的混浊水体,将菹草（Potamogeton cripus）石芽分别种植于上述水体中,测定萌发率和萌发苗的株高、叶片数,并利用水下饱和脉冲荧光仪（DIVING-PAM）测定萌发苗的光合荧光特性。结果表明,水体浊度对石芽萌发率没有显著影响,但对萌发速率有一定影响;随着浊度的升高萌发苗株高和叶片数均显著降低（p＜0．05）;菹草萌发苗的有效荧光产量Yield也随水体浊度升高而降低,表明在高浊度水体中萌发苗天线色素吸收光子供给PSⅡ反应中心的效率下降;高浊度导致萌发苗吸收光能用于光化学电子传递的份额（qP）减少,第23天时90NTU水体中的妒为对照的91．4％;水体浊度上升导致qN显著升高,表明在高浊度、低光照胁迫下,萌发苗接收的光能更多的以热的形式耗散掉了,以避免光系统PSⅡ受到过剩光能的伤害;浊度升高引起电子在光合链中的传递速率（ETR）显著下降,第23天时在30、60NTU和90NTU水体中ETR分别为对照的93．3％、88．5％、75．8％,导致参与CO2固定的电子减少,光合作用降低。快速光响应曲线测定结果表明．萌发苗ETRmax和最小饱和光照强度随水体浊度的增加呈下降趋势,光响应能力随水体浊度的增加而显著下降,特别是在90NTU水体中萌发苗的光合作用能力下降显著。因此,在浅而混浊的水体中（水深70cm,浊度低于90NTU）,菹草石芽均能萌发,但是,水体浊度对萌发苗光合作用、生长速率有一定抑制作用。     

长期弱光对苦草幼苗生长发育的影响

用遮光法研究弱光(5%、1%、0.5%、0.1%全光照)对苦草幼苗生长发育的影响,统计了苦草的生物学参数,测定了叶片叶绿素荧光参数。结果表明:1)0.1%组无新株萌发,随着实验时间的延长其余组新株萌发逐渐被抑制。2)随着实验时间增加和光照强度降低,老株叶片形成受到的抑制程度呈增大趋势;前20d时新株叶片形成未被抑制,但随着实验时间延长显著被抑制。3)老株、新株的叶宽均受到显著抑制。4)老株叶片的伸长显著被抑制,且随着光强降低叶片伸长的幅度呈显著降低趋势;前20天时新株叶长被促进,随着实验时间延长叶片伸长显著被抑制。5)随实验天数的增加,老株叶片光化学最大量子产量(Fv/Fm)呈显著降低趋势,第80天时相对电子传递速率(rETR)和非光化学淬灭(NPQ)显著降低。6)新、老植株根、茎、叶的鲜重均显著低于对照,且随着光照强度降低老株的茎重/株重和根重/株重呈增加趋势,而叶重/株重呈显著的降低趋势。第80天时苦草植株仍具有一定的光合能力,地下茎的生物量比例较高,因此,≤1%全光照下苦草植株具有较强的耐受能力。     

Spatial variability in the abundance of pelagic invertebrate predators in relation to depth and turbidity

The abundance of pelagic invertebrate predators in relation to turbidity and depth gradients in Lake Hiidenvesi (southern Finland) were studied. In the shallow (<5 m) and the most turbid (up to 75 NTU) part of the lake, the community of invertebrate predators consisted of cyclopoid copepods (max biomass >500 μg dw l⁻¹) and Leptodora kindtiii (Focke) (17 μg dw l⁻¹), while in the less turbid (10–40 NTU) stratifying area Chaoborus flavicans (Meigen) dominated (max 146 μg dw l⁻¹). In the temporarily stratifying and moderately turbid basin Chaoborus and small-bodied invertebrate predators co-existed. Mysis relicta (Lovén) occurred only in the stratifying area (max 15 μg dw l⁻¹). The results suggested that both water depth and turbidity contributed to the community structure of Chaoborus flavicans. Depth great enough for stratification was of special importance and its effect was amplified by elevated turbidity, while high turbidity alone could not maintain chaoborid populations. Mysis relicta also requires a hypolimnetic refuge but is more sensitive to low oxygen concentrations and may therefore be forced to the epilimnion where it is vulnerable to fish predation. Cyclopoids as rapid swimmers can take advantage at elevated turbidity levels and coexist in high biomass with fish even in shallow water. Leptodora kindtii can form high biomass despite planktivorous fish providing that turbidity exceeds 20 NTU. The results demonstrated that depth and water turbidity can strongly regulate the abundance and species composition of invertebrate predators. These factors must thus be taken into account when applying food web management, which aims to reduce phytoplankton biomass by depressing planktivorous fish.     

Biomass allocation of branches and leaves in Phyllostachys heterocycla ‘Pubescens’ under different management modes: allometric scaling analysis

Aims Allometric relationship between branch and leaf is limited by plant ontogeny and affected by environmental conditions, which is not well investigated in giant clone species such as Phyllostachys heterocycla ‘Pubescens’. Our objectives were to study the effects of different management modes (obtruncation and fertilization) on branch and leaf biomass allocations of P. heterocycla ‘Pubescens’ and to discuss the effects within canopy.
Methods Obtruncation is a particular pruning operation cutting off the top (about 40%–70% canopy) of P. heterocycla ‘Pubescens’. This management methods used in north Zhejiang of China to reduce trees falling from strong wind or heavy snow. A replicated 2 × 2 factorial experiment (obtruncation and fertilization) was established in Zhejiang Province in 2004. In 2010 and 2011, a total of 50 plants were cut down to investigate branch and leaf biomass, as well as leaf area of selected leaves within the canopy. Allometric scaling was applied to analyze the relation of branch and leaf biomass.
Important findings Averaged branch and leaf biomass for individual plant were decreased 40.23% and 41.01%, respectively, following obtruncation and increased 20.18% and 30.23%, respectively, following fertilization. Obtruncation severely changed the growth trajectory and resulted in a greater standardized major axis (SMA) slope, which indicated relatively more biomass was allocated to leaves. This was more significant under non-fertilization treatments. When compared to non-fertilization, fertilization significantly decreased SMA slope in unobtruncated trees, which was attributed to relatively larger leaf photosynthetic products partitioning to branches after fertilization. In addition, allocation patterns of branch and leaf biomass at different canopy parts were affected by light availability that was different in different fertilization treatments. Obtruncation changed SMA slope by nearly 50% and <10% for fertilization, which indicated that direct interference (obtruncation) easily changed the growntrajectory and indirect effects (fertilization) were more limited by plant ontogeny.     

Effect of point-of-use disinfection, flocculation and combined flocculation-disinfection on drinking water quality in western Kenya

AIMS: Point-of-use drinking water disinfection with sodium hypochlorite has been shown to improve water quality and reduce diarrhoeal disease. However, the chlorine demand of highly turbid water may render sodium hypochlorite less effective. METHODS AND RESULTS: We evaluated a novel combined flocculant-disinfectant point-of-use water treatment product and compared its effect on drinking water quality with existing technologies in western Kenya. In water from 30 sources, combined flocculant-disinfectant reduced Escherichia coli concentrations to <1 CFU100 ml(-1) for 29 (97%) and reduced turbidity to <5 nephelometric turbidity units (NTU) for 26 (87%). By contrast, water from 30 sources treated with sodium hypochlorite reduced E. coli concentrations to <1 CFU 100 ml(-1) for 25 (83%) and turbidity to <5 NTU for 5 (17%). CONCLUSIONS: For source waters over a range of turbidities in western Kenya, combined flocculant-disinfectant product effectively reduces turbidity to <5 NTU and reduces E. coli concentrations to <1 CFU 100 ml(-1). SIGNIFICANCE AND IMPACT OF THE STUDY: The novel flocculant-disinfectant product may be acceptable to consumers and may be effective in reducing diarrhoeal disease in settings where source water is highly turbid.     

施肥对降香黄檀营养生长和生殖生长的影响

研究施肥对降香黄檀（Dalbergia odorifera T.Chen.）营养生长和生殖生长的影响,为不同经营目标的降香黄檀人工林培育提供技术支撑。本研究以8年生降香黄檀为对象,设置N（185.6 g N/株）、P（120 g P₂O₅/株）、K（120 g K₂O/株）、PK（120 g P₂O₅+120 g K₂O/株）、NPK（185.6 g N+120 g P₂O₅+120 g K₂O/株）以及不施肥（对照）等六个处理,调查施肥后盛花期内一年生新梢、叶、花的生长情况。结果表明：6个施肥处理间降香黄檀营养生长和生殖生长均差异显著（P<0.05）。N处理的营养枝率、营养枝复叶数和小叶宽分别比对照提高40.25%、21.75%和9.52%,花序直径和花序生物量则降低12.75%和48.63%,显示N肥能促进降香黄檀营养生长,抑制生殖生长,有利于大径材培育;P、PK处理的营养枝率较对照显著降低47.96%和46.84%,表明P肥和K肥能促进生殖生长,有利于良种选育;NPK处理能同时显著促进营养生长和生殖生长,其营养枝率、营养枝长度、营养枝复叶数、营养枝小叶长、宽和枝生物量比对照提高26.04%、68.16%、32.98%、15.20%、11.40%和83.60%,花序数量和花序生物量亦提高54.20%和49.84%。因此,在降香黄檀人工林培育实践中,可通过调整肥料的NPK配比（偏向N或PK）以实现营养生长或生殖生长调控之目的。     

Influence of visual conditions on foraging and growth of juvenile fishes with dissimilar sensory physiology

The influence of turbidity on foraging and growth of young-of-the-year (YOY) of two percid species with relatively dissimilar sensory physiology, perch Perca fluviatilis and pikeperch Sander lucioperca was tested. A littoral mysid, Neomysis integer , was used as prey. Functional response was investigated indoors at two levels of turbidity, 3 NTU (clear) and 25 NTU (turbid). Growth and consumption rate were studied both during day and night in outdoor experiments at similar turbidity levels. Pikeperch were not affected by turbid conditions in either of the experiments. Foraging of perch, on the other hand, was significantly negatively affected by higher turbidity in the functional response experiments and during the night-time in the outdoor experiments. As opposed to pikeperch, consumption rates of perch decreased markedly during nights. Perch also grew more slowly in the treatments with turbid water. The dissimilar reactions of the two species indicate that sensory physiological adaptations and foraging behaviour are important factors that partly can explain disparate reactions of YOY fishes to the level of turbidity.     

Effect of adult pheromones on the avoidance of suspended sediment by migratory banded kokopu juveniles

Migratory banded kokopu Galaxias fasciatus juveniles exhibited an attraction to adult odours and an avoidance towards suspended sediment with a turbidity of 25 nephelometric turbidity units (NTU) in a two-choice chamber apparatus. When the adult odours were mixed with suspended sediment at a turbidity of 25 or 35 NTU, an attraction towards the odour and suspended sediment chamber resulted. When adult odours were paired with turbid water at 50 NTU, juveniles would avoid the odour and suspended sediment chamber. These results demonstrate adult pheromones can increase the threshold for an avoidance response to suspended sediment in banded kokopu juveniles. This provides supporting evidence that odours released by adult conspecifics may provide an important migratory cue for juveniles in stream and habitat selection.     

Feeding efficiency of white bream at different inorganic turbidities and light climates

Experiments were conducted to test the effects of turbidity (10–50 NTU) and light (0–2 μE m⁻² s⁻¹) on the feeding efficiency of white bream Abramis björkna preying on Chaoborus flavicans . Increased turbidity and low light levels did not have a significant impact on the feeding of white bream. In total darkness feeding was impeded indicating that white bream depends on vision for feeding. The dominance of white bream in temperate eutrophic lakes could be attributed to their success of feeding in turbid and low light environments.     

散孔材与环孔材树种枝干、叶水力学特性的比较研究

为揭示散孔材与环孔材树种树木水分生理特性的差异,选取了常见的3种散孔材落叶树种(毛白杨、法国梧桐和樱花)和3种环孔材落叶树种(刺槐、合欢和白蜡),研究了其枝干与叶水力学性质的差异及其协调性。结果表明:3种环孔材树种枝干横截面积基础上的最大比导水率(Ks-max)大于3种散孔材树种,但其木质部对空穴化的脆弱性(P50branch)高于散孔材树种,6种树木枝干的水分传输能力和抵抗空穴化能力之间存在一种相互制约的权衡关系。3种散孔材与3种环孔材树种的叶最大水力导度(Kl-max)和水力脆弱性(P50leaf)并无显著差异;对于3种散孔材树种,叶的水力脆弱性要高于枝干,但对3种环孔材树种而言,枝干的水力脆弱性要高于叶。6种树木枝干和叶的水力学性质(Kmax、P50)之间并无相关关系。这些结果表明:散孔材与环孔材树种的枝干水力学特性有明显差异,但叶水力学特性无差异;枝干与叶水力学性质之间是相互独立的。     

Wetland macrophyte diversity, trophic status and phytoplankton： a case study of the cascading effects of an invasive herbivore

Shallow water bodies can exist in alternative stable states, a clear water state with high coverage of macrophytes or a turbid state with high phytoplankton biomass. The alternative equilibria hypothesis has been proposed to explain the occurrence of the alternative stable states (Scheffer et al., 1993)[1], which assumes that: 1),