斜生栅藻在不同磷条件下氮生态幅的研究

为获得斜生栅藻（Scendesmus obliquus）的氮生态幅,研究根据中华人民共和国地表水环境质量标准磷浓度界定,利用谢尔福德（Shelford）耐受定律进行曲线拟合对斜生栅藻在低磷（0.02 mg/L）、中磷（0.2 mg/L）和高磷（0.4 mg/L）三种不同磷浓度下氮的生态幅进行定量表达,获得三种磷起始条件下斜生栅藻生长的最佳氮浓度、氮适宜生长范围和氮耐受范围。研究表明,在三种磷条件下斜生栅藻生长的最佳氮浓度分别为1.02、8.91和18.05 mg/L,对应的最大比生长速率分别为（0.1420.006）、（0.3140.002）和（0.3460.007） /d,氮适宜生长范围分别为（0.521.52）、（4.4813.34）和（11.7224.38） mg/L,氮耐受限度分别为（0.022.02）、（0.0517.77）和（5.3930.71） mg/L。这表明富营养化水体可能引起斜生栅藻的大量生长、繁殖,也暗示了斜生栅藻能作为高氮水环境的一个良好指示生物。       

有毒赤潮甲藻塔玛亚历山大藻（香港株Ⅱ）的生长特性研究

在室内条件下研究温度、N和P、维生素、抗生素对有毒赤潮甲藻塔玛亚历山大藻(香港株Ⅱ生长的影响。结果表明,塔玛亚历山大藻的适宜生长温度和N、P浓度分别为21-25℃,882-1765μmol／L和18-72μmol／L。复合维生素B的加入有利于塔玛亚历山大藻的生长,而50Uml^-1以上的抗生素则对其有明显的抑制作用。     

塔玛亚历山大藻对氮和磷的吸收及其生长特性

参照塔玛亚历山大藻(Alexandrium tamarense)赤潮爆发时的物理条件,以f／2加富的人工海水为培养基,设定了不同的氮、磷水平,研究了在室内批量培养条件下,塔玛亚历山大藻对无机氮、磷的吸收和无机氮、磷对塔玛亚历山大藻细胞生长的影响．结果表明,3种氮浓度条件下,塔玛亚历山大藻的比生长速率几乎没有差异,但低氮(0．0882mmol·L-1)条件下,藻细胞的生物量最低;中氮(0．882mmol·L-1)条件下,藻细胞具有最大的生物量,分别比高氮(2．646mmol·L-1)和低氮下增加44．7％和53．6％．随着培养基中磷浓度的升高,藻细胞生物量也升高,在高磷(0．108mmol·L-1)条件下达到最大值17200cell·ml-1,但在中磷(0．036mmol.L-1)条件下藻细胞具有最大的比生长速率．藻细胞对氮、磷的吸收速率与生长状态有密切关系,氮、磷限制条件下生长的藻细胞对氮、磷有快速的吸收．研究显示,低的N／P比有利于塔玛亚历山大藻的生长分裂,对数生长后期适当补氮则有利于其生物量的积累．     

N、P营养盐胁迫对两株布朗葡萄藻生长的影响

采用批次培养方法,在光照强度60、110mol/m2s下分别设置了7个不同的氮、磷浓度(N:0-3500g/L,P:15-775g/L),研究两株布朗葡萄藻(Botryococcus braunii)对氮、磷胁迫的敏感性差异,筛选高营养利用效率的优良藻株。结果表明:两株藻对氮磷营养胁迫的耐受性存在差异,B.braunii764株对氮胁迫具有较高耐受性,而B.braunii765株对磷胁迫具有较高耐受性。光照强度110mol/m2s,不同氮浓度下B.braunii764株其平均生长速率均显著高于其他各处理组;不同磷浓度下B.braunii765株其平均生长速率显著高于B.braunii764株。在试验设定的光照强度条件下,适当增加光照强度能够显著降低氮胁迫对布朗葡萄藻生长的抑制效应。在光照强度110mol/m2s下,氮浓度3500g/L时两株布朗葡萄藻平均生长速率与在正常Chu-10培养基条件下无显著差异。磷浓度775g/L时两株布朗葡萄藻的平均生长速率均显著低于正常Chu-10培养基条件,增加光照强度对磷胁迫下藻细胞的生长无显著作用。两株布朗葡萄藻在第2天时磷吸收与初始磷浓度呈正相关关系,氮吸收在3500g/L时出现饱和现象。布朗葡萄藻的生长更容易受到培养基中磷营养胁迫的影响。       

塔玛亚历山大藻的生长研究

在室内条件下研究了温度、N和P、维生素、抗生素对有毒赤潮甲藻塔玛亚历山大藻(香港株Ⅱ)生长的影响。结果表明,塔玛亚历山大藻的最适生长温度为21—25℃,最适N、P浓度分别为882—1765μmol/L和18—72μmol/L。复合维生素B1、B6、B12的加入有利于塔玛亚历山大藻的生长,而50U/mL以上的抗生素(氨苄青霉素液体)则对其有明显的抑制作用。     

不同光照条件下米氏凯伦藻和东海原甲藻生长的温度生态幅

米氏凯伦藻和东海原甲藻是我国东南沿海地区赤潮的主要优势种。为定量获取米氏凯伦藻和东海原甲藻生长的温度生态幅,根据3个光照水平(28.32,75.06,111.66μmol m~(-2)s~(-1))条件下4个温度水平(18,22,25,28℃)对米氏凯伦藻和东海原甲藻生长特性的室内培养实验结果,并结合Shelford耐受性定律建立了基于温度的米氏凯伦藻和东海原甲藻比生长率的耐受性模型,最后根据前期的研究成果分别获取了米氏凯伦藻和东海原甲藻生长的最适温度、适温范围及耐受温度范围。结果表明,无论是米氏凯伦藻还是东海原甲藻,在相同培养光照条件下,在设定的温度水平范围内,分别存在一个适宜米氏凯伦藻和东海原甲藻的最适生长温度T_(opt),且当T≤T_(opt)时,米氏凯伦藻和东海原甲藻细胞密度和比生长率随着温度的升高而显著增大;而当T≥T_(opt)时,米氏凯伦藻和东海原甲藻细胞密度和比生长率随着温度的升高而显著减小。随着培养光照强度的升高,米氏凯伦藻和东海原甲藻细胞密度和比生长率均呈现"先升后降"的变化趋势。建立的藻类生长温度耐受性模型与谢尔福德耐受定律较为吻合,定量获取米氏凯伦藻在3个光照水平(28.32,75.06,111.66μmol m~(-2)s~(-1))下的最适生长温度分别为22.48,22.37,22.33℃;适温范围分别为17.93—27.03,17.82—26.92,17.78—26.88℃;耐受温度范围分别为13.38—31.58,13.27—31.47,13.23—31.43℃;东海原甲藻在3个光照水平(28.32,75.06,111.66μmol m~(-2)s~(-1))下的最适生长温度分别为22.10,21.99,21.93℃;适温范围分别为17.59—26.61,17.48—26.5,17.42—26.44℃;耐受温度范围分别为13.08—31.12,12.97—31.01,12.91—30.95℃。     

温度、光照和pH值对锥状斯氏藻和塔玛亚历山大藻光合作用的影响及光暗周期对其生长速率和生物量的影响

用测定净光合放氧速率的方法研究了温度、光照和pH对锥状斯氏藻(Scrippsiella trochoidea)和塔玛亚历山大藻(Alexandrium tamarense)光合作用的影响.在不同光暗周期(L∶D)条件下培养锥状斯氏藻和塔玛亚历山大藻,研究了光暗周期对生长繁殖速率和生物量的影响.2种藻对温度的变化敏感,适宜的温度范围是17～25℃,最适温度20～22℃,低于10℃和高于30℃不能生长;锥状斯氏藻的光饱和点是400 μmol·m-2·s-1,塔玛亚历山大藻的光饱和点是650 μmol·m-2·s-1, 都属于喜高光强的微藻;2种藻对pH值的变化极其敏感,适宜的pH值范围很小,为7.0～9.0, 最适pH值7.5～8.0, 与其生活的海洋环境一致,pH值高于9.5时, 不能进行有效的光合作用,pH值10.0可致全部细胞死亡;在一定范围内,2种藻的生长速率(μ)和生物量随着光照时间的延长呈比例增加.     

磷限制下大型海藻与微藻间资源竞争理论的实验验证

用一次性培养法结合Monod方程测得海洋微藻-亚心型扁藻(Tetraselmis subcordiformis (Wile) Hazen)与大型海藻-孔石莼(Ulva pertusa Kjellm.)磷限制下的生长动力参数.孔石莼具有较低的半饱和生长常数及最大生长率,其分别为0.016 μmol/L和0.16 d-1,而亚心型扁藻的半饱和生长常数和最大生长率分别是0.021 μmol/L 和0.83 d-1. 两种藻类间的营养竞争实验采用半连续培养法在磷限制条件下进行,实验过程中,分别对两者施予相同或不同的去除率,使两者享有相同或不同的资源需求值R*.由Monod方程所作的竞争预测与实验观察结果的比较显示:仅在两种藻类间的资源需求值R*差异显著(t检验,P＜0.01)时,Monod方程才能对竞争结果作出较为准确的预测;在两种藻类享有相同的资源需求值R*时,亚心型扁藻在竞争中取代孔石莼.Monod模型仅能部分预测大型海藻与海洋微藻间的竞争结果.     

凤眼莲根系分泌物对塔玛亚历山大藻的化感作用(英文)

以塔玛亚历山大藻香港株(Alexandriumtamarense,HKstrain)为材料,研究了凤眼莲(Eichhorniacrassipes)根系分泌物及其丙酮、乙酸乙酯提取物对塔玛亚历山大藻的化感作用(Allelopathic effect)。凤眼莲根粉末的用量为0.1g/L、0.5g/L、1.0g/L、1.5g/L和2.0g/L;丙酮、乙酸乙酯提取物的用量为0.01g/L、0.03g/L、0.05g/L和0.07g/L。由于凤眼莲根系丙酮、乙酸乙酯提取物水溶性比较低,实验中,溶剂提取物置于盖玻片上。培养体系中溶剂提取物的实际浓度通过实验前后盖玻片的差值获得。实验结果表明,凤眼莲根粉末用量大于1.5g/L,对塔玛亚历山大藻抑制率100%,0.5g/L和1.0g/L4d后开始有促进生长的作用。凤眼莲根系丙酮、乙酸乙酯提取物的实际浓度达到0.038g/L、0.022g/L时,对塔玛亚历山大藻抑制超过50%。凤眼莲作为杀藻剂的材料有一定的应用前景。       

氮源对塔玛亚历山大藻生长和毒性的影响

为了掌握不同氮源对塔玛亚历山大藻(Alexandrium tamarense)生长和毒性的影响,实验选定硝酸钠、氯化铵、尿素和甘氨酸作为4种氮源,在温度和光强分别为20℃和200μmol photons·m-2·s-1的培养箱中,采用人工海水一次性培养藻细胞,培养基N和P浓度分别以F/20加富,并收集对数期细胞用于斑马鱼胚胎48 h急性毒理实验。结果表明:4种氮源都可以支持细胞生长,但不同氮源培养的藻细胞生长速率不同,表现为铵氮(0.25 d~(-1))硝氮(0.20 d~(-1))尿素=甘氨酸(0.12 d~(-1));4种氮源对细胞色素的含量无显著影响;与对照组(胚胎培养液)相比,在细胞密度为2×10~4cells·mL~(-1)时,塔玛亚历山大藻细胞粗提液对斑马鱼胚胎表现出显著的毒性作用,可造成胚胎的凝固、发育迟缓、卵黄膜破裂、卵黄囊水肿及尾巴弯曲等;当细胞密度增加到8×10~4cells·mL-1时,毒性进一步增加,且4种氮源对毒性的影响出现显著差异,表现为硝氮尿素=甘氨酸铵氮。综上所述,塔玛亚历山大藻的生长和毒性对氮源的响应机制存在差异,但4种氮源都支持生长,因此,在环境变化和水体营养盐结构复杂化的情况下,塔玛亚历山大藻仍可维持生长并持续爆发藻华,对生态环境造成威胁。     

Phosphorus concentration in barley (Hordeum vulgare L.) seed: Influence on seedling growth and dry matter production

The effect of phosphorus (P) concentration in barley seed on seedling growth has not been much investigated. Consequently, two experiments were conducted in the greenhouse to determine the effect of P concentration in barley seed (Hordeum vulgare L., cv. Empress) on the seedlings grown in sand-filled boxes receiving a culture solution without P. Seeds were selected with three P concentrations: high-P (113.0 mmol P kg⁻¹), medium-P (80.7 mmol P kg⁻¹) and low-P (54.9 mmol P kg⁻¹). At 21 days after sowing, the shoot and root yield or shoot height was the least with seedlings from low-P seed. In the other experiment, high-P and low-P seeds were wetted with distilled water or with a solution of 25.8 cmol L⁻¹ of NaH₂PO₄ for 24 h, and then grown for 31 days. Solution P had been imbibed by seeds whether low or high in native P, but only the imbibed P held by low native P seed benefited seedling dry matter accumulation and shoot elongation. The lack of benefit from seed-imbibed P on seedlings grown from high-P barley seed was associated with low recovery of the imbibed P in those seedlings.     

Influence of Phosphorus Nutrition on Growth and Carbon Partitioning in Glycine max

Soybean plants (Glycine max [L.] Merr var Amsoy 71) were grown in growth chambers with high-phosphorus (high-P) and low-phosphorus (low-P) culture solutions. Low-P treatment reduced shoot growth significantly 7 days after treatment began. Root growth was much less affected by low-P, there being no significant reduction in root growth rate until 17 days had elapsed. The results suggest that low-P treatment decreased soybean growth primarily through an effect on the expansion of the leaf surface which was diminished by 85%, the main effect of low-P being on the rate of expansion of individual leaves. Low-P had a lesser effect on photosynthesis; light saturated photosynthetic rates at ambient and saturating CO₂ levels were lowered by 55 and 45%, respectively, after 19 days of low-P treatment. Low-P treatment increased starch concentrations in mature leaves, expanding leaves and fibrous roots; sucrose concentrations, however, were reduced by low-P in leaves and increased in roots. Foliar F-2,6-BP levels were not affected by P treatment in the light but in darkness they increased with high-P and decreased with low-P. The increase in the starch/sucrose ratio in low-P leaves was correlated primarily with changes in the total activities of enzymes of starch and sucrose metabolism.     

Exploitation of localized phosphorus-patches by common bean roots

Phosphorus (P) uptake from patches was investigated in high-P and low-P common bean (Phaseolus vulgaris L.) plants using a split-root system. A P-patch was developed by exposing a small sub-section of the root system to localized P enrichment. A soil-based media was used to provide realistically low, buffered levels of P. In addition, nutrient solution provided zero and 1 mM P to low-P and high-P plants, respectively. Overall, growth of low-P plants was approximately 40% that of high-P plants. Mycorrhizal infection by G. etunicatum had little detectable influence on plant growth. Root length exploring a P-patch was comparable for low-P and high-P plants, yet low-P plants allocated half as much root biomass and P to a P-patch compared to high-P plants. This was achieved by an increase in the investment in fine, terminal roots exploring a P-patch in low-P plants. P uptake per investment of dry weight in the P-patch was over 50% higher for high-P plants compared to low-P plants. The higher P-uptake efficiency in high-P plants was achieved despite the greater production of fine roots in low-P plants.     

Influence of Mycorrhizal Fungus, Phosphorus,and Burrowing Nematode Interactions on Growth of Rough Lemon Citrus Seedlings

Rough lemon seedlings were grown in mycorrhizal-infested or phosphorus-amended soil (25 and 300 mg P/kg) in greenhouse experiments. Plants Were inoculated with the citrus burrowing nematode, Radopholus citrophilus (0, 50, 100, or 200 nematodes per pot). Six months later, mycorrhizal plants and nonmycorrhizal, high-P plants had larger shoot and root weights than did non-mycorrhizal, low-P plants. Burrowing nematode population densities were lower in roots of mycorrhizal or nonmycorrhizal, high-P plants than in roots of nonmycorrhizal, low-P plants; however, differences in plant growth between mycorrhizal and nonmycorrhizal plants were not significant with respect to initial nematode inoculum densities. Phosphorus content in leaf tissue was significantly greater in mycorrhizal and nonmycorrhizal, high-P plants compared with nonmycorrhizal, low-P plants. Nutrient concentrations of K, Mg, and Zn were unaffected by nematode parasitism, whereas P, Ca, Fe, and Mn were less in nematode-infected plants. Enhanced growth associated with root colonization by the mycorrhizal fungus appeared to result from improved P nutrition and not antagonism between the fungus and the nematode.     

The endemic kelp Lessonia corrugata is being pushed above its thermal limits in an ocean warming hotspot

Kelps are in global decline due to climate change, which includes ocean warming. To identify vulnerable species, we need to identify their tolerances to increasing temperatures and determine whether tolerances are altered by co-occurring drivers such as inorganic nutrient levels. This is particularly important for those species with restricted distributions, which may already be experiencing thermal stress. To identify thermal tolerance of the range-restricted kelp Lessonia corrugata, we conducted a laboratory experiment on juvenile sporophytes to measure performance (growth, photosynthesis) across its thermal range (4–22°C). We determined the upper thermal limit for growth and photosynthesis to be ~22–23°C, with a thermal optimum of ~16°C. To determine if elevated inorganic nitrogen availability could enhance thermal tolerance, we compared the performance of juveniles under low (4.5 μmol · d⁻¹) and high (90 μmol · d⁻¹) nitrate conditions at and above the thermal optimum (16–23.5°C). Nitrate enrichment did not enhance thermal performance at temperatures above the optimum but did lead to elevated growth rates at the thermal optimum. Our results indicate L. corrugata is likely to be extremely susceptible to moderate ocean warming and marine heatwaves. Peak sea surface temperatures during summer in eastern and northeastern Tasmania can reach up to 20–21°C, and climate projections suggest that L. corrugata's thermal limit will be regularly exceeded by 2050 as southeastern Australia is a global ocean-warming hotspot. By identifying the upper thermal limit of L. corrugata, we have taken a critical step in predicting the future of the species in a warming climate.     

Influence of Vesicular-Arbuscular Mycorrhizal Fungi on the Response of Potato to Phosphorus Deficiency

Morphological and biochemical interactions between a vesicular-arbuscular mycorrhizal (VAM) fungus (Glomus fasciculatum [Thaxt. sensu Gerdemann] Gerdemann and Trappe) and potato (Solanum tuberosum L.) plants during the development of P deficiency were characterized. Nonmycorrhizal (NM) plants grown for 63 d with low abiotic P supply (0.5 mM) produced 34, 52, and 73% less root, shoot, and tuber dry matter, respectively, than plants grown with high P (2.5 mM). The total leaf area and the leaf area:plant dry weight ratio of low-P plants were substantially lower than those of high-P plants. Moreover, a lower shoot:root dry weight ratio and tuber:plant dry weight ratio in low-P plants than in high-P plants characterized a major effect of P deficiency stress on dry matter partitioning. In addition to a slower rate of growth, low-P plants accumulated nonreducing sugars and nitrate. Furthermore, root respiration and leaf nitrate reductase activity were lower in low-P plants than in high-P plants. Low abiotic P supply also induced physiological changes that contributed to the greater efficiency of P acquisition by low-P plants than by high-P plants. For example, allocation of dry matter and P to root growth was less restricted by P deficiency stress than to shoot and tuber growth. Also, the specific activities of root acid phosphatases and vanadate-sensitive microsomal ATPases were enhanced in P-deficient plants. The establishment of a VAM symbiosis by low-P plants was essential for efficient P acquisition, and a greater root infection level for P-stressed plants indicated increased compatibility to the VAM fungus. By 63 d after planting, low-P VAM plants had recovered 42% more of the available soil P than low-P NM plants. However, the VAM fungus only partially alleviated P deficiency stress and did not completely compensate for inadequate abiotic P supply. Although the specific activities of acid phosphatases and microsomal ATPases were only marginally influenced by VAM infection, VAM roots characteristically had a higher protein concentration and, consequently, enhanced microsomal ATPase and acid phosphatase activities on a fresh weight basis compared with NM roots. Morphological and ultrastructural details of VAM plants are discussed in relation to the influence of the VAM symbiosis on P nutrition of potato.     

Nitrate regulation of nitrate uptake and nitrate reductase expression in barley grown at different nitrate:ammonium ratios at constant relative nitrogen addition rate

Barley (Hordeum vulgare L. cv. Golf) was cultured using the relative addition rate technique, where nitrogen is added in a fixed relation to the nitrogen already bound in biomass. The relative rate of total nitrogen addition was 0.09 day^?1 (growth limiting by 35%), while the nitrate addition was varied by means of different nitrate: ammonium ratios. In 3- to 4-week-old plants, these ratios of nitrate to ammonium supported nitrate fluxes ranging from 0 to 22 μmol g^?1 root dry weight h^?1, whereas the total N flux was 21.8 ± 0.25 μmol g^?1 root dry weight h^?1 for all treatments. The external nitrate concentrations varied between 0.18 and 1.5 μM. The relative growth rate, root to total biomass dry weight ratios, as well as Kjeldahl nitrogen in roots and shoots were unaffected by the nitrate:ammonium ratio. Tissue nitrate concentration in roots were comparable in all treatments. Shoot nitrate concentration increased with increasing nitrate supply, indicating increased translocation of nitrate to the shoot. The apparent V_max for net nitrate uptake increased with increased nitrate fluxes. Uptake activity was recorded also after growth at zero nitrate addition. This activity may have been induced by the small, but detectable, nitrate concentration in the medium under these conditions. In contrast, nitrate reductase (NR) activity in roots was unaffected by different nitrate fluxes, whereas NR activity in the shoot increased with increased nitrate supply. NR-mRNA was detected in roots from all cultures and showed no significant response to the nitrate flux, corroborating the data for NR activity. The data show that an extremely low amount of nitrate is required to elicit expression of NR and uptake activity. However, the uptake system and root NR respond differentially to increased nitrate flux at constant total N nutrition. It appears that root NR expression under these conditions is additionally controlled by factors related to the total N flux or the internal N status of the root and/or plant. The method used in this study may facilitate separation of nitrate-specific responses from the nutritional effect of nitrate.     

Effects of irradiance, water temperature and nutrients on the growth of sporelings of the crustose coralline alga Lithophyllum yessoense Foslie (Corallinales, Rhodophyceae)

Lithophyllum yessoense Foslie is a markedly dominant subtidal, crustose coralline alga in south–western Hokkaido, Japan. In this study, the effects of irradiance, water temperature and nutrients (nitrate and phosphate) on the growth of sporelings of the alga were examined. The relative growth rate (RGR) was saturated at 17.6% d^?1 at a high irradiance (240 umol photon m²s^?1). Even at a low irradiance (10.7–49.9 umol photon m^?2s^?1), RGR was 7.1–12.7% d^?1 The survival rate of sporelings was greater than 80% at irradiance above 10.7 μmol photon m^?2s^?1 throughout the culture period. The growth of L. yessoense sporelings was promoted at 15°C and 20°C, but inhibited at 5°C. The half‐saturation constants (Ks) for growth were about 0.5 umol L^?1 and 0.14 umol L^?1 for nitrate and phosphate, respectively. Saturated nitrate and phosphate concentrations for the growth were about 4.0 μmol L^?1 and 0.4 μmol L^?1, respectively, suggesting that L. yessoense is adaptable to a relatively high water temperature, a wide range of irradiance, and low ambient nitrate and phosphate concentrations. The results provide a possible explanation of why L. yessoense is dominant in the environments of south‐western Hokkaido.