Mucuna pruriens seed powder feeding influences reproductive conditions and development in Japanese quail Coturnix coturnix japonica

This study was designed to test whether Mucuna pruriens, a natural source of l-dihydroxyphenylalanine (l-DOPA, a dopamine precursor) feeding, can influence development and reproductive conditions in the high food value bird, Japanese quail, Coturnix coturnix japonica. Experiments were performed in both male and female Japanese quail. One-week-old quail chicks were divided into three groups of 36 birds each. Group I was provided with normal diet and served as control. Group II was provided with food mixed with l-DOPA (50 mg/15 g food) and Group III was provided with food mixed with M. pruriens seed powder (480 g/kg food). At the age of 3 weeks (when birds were sexually distinguished) Group I was divided into two sub-groups IA (male) and IB (female) of six birds each. Similarly, Groups II and III were sub-divided into IIA (male), IIB (female) and IIIA (male), IIIB (female), respectively, of six birds each. Observations were made up to the age of 5 weeks. Male experimental groups (IIA and IIIA) showed significantly increased testicular activity, cloacal gland volume, body weight (BW), plasma testosterone and LH level in comparison to control (IA). Similarly female experimental groups (IIB and IIIB) showed significantly greater weight of reproductive organs (uterus, ovary, oviduct and ovarian follicle), BW, egg weight and size and number of follicles. On the other hand, plasma prolactin level was significantly low in comparison to control (IB). Results suggest that M. pruriens is a rich natural source of l-DOPA and the development and reproduction in Japanese quail might be associated with the dopaminergic system of the brain.     

Effects of growth under elevated UV-B on photosynthesis and isoprene emission in Quercus gambelii and Mucuna pruriens

Increasing surface levels of UV-B resulting from stratospheric ozone reduction directly affect tropospheric photochemistry. There may also be indirect tropospheric effects due to changes in emission of organic compounds from vegetation. We treated woody and herbaceous isoprene-emitting species in the field with supplemental UV-B simulating 30% ozone depletion. For Quercus gambelii, photosynthesis and isoprene emission were significantly greater in elevated UV-B treatments when expressed on a leaf area basis, but not on a leaf mass basis. Leaves of Mucuna pruriens, however, showed no significant differences in photosynthesis or isoprene emission between treatments, nor when exposed for 45 min to acute high levels of UV-B. Elevated UV-B during growth did not elicit significant isoprene emission from Acer platanoides, a non-emitting species. Other potential UV-B effects, such as changes in leaf area or species composition, which may influence regional isoprene emissions, should be examined.     

The reallocation of carbon in P deficient lupins affects biological nitrogen fixation

It is not known how phosphate (P) deficiency affects the allocation of carbon (C) to biological nitrogen fixation (BNF) in legumes. The alteration of the respiratory and photosynthetic C costs of BNF was investigated under P deficiency. Although BNF can impose considerable sink stimulation on host respiratory and photosynthetic C, it is not known how the change in the C and energy allocation during P deficiency may affect BNF. Nodulated Lupinus luteus plants were grown in sand culture, using a modified Long Ashton nutrient solution containing no nitrogen (N) for ca. four weeks, after which one set was exposed to a P-deficient nutrient medium, while the other set continued growing on a P-sufficient nutrient medium. Phosphorus stress was measured at 20 days after onset of P-starvation. During P stress the decline in nodular P levels was associated with lower BNF and nodule growth. There was also a shift in the balance of photosynthetic and respiratory C toward a loss of C during P stress. Below-ground respiration declined under limiting P conditions. However, during this decline there was also a shift in the proportion of respiratory energy from maintenance toward growth respiration. Under P stress, there was an increased allocation of C toward root growth, thereby decreasing the amount of C available for maintenance respiration. It is therefore possible that the decline in BNF under P deficiency may be due to this change in resource allocation away from respiration associated with direct nutrient uptake, but rather toward a long term nutrient acquisition strategy of increased root growth.     

松嫩平原草甸三种植物叶片N、P化学计量特征及其与土壤N、P浓度的关系

测定了松嫩平原草甸3种主要植物羊草(Leymus chinensis)、芦苇(Phragmites communis)和尖叶胡枝子(Lespedeza hedysaroides)叶片全氮、全磷浓度,并分析了它们与土壤全氮、全磷浓度的关系.结果表明:3种植物叶片全氮浓度种间差异显著(P＜0.05),而全磷浓度种间差异不显...     

Differential growth costs and nitrogen fixation in Cytisus multiflorus (L′Hér.) Sweet and Cytisus scoparius (L.) Link are mediated by sources of inorganic N

• Shrubby legumes in Mediterranean‐type ecosystems face strong nutrient limitations that worsen in summer, when water is absent. Nitrogen‐fixing legumes are likely to be able to switch between soil N and atmospheric N (N₂) sources to adjust the C costs of N acquisition in different seasons.
• We investigated the utilisation of different inorganic N sources by two indigenous shrubby legumes (Cytisus multiflorus and Cytisus scoparius). Plant performance in terms of photosynthesis and biomass production was also analysed. Plants were cultivated in sterile river sand supplied with Hoagland nutrient solution, grown in N‐free nutrient solution and inoculated with effective rhizobial strains from nodules of adult plants of the same species. A second treatment consisted of plants given 500 μm NH₄NO₃ added into the nutrient solution. In a third treatment, plants were watered with another source of N (500 μm NH₄NO₃) as well as being inoculated with effective rhizobial strains.
• The application of NH₄NO₃ to the legumes resulted in a larger increase in plant dry matter. Carbon construction costs were higher in plants supplied with mineral and symbiotic N sources and always higher in the endemic C. multiflorus. Differences in photosynthesis rates were only observed between species, regardless of the N source. Non‐fertilised inoculated plants had more effective root nodules and a clear dependence on N₂ fixation.
• We propose that the ability of C. scoparius to change N source makes it a plastic species, which would account for its broader distribution in nature.

     

土壤氮磷添加下豆科草本植物生物固氮与磷获取策略的权衡机制

豆科草本植物固氮是陆地生态系统重要的自然氮输入方式, 影响着草地生产的经济性和可持续性。为探讨氮磷交互作用影响豆科草本植物生物固氮率的潜在生理生态机制, 该研究选取8种豆科草本植物分别种植在对照、氮肥添加、磷肥添加和氮磷耦合添加处理的土壤中, 进行野外盆栽实验。测定了初花期植物生物量和营养含量、根部碳水化合物含量、根际pH、根际柠檬酸含量、根际有效磷含量、植物根瘤生物量、磷含量及其生物固氮率。主要结果: 依赖于豆科物种, 氮添加显著促进了豆科草本植物根际磷的活化, 降低了根生物量分配以及根系非结构性碳水化合物含量。在两种磷添加处理下, 氮添加导致8种豆科草本植物根瘤生物量平均下降27%-36%, 生物固氮率平均下降20%-33%。磷添加降低了根际的磷活化, 但促进了豆科草本植物根系发育和非结构性碳水化合物的积累。在施氮和不施氮条件下, 磷添加分别使8种豆科草本植物的生物固氮率提高了45%-69%和0-47%。氮添加降低豆科草本植物生物固氮率, 其原因是氮添加提高了植物磷需求, 为活化更多磷, 豆科草本植物降低根系生物量和根系非结构性碳水化合物的含量, 导致根瘤发育受到限制。在氮添加的同时进行磷添加, 能够改善土壤氮磷平衡, 促进根系生长和非结构性碳水化合物积累, 缓解了增氮对生物固氮的抑制作用。     

Fertilizers and biological nitrogen fixation as sources of plant nutrients: Perspectives for future agriculture

Biological nitrogen fixation (BNF) has an assured place in agriculture, mainly as a source of nitrogen for legumes. Legumes are currently grown mostly as a source of vegetable oil and as food for humans and animals, but not as nitrogen source.Other crops with BNF capability may be eventually be developed eventually. Such crops will also need mineral fertilizers to maintain a good status of soil nutrients, but their possible effects to the environment is also a concern. Fertilizers, however, will remain a necessary and sustainable input to agriculture to feed the present and increasing human population. It is not a case of whether BNF is better or worse than mineral fertilizers because both plays an important role in agriculture.     

Leaf nitrogen and phosphorus stoichiometry across 753 terrestrial plant species in China

Leaf nitrogen and phosphorus stoichiometry of Chinese terrestrial plants was studied based on a national data set including 753 species across the country. Geometric means were calculated for functional groups based on life form, phylogeny and photosynthetic pathway, as well as for all 753 species. The relationships between leaf N and P stoichiometric traits and latitude (and temperature) were analysed. The geometric means of leaf N, P, and N : P ratio for the 753 species were 18.6 and 1.21 mg g(-1) and 14.4, respectively. With increasing latitude (decreasing mean annual temperature, MAT), leaf N and P increased, but the N : P ratio did not show significant changes. Although patterns of leaf N, P and N : P ratios across the functional groups were generally consistent with those reported previously, the overall N : P ratio of China's flora was considerably higher than the global averages, probably caused by a greater shortage of soil P in China than elsewhere. The relationships between leaf N, P and N : P ratio and latitude (and MAT) also suggested the existence of broad biogeographical patterns of these leaf traits in Chinese flora.     

茯苓碳氮磷化学计量学特征

为探明茯苓的碳、氮、磷生态化学计量学特征,采集了云南省11个州、市42个居群的茯苓样本,分析了其菌核与表皮中碳(C)、氮(N)、磷(P)的化学计量特征.结果 表明:茯苓菌核中C、N、P的含量分别为40.24％-43.58％、0.176％-0.532％和0.020％-0.077％;C∶N、C∶P和N∶P的范围分别为93....     

松嫩草地80种草本植物叶片氮磷化学计量特征

以松嫩草地常见草本植物为研究对象, 分析了各生活型和功能群叶片氮磷化学计量特征。结果显示: 松嫩草地80种草本植物的叶片氮、磷质量浓度分别为(24.2 ± 0.96) mg·g ^-1和(2.0 ± 0.10) mg·g ^-1, 面积浓度分别为(13.0 ± 0.54) mg·cm ^-2和(1.0 ± 0.05) mg·cm ^-2, 氮磷比为13.0 ± 0.39, 氮磷比与叶片磷质量浓度、叶片氮、磷面积浓度有显著相关关系; 松嫩草地植物生长受到氮限制。一年生植物叶片氮、磷质量浓度和变异系数高于其他生活型, 各生活型之间氮面积浓度和氮磷比差异不显著。豆科植物叶片氮的质量浓度、面积浓度和氮磷比高于其他功能群。在不同生活型或功能群之间, 植物叶片磷的面积浓度差异不显著, 都在1.0 mg·cm ^-2左右; 适当地增加群落中豆科植物的比例, 可能有助于提高松嫩草地产量和质量。     

增温对苔原土壤和典型植物叶片碳、氮、磷化学计量学特征的影响

为探讨苔原植被对气候变暖的响应模式, 采用开顶箱增温法, 研究了3个生长季增温对长白山苔原3种代表植物——牛皮杜鹃(Rhododendron aureum)、笃斯越桔(Vaccinium uliginosum)和东亚仙女木(Dryas octopetala var. asiatica)的叶片及土壤碳(C)、氮(N)、磷(P)含量及其比值的影响。结果表明: 增温使土壤N和P的含量分别增加5.88%和4.83%, C含量降低13.19%; 增温和对照(不增温)条件下, 植物叶片的C、N、P含量及其比值在生长季有明显的变化。增温使笃斯越桔和东亚仙女木叶片的P含量分别增加10.34%和12.87%, 牛皮杜鹃则降低了16.26%, 增温并没有明显改变3种植物叶片的C、N含量, 但牛皮杜鹃和东亚仙女木叶片的C:N值在增温条件下呈现增加趋势。增温使土壤可利用的N、P含量增加。增温对3种植物的C:N值, 牛皮杜鹃、笃斯越桔的P含量, 以及东亚仙女木的C:P值都产生了显著的影响。结果表明增温增加了长白山苔原P元素对植物生长的限制, 且3种植物叶片的C、N、P化学计量学特性对增温的响应模式和尺度没有表现出一致性。     

土壤食细菌线虫与细菌的相互作用及其对N、P矿化生物固定的影响及机理

采用悉生微缩体系,研究了４０ｄ 培养期内不添加外源基质条件下食细菌线虫（Ｐｒｏｔｏｒｈａｂｄｔｉｓ ｓｐ．）和细菌（Ｐｓｅｕｄｏｍ ｏｎａｓｓｐ．）的相互作用及其对Ｎ、Ｐ转化的影响。在种植及不种植小麦的土壤中,发现接种线虫后细菌数量显著增加,非根标土壤细菌的增加量又比根际土明显。在种植小麦体系中,根际与非根际土壤线虫均比不种作物体系有增加趋势,其中根际土壤线虫种群的提高尤为显著。只加细菌处理中土壤Ｎ、Ｐ均无净矿化,相反培养前期出现轻微的生物固定。线虫的引入显著提高了土壤矿质Ｎ、微生物量Ｎ 和微生物量Ｐ的含量,但对土壤有效Ｐ影响很小。这表明线虫活动主要是促进了Ｎ的矿化,而Ｐ表现出较强的生物固定。文中还分析了线虫捕食对细菌的增殖作用以及线虫——细菌相互作用在Ｎ、Ｐ矿化和生物固定中的机理。     

Biological nitrogen fixation in mixed legume-cereal cropping systems

Cereal/legume intercropping increases dry matter production and grain yield more than their monocultures. When fertilizer N is limited, biological nitrogen fixation (BNF) is the major source of N in legume-cereal mixed cropping systems. The soil N use patterns of component crops depend on the N source and legume species. Nitrogen transfer from legume to cereal increases the cropping system's yield and efficiency of N use. The use of nitrate-tolerant legumes, whose BNF is thought to be little affected by application of combined N, may increase the quantity of N available for the cereal component. The distance between the cereal and legume root systems is important because N is transferred through the intermingling of root systems. Consequently, the most effective planting distance varies with type of legume and cereal. Mutual shading by component crops, especially the taller cereals, reduces BNF and yield of the associated legume. Light interception by the legume can be improved by selecting a suitable plant type and architecture. Planting pattern and population at which maximum yield is achieved also vary among component species and environments. Crops can be mixed in different proportions from additive to replacement or substitution mixtures. At an ideal population ratio a semi-additive mixture may produce higher gross returns.     

Growth and nitrogen acquisition strategies of Acacia senegal seedlings under exponential phosphorus additions

There remains conflicting evidence on the relationship between P supply and biological N₂-fixation rates, particularly N₂-fixing plant adaptive strategies under P limitation. This is important, as edaphic conditions inherent to many economically and ecologically important semi-arid leguminous tree species, such as Acacia senegal, are P deficient. Our research objective was to verify N acquisition strategies under phosphorus limitations using isotopic techniques. Acacia senegal var. senegal was cultivated in sand culture with three levels of exponentially supplied phosphorus [low (200 μmol of P seedling⁻¹ over 12 weeks), mid (400 μmol) and high (600 μmol)] to achieve steady-state nutrition over the growth period. Uniform additions of N were also supplied. Plant growth and nutrition were evaluated. Seedlings exhibited significantly greater total biomass under high P supply compared to low P supply. Both P and N content significantly increased with increasing P supply. Similarly, N derived from solution increased with elevated P availability. However, both the number of nodules and the N derived from atmosphere, determined by the ¹⁵N natural abundance method, did not increase along the P gradient. Phosphorus stimulated growth and increased mineral N uptake from solution without affecting the amount of N derived from the atmosphere. We conclude that, under non-limiting N conditions, A. senegal N acquisition strategies change with P supply, with less reliance on N₂-fixation when the rhizosphere achieves a sufficient N uptake zone.     

Effects of nitrogen: phosphorus supply ratios on nitrogen fixation in agricultural and pastoral ecosystems

An analysis of data compiled from the literature confirms a strong inverse relationship between annual rates of nitrogen fixation and the soil nitrogen content in agricultural and pastoral ecosystems. However, this inverse relationship is strongly modified by the rate of application of phosphorus fertilizer, which strongly influences the activities of both symbiotic and non-symbiotic nitrogen fixing organisms. In the case of symbiotic legumes, the response of N-fixation to N and P is in part a result of changes in legume dominance within the plant community. These results, as well as supporting data presented from a review of experiments on nitrogen fixation in a variety of other terrestrial and aquatic ecosystems, provide important support for the hypothesis that phosphorus availability is a key regulator of nitrogen biogeochemistry. Published as Paper No. 9950, Journal Series, Nebraska Agricultural Research Division, University of Nebraska, Lincoln, NE, USA.     

高寒草甸植物化学计量比对磷添加的分层响应

为了探明氮(N)限制的植物群落中物种水平和功能群水平的碳(C)、N、磷(P)含量以及C:N:P对P添加的响应是否一致,明确P添加对群落物种构成改变的内在机制。以青藏高原高寒草甸为研究对象, 通过P添加试验, 研究了功能群水平和物种水平生态化学计量比对P添加的响应, 以及P添加对物种水平的优势度和功能群水平生物量的影响。结果表明: 在青藏高原高寒草甸连续5年添加P显著改变了植物的C、N、P含量以及C:N:P, 且在物种水平和功能群水平(不含典型物种)的响应规律基本一致。在禾本科、莎草科和杂类草功能群(不含典型物种)和相应物种水平上P添加对C含量影响不显著。P添加显著增加了禾本科、莎草科、豆科和杂类草4个功能群(不含典型物种)和相应物种水平的植物P含量, 降低了C:P和N:P。禾本科和莎草科的N含量和C:N对P添加在物种水平和功能群水平上(不含典型物种)的响应规律一致, 表现为N含量显著降低, C:N显著增加; P添加使豆科物种水平上N含量显著增加而C:N显著降低, 但在功能群水平上(不含典型物种)无显著作用; 杂类草的N含量和C:N对P添加在物种水平和功能群水平上(不含典型物种)的响应规律均不一致。在N限制的生境中添加P, 禾本科物种在群落中逐渐占据优势跟其增高的N、P利用效率相关, 而杂类草由于逐渐降低的N和P利用效率使其生物量在群落中所占的比重逐渐下降。     

Improvement of biological nitrogen fixation in Egyptian winter legumes through better management of Rhizobium

The diversity of rhizobia nodulating common bean ( Phaseolus vulgaris), berseem clover (Trifolium alexanderinum) and lentil (Lens culinaris) was assessed using several characterization techniques, including nitrogen fixation efficiency, intrinsic antibiotic-resistance patterns (IAR), plasmid profiles, serological markers and rep-PCR fingerprinting. Wide diversity among indigenous rhizobial populations of the isolates from lentil, bean and clover was found. Strikingly, a large percentage of the indigenous rhizobial population was extremely poor at fixing nitrogen. This emphasizes the need to increase the balance of highly efficient strains within the rhizobial population. Use of high-quality inocula strains that survive and compete with other less-desired and less-efficient N2-fixing rhizobia represents the best approach to increase biological nitrogen fixation of the target legume. In field-grown lentils, the inoculant strains were not able to outcompete the indigenous rhizobia and the native lentil rhizobia occupied 76–88% of the total nodules formed on inoculated plants. Nitrogen fixation by lentils, estimated using the ¹⁵N isotope dilution technique, ranged between 127 to 139 kg ha-1 in both inoculated and un-inoculated plants. With berseem clover, the inoculant strains were highly competitive against indigenous rhizobia and occupied 52–79% of all nodules. Inoculation with selected inocula improved N2 fixation by clover from 162 to 205 kg ha-1 in the three cuts as compared with 118 kg ha-1 in the un-inoculated treatment. The results also indicated the potential for improvement of N2 fixation by beans through the application of efficient N2-fixing rhizobia.