Mineral nutrition of plants: a short history of plant physiology.

The development of the knowledge on the mineral nutrition of plants begins between the 17th and 18th centuries when some European naturalists gave the first experimental evidences of what had been empirically known for about two millennia. The works of Hales and Ingenhousz were of absolute importance in relation to the transport of water and solutes, and assimilation of "fixed air" (carbon dioxide), respectively. The early chemistry introduced by Lavoisier benefited the first physiologists Senebier and De Saussure to reject the "theory of humus", which imposed the soil as the unique source of carbon. During the first half of the 19th century, Sprengel and Liebig investigated on the problems related to some indispensable mineral salts, while Boussingault and Ville attempted to prove the nitrogen fixation from air without giving any convincing evidence. Liebig was the pioneer of the agricultural chemistry: he epitomised the knowledge of that period by imposing the so-called "law of the minima", already acknowledged by Sprengel, and patronised the use of mineral fertilisers in Europe by devising several formulas of mineral manure. He, however, did not recognise the needs of external supplies of nitrogen salts for the crops, in open dispute with the English school of Lawes and Gilbert, who were instead convinced assertors of such needs. At the end of the 19th century Hellriegel showed that leguminous plants presenting peculiar nodules on their roots could really fix the gaseous nitrogen. From these nodules Beijerinck and Prazmowski isolated for the first time some bacteria which were recognised as the real agents fixing nitrogen. This discovery was of fundamental importance for plant nutrition, only second to the discovery of photosynthesis. Another basic contribution came from early research of Sachs on plants grown on aqueous solutions: these techniques allowed to impose the concept of "essential elements", which was fixed as a principle by Arnon and Stout in 1939. This principle benefited further research concerning the effects of states of deficiency on plant growth and development through investigation on the anatomical, histologic and biochemical nutritional disorders of plants.     

Stephen Hales: neglected respiratory physiologist

Stephen Hales was an eminent early 18th century scientist and minister of the parish of Teddington near London. He is well known for his early work on blood pressure. However, he made many contributions to respiratory physiology. He clarified the nature of the respiratory gases, distinguishing between their free (gaseous) and fixed (chemically combined) forms, demonstrated that rebreathing from a closed circuit could be extended if suitable gas absorbers were included (to remove carbon dioxide), suggested a similar device as a respirator for noxious atmospheres, invented the pneumatic trough for collecting gases, measured the size of the alveoli, calculated the surface area of the interior of the lung, calculated the time spent by the blood in a pulmonary capillary, invented the U-tube manometer, and measured intrathoracic pressures during normal and forced breathing. Hale's work is remarkable for its emphasis on the "statical" method, i.e., meticulous attention to detail in measurement and careful calculations. In his later life he made important contributions in the area of public health. He was a trustee of the new colony of Georgia and willed his own library of books to the colony though their whereabouts is unknown. He deserves more recognition in the history of respiratory physiology.     

Ternary effects on the gas exchange of isotopologues of carbon dioxide

The ternary effects of transpiration rate on the rate of assimilation of carbon dioxide through stomata, and on the calculation of the intercellular concentration of carbon dioxide, are now included in standard gas exchange studies. However, the equations for carbon isotope discrimination and for the exchange of oxygen isotopologues of carbon dioxide ignore ternary effects. Here we introduce equations to take them into account. The ternary effect is greatest when the leaf-to-air vapour mole fraction difference is greatest, and its impact is greatest on parameters derived by difference, such as the mesophyll resistance to CO(2) assimilation, r(m) . We show that the mesophyll resistance to CO(2) assimilation has been underestimated in the past. The impact is also large when there is a large difference in isotopic composition between the CO(2) inside the leaf and that in the air. We show that this partially reconciles estimates of the oxygen isotopic composition of CO(2) in the chloroplast and mitochondria in the light and in the dark, with values close to equilibrium with the estimated oxygen isotopic composition of water at the sites of evaporation within the leaf.     

A re-examination of the problem of photochemical nitrogen reduction by blue-green algae

Summary Although it was possible in the light in the absence of carbon dioxide to obtain a ratio of nitrogen fixed to oxygen evolved in nitrogen-starved cells of A. cylindrica near to 1:1.5, that quoted by other workers, ratios varying between 1:0.9 and 1:3.0 were also obtained. The amount of oxygen evolved under the same conditions by normal cells in the presence of pyruvate was increased considerably. Since the addition of pyruvate also resulted in increased carbon dioxide output in the dark with the same algal material, oxygen output in the light was attributed to the production of factors necessary for carbon assimilation.Addition of pyruvate to nitrogen-starved and normal cells in the light resulted in similar rates of oxygen evolution after an initially higher rate in the starved cells. The ratio of overall nitrogen fixed to oxygen evolved, was 1:6.6 for the starved cells and 1:6.4 for the normal cells, showing that the presence of an added substrate increased oxygen output relative to nitrogen uptake. ¹⁴CO₂ was recovered from sodium pyruvate-1-¹⁴C in flasks incubated in the dark, showing that, at least in the dark, pyruvate was decarboxylated.The interpretation of these results is that endogenous and exogenous substrates available to cells of A. cylindrica become decarboxylated and that, in the light, carbon dioxide produced may be assimilated photochemically with accompanying oxygen evolution. This interpretation has been discussed in relation to reports of photochemical nitrogen reduction in blue-green algae.     

Effects of oxygen,carbon dioxide,and nitrogen on hatching behavior and hatching time in the katydid,Eobiana engelhardti subtropica Bey-Bienko (Orthoptera: Tettigoniidae)

The trigger for the hatching behavior and determination of hatching time of the katydids, Eobiana engelhardti subtropica (Orthoptera: Tettigoniidae) have been shown to be influenced by light–dark signals or temperature. In this study, I investigated the effects of oxygen, carbon dioxide, and nitrogen on the hatching behavior and hatching time of the katydid. Eggs rarely hatched under a constant temperature of 25°C and hatched sporadically at a constant temperature of 15°C under continuous light in the air. However, when eggs were exposed to 100% oxygen or a mixture of oxygen and nitrogen (2:1 or 1:1), hatching occurred within a few seconds. Hatching behavior was directly triggered by high concentrations of oxygen. It was inhibited by exposure to 100% carbon dioxide, 100% nitrogen, or a mixture of oxygen and nitrogen (1:2). The hatching time, determined by the temperature fall (transfer from 25°C to 15°C), was delayed by these gases, and was reset by the transfer back of eggs to the air. This suggests the existence of a time-measuring mechanism that is triggered by the transfer of eggs to the air. These results, indicating that hatching behavior was directly triggered by high concentrations of oxygen and that hatching time was set by the transfer from carbon dioxide or nitrogen to the air, are new findings to the best of my knowledge.     

Temporality, sequential iconography and linearity in figures: the impact of the discovery of division in infusoria

The paper analyses the impact of the discovery of the division of infusoria on eighteenth century microscopical iconography. In Autumn 1765, when reproducing the antispontaneist experiments of Lazzaro Spallanzani, Horace-Bénédict de Saussure (1740-1799) discovered a new method of generation of the animalcules of the infusions, namely their division. Drawing a dividing animalcule raised particular problems, notably the question of how to depict the time sequence of a microscopical creature. Although Saussure's journal of microscopical experiments remained unpublished, the discovery was soon diffused and acknowledged by the European naturalists who began to repeat the observations and quickly faced iconographic problems similar to those experienced by Saussure. Indeed, linearity, used to picture time, is a construction, and, notably for public images, scholars had to contend with the conventions of drawers and engravers. The analysis of microscopical iconographic material of the period 1740-1786 shows that during this period, certain naturalists invented new solutions for depicting time, but diffusion of their innovations was not immediate. Nevertheless, in regards to the illustration of microscopical creatures, it is between 1765 and 1776 that the use of linearity was established as a solution enabling an audience to read an iconographic time process as a text.     

Oxygen and carbon dioxide fluxes from barley shoots depend on nitrate assimilation

A custom oxygen analyzer in conjunction with an infrared carbon dioxide analyzer and humidity sensors permitted simultaneous measurements of oxygen, carbon dioxide, and water vapor fluxes from the shoots of intact barley plants (Hordeum vulgare L. cv Steptoe). The oxygen analyzer is based on a calciazirconium sensor and can resolve concentration differences to within 2 microliters per liter against the normal background of 210,000 microliters per liter. In wild-type plants receiving ammonium as their sole nitrogen source or in nitrate reductase-deficient mutants, photosynthetic and respiratory fluxes of oxygen equaled those of carbon dioxide. By contrast, wild-type plants exposed to nitrate had unequal oxygen and carbon dioxide fluxes: oxygen evolution at high light exceeded carbon dioxide consumption by 26% and carbon dioxide evolution in the dark exceeded oxygen consumption by 25%. These results indicate that a substantial portion of photosynthetic electron transport or respiration generates reductant for nitrate assimilation rather than for carbon fixation or mitochondrial electron transport.     

Underwater photosynthesis in flooded terrestrial plants: a matter of leaf plasticity

BACKGROUND: Flooding causes substantial stress for terrestrial plants, particularly if the floodwater completely submerges the shoot. The main problems during submergence are shortage of oxygen due to the slow diffusion rates of gases in water, and depletion of carbohydrates, which is the substrate for respiration. These two factors together lead to loss of biomass and eventually death of the submerged plants. Although conditions under water are unfavourable with respect to light and carbon dioxide supply, photosynthesis may provide both oxygen and carbohydrates, resulting in continuation of aerobic respiration. SCOPE: This review focuses on evidence in the literature that photosynthesis contributes to survival of terrestrial plants during complete submergence. Furthermore, we discuss relevant morphological and physiological responses of the shoot of terrestrial plant species that enable the positive effects of light on underwater plant performance. CONCLUSIONS: Light increases the survival of terrestrial plants under water, indicating that photosynthesis commonly occurs under these submerged conditions. Such underwater photosynthesis increases both internal oxygen concentrations and carbohydrate contents, compared with plants submerged in the dark, and thereby alleviates the adverse effects of flooding. Additionally, several terrestrial species show high plasticity with respect to their leaf development. In a number of species, leaf morphology changes in response to submergence, probably to facilitate underwater gas exchange. Such increased gas exchange may result in higher assimilation rates, and lower carbon dioxide compensation points under water, which is particularly important at the low carbon dioxide concentrations observed in the field. As a result of higher internal carbon dioxide concentrations in submergence-acclimated plants, underwater photorespiration rates are expected to be lower than in non-acclimated plants. Furthermore, the regulatory mechanisms that induce the switch from terrestrial to submergence-acclimated leaves may be controlled by the same pathways as described for heterophyllous aquatic plants.     

Use of "complementary methods" for experimental animal studies of digestion in the 18th and 19th centuries

The use of complementary methods to animal experiments is very old. Spallanzani (1785) apparently was the first who used such methods in his studies on digestion. In the 19th century Eberle, Pappenheim, Purkyné and others used on their studies on the process of digestion artificial chyme. On this view, Beaumont published in 1834 an interesting paper on the digestion of men after observations in vivo and parallel in vitro. All papers show, that the using of complementary methods to animal experiments was not unusual in the 19th century.     

The Effect of Storage in Various Gaseous Atmospheres on the Microflora of Lamb Chops Held at—1°C

The effect of different gaseous atmospheres on the development of the bacterial flora on lamb chops stored at –1°C was examined. The atmospheres were air, nitrogen, hydrogen, and mixtures of air + carbon dioxide, oxygen + nitrogen, oxygen + carbon dioxide, nitrogen + carbon dioxide and hydrogen + carbon dioxide (gas ratio = 80:20, v/v). Storage life of chops ranged from two weeks in air to eight weeks in oxygen-free atmospheres. At the end of storage life Microbacterium thermosphactum was present as a major constituent of the bacterial flora in all atmospheres. In oxygen + carbon dioxide it was the predominant organism. In all other oxygen containing atmospheres, Pseudomonas spp. made up a large proportion of the flora. Strains of Enterobacteriaceae occurred in low-oxygen and oxygen-free atmospheres, and Lactobacillus spp. occurred in oxygen-free atmospheres.     

Early Modern Experimentation on Live Animals

Starting from the works by Aselli (De lactibus sive lacteis venis, 1627) on the milky veins and Harvey (1628, translated in 1993) on the motion of the heart and the circulation of the blood, the practice of vivisection witnessed a resurgence in the early modern period. I discuss some of the most notable cases in the century spanning from Aselli’s work to the investigations of fluid pressure in plants and animals by Stephen Hales (Vegetable Staticks, 1727). Key figures in my study include Johannes Walaeus, Jean Pecquet, Marcello Malpighi, Reinier de Graaf, Richard Lower, Anton Nuck, and Anton de Heide. Although vivisection dates from antiquity, early modern experimenters expanded the range of practices and epistemic motivations associated with it, displaying considerable technical skills and methodological awareness about the problems associated with the animals being alive and the issue of generalizing results to humans. Many practitioners expressed great discomfort at the suffering of the animals; however, many remained convinced that their investigations were not only indispensable from an epistemic standpoint but also had potential medical applications. Early modern vivisection experiments were both extensive and sophisticated and cannot be ignored in the literature of early modern experimentation or of experimentation on living organisms across time.     

Oxygen effect on lactose catabolism by a Leuconostoc mesenteroides strain: modeling of general O2-dependent stoichiometry

Lactose metabolism of a Leuconostoc mesenteroides strain was studied in batch cultures at a pH of 6.5 and 30 degrees C in 10 L of a modified MRS (De Man, Rogosa, Sharp) broth. The end products of this heterolactic bacterium were D-lactate, acetate, ethanol, and carbon dioxide. To test the effect of oxygen on their synthesis, the medium was sparged with different gases: nitrogen, air, and pure oxygen. When oxygen was available, oxygen uptake occurred, which caused a modification in acetate and ethanol production but not in lactate or carbon dioxide production; acetate plus ethanol together were produced in constant amounts, which were independent of the level of aeration. The influence of oxygen on end-product formation could be summed up by the general equation: lactose + x O(2) --> 2 D-lactate + (x + 0.1) acetate + (2 - x) ethanol + 2 CO(2). Maximal oxygen uptake (x = 2) was reached under a 120 L/h flow rate of pure oxygen. In addition, this equation provided useful information on the possible pathway of galactose catabolism by a heterofermentative microorganism. (c) 1996 John Wiley & Sons, Inc.     

Oxidation of methane in the absence of oxygen in lake water samples.

Methane was oxidized to carbon dioxide in the absence of oxygen by water samples from Lake Mendota, Madison, Wis. The anaerobic oxidation of methane did not result in the assimilation of carbon from methane into material precipitable by cold 10% trichloracetic acid. Only samples taken at the suface of the sediment of Lake Mendota were capable of catalyzine the anaerobic oxidation of methane. The rate of methane oxidation in the presence of oxygen was highest in samples taken from near the thermocline. Of the radioactive methane oxidized, 30 to 60% was assimilated into material precipitable by cold 10% trichloroacetic acid during aerobic incubation of the samples. These data support the conclusion that two distinct groups of methane-oxidizing organisms occur in stratifield lakes. Enrichments with acetate and methane as the sole sources of carbon and energy and sulfate as the electron acceptor resulted in the growth of bacteria that oxidize methane. Sulfate, acetate, and methane were all required for growth of enrichments. Acetate was not oxidized to carbon dioxide but was assimilated by cells. Methane was not assimilated but was oxidized to carbon dioxide in the absence of air.     

O3浓度升高对植物活性氧代谢系统影响的研究进展

为了揭示臭氧（O3）浓度升高对植物活性氧代谢系统的影响机理,从代谢生理角度,总结了近年来国内外关于臭氧浓度升高对植物活性氧自由基代谢速率、细胞膜脂过氧化程度、抗氧化系统及生物量和产量影响的研究进展,同时,就臭氧浓度升高与二氧化碳浓度升高的复合作用对植物活性氧代谢系统的影响,及阐明二者相互作用对植物抗氧化系统影响机理的研究进行了综述。在此基础上指出在未来研究中,要在分子水平上进一步深入研究植物活性氧代谢系统对高浓度臭氧、二氧化碳复合作用的响应机理,并应加强高浓度二氧化碳对臭氧胁迫下植物抗氧化系统影响的研究,为解决如何减轻臭氧浓度升高对植物造成的氧化伤害提供基础理论依据。     

Oxidation of methane in the absence of oxygen in lake water samples.

Methane was oxidized to carbon dioxide in the absence of oxygen by water samples from Lake Mendota, Madison, Wis. The anaerobic oxidation of methane did not result in the assimilation of carbon from methane into material precipitable by cold 10% trichloracetic acid. Only samples taken at the suface of the sediment of Lake Mendota were capable of catalyzine the anaerobic oxidation of methane. The rate of methane oxidation in the presence of oxygen was highest in samples taken from near the thermocline. Of the radioactive methane oxidized, 30 to 60% was assimilated into material precipitable by cold 10% trichloroacetic acid during aerobic incubation of the samples. These data support the conclusion that two distinct groups of methane-oxidizing organisms occur in stratifield lakes. Enrichments with acetate and methane as the sole sources of carbon and energy and sulfate as the electron acceptor resulted in the growth of bacteria that oxidize methane. Sulfate, acetate, and methane were all required for growth of enrichments. Acetate was not oxidized to carbon dioxide but was assimilated by cells. Methane was not assimilated but was oxidized to carbon dioxide in the absence of air.     

Effect of free-radical and oxygen scavengers on photochemically generated oxygen toxicity and on the aerotolerance of Campylobacter jejuni

Exposure of a nutrient agar medium to the combined action of fluorescent light and air produced toxic factors in the medium which affected the growth of Campylobacter jejuni. Sodium dithionite (5-10 mM), a powerful reducing agent, and catalase were effective in counteracting the injurious action of light and air. Among the quenchers of singlet oxygen tested, only histidine had a beneficial effect on the recovery of C. jejuni in the photo-oxidized medium, while the addition of superoxide dismutase, a hydroxyl radical scavenger such as cysteamine, or the free radical antioxidants tocopherol and butylated hydroxy toluene, did not increase the recovery rate of photochemically injured cells. Histidine (40 mM) and dithionite (5-10 mM) also assisted recovery of C. jejuni inoculated on nutrient agar stored in air in the dark. Cysteamine and dithionite were toxic to Campylobacter when added at concentrations of greater than or equal to 10 mM and greater than or equal to 20 mM, respectively. A high inoculum of C. jejuni could not be recovered in unsupplemented nutrient agar incubated in air but was recovered in atmospheres containing 17 or 21% oxygen plus 10% carbon dioxide. The addition of dithionite, catalase or histidine resulted some colony formation on nutrient agar incubated in air. Among the scavengers tested, only dithionite was consistently able to maintain the viability of C. jejuni on nutrient agar stored in air for longer than 4 weeks. In view of the ability of catalase, dithionite and histidine to enhance the aerotolerance of C. jejuni, it is concluded that various oxygen species might be involved in the toxicity of high levels of oxygen.     

From Lithium‐Oxygen to Lithium‐Air Batteries: Challenges and Opportunities

Lithium ‐ air batteries have become a focus of research on future battery technologies. Technical issues associated with lithium‐air batteries, however, are rather complex. Apart from the sluggish oxygen reaction kinetics which demand efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts, issues are also inherited from the nature of an open battery system and the use of reactive metal lithium as anode. Lithium‐air batteries, which exchange oxygen directly with ambient air, face more challenges due to the additional oxidative agents of moisture, carbon dioxide, etc. which degrade the metal lithium anode, deteriorating the performance of the batteries. In order to improve the cycling performance one must hold a full picture of lithium‐oxygen electrochemistry in the presence of carbon dioxide and/or moisture and fully understand the fundamentals of chemistry reactions therein. Recent advances in the exploration of the effect of moisture and CO₂ contaminants on Li‐O₂ batteries are reviewed, and the mechanistic understanding of discharge/charge process in O₂ at controlled level of moisture and/or CO₂ are illustrated. Prospects for development opportunities of Li‐air batteries, insight into future research directions, and guidelines for the further development of rechargeable Li‐air batteries are also given.     

祁连山东段高原鼢鼠采食洞道气体研究

研究高原鼢鼠（Myospalax baileyi）洞道气体环境对了解其低氧适应机制具有重要作用。本试验在祁连山东段高寒草甸利用土壤原位气体测定仪,对高原鼢鼠采食活动洞道、非活动洞道、地表空气及无洞道土壤内的温度、氧气、二氧化碳、甲烷含量进行了连续12个月的监测。通过One-Way ANOVA检验、重复测量方差分析以及Pearson相关性分析发现,（1）高原鼢鼠活动洞道氧气含量,除10月、11月与非活动洞道无显著性差异外（P>0.05）,均显著小于非活动洞道、地表空气和无洞道土壤（P<0.05）;活动洞道二氧化碳含量,除7月、8月份与非活动洞道无显著性差异外（P>0.05）,均显著大于非活动洞道、地表空气和无洞道土壤（P<0.05）;活动洞道内甲烷含量各月均显著高于地表空气甲烷含量（P<0.05）,与非活动洞道、无洞道土壤的月季差异各异。（2）高原鼢鼠活动洞道内氧气含量的最小值和二氧化碳的最大值均出现在5月和9月,其它处理下氧气最小值和二氧化碳最大值均出现在6-8月;4个处理下甲烷含量最小值在1月与12月出现,最大值出现在5月和9月。（3）月份、处理以及月份和处理间的交互作用均对氧气、二氧化碳、甲烷含量有显著影响（P<0.05）。可见,高原鼢鼠生存在低氧、高二氧化碳和较高甲烷含量的环境中,且洞道内部的气体环境会受季节和高原鼢鼠活动的影响。