Entropy of radiation in biology.

The concept of the entropy of electromagnetic radiation and the relationship between entropy and probability for radiation fields are explained. Equations for the variations of entropy and temperature in the reversible and irreversible volume changes of black radiation fields are given. Following Boltzmann and Schrödinger, it is pointed out that living matter, e.g., in a stationary state, struggles for the chance of acquiring the needed free energy by converting low-entropy solar energy radiation into high-entropy terrestrial energy radiation. The amount of energy available from a Carnot process with utilization of high-temperature (low-entropy) radiation and the influence of radiation scattering are computed. The considerations are applied to photosynthesis. Technically useful amounts of hydrogen could in principle be obtained through water photolysis by means of artificial, simulated, photosynthesis. For the purpose, the membrane principle has central importance, i.e., by means of asymmetric, vectorial, membranes separation of the primary products of photolysis is sought.     

Minimum entropy production in photosynthesis

In this paper a flux-coupling model of photosynthesis is presented. By requiring minimum entropy production, it is found that the photosynthetic efficiency is essentially given by the square root of D/λ. D and λ are the diffusion coefficient and thermal conductivity of the rate-limiting processes in the chloroplast, respectively. For experimental values of D and λ, the efficiency is found to be 2.4–7.5%, with a likely value of 6.1%, whereas C4-plants are known to have an efficiency of 6.2%. We conclude that the process of photosynthesis is in quantitative agreement with the principle of minimum entropy production.     

On the measurement of shear elastic moduli and viscosities of erythrocyte plasma membranes by transient deformation in high frequency electric fields.

We present a new method to measure the shear elastic moduli and viscosities of erythrocyte membranes which is based on the fixation and transient deformation of cells in a high-frequency electric field. A frequency domain of constant force (arising by Maxwell Wagner polarization) is selected to minimize dissipative effects. The electric force is thus calculated by electrostatic principles by considering the cell as a conducting body in a dielectric fluid and neglecting membrane polarization effects. The elongation A of the cells perpendicular to their rotational axis exhibits a linear regime (A proportional to Maxwell tension or to square of the electric field E2) at small, and a nonlinear regime (A proportional to square root of Maxwell tension or to the electric field E) at large extensions with a cross-over at A approximately 0.5 micron. The nonlinearity leads to amplitude-dependent response times and to differences of the viscoelastic response and relaxation functions. The cells exhibit pronounced yet completely reversible tip formations at large extensions. Absolute values of the shear elastic modulus, mu, and membrane viscosity, eta, are determined by assuming that field-induced stretching of the biconcave cell may be approximately described in terms of a sphere to ellipsoid deformation. The (nonlinear) elongation-vs.-force relationship calculated by the elastic theory of shells agress well with the experimentally observed curves and the values of mu = 6.1 x 10(-6) N/m and eta = 3.4 x 10(-7) Ns/m are in good agreement with the micropipette results of Evans and co-workers. The effect of physical, biochemical, and disease-induced structural changes on the viscoelastic parameters is studied. The variability of mu and eta of a cell population of a healthy donor is +/- 45%, which is mainly due to differences in the cell age. The average mu value of cells of different healthy donors scatters by +/- 18%. Osmotic deflation of the cells leads to a fivefold increase of mu and 10-fold increase of eta at 500 mosm. The shear modulus mu increases with temperature showing that the cytoskeleton does not behave as a network of entropy elastic springs. Elliptic cells of patients suffering from elliptocytosis of the Leach phenotype exhibit a threefold larger value of mu than normal discocytes of control donors. Cross-linking of the spectrin by the divalent S-H agents diamide (1 mM, 15 min incubation) leads to an eightfold increase of mu whereas eta is essentially constant. The effect of diamide is reversed after treatment with S-S bond splitting agents.     

杉木人工林单叶至冠层光合作用的扩展与模拟研究

根据野外条件下杉木（Ｃｕｎｎｉｎｇｈａｍｉａ ｌａｎｃｅｏｌａｔａ（Ｌａｍｂ．）Ｈｏｏｋ．）针叶光合作用的测定结果。考虑到光合作用对光的非线性响应特性,及其与叶所处的实际冠层环境变量和冠层的空气动力学特性的相关,以筒化的林冠辐射传输模型为基础,结合不同部位和年龄针叶的光响应曲线,实现了叶室测量结果向冠层环境的调整,并进行了冠层光合作用模拟的初步研究。经过调整后的冠层光合作用平均比未经过调整的值高１     

Long-wave limit of visual reception

It is shown that the community of the eyesight red boundary and photosynthesis in plant processes is defined by the upper level of the sun energy flux density near the Earth. The entropy production rate in relation to irreversible processes of the eyesight is calculated.     

Plant transpiration and net entropy exchange on the Earth’s surface in a Czech watershed

The influence of plant transpiration on the entropy exchange was quantified as associated with the degradation of solar energy on the Earth’s surface covered by plants. Two surfaces were studied: (1) productive surface — plant transpiration taken as equal to the potential one, (2) non-productive surface — plant transpiration taken as equal to zero. The entropy exchanges associated with the absorption of solar radiation and with the conversion of absorbed solar radiation into the sensible heat and latent heat were taken into account. These processes were examined in the experimental watershed Liz (828–1074 m a.s.l.) located in the Bohemian Forest (Czech Republic). We found that in the growing season 1992 the net entropy exchange in humid hydrologic period (the Earth’s surface is productive) was considerably higher than in the arid one (the Earth’s surface was productive in 39% of days, and non-productive in 61% of days). Considering that the biotic effect on the Earth’s functioning can be measured with the help of the net entropy exchange, we can assume that the theory that biotic activities — represented by plant transpiration here — are the cause of the self-organizing processes in Earth’s environment is proved in the watershed scale. Presented at the International Conference on Bioclimatology and Natural Hazards, Poľana nad Detvou, Slovakia, 17–20 September 2007.     

金钟藤叶片的气体交换特性

用LI-6400便携式光合测定系统(Li-CorInc.,USA)对广州林区新发现的入侵杂草金钟藤(Merremiaboisiana)叶片的气体交换进行了测定。结果表明(1)净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(E)的日变化均表现为单峰型曲线,中午金钟藤未出现光合作用抑制;最大光合速率可达20μmolCO2.m-2.s-1左右,Pn日平均值为8.8±0.75μmolCO2.m-2.s-1。(2)金钟藤光合作用的光饱和点较高,为1000~1200μmolphotons.m-2.s-1,表现出比较典型的阳生植物的特性。结果表明,金钟藤在自然环境中具有快速生长的特性可能与其较强和较稳定的光合能力有关。研究的初步结果对了解金钟藤迅速生长、具有高生产力和强大入侵力的原因提供了进一步深入探讨的思路和基础数据。     

Effects of ultraviolet-C radiation on net photosynthesis, transpiration and dark respiration of Spathiphyllum wallisii

Electric arc welding was suspected to have damaged about 25000 potted Spathiphyllum wallisii plants in a commercial greenhouse. Therefore, the effects of UV-C radiation, phytotoxic gases and smoke particles on some basic physiological processes and on growth of Spathiphyllum plants were investigated in a controlled environment. The phytotoxic gases (NO, NO₂, O₃), separately and in combination, were harmless at exposure concentrations (2 mg m⁻³) well above incident levels, for several hours. The smoke particles, mainly ZnO, Fe₂O₃ and MnO, did not disturb the root environment and plant growth, even at 25 g m⁻², which is approximately 400 times the calculated dose after the adverse incident. UV-C radiation from electric welding significantly reduced photosynthesis and transpiration shortly after exposure at 1 m (80 μW cm⁻² nm⁻¹ at 254 nm), while dark respiration was significantly increased. Effects at 3 m were less pronounced. The effect persisted for 2–4 days, after which recovery was complete. Further experiments with continuous measurement of gas exchange in whole plants confirmed that short-term UV-C radiation (Philips 30W germicidal tubes) dramatically affects photosynthesis, dark respiration and transpiration. Plants irradiated with more than 10 μW cm⁻² nm⁻¹ at 254 nm did not recover completely within the week of the experiments. The immediate effects of UV-C on photosynthesis is caused by stomatal closure. However, most effects are transient, and electric are welding does not appear to have caused the investigated damage.     

UV-B辐射增强和CO2浓度倍增的复合作用对番茄生长和果实品质的影响

以番茄（Lycopersicon esculeutum）为研究对象,在人工模拟8.40 kJ·m^-2的UV-B辐射和700 μmol·mol^-1的CO₂浓度复合处理下,研究了番茄的生长和果实品质变化.结果表明,UV-B辐射使番茄的株高、鲜重、干重、总叶绿素、叶绿素a、叶绿素b、光合速率、水分利用效率、可溶性蛋白、维生素c及番茄红素等降低,导致果实品质恶化;而CO₂浓度倍增作用相反.在UV-B辐射增强和CO₂浓度倍增复合作用下,番茄的上述指标与对照相比差异不明显.分析认为,CO₂倍增与UV-B辐射增强复合处理下,CO₂的正效应作用可以减轻甚至抵消UV-B辐射的负效应.     

美国黑核桃实生苗单叶片光合作用生理生态模型的建立与验证

在对叶片光合过程机理分析的基础上,结合数学分析方法,建立了模拟美国黑核桃单叶片光合作用的机理模型,该模型包含了叶片光合作用的限速的生化过程和气孔调节因素,对光合作用一气孔导度的耦合模型进行了简化,使之既便于应用,又能较准确地反映田间条件下的情况,并就光合作用对环境因子(太阳辐射、温度及CO2浓度等）变化的响应特征及响应的合理性进行了分析,使用整个生长季实测的叶片生理数据及生态环境数据对所建模型进行了验证,结果表明,模型可以较准确地模拟田间美国黑核桃叶片的光合速率;确定了美国东部黑核桃、北加州黑核桃等两种黑核桃单叶片光合作用与环境因子互作的数量美系。     

IMPACTS OF SOLAR UV RADIATION ON THE PHOTOSYNTHESIS,GROWTH, AND UV‐ABSORBING COMPOUNDS IN GRACILARIA LEMANEIFORMIS (RHODOPHYTA) GROWN AT DIFFERENT NITRATE CONCENTRATIONS1

Solar ultraviolet radiation (UVR, 280–400 nm) is known to affect macroalgal physiology negatively, while nutrient availability may affect UV‐absorbing compounds (UVACs) and sensitivity to UVR. However, little is known about the interactive effects of UVR and nitrate availability on macroalgal growth and photosynthesis. We investigated the growth and photosynthesis of the red alga Gracilaria lemaneiformis (Bory) Grev. at different levels of nitrate (natural or enriched nitrate levels of 41 or 300 and 600 μM) under different solar radiation treatments with or without UVR. Nitrate‐enrichment enhanced the growth, resulted in higher concentrations of UVACs, and led to negligible photoinhibition of photosynthesis even at noon in the presence of UVR. Net photosynthesis during the noon period was severely inhibited by both ultraviolet‐A radiation (UVA) and ultraviolet‐B radiation (UVB) in the thalli grown in seawater without enriched nitrate. The absorptivity of UVACs changed in response to changes in the PAR dose when the thalli were shifted back and forth from solar radiation to indoor low light, and exposure to UVR significantly induced the synthesis of UVACs. The thalli exposed to PAR alone exhibited higher growth rates than those that received PAR + UVA or PAR + UVA + UVB at the ambient or enriched nitrate concentrations. UVR inhibited growth approximately five times as much as it inhibited photosynthesis within a range of 60–120 μg UVACs · g^?1 (fwt) when the thalli were grown under nitrate‐enriched conditions. Such differential inhibition implies that other metabolic processes are more sensitive to solar UVR than photosynthesis.     

Dissipative functions of processes of electromagnetic radiation interaction with biological objects

Entropy generation rate inside the biological systems due to internal irreversible processes of the interaction with electromagnetic radiation is calculated for the processes of chemical free-energy increase. The irreversibility of several processes (photosynthesis in plants, eyesight of man, bioresonance effects of high frequencies of microwaves) is estimated under concrete experimental conditions. It is shown that the irreversible of five biological processes differs very much (by 10(8) times).     

Motility and photosynthetic responses of the green microalga Tetraselmis subcordiformis to visible and UV light levels

To test the effects of photosynthetic active radiation (PAR, 400–700 nm) and ultraviolet radiation (UVR, 280–400 nm) on phototaxis and photosynthesis of free swimming microalgae, experiments were performed with Tetraselmis subcordiformis (Wille) Butcher under a solar simulator. In particular, we evaluated the effects of different PAR levels and radiation regimes (i.e., PAR only and PAR+UVR) on those two processes. We found that the cells preferred to move to a particular area (e.g., receiving 100 W m^?2 PAR) with little photochemical suppression or inhibition of carbon fixation. Adding UV-A to high PAR decreased its swimming capacity and photosynthetic capability, and further adding UV-B led to more inhibition. The suppression of the moving capability of T. subcordiformis was reversible but the cells exposed to PAR combined with UVR needed longer time intervals to recover their motility as compared with those irradiated only with PAR. Based on the above results, we postulate that in nature, the motile capability and photosynthesis of free swimming the green microalga might be impaired by enhanced solar UVR. On the other hand, the cells can reduce the damage caused by high irradiances (and even get the optimum light level for photosynthesis) by a behavioral swimming response.     

Acclimation to UV radiation and antioxidative defence in the endemic Antarctic brown macroalga Desmarestia anceps along a depth gradient

The endemic Antarctic brown macroalga Desmarestia anceps colonizes the subtidal between 5 and 30 m in Potter Cove on King George Island (South Shetland Islands, Antarctica). Experiments were conducted to study photosynthetic activities, antioxidative enzymes and UV tolerance of field-grown individuals with respect to the light histories along different subtidal positions. Individuals collected from the upper (5.5 m) and mid-subtidal (9.0 m) are characterized by high maximum electron transport rates (ETRmax) measured by PAM-fluorometry and high activities of superoxide dismutase (SOD) supported by considerable activities of glutathione reductase. Individuals of this species from the upper subtidal are able to tolerate high irradiances of UV-B radiation because its photosynthetic apparatus is putatively well protected by phlorotannins. In contrast, individuals from lower subtidal positions (13.5 and 15.5 m) showed an opposite trend: lower ETRmax and SOD activities as well as a lower UV tolerance of photosynthesis. Moreover, a non-denaturing polyacrylamide gel electrophoresis (native PAGE) of a partially purified crude extract reveals that D. anceps has probably six isoforms of SOD. These intra-specific patterns imply a high phenotypical plasticity of D. anceps with respect to its photosynthesis and photoprotective mechanisms. Overall, photosynthesis, UV tolerance and antioxidative potential are highly regulated in D. anceps corresponding to the respective light regimes along its natural growth sites.     

Role of DNA polymerase eta in the UV mutation spectrum in human cells

In humans, inactivation of the DNA polymerase eta gene (pol eta) results in sunlight sensitivity and causes the cancer-prone xeroderma pigmentosum variant syndrome (XP-V). Cells from XP-V individuals have a reduced capacity to replicate UV-damaged DNA and show hypermutability after UV exposure. Biochemical assays have demonstrated the ability of pol eta to bypass cis-syn-cyclobutane thymine dimers, the most common lesion generated in DNA by UV. In most cases, this bypass is error-free. To determine the actual requirement of pol eta in vivo, XP-V cells (XP30RO) were complemented by the wild type pol eta gene. We have used two pol eta-corrected clones to study the in vivo characteristics of mutations produced by DNA polymerases during DNA synthesis of UV-irradiated shuttle vectors transfected into human host cells, which had or had not been exposed previously to UV radiation. The functional complementation of XP-V cells by pol eta reduced the mutation frequencies both at CG and TA base pairs and restored UV mutagenesis to a normal level. UV irradiation of host cells prior to transfection strongly increased the mutation frequency in undamaged vectors and, in addition, especially in the pol eta-deficient XP30RO cells at 5'-TT sites in UV-irradiated plasmids. These results clearly show the protective role of pol eta against UV-induced lesions and the activation by UV of pol eta-independent mutagenic processes.     

Some Observations on the Irradiance and Carbon Fixation in Grane Langsø

Photosynthetically active radiation (PAR) was registered daily in 0.25 m and 11.25 m in 3 years. Upwards irradiance of green light was 1 % of downward irradiance. Incubator ¹⁴C experiments showed that the phytoplankton enhanced its carbon uptake substantially with increasing concentrations of the carrier CO₂ in the ampoules. Severe carbon limitation of photosynthesis occurred in spring and summer 1961, where the real carbon fixation was only about 34 % of that calculated by the usual procedure. Utilization of light and DIC by the phytoplankton and its compensation depth was determined. Photoinhibition occurred down to 10–11 m, and net primary production was nearly always positive in any depth down to the lake bottom.     

Influence of preparative procedures on the membrane viscoelasticity of human red cell ghosts

The effects of systematic variations in the preparative procedures on the membrane viscoelastic properties of resealed human red blood cell ghosts have been investigated. Ghosts, prepared by hypotonic lysis at 0 degrees C and resealing at 37 degrees C, were subjected to: measurement of the time constant for extensional recovery (tc); measurement of the membrane shear elastic modulus (mu) via three separate techniques; determination of the membrane viscosity (eta m) via a cone-plate Rheoscope. Membrane viscosity was also determined as eta m = mu X tc. Compared to intact cells, ghosts had shorter tc, regardless of their residual hemoglobin concentration (up to 21.6 g/dl). However, prolonged exposure to hypotonic media did increase their recovery time toward the intact cell value. The shear elastic modulus, as judged by micropipette aspiration of membrane tongues (mu p), was similar for all ghosts and intact cells. This result, taken with the tc data, indicates that ghosts have reduced membrane viscosity. Rheoscopic analysis also showed that eta m was reduced for ghosts, with the degree of reduction (approx. 50%) agreeing well with that estimated by the product mu p X tc. However, flow channel and pipette elongation estimates indicated that the ghost membrane elastic modulus was somewhat elevated compared to intact cells. We conclude that: ghosts have reduced membrane viscosity; ghosts have membrane rigidities close to intact cells, except possibly when the membrane is subjected to very large strains; the reduction in eta m is not directly related to the loss of hemoglobin; prolonged exposure of ghosts to low-ionic strength media increases the membrane viscosity toward its initial cellular level. These data indicate that the mechanical characteristics of ghost membranes can be varied by changing the methods of preparation and thus have potential application to further studies of the structural determinants of red cell membrane viscoelasticity.     

落叶阔叶林内的光合作用和气孔传导率特征(英文)

本文根据Wang和BMdocchi(1989)最近提出的冠层辐射模型,进一步给出了一个模拟冠层光合作用速率和气孔传导率的模式.模式将冠层中每一层的叶面积分为向光叶、半影叶、和全遮荫叶三种,并分别计算其光合作用速率和气孔传导率。计算得到的光合速率廓线表明,在落叶阔叶林内,冠层下部的叶片常处于光照不足状态;半影效应使得透过林冠达于底部的辐射量增大,这对于林下植物的光合作用是有利的。 模式计算值与实测值之间的微弱差别应归因于纯辐射模型无法考虑湍流输送机制造成的CO_2传输和冠层底部耐荫性叶对于低光照的适应能力。     

作物光合、蒸腾与水分高效利用的试验研究

通过田间试验,对作物光合、蒸腾、气孔行为及其影响因素进行了研究。结果表明,光合与蒸腾的非线性关系可以用抛物线方程表述,其中光合速率最高时的蒸腾速率为临界值,超出该值即为奢侈蒸腾,干旱处理的临界值较低,通过合适的调控措施,抑制奢侈蒸腾并不影响光合生产,综合分析光合速率、蒸腾速率与气孔导度的关系,气孑L导度大于0．12mol·m^-2·s^-1,实施提高气孔阻力并抑制蒸腾的措施,既节约水分又促进光合作用,增加产量．光合速率基本上随光合有效辐射的增加而提高,并有光饱和点存在,水分条件影响叶片光合作用达到饱和的早晚,干旱处理的光饱和点远远低于湿润处理,强光需要水分充足相耦合,才能充分发挥光能利用率,蒸腾与辐射的线性关系十分显著。从光合有效辐射入手,在光合有效辐射大于1000μmol·m^-2·s^-1时实施措施,既可大大降低蒸腾,又可改善光合,节水增产效果不言而喻。     

A thermodynamic optimization analysis of a possible relation between the parameters that determine the energetics of muscle contraction in steady state.

Given the phenomenological relations for muscle's steady-state contraction and proper definitions of power p and efficiency eta, the behavior of these quantities is analysed in terms of the parameters that determine the energetics of the muscle, here denoted by s(o)and alpha. s(o)is proportional to the so-called maintenance heat, while alpha is the parameter that determines the curvature of the Hill's force-velocity curve. The dependence of the muscle's power and efficiency, averaged over the whole range of force the muscle can exert, on the parameters s(o)and alpha is studied. The average power p(avg)is a function only of alpha, and is a growing function that approaches 1/6 asymptotically as alpha goes to infinity. The average efficiency eta(avg)is a function of both alpha and s(o). With the value of s(o)fixed, the graph of the function eta(avg)(s(o), alpha) is a convex curve with a single maximum. The value and the position of this maximum point both depend on s(o). In the limit alpha-->0, s(o)-->0, eta(avg)tends to 1. The points (s(o), alpha(m)(s(o))), with alpha(m)(s(o)) the value of alpha that maximizes eta(avg)for a given s(o), are fitted by the curve alpha=s(o 1/2). This relation was experimentally found by A.V. Hill in his early studies of muscle energetics. Other experimental data are found to qualitatively satisfy the same relation. Although some dynamical microscopic models for muscle contraction, based upon Huxley's cross-bridge model, show that the same kinetic parameters control both the maintenance heat (s(o)) and the muscle's power output (alpha), we suggest that the exact relation between them has been reached due to the evolutive stresses that made individuals with equally powerful and more efficient muscles more suitable to reproduce.