Law of the Minimum Paradoxes

The “Law of the Minimum” states that growth is controlled by the scarcest resource (limiting factor). This concept was originally applied to plant or crop growth (Justus von Liebig, 1840, Salisbury, Plant physiology, 4th edn., Wadsworth, Belmont, 1992) and quantitatively supported by many experiments. Some generalizations based on more complicated “dose-response” curves were proposed. Violations of this law in natural and experimental ecosystems were also reported. We study models of adaptation in ensembles of similar organisms under load of environmental factors and prove that violation of Liebig’s law follows from adaptation effects. If the fitness of an organism in a fixed environment satisfies the Law of the Minimum then adaptation equalizes the pressure of essential factors and, therefore, acts against the Liebig’s law. This is the the Law of the Minimum paradox: if for a randomly chosen pair “organism–environment” the Law of the Minimum typically holds, then in a well-adapted system, we have to expect violations of this law.     

Derivation of non-acetifying „quasiacetobacters” from a trueAcetobacter strain,andvice versa

Summary A strain ofAcetobacter rancens gave rise to “quasi-acetobacters” which had lost the essential generic character of oxidation of ethanol to acetic acid, whilst retaining all the other characteristics of the genus. Other quasi-acetobacters with other acetobacter properties were also obtained. Conversely a starch-producing quasi-acetobacter gave rise to two trueAcetobacter strains indistinguishable biochemically fromA. pasteurianus andA. rancens respectively. These phenomena were associated with the presence, in the parent strains, of many swollen filaments and large bodies. It is tentatively suggested that the changes from true to quasi-acetobacter, andvice versa, may be correlated with the production of such bodies, and may indicate some heterodox form of reproduction other than simple fission. The advent of “quasi-acetobacters” seems largely to demolish the genusAcetobacter, whilst failing to indicate an alternative under the existing rigid botanical taxonomic conventions.     

The probabilistic approach to the effects of radiations and variability of sensitivity

The calculation of the size of the “sensitive volume” or “control center” in biological effects of radiations is discussed from the viewpoint of the probabilistic theory of these phenomena based on the concept of random “effective events”. On the bases of that theory, the resistivity of a microorganism to radiation is defined as its “mean life” under a radiation of one roentgen per minute. This mean is calculated for processes with and without recovery. The case of variable sensitivity, as it occurs for instance during mitosis, is discussed in detail. Methods are given to calculate this variability from survival curves or similar experimental data. The theory is applied to experiments of A. Zuppinger on irradiation ofAscaris eggs with X-rays.     

Genes encoding giant danio and golden shiner ependymin

Ependymin (EPN) is a brain glycoprotein that functions as a neurotrophic factor in optic nerve regeneration and long-term memory consolidation in goldfish. To date, trueepn genes have been characterized in one order of teleost fish,Cypriniformes. In the study presented here, polymerase chain reactions were used to analyze the completeepn genes,gd (1480 bp), andsh (2071 bp), fromCypriniformes giant danio and shiner, respectively. Southern hybridizations demonstrated the existence of one copy of each gene per corresponding haploid, genome. Each gene was found to contain six exons and five introns. Genegd encodes a predicted 218-amino acid (aa) protein GD 93% conserved to goldfish EPN, whilesh encodes a predicted 214-aa protein SH 91% homologous to goldfish. Evidence is presented classifying proteins previously termed “EPNs” into two major categories: true EPNs and non-EPN cerebrospinal fluid glycoproteins. Proteins GD and SH contain all the hallmark features of true EPNs.     

Critical notice:<Emphasis Type="Italic"> Darwinian reductionism</Emphasis>

This notice provides a critical discussion of some of the issues from Alex Rosenberg’s Darwinian Reductionism, in particular proper functions and the relationship of proximate and ultimate biology, developmental programs and genocentrism, biological laws, the principle of natural selection as a fundamental law, genetic determinism, and the definition of “reductionism.”     

Primary culture and characteristic morphologies of neurons from the cerebral ganglion of the mud crab, <Emphasis Type="Italic">Scylla paramamosain</Emphasis>

Crustacean neurons, obtained from the cerebral ganglion of the mud crab Scylla paramamosain, were successfully cultured in vitro. They maintained typical morphological characteristics and showed better outgrowth in modified Medium 199 (M199) medium than that in Liebowitz’s L-15 medium. Fetal bovine serum (FBS), muscle extracts, and hemolymph of the mud crab S. paramamosain were added as supplements. Only 20% FBS could promote neuron outgrowth, while muscle extracts and hemolymph of S. paramamosain did not improve neuron outgrowth. For cell dissociation, both collagenase type I and trypsin worked well as determined by initial cell viability and following cell outgrowth potential. More than six kinds of cells with different morphological characteristics were identified in the neuron outgrowth. They were “small cells”, “veilers”, “branchers”, “multipolar cells”, “super-large cell”, and “bipolar cells”. Among all of the cells, bipolar cells were identified for the first time in crustacean neurons culture and they could live longer than other cells. The neurons could grow for more than a week before retraction and eventual degradation.     

Ultra-fastChara myosin: A test case for the swinging lever arm model for force production by myosin

Recent breakthroughs and technological improvements are rapidly generating evidence supporting the “swinging lever arm model” for force production by myosin. Unlike previous models, this model posits that the globular domain of the myosin motor binds to actin with a constant orientation during force generation. Movement of the neck domain of the motor is hypothesized to occur relative to the globular domain much like a lever arm. This intramolecular conformational change drives the movement of the bound actin. The swinging lever arm model is supported by or consistent with a large number of experimental data obtained with skeletal muscle or slime mold myosins, all of which move actin filaments at rates between 1 and 10 μm/sin vitro. Recently myosin was purified, fromChara internodal cells.In vitro the purifiedChara myosin moves actin filaments at rates one order of magnitude faster than the “fast” skeletal muscle myosin. While this ultra fast movement is not necessarily inconsistent with the swinging lever arm model, one or more specific facets of the motor must be altered in theChara motor in order to accommodate such rapid movement. These characteristics are experimentally testable, thus the ultra fast movement byChara myosin represents a powerful and compelling test of the swinging lever arm model.     

Selection of Reference Genes for Normalizing Gene Expression During Seed Priming and Germination Using qPCR in Zea mays and Spinacia oleracea

Quantitative real-time RT-PCR (qPCR) has been widely used to investigate gene expression during seed germination, a process involving seed transition from dry/physiologically inactive to hydrated/active state. This transition may result in altered expression of many housekeeping genes (HKGs), conventionally used as internal controls, thereby posing a challenge about selection of HKGs in such scenarios. The objectives of this study included identifying valid reference genes for seed priming and germination studies, both of which involve the transition of seed hydration status, and assessing whether or not findings derived from the “seed model” used in this study would also be applicable to other plant species. Eight commonly used HKGs were evaluated in maize seeds during hydropriming and germination. Using Bestkeeper, geNorm, and NormFinder, we provided a rank of stability for these HKGs. Actdf, UBQ, βtub, 18S, Act, and GAPDH were adjudged as valid internal controls by geNorm and NormFinder. Under the second objective, we conducted a case study with spinach seeds collected during osmopriming and germination. Our results indicate that the conclusions derived from maize were applicable to spinach as well, in that 18S exhibited greater expression stability than GAPDH in osmoprimed and germinated seeds; this held true even under stress conditions. While both of these genes were rejected by BestKeeper, we found that 18S exhibited stable expression when “dry” and “hydrated” seeds were analyzed as separate data sets. Although this approach precludes the comparison between “hydrated” and “dry” seeds, it still provides effective comparison among samples of same hydration status.     

A teleological explanation of Weber's law and the motor unit size law

It is shown that the Weber-Fechner law. which relates the response of a sensory biosystem to the intensity of the input stimulus, can be derived from a teleological principle of minimum transentropy (maximal noise reduction) provided the relative mean fluctuation (coefficient of variation) of the input intensity can be assumed to be (approximately) constant for all feasible mean input intensities. A law is then deduced from experimental results which quantifies the relationship existing between the relative amount of activated muscle mass and the “size” (which term is clearly defined) of a newly recruited motor unit. This law is found to be formally equivalent to the Weber-Fechner law when applied to motor unit recruitment. It is then shown that, in general, the ratio of the force increment upon recruitment, to the present force output does not obey Weber's law. Finally, it is proved that the “motor unit size law” as derived in this paper implies a fixed sequential order in the recruitment of motor units and that it may be viewed as the realization, by the mammalian neuromuscular system, of a general principle of maximum grading sensitivity.     

Production and metabolic engineering of bioactive substances in plant hairy root culture

In the past three decades, hairy roots research for the production of valuable biological active substances has received a lot of attention. The addition of knowledge to enhance the yields of desired substances and the development of novel tools for biomass engineering offer new possibilities for large-scale cultivation of the plant hairy root. Hairy roots can also produce recombinant proteins through the transfer of Agrobacterium T-DNA into the plant genome, and thereby hold immense potential for the pharmaceutical industry. This review highlights some of the significant progress made in the past few years and outlines future prospects for exploiting the potential utility of hairy root cultures as “chemical factories” for producing bioactive substances.     

Gas exchange,chlorophyll fluorescence,and osmotic adjustment in two mango cultivars under drought stress

The responses of photosynthetic gas exchange, chlorophyll fluorescence, content of pigments, main osmolytes, and malondialdehyde (MDA) to water-withholding for 15 days and re-hydration in seedlings of two mango cultivars (Mangifera indica L. var. “Choke Anand’ and var. “Khieo Sawoei”) under 50% sunlight and full sunlight were investigated. For both cultivars, the water-witholding resulted in progressively decreases in leaf relative water content, net photosynthesis (P _n), stomatal conductance (g _s), and increases in the conversion of xanthophyll cycle pigments estimated by an index of leaf spectral reflectance (ΔPRI), carotenoid to chlorophyll ratio, non-photochemical quenching (NPQ), the contents of malondialdehyde (MDA) and compatible solutes (total soluble sugar and proline). The effect of the water stress was more pronounced in full sunlight than 50% sunlight. The maximum photochemistry efficiency measured at dawn was fairly constant during the period of the treatment for both cultivars under both light regimes. The water stress caused less pronounced inhibition of photosynthesis in “Choke Anand” than in “Khieo Sawoei” cultivar under both light regimes. After re-hydration, the recovery was relatively quicker in “Choke Anand” than in “Khieo Sawoei” cultivar. Both cultivars in both 50% and full sunlight showed complete recovery in photochemistry after 5 days of re-watering but photosynthesis did not show a complete recovery as indicated by gas exchange rates. As the results of lower NPQ, ΔPRI and osmotic adjustment in the cultivar “Khieo Sawoei” compared to the cultivar “Choke Anand”, the former cultivar was less tolerant to drought than the latter. Our study further showed that partial shading (e.g., 50% of sunlight) significantly alleviated the harmful effect of drought stress on mango cultivars but in fact stomata of seedlings grown in partial shade was more responsive to water deficit than in full light.     

The biology behind lichenometric dating curves

Lichenometry is used to date late-Holocene terminal moraines that record glacier fluctuations. Traditionally, it relies upon dating curves that relate diameters of the largest lichens in a population to surface ages. Although widely used, the technique remains controversial, in part because lichen biology is poorly understood. We use size-frequency distributions of lichens growing on well-dated surfaces to fit demographic models for Rhizocarpon geographicum and Pseudophebe pubescens, two species commonly used for lichenometry. We show that both species suffer from substantial mortality of 2–3% per year, and grow slowest when young-trends that explain a long-standing contradiction between the literatures of lichenometry and lichen biology. Lichenometrists interpret the shape of typical dating curves to indicate a period of rapid juvenile “great growth,” contrary to the growth patterns expected by biologists. With a simulation, we show how the “great growth” pattern can be explained by mortality alone, which ensures that early colonists are rarely found on the oldest surfaces. The consistency of our model predictions with biological theory and observations, and with dozens of lichenometric calibration curves from around the world, suggests opportunities to assess quantitatively the accuracy and utility of this common dating technique.     

Word organization in coding DNA: A mathematical model

This article deals with the relationship between vocabulary (total number of distinct oligomers or “words”) and text-length (total number of oligomers or “words”) for a coding DNA sequence (CDS). For natural human languages, Heaps established a mathematical formula known as Heaps' law, which relates vocabulary to text-length. Our analysis shows that Heaps' law fails to model this relationship for CDSs. Here we develop a mathematical model to establish the relationship between the number of type of words (vocabulary) and the number of words sampled (text-length) for CDSs, when non-overlapping nucleotide strings with the same length are treated as words. We use tangent-hyperbolic function, which captures the saturation property of vocabulary. Based on the parameters of the model, we formulate a mathematical equation, known as “equation of word organization”, whose parameters essentially indicate that nucleotide organization of coding sequences are different from one another. We also compare the word organization of CDSs with the random word distribution and conclude that a CDS is neither similar to a natural human language nor to a random one. Moreover, these sequences have their unique nucleotide organization and it is completely structured for specific biological functioning. IM and AS contributed equally to this work.     

Salt tolerance in Lycopersicon species VI. Genotype-by-salinity interaction in quantitative trait loci detection: constitutive and response QTLs

 A study of genotype-by-salinity interaction was carried out to compare the behavior of quantitative trait loci (QTLs) in two F₂ populations derived from crosses between the cherry tomato, Lycopersicon esculentum Mill. var. cerasiforme, and two wild relatives Lycopersicon pimpinellifolium (Jusl.) Mill. and Lycopersicon chesmannii f. minor (Hook. f.) Mull., grown at two environmental conditions (optimum and high salinity). QTLs for earliness and fruit yield could be classified into four groups: “response-sensitive”, those detected only under control conditions or whose contribution significantly decreased in salinity; “response-tolerant”, detected only in salinity or in which the direction of their additive effects changed; “constitutive”, detected in both growing conditions; and “altered” QTLs, those where the degree of dominance changed according to the presence or absence of salt. Epistatic interactions were also influenced by the salt treatment. This differential allele effect at some (non-constitutive) QTLs induced by salt stress will make selection under an “optimum environment” unfruitful for the “response-tolerant” QTLs. Similarly, selection under salinity will ignore “response-sensitive” QTLs. Given that salinity is highly variable in the field, marker-assisted selection should take into account not only the “response-tolerant” but also the “response-sensitive” QTLs although there might be cases where selection in some QTLs for both conditions is not feasible. Comparing both populations, very few QTLs showed the same behavior. Received: 5 August 1996 / Accepted: 25 October 1996     

Muscles within muscles: the neuromotor control of intra-muscular segments

The aim of this investigation was to anatomically identify, and then determine the function of, individual segments within the human deltoid muscle. The anatomical structure of the deltoid was determined through dissection and/or observation of the shoulder girdles of 11 male cadavers (aged 65–84 years). These results indicate that the deltoid consists of seven anatomical segments (D1–D7) based upon the distinctive arrangement of each segment's origin and insertion. Radiographic analysis of a cadaveric shoulder joint suggested that only the postero-medial segment D7 has a line of action directed below the shoulder joint's axis of rotation. The functional role of each individual segment was then determined utilising an electromyographic (EMG) technique. Seven miniature (1 mm active plate; 7 mm interelectrode distance) bipolar surface electrodes were positioned over the proximal portion of each segment's muscle belly in 18 male and female subjects (18–30 years). EMG waveforms were then recorded during the production of rapid isometric shoulder abduction and adduction force impulses with the shoulder joint in 40 degrees of abduction in the plane of the scapula. Each subject randomly performed 15 abduction and 15 adduction isometric force impulses following a short familiarisation period. All subjects received visual feed back on the duration and amplitude of each isometric force impulse produced via a visual force-time display which compared subject performance to a criterion force-time curve. Movement time was 400 ms (time-to-peak isometric force) at an intensity level of 50% maximal voluntary contraction. Temporal and intensity analyses of the EMG waveforms, as well as temporal analysis of the isometric force impulses, revealed the neuromotor control strategies utilised by the CNS to control the activity of each muscle segment. The results showed that segmental neuromotor control strategies differ across the breadth of the muscle and that individual segments of the deltoid can be identified as having either “prime mover”, “synergist”, “stabiliser” or “antagonist” functions; functional classifications normally associated with whole muscle function. Therefore, it was concluded that the CNS can “fine tune” the activity of at least six discrete segments within the human deltoid muscle to efficiently meet the demands of the imposed motor task. Accepted: 15 December 1997     

Study on high-temperature-resistant and high-yield <Emphasis Type="Italic">Laminaria</Emphasis> variety “Rongfu”

Hybridization of gametophytes, continuous self-crossing and targeted selection were utilized to breed a new Laminaria variety. After five-generation selection breeding, the new variety “Rongfu” was obtained. Its male parent “Yuanza No.10” was the high-yield cultivation variety, and its female parent was variety “Fujian” which could tolerate relatively high seawater temperature. “Yuanza No.10” and “Fujian” were different but complement in their morphological characteristics and biological habits. Variety “Rongfu” was bred through their hybridization which exhibited high-yield potential and high seawater temperature tolerance. The results of traits evaluation in consecutive years showed that “Rongfu” attained higher yields by 24–27% compared to the control (widely used commercial variety) and also contained considerable amounts of iodine, mannitol, and algin. When seawater temperature was 18–21°C, the blade growth of “Rongfu” was maintained and tissue loss by abrasion was significantly lower than the control. Since the adoption of variety “Rongfu” in 2001, its cultivation areas have been extended to Shandong, Fujian and Guangdong province and have reached 14,133 ha currently, i.e., almost one-tenth of the total cultivation areas of Laminaria in China. The results of Random Amplified Polymorphic DNA analysis showed that the relationship between “Rongfu” and other cultivation varieties in China was very close.     

Laws of biological design: a reply to John Beatty

In this paper, I argue against John Beatty’s position in his paper “The Evolutionary Contingency Thesis” by counterexample. Beatty argues that there are no distinctly biological laws because the outcomes of the evolutionary processes are contingent. I argue that the heart of the Caspar–Klug theory of virus structure—that spherical virus capsids consist of 60T subunits (where T = k ² + hk + h ² and h and k are integers)—is a distinctly biological law even if the existence of spherical viruses is evolutionarily contingent.