TIME RELATIONS OF GROWTH : III. GROWTH CONSTANTS DURING THE SELF-ACCELERATING PHASE OF GROWTH.

Growth curves consist, in all cases, of two major segments. The first major segment is, in the case of higher animals and plants, made up in turn of several (probably five) shorter segments during each of which growth takes place at a constant percentage rate. The transitions between the successive stages are abrupt, the abruptness being of the order of metamorphosis in cold blooded animals. It has been made clear in the first paper of this series that the time rate of growth following the major inflection declines at a constant percentage rate. The junction between the two major segments occurs at puberty in animals and flowering in plants. The two major segments are not symmetrical about the major inflection. The slope of the segment following the inflection is always less than the slope of the segment preceding the inflection. The major inflection does not occur in the center of the growth curve. The instantaneous rate of growth at the beginning of growth is of the order of 100–200 per cent per day (i.e. the body weight is doubled in from 7 to 17 hours). It may be mentioned that 2 months after conception the rate of growth in man is only 8 per cent per day. This is contrary to all the published statements. Thus, Minot concluded that growth begins at 1000 per cent per day; Jackson concluded that in man, growth during the 1st month takes place at 57.5 million per cent per month; during the 2nd month 990 per cent per month; during the 3rd month 390 per cent per month (8 per cent per day is only 240 per cent per month). The reason for the discrepancy between the values derived, by the method adopted by the writer, and the values given in the literature is explained by Fig. 1.     

THE RATE OF GROWTH OF THE DAIRY COW : V. EXTRAUTERINE GROWTH IN LINEAR DIMENSIONS.

Barring fluctuations due to the cyclic phenomena, the extrauterine course of growth in linear dimensions and in weight of the dairy cow follows an exponential law having the same form as the law representing the course of monomolecular change in chemistry. This suggests the interpretation that the general course of growth is limited by a monomolecular chemical process, and that the cyclic phenomena are due to subsidiary processes in the fundamentally exponential course of growth. The fact that growth follows or tends to follow an exponential course may be stated more simply as follows: if the unit of time is taken sufficiently large so that fluctuations due to the cyclic phenomena are balanced or eliminated, then the amount of growth made during the given unit of time at any age tends to be a constant percentage of the growth made during the preceding unit of time. Thus, the growth in height at withers made during any year is about 34 per cent of the growth made during the preceding year. Similarly the growth in weight made during any year is about 56 per cent of the growth in weight made during the preceding year. This is in accordance with expectations if it is assumed that each animal begins life with a definite endowment of limiting substance necessary for the process of growth, and that this endowment is used up at a constant rate (or percentage) of itself.     

STUDIES ON THE GROWTH HORMONE OF PLANTS : VI. THE DISTRIBUTION OF THE GROWTH SUBSTANCE IN PLANT TISSUES

1. It is shown that when plant tissues are ground with water the growth substance contained therein is inactivated by the oxidizing enzymes. 2. A simple method of extraction is described which enables the quantitative determination of growth substance in such tissues. 3. The amount and distribution of growth substance in the Avena coleoptile is determined by this method, and it is shown that while the substance does not diffuse out from the lower parts of the coleoptile, it is nevertheless present in considerable amounts, the concentration decreasing steadily with the distance from the tip. 4. Growth substance is also present in considerable amounts in Avena roots, and here also its concentration decreases steadily with distance from the tip. 5. The amount of growth substance diffusing out of root tips into dextrose agar, even during long periods of time, is not greater than the amount obtainable by direct extraction. Actual production in the root tip therefore either does not take place at all, or else takes place under quite different conditions from the production in the tip of the coleoptile.     

THE ACTION OF THE PLANT GROWTH HORMONE

1. Sections of Avena coleoptiles are found to show a considerable elongation when suspended in solutions of growth substance. 2. This elongation does not take place in the absence of O₂ and is inhibited by KCN and phenylurethane. 3. The rate of respiration of sections of coleoptiles is increased by the addition of growth substance in concentrations which cause growth. High concentrations of growth substance inhibit growth and also respiration. 4. The increase in respiration is inhibited by KCN and phenylurethane in the concentrations which inhibit normal respiration. These concentrations are the same as those which inhibit growth. 5. From 2, 3, and 4, it seems possible that the increase in respiration caused by growth substance may be an essential part of its action in growth.     

THE GROWTH OF BACTERIOPHAGE

1. An anti-Escherichia coli phage has been isolated and its behavior studied. 2. A plaque counting method for this phage is described, and shown to give a number of plaques which is proportional to the phage concentration. The number of plaques is shown to be independent of agar concentration, temperature of plate incubation, and concentration of the suspension of plating bacteria. 3. The efficiency of plating, i.e. the probability of plaque formation by a phage particle, depends somewhat on the culture of bacteria used for plating, and averages around 0.4. 4. Methods are described to avoid the inactivation of phage by substances in the fresh lysates. 5. The growth of phage can be divided into three periods: adsorption of the phage on the bacterium, growth upon or within the bacterium (latent period), and the release of the phage (burst). 6. The rate of adsorption of phage was found to be proportional to the concentration of phage and to the concentration of bacteria. The rate constant k_a is 1.2 x 10^–9 cm.⁸/min. at 15°C. and 1.9 x 10^–9 cm.⁸/min. at 25°. 7. The average latent period varies with the temperature in the same way as the division period of the bacteria. 8. The latent period before a burst of individual infected bacteria varies under constant conditions between a minimal value and about twice this value. 9. The average latent period and the average burst size are neither increased nor decreased by a fourfold infection of the bacteria with phage. 10. The average burst size is independent of the temperature, and is about 60 phage particles per bacterium. 11. The individual bursts vary in size from a few particles to about 200. The same variability is found when the early bursts are measured separately, and when all the bursts are measured at a late time.     

PATTERNS OF GROWTH IN BIRDS. II. GROWTH RATE AND MODE OF DEVELOPMENT

This analysis was initiated to examine the relationship between the rate of growth in birds and their development of mature function. The literature was surveyed for data on growth and development, and the growth curves of 81 species were chosen for the analysis. Growth curves of most species were fitted with the Gompertz equation, and the rate constants of the equation were used as an index of the growth rate. For those species whose curves were fitted better by other equations, with a slightly different form, appropriate conversion factors, derived in this paper, were employed.
Among species with similar modes of development, growth rate decreases with increasing body weight in an allometric manner, with slopes of –0.26 to –0.42, depending on the group. Between groups, the rate of growth in body weight was found to be closely associated with the rate of development of function, in particular, the acquisition of flight. Among those species that can walk at an early age, but acquire flight relatively late, the rate of growth depends primarily on the relative size of the musculature of the lower extremities.
Data are presented to refute the hypotheses that growth rate is adjusted to nestling mortality, or that the energy requirements of the young (and hence their growth rates) are balanced against brood size. It is concluded that most species grow at some physiologically maximum rate, but as yet it is not possible to distinguish between limitation of growth rate at the level of the organism or at the level of the tissue.     

THE GROWTH AND RESPIRATION OF THE AVENA COLEOPTILE

1. Transport of the plant growth hormone into the Avena coleoptile as well as the action of the hormone on cell elongation in the coleoptile are shown to depend upon aerobic metabolism. 2. Crystalline auxine, in contrast with impure preparations, affects neither the magnitude nor the respiratory quotient of coleoptile respiration. 3. Increasing age of the coleoptile cell decreases its rate of elongation much more than its rate of respiration. HCN or phenylurethane on the other hand decrease the two processes to the same extent, in spite of the fact that only a small portion of the energy liberated by respiration can be used in the mechanical process of growth. 4. From 2 and 3 it is concluded that processes of a respiratory nature but of relatively small magnitude form one or more integral steps in the chain of reactions by which the plant growth hormone brings about cell elongation.     

THE LIGHT GROWTH RESPONSE AND THE GROWTH SYSTEM OF PHYCOMYCES

1. The Roscoe-Bunsen law holds for the light growth response of Phycomyces if the time component of stimulation is short. With exposures longer than a few seconds, the reaction time to light is determined by the intensity and not by the energy of the flash. 2. The possible nature of the very long latency in the response to light is considered in terms of the structure of the cell and its mechanism of growth. It is suggested that during the latency some substance produced by light in the protoplasm is transported centrifugally to the cell wall or outermost layer of protoplasm. 3. The total elongation occurring over a period of 1 to 2 hours is independent of flashes of light or temporary darkening. Light acts by facilitating some change already under way in the growth system, and during the principal phase of elongation is not a necessary or limiting factor for growth. 4. Judged by the reaction time, the original sensitivity is restored in the light system following exposure to light in about one-third the time required for equilibrium to be reattained in the growth system.     

GROWTH SUBSTANCE CURVATURES OF AVENA IN LIGHT AND DARK

An attempt has been made to analyze the base response, one of the light growth responses of Avena coleoptiles, by means of growth substance curvatures. The decrease in growth rate (first part of the base response) after exposure to light does not show if hetero-auxin is substituted for auxin-a (Sections 5, 6, and 10). This decreased growth after exposure very likely is due to an oxidative inactivation of auxin-a (Sections 8 and 9). Hetero-auxin can be inactivated too but in a much lesser degree than auxin-a (Section 9). The increase in growth rate following on the decreased growth (second part of the base response) is due to an increase in response of the plant to growth hormone which is independent of the type of hormone (Sections 1, 2, 7, 8, and 10). Under conditions of continuous exposure to light, however, the inactivation of the auxin-a under influence of the light is superimposed on this increased response to growth hormone. This inactivation can be eliminated from the light growth response by replacing the auxin-a by hetero-auxin. More detailed information on this subject can be found in Section 10. A review of the experiments and their results can be obtained from the scheme in Section 8. In Section 11 it is shown that light inhibits the formation of growth hormone in the decapitated coleoptile (regeneration). Very small amounts of light (25 m.c.s.) inhibit the regeneration markedly.     

THE GROWTH AND DURATION OF LIFE OF CELOSIA CRISTATA SEEDLINGS AT DIFFERENT TEMPERATURES

Daily measurements of hypocotyl length were made on Celosia cristata seedlings cultured in darkness under aseptic conditions at six constant temperatures between 14.5° and 40.5°C. At 40.5° roots did not penetrate the agar and only the hypocotyls that were supported by the wall of the test tube could be measured. The growth curves were of the generalized logistic type, but of different degrees of skewness. The degree of symmetry of the growth curves was influenced by temperature. At the lower temperatures the maximal growth rate came relatively late in the grand period of growth; at successively higher temperatures it came progressively earlier. The mean total time rate of growth (millimeter per diem) was found to be a parabolic function of the temperature. The maximum rate of growth was found from the curve to be at 30.48°C. The maximum observed rate of growth, and the maximum yield, were found to be at 30°C. At all temperatures above 14.5° the maximum growth activity fell in the second quarter of the whole growth period. At all temperatures tested other than 30°, and at all parts of the growth cycle, the growth yield as measured by height of hypocotyl at any given equivalent point was less than at 30°. The total duration of life of the seedlings, and the duration of life after the end of the growth period (intermediate period) were inversely proportional to the mean total growth rate. The observations on Celosia cristata seedlings are thus in accord with the "rate of living" theory of life duration. The optimal temperature for life duration is the minimum temperature, within the range of these observations.     

THE EFFECTS OF SULFATHIAZOLE AND OF PROPYL CARBAMATE ON THE RATE OF OXYGEN CONSUMPTION AND GROWTH IN ESCHERICHIA COLI

1. The rates of growth and of oxygen consumption by cells of E. coli have been measured under identical conditions, and the effects of sulfathiazole (ST) and of n-propyl carbamate (PC) on these two processes have been compared. 2. The rate of growth was measured by (a) the increase in the viable cell count, (b) the increase in the optical density of the culture, (c) the increase in the rate of oxygen consumption, and (d) the decrease in the ammonia of the medium. The results as indicated by these several measures were identical under the conditions of these experiments. 3. Concentrations of ST or of PC which are just sufficient to stop growth completely, lower the rate of oxygen consumption per unit of bacterial protoplasm to a value approximately 50 per cent of that seen in the absence of the inhibitor. 4. It is shown that the rate of oxygen consumption in cells from old cultures is less affected by ST than is the rate of oxygen consumption by cells from young cultures. It is probable that the rate of oxygen consumption by "old" cells is lower than that of "young" cells. 5. The effects of ST and PC on both the rate of oxygen consumption and the rate of growth are very similar, indicating in a general way, that the mechanism of the actions of these two inhibitors is similar. Furthermore, since both of them produce appreciable inhibition of the rate of oxygen consumption while they are inhibiting growth, the possibility that the effect on oxygen consumption is the immediate cause of the effect on growth must be entertained.     

Lemna paucicostata Hegelm. 6746: DEVELOPMENT OF STANDARDIZED GROWTH CONDITIONS SUITABLE FOR BIOCHEMICAL EXPERIMENTATION

Photoautotrophic and mixotrophic growth of Lemna paucicostata Hegelm. 6746 (formerly Lemna perpusilla Torr. 6746) was investigated to establish standardized conditions for biochemical studies. Optimal temperature for growth was 29 to 30 C. The medium used previously (Datko AH, Mudd SH, Giovanelli J 1977 J Biol Chem 252: 3436-3445) was modified by inclusion of NH₄Cl, decreasing macronutrient and ethylenediamine tetraacetate concentration, increasing micronutrient concentration, and inclusion of bicarbonate (for photoautotrophic growth) or 2-(N-morpholino)ethanesulfonic acid (for mixotrophic growth) buffers. Varying the sulfate concentration between 14 and 1 millimolar had no effect on growth. For photoautotrophic growth in the new medium (medium 4), the effects of CO₂ concentration, light intensity, and pH were measured. Under the optimal conditions, a multiplication rate (MR) of 300 to 315, equivalent to a doubling time of 23 to 24 hours was obtained. Addition of glutamine or asparagine did not increase this MR. For mixotrophic growth in low light, the effects of sucrose concentration and pH were determined. Under optimal conditions, MR was 210. A concentration of sucrose less than maximal for growth was chosen for the medium for experiments which will include ¹⁴C-labeling of intermediates. MR under these conditions was 184. Growth was equally good in medium 4 and in half-strength Hutner's medium when sulfate was high (0.4 to 1 millimolar), but better in medium 4 when sulfate was low (20 micromolar). Growth rates could be restored to normal in half-strength Hutner's with low sulfate by decreasing the molybdate concentration.     

THE INFLUENCE OF ALCOHOL UPON THE GROWTH OF SEEDLINGS

In this paper it is shown that if the dry seeds of the cantaloupe (Cucumis melo) are soaked for 3 hours in solutions of ethyl alcohol of concentration ranging from 2 to 16 per cent by volume, and then germinated and grown in distilled water in the dark, the total growth attained is greater by amounts ranging from 9 to 35 per cent than is that made by seeds treated in every way identically except that they are initially soaked in distilled water instead of alcohol. It is shown that this result is not due simply to differences in osmotic pressure in the different alcohol solutions. It is probably due to a simple selective action of the alcohol which eliminates the constitutionally weak and defective seeds.     

LICHEN PENDANTS FOR TRANSPLANT AND GROWTH EXPERIMENTS

Lichens were cultured by attaching a thallus fragment to a nylon monofilament loop with silicone sealer. Two effective methods for adjusting lichen mass to a standard moisture content were developed (the ‘reference-sample’ and ‘sacrificial’ methods). These corrections for moisture content allow detection of very small changes in dry mass without having to oven dry (and kill) all transplants. Average annual biomass growth rates for non-fragmenting species were typically between 5 and 30%. Annual biomass growth rates of healthy, vigorous individuals, as indicated by the 75th percentile, were mostly between 10 and 40%.Alectoria sarmentosawas prone to fragmentation despite the maintenance of healthy thalli. The other species can be ranked by biomass growth rates as follows:Evernia prunastri>Lobaria pulmonaria=Usnea longissima>Pseudocyphellaria rainierensis=Lobaria oregana. 1996 The British Lichen Society     

INHIBITION OF FUNGAL GROWTH BY WATER EXTRACTS FROM THE LICHENNEPHROMA ARCTICUM

Water extracts fromNephroma arcticumwere prepared and tested for inhibitory effects against various yeast, mould, blue-stain and rot fungi. A water extract fromPeltigera aphthosawas used as a reference. Two different diffusion assays were used, wells (cup-plate method) and droplets (drop-plate method). For the majority of fungi studied using the former method there were clear zones with a sharp boundary (fungicidal effect), whereas the latter method yielded more or less hazy zones with inhibition or reduction in growth (fungistatic effect). No clear or hazy zones were seen with the extract fromP. aphthosa. ForCandida glabrataE,Saccharomyces cerevisiaeK andHormonema dematioidesS there were clear zones for both methods. The MIC (Minimum Inhibitory Concentration) values were determined in liquid medium forS. cerevisiaeK andC. glabrataE and were, respectively, 1 and 10 mg ml⁻¹of a crude extract fromN. arcticum. The MFC (Minimum Fungicidal Concentration) values were found to be identical to the MIC values.     

QUANTITATIVE PATTERNS OF LEAF EXPANSION: COMPARISON OF NORMAL AND MALFORMED LEAF GROWTH IN VITIS VINIFERA CV. RUBY RED

Developmental patterns produced during normal expansion of the leaf of Vitis vinifera cv. Ruby Red are quantitatively characterized from the distribution of relative growth rates and growth velocity vectors and are compared to patterns produced during the development of an abnormally shaped leaf. The bilateral symmetry of the V. vinifera leaf, which is present in the normal leafand absent in the malformed leaf, is shown during growth by the patterns of velocity isolines. Ellipses formed by the isolines around the midrib during normal development are distorted during development of the malformed leaf. During normal growth, tissue elements are displaced in rather straight lines, resulting in streamlines which radiate outward from the petiole. Element motion in the abnormally developing leaf causes curving of streamlines. Relative growth in area of elements located in an area in the normal leaf are higher than those in the malformed leaf. The most frequently observed category of relative area growth in the normal leaf is 40%-59% d~¹, while 20%–39% d^−-1 predominates in the abnormal leaf. A spatial gradient in growth appears during normal development with lowest relative growth (20%–39% d^−-1) present in the tip region, intermediate values (40%–59% d^−-1) in the midsection, and maximum growth (> 60% d^−-1) appearing in the basal region. During development of the abnormally shaped leaf, the gradient along the midrib is disrupted with low magnitudes of growth (<20% d^−-1) appearing in the midsection of the leaf where intermediate values are expected. The theoretical and numerical distinctions between two common expressions for relative growth (relative elemental growth and exponential growth rate) are discussed. Relative elemental growth is shown to become increasingly larger than the exponential growth rate as the magnitude of growth increases relative to initial size of the tissue element. Numerical methods for evaluating relative growth based on finite element areas are compared to methods based on displacement and velocity gradients and are shown to produce similar results.     

STUDIES IN THE DYNAMICS OF HISTOGENESIS : I. TENSION OF DIFFERENTIAL GROWTH AS A STIMULUS TO MYOGENESIS.

1. The region of most active mitosis per mm. of cross-section in the intestine is the entodermal epithelial tube. The mitotic figures primarily follow the path of a right-handed helix. In one of the twenty embryos the mitotic figures describe the path of a right-handed helix. 2. The region of least active or relatively passive growth per mm. of cross-section is the mesenchyme, derived from the splanchnic mesoderm surrounding the epithelial tube. 3. The rapid expansion, due to epithelial growth in a rotating spiral manner, of the intestinal lumen is greater than the activity manifest in the surrounding mesenchyme. This causes a pressure in the latter resulting in a flattening and elongation of the mesenchymal cells. The successive changes in shape of these cells through the spherical, ellipsoidal, and spindle cellular phases are seen. The mesenchymal wall decreases in thickness, due to tension caused by epithelial tubular dilation. 4. The rotating spiral growth of the epithelial cells causes the formation of a series of mesenchymal cellular and fibrillar concentric rings due to the centripetal force of the former. 5. The circular, smooth muscle cells are differentiated in the outer, more condensed margins of the ring. At these points the developing tensional stresses are greater than within the ring. 6. The inner circular smooth muscle coat is the first one differentiated and is incident to the rapid growth of the epithelial tube in diameter. The former soon tends to restrict the growth of the epithelial tube in diameter. The tube, pursuing the lines of least resistance, grows in length. During the period of rapid growth in length the outer longitudinal muscle coat is in the process of formation. 7. The tensional stresses to which the elongated strained mesenchymal cells are subjected appear to be a dynamic stimulus to smooth muscle differentiation. 8. From this study of a closely graded and progressive series of sections of intestinal development, the conclusion is drawn that muscle tissue is not self-differentiating, in the strict sense of the term, but that the tension of differential growth acts as the stimulus to smooth muscle differentiation.     

CONCERNING THE INFLUENCE OF POLARIZED LIGHT ON THE GROWTH OF SEEDLINGS

While these experiments are not exhaustive, a sufficient number have been made to warrant the statement that the effect of polarized light of the visible spectrum on the growth of various seedlings and See PDF for Structure more particularly on the growth of Lupinus albus is somewhat different from that of non-polarized light. This is especially convincing in view of the results obtained with double sets of plants which were alternately exposed to polarized and non-polarized lights of the same intensities and at the same temperature. In every experiment thus performed the set which was placed in a polarizing chamber grew better. It is, furthermore, interesting to note that the phenomenon above observed did not take place when the seed portion of the plants was protected from light by wrapping with tinfoil. This agrees well with previous findings concerning the action of diastase on starch in polarized light. The above researches will be continued on a more elaborate scale but the results so far obtained are deemed worthy of publication in the form of a preliminary communication at the present time.     

PRELIMINARY OBSERVATIONS ON THE GROWTH OF TRANSPLANTEDPELTIGERA CANINAUNDER SEMI-NATURAL CONDITIONS

Peltigera caninathalli have been successfully transplanted onto soil in a garden and in flowerpots. Garden samples showed marked seasonality and achieved growth rates of 6·4 cm per year. Pot-grown samples showed variation in the growth of individual thallus lobes and established that, under different soil hydration regimes, permanently hydrated thalli could sustain considerable linear growth rates for at least 140 days.     

GROWTH AND ORGANIZED DEVELOPMENT OF CULTURED CELLS. V. THE GROWTH OF COLONIES FROM FREE CELLS ON NUTRIENT AGAR

When angiosperm cells are cultured in a liquid medium they may grow in the form of free, single cells and form small to large groups of cells. This has been shown in earlier papers. This paper deals with the growth of strains of cells (Daucus carota and Haplopappus gracilis cells were used), washed and filtered free from the larger groups, on nutrient agar media in Petri dishes, thus simulating familiar microbiological technique. Each discrete member of a suspension is referred to as a “unit.” On the order of 1–10% of the separate units of a suspension may be induced to grow into viable colonies, depending on the strain and the conditions employed. Whereas at least 30% of the free single carrot cells were shown to be capable of division, only up to about 4% continued their growth to form macroscopically visible colonies when they were widely dispersed. Coconut milk promotes the growth of carrot cells into colonies. Both coconut milk and napthaleneacetic acid, which interact synergistically, arc required for the growth of Haplopappus cells. Various techniques which affect viability (the frequency with which units grow into colonies) were investigated. The viability of carrot units was found (1) to increase with their density on the plates; (2) to decrease upon washing the suspensions prior to plating; (3) to increase with increasing initial size; and (4) to decrease to a vanishingly low value in rigorously filtered suspensions which consist principally of single cells, although the single cells were found to grow with appreciable frequency when the larger units were also present; and (5) to increase dramatically (100-fold) when a rigorously filtered suspension was plated on a medium upon which pieces of growing cultured tissue were placed. Thus, the induction of growth in free cells is enhanced, even in an environment nutritionally optimal for the growth of the larger cell masses, by as yet unknown factors which are contributed by the cells themselves, or by adjacent cells or groups of cells. It is suggested that within a group of cells growing in culture, and perhaps also in the organized growing regions of intact plants, the dividing cells are nourished or stimulated by adjacent but less frequently dividing cells. The implications of these results are discussed.