INTERCELLULAR COMMUNICATION AND TISSUE GROWTH : II. Tissue Regeneration

Intercellular communication was examined in regenerating rat liver and urodele skin, two tissues of fast but normal growth. In both, cellular communication is in general as good as in their respective normal intact state. This stands in striking contrast to the lack of cellular communication in tissues with cancerous growth. Upon wounding of the urodele skin, the normally permeable junctional membranes of cells near the wound border seal themselves off, thereby insulating the interiors of the communicated cell systems from the exterior. When the cells of two opposing borders make mechanical contact in the course of wound closure, communication between them ensues within 30 min. Within this period all cell movement also ceases ("contact inhibition"). The possible implications of these findings in the control of tissue growth are discussed.     

INTERCELLULAR COMMUNICATION AND TISSUE GROWTH : III. Thyroid Cancer

Intercellular communication was examined in normal and cancerous isolated thyroids with an intracellular electrical technique. The cells of normal thyroid (rat, mouse, hamster, man) communicate, within any given follicle, through permeable junctions. The cells of a wide variety of thyroid cancers (rat, hamster) do not communicate to any detectable degree and have resting membrane potentials lower than those of normal cells.     

AUXIN-INDUCED GROWTH OP TUBER TISSUE OP JERUSALEM ARTICHOKE: III. EFFECT OF ACTINOMYCIN D ON AUXIN-INDUCED EXPANSION GROWTH AND RNA SYNTHESIS

1. The following results were obtained using tissue slices excisedfrom cold-stored Jerusalem artichoke tubers.
2. Actinomycin Dat the concentration of 20 µg/ml given duringthe agingperiod did not affect the subsequent expansion growthcausedby auxin or auxin plus kinetin.
3. Actinomycin D given in thegrowth period, on the other hand,strongly inhibited the expansiongrowth of tissue slices agedin the absence of the antibiotic.
4. In the growth period, auxin or auxin plus kinetin promotedtheincorporation of uracil-2-¹⁴C into RNA fraction.
5. ActinomycinD inhibited the incorporation of ³²P orthophosphateinto ribosomalRNA during the aging period.
6. In the growth period, the incorporationof ³²P into RNA wasenhanced by auxin and was inhibited by actinomycinD, more remarkablyin ribosomal RNA than in lighter RNA.

¹A part of this paper was presented at the Conference on PlantGrowth Regulators held by the New York Academy of Sciences onMay 16, 1966.     

麝腓腺生长发育与化学通讯机能的探讨

本文对麝的腓腺进行了生长发育与组织化学观察。腓腺由丰富的顶泌汗腺组成,分泌混合性粘多糖成分的信息素。出生８０日龄幼麝的腓腺开始有分泌功能,成体时其分泌功能旺盛。麝以直接和间接方式释放信息素。     

SEEDLING GROWTH STUDIES OF EARLY-RIPENING PEACHES. I. INTERRELATIONSHIP BETWEEN EMBRYO MATURITY,GROWTH SUBSTANCES AND SEEDLING GROWTH

Weaver , Gerald M., and L. Fredric Hough . (Rutgers, The State Univ., New Brunswick, N. J.) Seedling growth studies of early-ripening peaches. I. Interrelationship between embryo maturity, growth substances and seedling growth. Amer. Jour. Bot. 46(10): 718–724. Illus. 1959.—Peach fruits of ‘Raritan Rose’ were harvested 75, 83, 91, 99 and 107 days after full bloom. Embryos were excised, and cultured on artificial media. Growth responses following 8 wk. cold treatment varied considerably with embryo maturity. No correlation existed between seedling survival and the initial responses of shoots. Root growth of 83-day embryos exceeded that of all other stages of maturity. This was reflected in maximum seedling survival and vigor. Initial shoot growth was greatest from embryos harvested at 91 days and at maturity (107 days), but all shoots developed into rosettes which may expand slightly or develop normally from axillary buds. Bioassays of growth substances suggest a strong correlation between early shoot development and auxin concentration. Root growth-responses appeared to be correlated with a promotor-inhibitor balance. The results of wheat coleoptile assays of embryo extracts chromatographed in an isopropanol: ammonia: water solvent (8:1:1) suggest the presence of three growth promotors, in greatest concentration at Rf 0.70, but also at Rf values 0.10 and 0.30. Two growth inhibitors were present in embryo tissue at Rf values 0.27 and 0.96, the former decreasing in concentration with increasing embryo maturity.     

GROWTH REGULATION BY ETHYLENE IN FERN GAMETOPHYTES. I. EFFECTS ON PROTONEMAL AND RHIZOIDAL GROWTH AND INTERACTION WITH AUXIN

Three responses resulted from the treatment with ethylene of dark-grown gametophytes of Onoclea sensibilis. Elongation of the filament was increased, elongation of the rhizoid was decreased, and cell division was inhibited. The optimal ethylene concentrations were between 0.01 and 0.1 ppm. Filament elongation was very tolerant of high ethylene concentrations, since up to 1,000 ppm did not inhibit growth below control levels. Enclosing cultures of gametophytes in chambers of limited volumes produced all the effects of treatment with ethylene, but the responses to sealing were eliminated if plants were enclosed in a chamber which contained a solution of mercuric Perchlorate. This evidence that gametophytes produced ethylene was substantiated by a direct gas chromatographic demonstration of ethylene formation. The growth-regulating effects of ethylene and auxin appeared to be independent in filament and rhizoid growth. Inhibition of elongation by supra-optimal auxin concentrations could not be attributed to an auxin-stimulated production of ethylene.     

The Role of Boron in Plant Growth: I. THE EFFECT ON GENERAL GROWTH, SEED PRODUCTION AND CYTOLOGICAL BEHAVIOUR

The relation of boron to vegetative growth and seed productionof Trifolium pratense L. and Vicia faba L. has been studiedusing sand and water culture techniques. It was found that theaddition of a very small quantity of boron was sufficient torestore deficient plants to normal growth and it would appearthat boron fertilizers will only be beneficial where deficiencysymptoms have been shown. The rapid cessation of cell division under conditions of borondeficiency was demonstrated and was responsible for a decreasein both vegetative and seed yields through reduced branchingand flower differentiation. No special association of boronwith the functioning of pollen or with chromosome behaviourwas found. The cessation of cell division is responsible forthe abnormalities associated with boron deficiency but the cellularreactions involved remain unknown. Previous suggestions of the role of boron in plant metabolismare discussed in the light of the conclusion that boron is essentialfor the maintenance of meristems.     

TIME RELATIONS OF GROWTH : I. GENETIC GROWTH CONSTANTS OF ANIMALS.

This paper is the first in a series proposing to evaluate growth constants from the viewpoint of and by the methods of the physical chemist. After discussing the physicochemical conception of growth, tentative numerical values of two growth constants are given for several species of animals including man, and the methods of computation are discussed in detail.     

TRICHOBLASTS IN HYDROCHARIS. I. ORIGIN. DIFFERENTIATION,DIMENSIONS AND GROWTH

In the root epidermis of Hydrocharis morsus-ranae L. distinctive trichoblasts, which later grow out as root hairs, are formed by the unequal division of protodermal (immature epidermal) cells. The trichoblast is the more proximal product of this division. Trichoblasts differ from adjacent epidermal cells in manner of growth, in size, amount of cytoplasm, degree of succinic dehydrogenase and cytochrome oxidase activity, and in the structure of their plastids. Plastids in the trichoblasts gradually become colorless and of less complex structure with increasing distance from the root tip, in contrast to those in adjacent epidermal cells. The trichoblasts do not divide, but they elongate to a considerable extent in the most distal 3000 μ of the root tip and less extensively in the next 3000 μ. By contrast the sister cells and their products divide, but the individual products do not become markedly longer than the mother cell until situated more than 3000 μ from the root tip, when they undergo extensive elongation. The trichoblasts are thus characterized by delayed maturation and inhibition of cytokinesis; it is suggested that delayed maturation is a necessary prerequisite for differentiation of root hairs in this and other species.     

GROWTH FACTOR INTERACTIONS IN THE TISSUE CULTURE OF TUMOROUS AND NONTUMOROUS NICOTIANA GLAUCA-LANGSDORFFII

Schaeffer , Gideon W., Harold H. Smith and Marion P. Perkus . (Brookhaven Natl. Lab., Upton, N. Y.) Growth factor interactions in the tissue culture of tumorous and nontumorous Nicotiana glauca-langsdorffii. Amer. Jour. Bot. 50(8): 766–771. Illus. 1963.—Tissues representing tumorous and nontumorous Nicotiana glauca-langsdorffii were cultured on high (5 ×) and low (1 ×) concentrations of a modified White's basal medium containing 2.9 × 10^–6m indoleacetic acid. The growth responses of tissues of both the tumorous and nontumorous genotypes to supplements of kinetin, glutamine, inositol and nucleic acid constituents added singly and in all combinations were noted on high-salt media. The nucleic acid components inhibited growth and were omitted from low-salt media. The best growth response was observed with glutamine and inositol for tissues from the tumorous hybrid and with glutamine, inositol and kinetin in the nontumorous type. Kinetin was a distinct and consistent requirement for rapid growth of nontumorous tissues, but no appreciable kinetin effect could be observed with tissues from the tumorous genotype.     

Freezing in Conifer Xylem: I. PRESSURE CHANGES AND GROWTH VELOCITY OF ICE

To determine whether freezing causes wide-spread cavitationin the xylem of freezing trees, pressure and temperature weremeasured inside freezing conifer sapwood blocks. Pressure risesof up to 3.3 MPa were recorded and average radial growth velocitiesof ice were between 1.75 and 2.3 µm s^–l. These growthvelocities of ice are less than the minimum growth velocityfor bubble nucleation during freezing. To complement this experimental study finite difference modelsof freezing in a single tracheid and freezing in an idealizedtree stem were constructed. The single tracheid model predictspressure rises similar to those measured experimentally. Thismodel also predicts that 5% to 8% of water in a tracheid lumenmigrates out of the tracheid during freezing. The tree stemmodel predicts growth velocities of ice three times faster thanthe values measured experimentally. These results are compared with previous contradictory theoriesof freezing in conifers. Key words: Freezing, xylem     

Control of Wheat Root Elongation Growth: I. EFFECTS OF IONS ON GROWTH RATE, WALL RHEOLOGY AND CELL WATER RELATIONS

Pritchard, J., Tomos, A. D. and Wyn Jones, R. G. 1987. Controlof wheat root elongation growth. I. Effects of ions on growthrate, wall rheology and cell water relations.—J. exp.Bot. 38: 948–959. The nature of the ions in the bathing medium of hydroponicallygrown wheat seedlings strongly influenced root growth rate.In 0·5 mol m^–3 CaSO₄ the growth rate was 32 mm24 h^–1 (used as 100% control rate). K⁺ and SO^– ions(10 mol m^–3) each inhibited extension growth (to about40% and 70% of the control value respectively). In the absenceof K⁺, Cl^– greatly reduced the inhibition due to SO₄^2–.Measurement of tissue plasticity and elasticity in the expandingzone with an Instron-type tensiometer indicated that both werea function of growth rate although relationship of plasticityto growth rate was the steeper and the more pronounced. Turgor pressure at the proximal end of the expanding zone wasnot correlated to growth, being approximately 0·65 MPain all treatments. In mature tissue turgor pressure varied withtreatment, but was also not related to growth rate. Cell membranehydraulic conductivity (5 x 10^–7 ± 1·3 (10)m s^–1 MPa^–2) was not influenced by the presenceof K⁺. We propose that K⁺ and SO₄^{2 –} influence root growthrates by modulating the rheological properties of the wallsof the expanding cell. The physiological significance of these properties is discussed. Key words: Growth, wall extensibility, turgor pressure, wheat roots     

The Potassium Relations of Lemna minor L.: I. POTASSIUM UPTAKE AND PLANT GROWTH

A simple expression has been derived to predict the rate ofnet K uptake into exponentially growing plants of Lemna minor.Net uptake predictions are in good quantitative agreement withmeasurements of ‘steady-state’ K influx, indicatingthat, in the ‘steady state’, K movements in theplant are essentially undirectional and that efflux is small.This close matching of inward K movement to the demands of theexpanding tissue is temporarily disturbed if plants are transferredto media of different K status. Uptake rates in the ‘step-up’are initially enhanced and then fall gradually towards a new‘steady-state’ rate. In contrast, the ‘step-down’causes an initial depression of uptake and then rates increasegradually towards the new ‘steady-state’ rate. Itis argued that these changes in uptake rates are associatedwith alterations in the cytoplasmic K content.