Growth-regulating Substances Research Articles

In vitro plantlet regeneration from plumule of Sorbus commixta seedlings : Effects of media and concentration of growth-regulating substances of plants and differences of individual stocks

In vitro plantlet regeneration from plumule of Sorbus commixta seedlings : Effects of media and concentration of growth-regulating substances of plants and differences of individual stocks

ETHYLENE PRODUCTION IN ANAEROBICALLY INCUBATED SOILS AMENDED WITH POULTRY LITTER

Ethylene is a plant growth-regulating substance that is produced by plants and soil microorganisms. Ethylene production and accumulation in soils is stimulated by the addition to the soil of compounds such as methionine, which serves as a direct precursor in ethylene biosynthesis, and by flooding, which encourages anaerobiosis. The objective of this laboratory study was to determine if the addition of either non-composted or composted broiler litter stimulated ethylene production in three ana-erobically incubated agricultural soils from eastern Arkansas. A completely randomized design was used, with non-composted and composted broiler litter as the two sources applied at three rates each. Check treatments received no litter. Both non-composted and composted poultry litter significantly increased production of ethylene in soils under flooded conditions, compared with the unamended control. At the highest rate of addition of non-composted litter (9.4 g kg-1), ethylene production in the Hilleman, Foley, and Bosket soils was 821, 678, and 327 nmol kg-1 soil, respectively. At the same rate of addition of composted litter, ethylene production in these same soils was 491, 440, and 254 nmol kg-1 soil. There were significant differences among soils in the quantities of ethylene produced, with the soil having the coarsest texture and lowest organic carbon content, the Bosket, producing the least ethylene. More ethylene was produced per gram of added carbon with non-composted litter than with composted litter. Differences in the abilities of the two wastes to promote ethylene production in soils may be due to differences in the bioavailability of carbon in the two materials. The compost had a lower total organic C content and a higher humic acid content than the non-composted material. The yield response of lowland rice to applications of poultry litter may be due in part to enhanced ethylene accumulation in the waste-amended soils.

Thienodolin, a New Plant Growth-regulating Substance Produced by a Streptomycete Strain: I. Taxonomy and Fermentation of the Producing Strain, and the Isolation and Characterization of Thienodolin

Thienodolin, a new plant growth-regulating substance, was isolated from the fermentation broth of a streptomycete strain identified as Streptomyces albogriseolus.The active principle was extracted with ethyl acetate and purified by silica gel column chromatography and preparative HPLC. The substance showed growth promoting activity with 1.2 × 10−6–1.2 × 10−5 M treatment to rice seedlings, and inhibitory activity with 4.0 × 10−5 M treatment.

Thienodolin, a New Plant Growth-regulating Substance Produced by a Streptomycete Strain: II. Structure of Thienodolin

Thienodolin is a new plant growth-regulating substance produced by a Streptomycete strain. The structure of thienodolin was determined to be 6-chloro-8H-thieno[2,3-b]indole-2-carboxamide by spectroscopic analyses and an X-ray crystallographic analysis.

Amidenin, a New Plant Growth-regulating Substance Isolated fromAmycolatopsissp.

Amidenin, a new plant growth-regulating substance, was isolated from the fermentation broth of an Amycolatopsis sp.The active principle was extracted with ethyl acetate and purified by silica gel column chromatography. The molecular formula of this substance was established as C10H17NO, and the structure was determined to be 2E,4Z-decadienamide by spectroscopic analyses. This substance showed growth-promoting activity with a 0.6 x 10−5-1.8 x 10−5M treatment to rice seedlings, and inhibitory activity with a 6.0 x 10−5M treatment.

MICROPROPAGACION DE NEPHROLEPIS EXALTATA L.

In vitro propagation of Nephrolepis exaltata L., was accomplished in 4 phases: 1. Initiation explants taken from apical portions of the stolon were cultivated in M.S. inorganic salts plus 0,4 mg/l Hcl tiamine, 100 mg/l m-inositol, 30 g/l Difco Bacto Agar at pH 5, 7. 2. Multiplication of that material in a similar medium as the one used before; but without kinetine. 3. Root of shoots took place in the multiplication medium devoided of the growth regulator substances, and decreasing sucrose to 10 g/l. 4. Plants were transplanted to sterilized medium (rice husk 2 parts, light sand 1 part, black soil 1 part, and horse manure 1/2 part), and placed under saran mesh. Starting with one explant, and considering 100% success in both the multiplicative and rooting phases, it's possible to obtain about 100.000 plants of Nephrolepis exaltata L. during a period of 6 months.

Role of cytokinin in enhanced productivity of maize supplied with NH4 + and NO3 −

Supplying both N forms (NH4 ++NO3 −) to the maize (Zea mays L.) plant can optimize productivity by enhancing reproductive development. However, the physiological factors responsible for this enhancement have not been elucidated, and may include the supply of cytokinin, a growth-regulating substance. Therefore, field and gravel hydroponic studies were conducted to examine the effect of N form (NH4 ++NO3 − versus predominantly NO3 −) and exogenous cytokinin treatment (six foliar applications of 22 μM 6-benzylaminopurine (BAP) during vegetative growth versus untreated) on productivity and yield of maize. For untreated plants, NH4 ++NO3 − nutrition increased grain yield by 11% and whole shoot N content by 6% compared with predominantly NO3 −. Cytokinin application to NO3 −-grown field plants increased grain yield to that of NH4 ++NO3 −-grown plants, which was the result of enhanced dry matter partitioning to the grain and decreased kernel abortion. Likewise, hydroponically grown maize supplied with NH4 ++NO3 − doubled anthesis earshoot weight, and enhanced the partitioning of dry matter to the shoot. NH4 ++NO3 − nutrition also increased earshoot N content by 200%, and whole shoot N accumulation by 25%. During vegetative growth, NH4 ++NO3 − plants had higher concentrations of endogenous cytokinins zeatin and zeatin riboside in root tips than NO3 −-grown plants. Based on these data, we suggest that the enhanced earshoot and grain production of plants supplied with NH4 ++NO3 − may be partly associated with an increased endogenous cytokinin supply.

The new plant physiology-molecular approaches to studying hormonal regulation of plant development

In early botany, the study of morphogenesis in higher plants started at the level of the whole plant and its organs, describing their life cycle and the formation of the vegetative and generative organs during plant development. This stage of morphology was followed by that of physiology, in which experimental interference with developmental processes aimed at the analysis of causal relationships in plant morphogenesis. The past century offers beautiful examples of sophisticated experimental analysis of such developmental processes as, e.g., apical dominance and flower induction. It became apparent that plant metabolism, growth and development are genetically determined, and that the expression of the genetic information is dependent upon and modulated by internal and environmental factors such as, e.g., hormones and light. Neither the nature of the genes and the extent of their expression in particular developmental processes, nor the mechanism of action of the endogenous growth-regulating substances mediating internal and external signals were understood, however, although it seemed reasonable to assume that hormones influence developmental processes by bringing about changes in gene expression. Application of biochemical knowledge and methodology allowed for extension of experimentation at the cellular and subcellular levels, leading in several cases to the unravelling of hormonal or light-induced effects on enzyme activities in metabolic pathways. However, the significance of research at the protein level for the explanation of morphogenetic effects at the organ or whole-plant level has been severely limited by the correlative nature of the argumentation. The evidence is largely derived from simultaneously occurring variations at both levels, but apart from such correlations a firm causal argument cannot be obtained from combining physiological and biochemical data alone. Moreover, cell division, extension and differentiation, as well as the formation of organs and the spatial and temporal integration of various meristematic activities all depend on the interplay between various hormonal signals. Different combinations of hormones may act independently, synergistically, or antagonistically, and can influence each other’s metabolism, recognition by cellular receptors, or signal-transduction pathways. These complex interactions stem in part from the stochastic nature of hormonal regulation in plants itself (Trewavas 1991) and give rise to the plasticity of plant development, in which the pattern of growth and development is open to modulation by internal and external constraints and growth of new organs is invariably linked to loss of function of old organs (Woolhouse 1978).

Root growth regulation and gravitropism in maize roots does not require the epidermis

We have earlier published observations showing that endogenous alterations in growth rate during gravitropism in maize roots (Zea mays L.) are unaffected by the orientation of cuts which remove epidermal and cortical tissue in the growing zone (Björkman and Cleland, 1988, Planta 176, 513-518). We concluded that the epidermis and cortex are not essential for transporting a growth-regulating signal in gravitropism or straight growth, nor for regulating the rate of tissue expansion. This conclusion has been challenged by Yang et al. (1990, Planta 180, 530-536), who contend that a shallow girdle around the entire perimeter of the root blocks gravitropic curvature and that this inhibition is the result of a requirement for epidermal cells to transport the growth-regulating signal. In this paper we demonstrate that the entire epidermis can be removed without blocking gravitropic curvature and show that the position of narrow girdles does not affect the location of curvature. We therefore conclude that the epidermis is not required for transport of a growth-regulating substance from the root cap to the growing zone, nor does it regulate the growth rate of the elongating zone of roots.

Cell cycle-dependent disruption of microtubules by methyl jasmonate in tobacco BY-2 cells

Methyl jasmonate, a growth-regulating substance that is ubiquitous in the plant kingdom, was found to disrupt cortical microtubules in tobacco cultured cells. It exerted a microtubule-disrupting effect only in cells at the S phase of the cell cycle. Neither microtubules in preprophase bands, spindles and phragmoplasts nor cortical microtubules at stages of the cell cycle other than the S phase were disrupted by methyl jasmonate. Jasmonic acid was as effective as methyl jasmonate in disrupting cortical microtubules.

Sugar unloading in roots of Ricinus communis L.

summaryThe intercellular pathway of sugar transport within tissues of Ricinus communis roots, which are available to exogenous solutions, was investigated to identify the route of phloem unloading. Less than 3%, of soluble translocate within the root system accumulates in root bathing media designed to influence the apoplastic movement of soluble sugars. Sucrose and hexoses make up 80% of the leaked translocate. The influence of plant growth regulator substances and of amino acid analogues upon the accumulation of translocate into the primary root has been evaluated and is discussed in relation to the symplastic transport of carbohydrate.

The role of water in the regulation of plant development

It is postulated that the changes in growth and metabolic activity that characterize many features of plant development are produced by the interaction between the hydraulic conductivity of the tissues and the influence of environmental factors, transpiration and osmotic gradients on the uptake, distribution, or loss of water. Mechanisms based on this concept are proposed for six aspects of development. These are (i) seed germination and stem elongation (water uptake), (ii) apical dominance and tropisms (water distribution), and (iii) leaf senescence and abscission (water loss). The postulated mechanisms are based on the hypothesis that water is the factor that normally limits the rate of growth and metabolic activity in the intact plant. The validity of the concept is supported by the unique capacity of water to perform three basic functions. These functions are (i) to mediate environmental effects on growth and metabolism, (ii) to correlate the growth of different parts of the plant, and (iii) to integrate growth and metabolic activity at the cellular level. It is also suggested that the responses induced by the application to plants of certain growth-regulating substances can be mainly attributed to the capacity of these substances to promote the uptake of water.

Cancer and normal ageing

Cancer has a monoclonal origin in a pre-mitotic cell and usually a multistep pathogenesis. The initiation of tumor development and most stages in tumor progression involve point mutations, chromosomal rearrangements, and often changes in gene dosage. Simultaneously, there is continuing selection of the cell clones most resistant to growth-regulating substances and/or lacking specific immunologic markers. Normal ageing is partly pre-programmed as demonstrated by the constancy of the maximum survival time for a species under various external conditions resulting in different mean survival times. Emerging evidence of characteristic DNA changes in post-mitotic cells of old individuals may turn out to be part of the programmed changes. However, random accumulation of mutational defects in both pre- and post-mitotic cells is an unavoidable consequence of physics and therefore contributes to normal ageing and the accompanying increase in cell diversity. Cancer incidence increases with age. Firstly, because extended exposure increases the risk of inflicting the DNA changes prerequisite to oncogenesis; secondly, because the progression from one malignant cell to detectable tumor is a matter of 10–30 per cent of a species maximum life span; and thirdly, because some alterations characteristic of normal ageing increase the susceptibility to carcinogens. There probably is an overlap of etiologic/accelerating factors for cancer and ageing. Such aspects of normal ageing such as decline in DNA repair capacity and decline in cellular immune reactivity should facilitate induction and early growth of neoplasia. Age changes that counteract cancer development include (hormonal) loss of proliferative stimulation and depletion of the pool of immature cells at greatest risk.

CARBOHYDRATE RESERVES AND PLANT GROWTH SUBSTANCE SENSITIVITY IN PLASTIDS, STOMATA AND STATOCYTES DURING SHOOT DEVELOPMENT

Starch grains are extremely rare in the plastids of dark-grown and greening cereals. Only plastids from very young dark-grown tissues (3–5 days from germination) or those cells which ultimately have a specialized function, such as statocytes, have prominent starch granules. Developing stomata are formed by dividing sub-epidermal cells which subsequently push into the epidermal layers. The plastids of such guard cells retain starch granules throughout this process. Studies using light-grown barley seedlings as a linear developmental model have shown that in a region close to the intercalary meristem above the earliest proplastids or eoplasts (which contain no starch grains) there is a distinctive amyloplast region which equally rapidly gives rise to a region above with starchless amoeboid plastids. Determination of patterns of carbohydrate content in light- grown, dark-grown and green cereal seedlings confirm that rapid starch accumulation and disappearance does appear to be an obligatory phase in the development of plastids in the light or in young, but not old, illuminated dark-grown tissue. In a preliminary study involving the use of various bioassays for plant growth regulator substances, regions in light-grown plants which rapidly form and mobilize starch grains have much higher contents of gibberellic acids and indol-3-yl-acetic acid than most other regions although the levels of abscisic acid are unchanged. It is concluded that a complex sequence of carbohydrate changes is involved in shoot development which is tissue specific and that only part of this synchronization is achieved by means of plant growth regulators. The sensitivity of such cells to growth substances changes as they mature.

Factors Affecting in Vitro Fatty Acid Content and Composition in Asexual Embryos of Theobroma cacao

Abstract Asexual embryos of cacao (Theobroma cacao L.) were grown for 45 days in a modified Murashige and Skoog (MS) liquid medium with sucrose concentration increased stepwise from 3% to 27% and supplemented with various concentrations of MS salts, inorganic and organic nitrogen (casein hydrolysate), phosphorus, potassium, coconut water, 6-benzylamino purine (BA), naphthaleneacetic acid (NAA), gibberellic acid (GA), and abscisic acid (ABA). Embryo growth decreased but fatty acid accumulation per gram dry weight was unaffected when total salt concentrations were less than full-strength MS levels. Growth and fatty acid accumulation was inhibited as total salt concentrations were increased from 1 × to 8 × full-strength MS levels. Eliminating inorganic nitrogen, organic nitrogen, potassium, and phosphorus from the medium tended to reduce embryo growth and fatty acid accumulation. None of the growth-regulating substances used increased fatty acid accumulation, but high concentrations of BA (10 and 100 ppm) or NAA (100 ppm) were inhibitory; there was little response to GA or ABA. An increase in total fatty acids in all experiments was associated with increased mole percentage of oleic and stearic acids and decreased linoleic and linolenic acids.

Effect of Combined Nitrogen in the Production of Plant-Growth Regulators by Azotobacter chroococcum

Summary A locally isolated strain of Azotobacter chroococcum was found to produce high amounts of plant-growth regulators when cultivated in a medium supplemented with combined nitrogen. In particular, ammonium sulphate and ammonium chloride were favourable for gibberellic acid and indole-3-acetic acid formation, respectively. In ammonium-enriched medium, production of the two growth-regulating substances increased by the addition of pyruvate, α-ketoglutarate and ascorbic acid. Molybdenum was required for the formation of high amount of indole-3-acetic acid, while molybdenum, iron (Fe ++ ) plus boron were favourable for active secretion of gibberellic acid. The relationship between the formation of plant-growth regulators and the sucrose concentration was studied in ammonium-enriched medium supplemented with pyruvate, α-ketoglutarate, ascorbic acid and the favourable trace elements. In case of indole-3-acetic acicl, 3% sucrose concentration was more efficient than higher concentrations. For gibberellic acid, 4% concentration was the best.

Production of Plant Growth-Regulating Substances by the Vesicular-Arbuscular Mycorrhizal Fungus Glomus mosseae

Glomus mosseae, a representative species of Endogonaceae (Phycomycetes) able to form vesicular-arbuscular mycorrhiza, was investigated for phytohormone production. Spores of G. mosseae were axenically germinated in water, and the resultant mycelial growth was assayed by standard procedures for extracting plant hormones from microbial cultures. Paper partition chromatography and specific bioassays were used to separate and identify plant growth-regulating substances. The microorganism synthesized at least two gibberellin-like substances, one with R(f) corresponding in position to authentic gibberellic acid, and four substances with the properties of cytokinins.

Influence of micro-organisms on the germination of the monocarpic Cirsium vulgare in relation to disturbance.

Cirsium vulgare is a plant species of disturbed sites. To understand this distribution the effect of micro-organisms on the germination in this species was investigated as the microflora of disturbed and non-disturbed sites shows differences. It was found that micro-organisms from fruitcoat and environment do influence germination. In an environment containing humus, germination is stimulated.Mortality of seedlings is higher in undisturbed sites, resulting in the observed distribution. It is hypothesized that this mortality is the result of germination, forced by microbial activity (break-down of the fruitcoat, exudation of growth-regulating substances) under conditions in which the survival chances of the seedling are low.

Growth-Regulating Substances and the Growth of Tiller Buds in Barley; Effects of Cytokinins

An hypothesis was set up from which it was predicted that application of cytokinin to barley seedlings grown without mineral nutrients would lead to rapid growth of the coleoptile and first leaf tiller buds. Application of cytokinins to the leaves was ineffective, but supplying a number of known cytokinins by steeping the roots of 4 d old seedlings in solution for 4 h led to significant growth of the coleoptile bud. Adenine and cytokinin analogues had no effect. Supplying cytokinins through the roots also further enhanced the growth of buds of plants given mineral nutrients. Cytokinin treatment reduced root dry matter, with small reductions in mean axis length and number of lateral roots. For plants not given mineral nutrients reduction in root weight was compensated by an increase in weight of the aerial parts; however, for plants supplied with mineral nutrients this was not so and the lower root weight resulted in a smaller total plant dry weight. An interpretation of tiller bud growth in terms of control by interacting effects of mineral nutrition, assimilate supply, and cytokinin availability is proposed.

Growth-Regulating Substances and the Growth of Tiller Buds in Barley; Effects of IAA and GA3

Application of cytokinin to barley seedlings grown without mineral nutrients leads to rapid growth of coleoptile and first leaf tiller buds. IAA and GA3 cannot substitute for cytokinin in this effect and applications of TIBA and CCC are also ineffective on bud growth. However, when bud growth was promoted, either by application of cytokinins or by supplying plants with mineral nutrients, IAA and GA3 applications caused enhanced tiller growth indicating that these compounds can stimulate growth of actively growing buds. The results are compatible with an interpretation which stresses the importance of cytokinin availability in determining tiller bud growth.