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At least 19 recordsLinked to original sources
PubMed1986

Resource allocation under poor growth conditions. A major role for growth substances in developmental plasticity.

This article argues that the basic function for growth substance is resource allocation under poor growth conditions. The following scheme is suggested. Plants in the wild frequently suffer a paucity of resources which result from interplant competition and ecological and local environmental variation. The strategy adopted by many plants particularly ruderals (from which crops may have evolved) to help mitigate these problems is phenotypic plasticity; the growth of the plant body is adjusted to best exploit the scarce resources and help achieve desirable growth and reproductive goals. Phenotypic plasticity requires decisions to be made concerning the diversion of scarce growth resources to one facet of development rather than another; for example, to height or leaf area rather than thickness; or, between tissues, stem rather than leaves. Growth substances are coupled to these individual facets of development. They represent a simple way in which the extent of resource diversion can be controlled. Cells in specific tissues acquire sensitivity to particular growth substances at a stage in their development when environmental variability often necessitates choices to be made. This acquisition of ontogenetic sensitivity may be all or none. It may reflect acquisition of receptor proteins coupled to specific metabolic events. However in well-nourished plants these phases of development are relatively insensitive to changes in the level of the growth substance/receptor complex. Cells become more sensitive under certain well-defined but specific circumstances, characterized by the general term, poor growth conditions. These are produced by imbalances in one or more of the major environmental (nutritional) requirements for growth, light, nitrogen, water and oxygen. Imbalance in one or more of these produces characteristic and far-reaching metabolic and protein synthesis changes which normally constrain the synthetic processes for growth but amplify metabolic events coupled to growth substances. It is the function of growth substances to circumvent some of these metabolically constraining steps and by applying a constant stimulus to one specific aspect of growth or metabolism permit continued development. The additional input of growth substances into particular facets of development ensures the better maintenance (protection) of that character when competition for resources inside the plant is severe. However competition for scarce resources ensures that continuation of one growth aspect generally leads to relative depletion of others.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Physiological↗
PubMed1979

Plant Growth Substances Produced by Azospirillum brasilense and Their Effect on the Growth of Pearl Millet (Pennisetum americanum L.).

Azospirillum brasilense, a nitrogen-fixing bacterium found in the rhizosphere of various grass species, was investigated to establish the effect on plant growth of growth substances produced by the bacteria. Thin-layer chromatography, high-pressure liquid chromatography, and bioassay were used to separate and identify plant growth substances produced by the bacteria in liquid culture. Indole acetic acid and indole lactic acid were produced by A. brasilense from tryptophan. Indole acetic acid production increased with increasing tryptophan concentration from 1 to 100 mug/ml. Indole acetic acid concentration also increased with the age of the culture until bacteria reached the stationary phase. Shaking favored the production of indole acetic acid, especially in a medium containing nitrogen. A small but biologically significant amount of gibberellin was detected in the culture medium. Also at least three cytokinin-like substances, equivalent to about 0.001 mug of kinetin per ml, were present. The morphology of pearl millet roots changed when plants in solution culture were inoculated. The number of lateral roots was increased, and all lateral roots were densely covered with root hairs. Experiments with pure plant hormones showed that gibberellin causes increased production of lateral roots. Cytokinin stimulated root hair formation, but reduced lateral root production and elongation of the main root. Combinations of indole acetic acid, gibberellin, and kinetin produced changes in root morphology of pearl millet similar to those produced by inoculation with A. brasilense.

Journal Article↗
PubMed2005

[Effects of plant growth substances on induction and culture of callus from Rhodiola quadrifida].

OBJECTIVE: To investigate the effect of plant growth substances on induction and culture of callus from Rhodiola quadrifida and also to analyze salidroside contents in the callus. METHOD: The optimum combination of plant growth substances in MS solid medium for induction and culture of callus was established using orthogonal design. The contents of salidroside was analyzed by HPLC. RESULT: MS medium containing 2,4-D 1 mg x L(-1), NAA 2 mg x L(-1), 6-BA 0.5 mg x L(-1) and KT 0.1 mg x L(-1) could induce the callus from R. quadrifida most effectively;the induction rate was 83.3%. The optimized combination of plant growth substances for callus subculture was 2,4-D 1 mg x L(-1), 6-BA 0.1 mg x L(-1) and KT 0.5 mg x L(-1). The dry weight could reach 11.77 g x L(-1) when the callus was cultured in the optimum medium for 30 d and salidroside content was 0.28%. CONCLUSION: The quantities of plant growth substances required for induction and culture of callus are different in R. quadrifida. The callus could produce salidroside.

Culture Media↗
PubMed2004

Growth stimulation of dwarf peas (Pisum sativum L.) through homeopathic potencies of plant growth substances.

BACKGROUND: Efficacy of higher homeopathic potencies is controversial. Universally accepted specific detection assays for homeopathic dilutions do not exist. Basic research has to develop a spectrum of standardized tools to investigate the mode of action and nature of homeopathic potencies. OBJECTIVE: Can the shoot growth reaction of dwarf peas (gibberellin- deficient mutants) be regarded as evidence of treatment with homeopathic potencies of plant growth substances? MATERIALS AND METHODS: Pea seed (Pisum sativum L. cv. Fruher Zwerg) is immersed for 24 hours in homeopathic potency or control solutions for soaking. Plants germinate and grow in a standard cultivation substrate under controlled environmental conditions. Shoot length is measured 14 days after planting. RESULTS: A screening of homeopathic potencies (12x-30x) of four different plant growth substances revealed biological activity of certain potency levels of gibberellin and kinetin (p < 0.05). Growth stimulation through gibberellin 17x (5 x 10(-18 M)) was assessed in six independent replications; results confirmed those of the screening (p < 0.05). The effect of gibberellin 17x seemed to weaken during the course of the experiments. CONCLUSION: The results back the hypothesis that homeopathic potencies of plant growth substances affect pea shoot growth. Dwarf peas might thus be an interesting system model for studying the action of homeopathic potencies. Further work is required to identify all boundary conditions modulating the reactivity of this system.

Adenine↗
PubMed1970

Effects of growth substances on the absorption and transport of iron plants.

The effects of a number of growth substances on the absorption and translocation of iron were studied in bean plants. Gibberellic acid application to the trifoliate leaf enhanced absorption of Fe applied to the primary leaf. 2-Chloroethyltrimethylammonium chloride increased absorption by the primary leaf while 6-furfurylaminopurine (kinetin) increased the transport of Fe from the primary leaf to other parts. When the roots were pretreated with gibberellic acid, the absorption of Fe by the primary leaf and subsequent transport to the trifoliate leaves were increased. Triiodobenzoic acid reduced the absorption and transport of Fe.Absorption of Fe by roots and transport to other parts were increased by pretreatment of the roots with gibberellic acid, 2-chloroethyltrimethylammonium chloride or N,N-dimethylaminosuccinamic acid for 3 days. An increase in the transport to other parts of Fe absorbed by roots was obtained when roots were exposed to the growth substances following Fe absorption.Absorption and transport of Fe in corn plants were much less than those of Rb and phosphate. Absorption and transport of Fe were greater in plants with decorticated roots than in those with intact roots. N,N-Dimethylaminosuccinamic acid significantly promoted the transport of root-absorbed Fe to the shoots of corn plants.

Journal Article↗