The plant‐growth‐promoting properties of gibberellic acid, a metabolic product of the fungus gibberella fujikuroi

Abstract

Gibberellic acid is a metabolic product of the fungus Gibberella fujikuroi, similar in physiological properties to the gibberellins described by Japanese investigators. Supplied in a nutrient solution to wheat plants growing in water culture, it causes increased growth of the shoots, as a result of increased length of stem internodes and leaves. The leaves are narrower and paler than those ot untreated plants. Under similar conditions pea seedlings develop much elongated stem internodes, but the leaves are little changed in size. These morphological responses are similar to those seen in etiolation.The total dry weight of both peas and wheat so treated is increased ; if shoots alone are considered the increase in dry weight is even greater ; the dry weight of roots is reduced, though this does not occur if the gibberellic acid is applied to the shoots in a lanolin paste. The increased dry weight is mainly attributable to increased carbon assimilation. Treated plants contain more soluble carbohydrate than controls, but this accounts only for a small part of the increased carboil assimilation. The increase in glucose content is particularly striking.Gibberellic acid is rapidly biologically degraded in soil. IntroductionA soil-borne fungus, Gibberella fujikuroi (Saw.) Wr. (conidial stage Fusarium m o d i f o r m eSheld.), is the cause of a disease of rice seedlings, not uncommon in Japan and other countries of the Far East, and recently found in Italy. A characteristic early symptom of the disease is elongation of the shoot, so that, in an infected crop, diseased plants are much taller than healthy ones, giving an impression that the crop has germinated unevenly. In the later stages of the disease fungal invasion causes considerable necrosis of basal tissues of the plant and the seedlings become weakly or die. Kurosawal showed in 1926 that the symptoms of overgrowth could be induced in rice seedlings by applying cell-free filtrates from liquid cultures of G. fujikuroi to the roots. This observation was confirmed and extended by other Japanese workers2-' shortly afterwards. The main features of the action established by this work were : (a) that though overgrowth of shoots 'was produced by culture filtrates, growth of roots was unaffected ; (b) that not only rice plants, but other plants, including dicotyledons as well as monocotyledons, responded by increased shoot growth ; (c) that the active material in culture filtrates could be adsorbed on charcoal and eluted by acetone or ether ; ( d ) that the increased height of plants was sometimes associated with an increase in dry weight, though more frequently dry weight was unaffected.An active material was isolated from culture filtrates in pure form by Yabuta & Hayashi,B which was named gibberellin A.e Another active material, gibberellin B, was also obtained, but gibberellin A was the main substance isolated. Its biological properties were described in a number of papers which will be referred to elsewhere in this paper. Gibberellin A produced overgrowth of seedlings ...

Effect of Biochemical Stimulants on Biomass Productivity and Metabolite Content of the Microalga, Chlorella sorokiniana

“…However, genetic manipulation leads to inheritable changes in a species that might affect the ecosystem adversely when used for environmental and agricultural applications. Attempts to improve microalgal biomass productivity using alternative means such as phytohormones and micronutrients has been reported a few times since the 1930's [3][4][5][6][7][8]. Although contemporary research on phytohormone action remains almost completely focused on the higher plants, there are a few studies devoted to auxins, in green algae from Chlorella and Scenedesmus genuses [9,10].…”

Gibberellic Acid Treatment Reduces the Tolerance of Field-Grown Common Bean to Leaf Removal

“…root/shoot ratio) in such a way that it could interfere with the ability of that plant to recover from a carbon stress like defoliation, whereas effects on hormone-treated, but otherwise healthy, plants not under biologic stress might go largely unnoticed. For example, gibberellic acid (GA 3 ) treatment in plants characteristically stimulates dry matter production in the shoot at the expense of dry weight increases in the root system, primarily through the creation of stronger photoassimilate sinks in the shoot (Brian et al 1954, Lovell 1971, Morris and Arthur 1985. If remobilization from root reserves is a component in the compensatory response of plants to leaf area removal, then GA 3 -treated plants may have fewer root reserves available to compensate for defoliation than untreated plants and may suffer greater growth and reproductive consequences following a defoliation event.…”

Influences of Gibberellic Acid on Metabolism of Indoleacetic Acid, Acetate, and Glucose in Roots of Higher Plants

“…In their study of photosynthesis in gibberellin treated leaves Haber and Tolbert (8) concluded that gibberellic acid neither enhanced the rate of CO2 fixation per unit of leaf tissue nor altered the general pathways of short time metabolism of the newly fixed C140, in the sugars, organic acids, and amino acid products. In long term experiments, great changes in carbohydrate constituents of gibberellin treated plants have been reported (4,9). Inhibition in the level of indoleacetic acid oxidase by gibberellic acid has been reported by Pilet (12).…”