Beijerinckia derxii releases plant growth regulators and amino acids in synthetic media independent of nitrogenase activity.

AIMS: This study aims at evaluating the ability of Beijerinckia derxii, a free-living nitrogen (N)-fixing bacterium frequently isolated from tropical soils, to release certain plant growth regulators [indoleacetic acid (IAA), ethylene, polyamines] and amino acids into the growth medium. METHODS AND RESULTS: The production of those substances was compared using both cultures in which nitrogenase was active (N-free medium) and cultures in which nitrogenase was repressed (combined-N cultures). Those cultures were grown under agitation and in absence of agitation. Total IAA production was higher in agitated, N-free cultures but specific production was greater in combined-N cultures under agitation. Putrescine and spermidine were detected under all conditions tested. Ethylene was produced in both N-free and combined-N cultures. A greatest diversity of amino acids was released in N-free cultures. CONCLUSIONS: There was no inhibition of the production of the analysed substances under conditions where nitrogenase was inactive. SIGNIFICANCE AND IMPACT OF THE STUDY: Beijerinckia derxii is potentially a producer of plant-active substances; its presence in the natural environment suggests that this bacterium may contribute to the development of other living organisms.

Plant growth regulators and amino acids released by Azospirillum sp in chemically defined media.

AIMS: To investigate the ability of Azospirillum sp., a facultative endophitic diazotrophic bacterium, to release plant growth regulators (PGR) such as polyamines, ethylene, indoleacetic acid and amino acids in both combined-N and N-free cultures. METHODS AND RESULTS: The presence of those substances was analysed by HPLC. Azospirillum sp. is capable of releasing PGR and amino acids into the culture medium. CONCLUSIONS: The type and quantity of the released substances varied, depending on the presence of combined-N in the medium. SIGNIFICANCE AND IMPACT OF THE STUDY: A better knowledge of PGR produced by Azospirillum sp. has been gained.

Phenylpropanoid derivatives and biflavones at different stages of differentiation and development of Araucaria angustifolia.

Chemical investigations carried out with tissues at different developmental stages of Araucaria angustifolia established the presence of E and Z isomers of octadecyl p-coumarate and octadecyl ferulate in undifferentiated callus; in the seedling stems, the source of explants, three biflavones of the amentoflavone-type were isolated, whereas the diterpene, trans-communic acid, was obtained from the seedling roots. Adult stems accumulated the benzaldehydes, vanillin, p-hydroxybenzaldehyde and coniferaldehyde; the lignans, pinoresinol, eudesmin and lariciresinol; and the isoflavones, cabreuvine and irisolidone.

Micropropagation of Stevia rebaudiana Through Leaf Explants from Adult Plants.

A micropropagation method for STEVIA REBAUDIANA plants was established by culturing young leaves of adult plants on medium containing 6-benzyladenine (BA) (2.0 mg/l) in the light or BA (2.0 mg/l) plus 1-naphthaleneacetic acid (NAA) (2.0 mg/l) in the dark. An open-ended system was obtained by transfer of the regenerating material to medium containing BA (0.1 mg/l), with continuous subculture and isolation of suitable shoots. Auxin addition to the rooting medium (especially at 0.1 mg/l 3-indolebutyric acid - IBA) favored root formation and improved EXTRA VITRUM plant survival. Regenerated plants transferred to the soil were uniform and cytological observation in root tip cells showed normal chromosome number (2n = 22). Cultures treated with colchicine originated altered plants.

Somatic embryogenesis and plant regeneration in embryo cultures of Euterpe edulis mart. (palmae).

The induction of somatic embryogenesis in embryo cultures of Euterpe edulis is described. The basal medium was composed of LS salts and Morel & Wetmore vitamins. Activated charcoal was added to prevent explant oxidation. 2,4-D higher than 50 mg/l was necessary for inducing embryogenesis which occurs 45-180 days after the start of cultures. Embryos arise directly from surface proliferating tissues on the matrix structure , without callus formation. The transfer of tissues with embryo clusters to medium with NAA plus 2iP, or without growth regulators, induces embryo development into plantlets.

Tissue, cell culture and micropropagation of Mandevilla velutina, a natural source of a bradykinin antagonist.

Leaf, stem and root explants of Mandevilla velutina were cultured in vitro and produced vigorous callus in LS basal medium containing one auxin (2,4-D or NAA) plus BAP. Calli can be subcultured indefinitely with vigorous growth. Subculture of calli to NAA (1.0 mg/l) plus BAP (5.0 mg/l) caused profuse regeneration of shoots. Isolated shoots were rooted in basal medium plus NAA (5.0 mg/l) or IBA (8.0 mg/l). Rapidly growing cell suspensions can be easily obtained from friable callus cultured in liquid medium.

Production, maintenance and plant regeneration from cell suspension cultures of Stevia rebaudiana (Bert.) Bertoni.

A method is described for producing and maintaining Stevia rebaudiana suspensions and regeneration of plants from calli derived from cell suspensions. Suspension cultures composed of isolated cells (ca. 10%) and cellular aggregates (5-100 cells) were obtained in 20-30 days by using friable callus as the initial inoculum in liquid media with BA (0.5 mg/l)+2,4-D (1.0 mg/l), and periodic filtering (100-500 µm sieves) with 6-7 days interval between subcultures. Cultures derived from actively growing calli are mainly diploid (2n=22) whereas those derived from senescent calli showed a wide variation in chromosome number (55-200). Stock cell suspensions which had been maintained for 3 years were plated on basal LS agar medium with BA (0.5 mg/l)+2,4D (0.5 mg/l) to form callus. Calli originating from predominantly 2n cell suspensions when transferred to medium with K (2.0 mg/l)+NAA (0.02 mg/l) were able to form buds. Shoot elongation and further rooting of isolated shoots was better on LS medium devoid of growth regulators. Variation in rooting capacity, plant vigour, morphological characters and chromosome number was found amongst regenerated plants.

Effects of some growth regulators on in vitro flowering of Streptocarpus nobilis.

Leaf discs from vegetative Streptocarpus nobilis plants were cultured in vitro in media with cytokinin (BAP or K at 0.35 mg.1(-1)) and auxin (IAA, NAA or 2,4-D at 0.1 mg.1(-1)). Under short days (8-h photoperiod) in medium with IAA and BAP, floral buds developed in 100% of the cultures; under long days (16-h photoperiod) only shoots were formed. In medium with IAA and K, flowering was reduced. Flowers rarely formed in medium containing NAA and K, but roots developed profusely. NAA + BAP promoted leafy shoots which rarely flowered later. The effect of 2,4-D was to inhibit flowering completely and to induce callusing and formation of teratomous structures.

Morphological patterns in Petunia hybrida plants regenerated from tissue cultures and differing by their ploidy.

Quantitative variation in seven morphological characteristics (leaf length and width, leaf length/ width ratio, flower, petal and stomata length, and number of chloroplasts in guard cells) were studied in Petunia hybrida plants regenerated from anther tissue culture and belonging to four different classes of ploidy (2n, 2n-3n, 3n-2n, 4n-8n). Results showed that leaf size is not a good characteristic for discriminating between plants of different ploidy - flower and stomata characteristics being more adequate for this purpose. After applying stepwise discriminant analysis the association "chloroplast number - leaf length/width ratio - petal length" was verified to be more appropriate for the discrimination of ploidy classes.