AUXIN,CYTOKININ AND GROWTH OF EXCISED ROOTS OF BRYOPHYLLUM CALYCINUM

Excised roots 1 cm long of Bryophyllum calycinum required exogenous auxin (α-naphthaleneacetic acid) for growth in still culture in a medium of sucrose, mineral salts and vitamins. Little or no growth occurred with the addition of cytokinin (6-benzylaminopurine) alone to the basal medium. Best growth was obtained with combinations of 1 μg of auxin and 1 or 2 μg of cytokinin in 50 ml of medium. Larger amounts of the two phytohormones resulted in reduced growth.     

Synergism between Gibberellin and Auxin in the Growth of Intact Tomato

Gibberellin A_4&7 was more effective than gibberellic acid in increasing shoot elongation when applied to the apex of intact Lycopersicum esculentum seedlings of Tiny Tim, a dwarf cultivar, and Winsall, a tall cultivar. After 14 days, gibberellic acid and gibberellin A_4&7 stimulated growth of the dwarf more than the tall tomato. In tall tomato the application of indole-3-acetic acid alone (6.1 μg/plant) showed an inhibitory growth effect, but when applied with 17.5 μg per plant of gibberellic acid, it had a synergistic effect at 7 days but not at 14 days. When the auxin concentration was reduced to 0.61 μg per plant a synergistic effect was observed on tall plants at 7 and 14 days between indole-3-acetic acid and gibberellic acid. Application of gibberellin A_4&7 with auxin did not give a synergistic response in tall or dwarf tomato.     

Effects of Organic Nutrients and Hormones on Growth and Development of Tissue Explants from Coconut (Cocos nucifera) and Date (Phoenix dactylifera) Palms Cultured in vitro

The growth response (increase in weight) of cultured explants from seedling date (Phoenix dactylifera L.) and mature coconut (Cocos nucifera L. cv. Malayan Dwarf) palms to source and concentration of organic nitrogen. carbohydrate, auxins, cytokinins and gibberellins was examined. Growth was strongly stimulated by the presence of auxins (10^?7 to 10^?6M), cytokinins (10^?6 to 10^?5M), high concentrations of sucrose (0.2 M), and in the absence of NH₄Cl, by organic sources of reduced nitrogen. Higher concentrations of auxin (2,4-D or NAA at 10^?6 to 10^?5M) which still stimulated growth of Phoenix tissue, proved inhibitory to growth of freshly excised Cocos tissues. Explants from both palms initiated roots when subcultured on a medium with increased levels of auxin (NAA, 2.5 × 10^?6 to 2.5 × 10^?5M) and reduced levels of cytokinin (6-BAP, 5 × 10^?8M). Isolated roots excised from these explants continued growth and produced new laterals when subcultured on media with GA₃ (5 × 10^?7M) and reduced levels of auxin, cytokinin, and either minerals or sucrose.     

Differentiation in Lilium Bulbscales Grown in vitro. Effect of Various Cultural Conditions

Tissue cultures of Lilium auratum Lindl. and L. speciosum Thunb., which were derived from bulbscales, all appeared to differentiate organs. The effect of cultural conditions on the differentiation of bulblets and roots was examined. The best material for bulblet formation was bulbscales of intact or in vitro produced bulblets. The optimum temperature was 20°C and optimum pH was 6. Effect of irradiance on organ formation was not obvious but leaf emergence was stimulated. Higher kinetin concentrations stimulate the formation of numerous bulbscalcs. High NAA concentrations induce roots. On the other hand kinetin inhibits the NAA effect on root formation. A high sucrose concentration stimulated organ formation, but the number of bulblets was at a constant level in the medium containing between 10 and 90 g/l of sucrose. The formation of bulblets and their growth were stimulated at increasing strength of Murashige-Skoog's (MS) medium, but the length of roots was inhibited. Inter action of strength of MS medium and sucrose concentration was examined. High concentration of both components stimulated bulb lei growth, but the second strength of MS medium containing 90 or 120 g/l sucrose stimulated callus induction and inhibited the growth of bulblets. Maximum growth took 100 days for bulblets and about 50 days for roots. The change of fresh weight/dry weight ratio during differentiation is also discussed.     

INFLUENCE OF THE TONIC EFFECT OF GRAVITATION AND AUXIN ON CELL ELONGATION AND POLARITY IN ROOTS

The influence of a longitudinal (tonic) gravitational force and of auxin on the pattern of growth and cell polarity has been studied on intact roots of wheat seedlings. A klinostat technique was used for controlling gravitation. Growth in length was evaluated as cell division activity, rate of cell elongation (μ/h) and duration of elongation (h). Exogenous auxin (1-NAA) increases the rate of cell elongation in all concentrations tested (10⁻⁸ — 3 × 10⁻⁷m ) and shortens the time of elongation with increasing concentration. It promotes rate of cell elongation in roots as it does in shoots. It also accentuates the polar insertion of root hairs and their growth. The tonic effect of gravitation resembles that of an increase in auxin both in light and darkness. The results are discussed in relation to plagiotropic growth of roots, root growth promotions by auxin, and the difference between root and shoot growth.     

Morphogenesis in cell colonies grown from Convolvulus cell suspensions plated on synthetic media

Filtered cell suspensions of cultured callus tissue derived from the roots of Convolvulus arvensis L. were plated out on synthetic agar nutrient media in petri plates. Cell colonies which formed from the single cells or small cell groups in the suspension showed a considerable range of developmental patterns depending upon the physical and chemical environment to which they were exposed. Variation of the auxin and kinin concentrations and the nature and concentration of the source of reduced N compounds had the most profound effects on colony development. High auxin favored cell enlargement, high kinin favored the development of compact colonies composed of many small cells. Both auxin and kinin were required for cell colony formation. Cell differentiation responses which were observed but not subject to experimental control included formation of starch- and crystal-storing cells, differentiation of tracheary elements, formation of cellular filaments, and development of chlorophyllous tissue. Organ initiation was studied in cell colonies developed directly from plated cell suspensions and in cell colonies subcultured on various nutrient media. Bud initiation was produced repeatedly on media containing NAA at 10^-8 to 10^-6 m combined with kinetin at 10^-6 m . Root initiation was induced infrequently and unpredictably. Once roots had been formed from cell colonies derived from cell suspensions, the roots could be subcultured and induced to form buds; these in turn grew into whole plants. Subculture of young cell colonies to media containing different combinations of growth substances made possible a study of the effects of auxin and kinin on organization of primordia by the cell colonies. By following marked single cells plated on synthetic media, it was possible to produce single-cell clones which under proper nutrient conditions were induced to form buds. The value of the combined techniques of cell suspension culture and cell plating for the study of the physical and chemical factors influencing cell differentiation and organized development are pointed out.     

Acclimative changes in root epidermal cell fate in response to Fe and P deficiency: a specific role for auxin?

Summary Root hair formation and the development of transfer cells in the rhizodermis was investigated in various existing auxinrelated mutants ofArabidopsis thaliana and in the tomato mutantdiageotropica. Wild-type Arabidopsis plants showed increased formation of root hairs when the seedlings were cultivated in Fe- or P-free medium. These extranumerary hairs were located in normal positions and in positions normally occupied by nonhair cells, e.g., over periclinal walls of underlying cortical cells. Defects in auxin transport or reduced auxin sensitivity inhibited the formation of root hairs in response to Fe deficiency completely but did only partly affect initiation and elongation of hairs in P-deficient roots. Application of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid or the auxin analog 2,4-dichlorophenoxyacetic acid did not rescue the phenotype of the auxin-resistantaxr2 mutant under control and Fe-deficient conditions, indicating that functionalAXR2 product is required for translating the Fe deficiency signal into the formation of extra hairs. The development of extra hairs inaxr2 roots under P-replete conditions was not affected by auxin antagonists, suggesting that this process is independent of auxin signaling. In roots of tomato, growth under Fe-deficient conditions induced the formation of transfer cells in the root epidermis. Transfer cell frequency was enhanced by application of 2,4-dichlorophenoxyacetic acid but was not inhibited by the auxin transport inhibitor N-1-naphthylphthalamic acid. In thediageotropica mutant, which displays reduced sensitivity to auxin, transfer cells appeared to develop in both Fe-sufficient and Fe-deficient roots. Similar to the wild type, no reduction in transfer cell frequency was observed after application of the above auxin transport inhibitor. These data suggest that auxin has no primary function in inducing transfer cell development; the formation of transfer cells, however, appears to be affected by the hormonal balance of the plants.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - TIBA triiodobenzoic acid - NPA N-1-naphthylphthalamic acid - STS silver thiosulfate     

Effect of sucrose application,minerals, and irradiance on the <Emphasis Type="Italic">in vitro</Emphasis> growth of <Emphasis Type="Italic">Cistus incanus</Emphasis> seedlings and plantlets

To study the effect of sucrose on the sink-source relationship in in vitro-grown plants, Cistus incanus seedlings and plantlets were grown horizontally in a two-compartment Petri dish (split dish), with the root system in one compartment and the shoot in the other. Shoots and roots were exposed to different sucrose concentrations (0–30 g dm⁻³), two irradiance levels (25 and 160 μmol m⁻²s⁻¹) and the presence or absence of a minimum medium containing minerals and vitamins (M medium). Root and shoot biomass of the seedlings was enhanced by an increase in irradiance when the growth medium was not supplemented with sucrose indicating the role of photosynthesis in biomass production. When sucrose was added to either organ growth was enhanced as well. In the presence of sucrose in the root compartment, sucrose applied to the shoot compartment enhanced growth of both organs under low irradiance, while under high irradiance, sucrose had no further additive effect. In the absence of sucrose in the root compartment, the enhancement of root biomass by sucrose added to the shoot compartment was lower under high irradiance than under low irradiance. The response of Cistus plantlets to sucrose and irradiance differed from that of seedlings, probably reflecting a greater susceptibility of the plantlets to sucrose feedback inhibition on photosynthesis and biomass accumulation. The decrease in root and shoot growth when M medium was added to the shoot compartment and the relatively better growth of these organs when the roots were supplied with minerals and the shoot with sucrose, indicate that growth of the two organs in our experimental set-up was regulated by opposing fluxes of C and nutrients.     

Optimization of culturing conditions for the production of biomass and phenolics from adventitious roots ofEchinacea angustifolia

We investigated different concentrations of auxins (1AA, IBA, NAA), the strength of the MS medium, sucrose and ammonium/nitrate contents, initial medium pH, and inoculum size to determine their effects on biomass increase and the accumulation of total phenols and flavonoids in adventitious roots ofEchinacea angustifolia. These roots were cultured under darkness in shake flasks for 4 weeks. IBA proved the best auxin for inducing root proliferation. Root growth was inhibited when the initial pH was maintained below 5.0 or above 6.0. Nitrate, rather than ammonium, was more necessary for root growth and phenolics accumulations. Overall, biomass increased and total phenol and flavonoid contents were maximized under the following conditions: half-strength MS medium supplemented with 2 mg L^-1 IBA, 5% (w/v) sucrose, 5:25 (mM) ammonium/nitrate ratio, pH adjusted to 6.0 before autoclaving, and an inoculum size of 10 g L^-1 FW. These results indicate that the type ofin vitro environment strongly affects growth and the accumulation of phenolics from adventitious root cultures ofE. angustifolia. Such optimization is beneficial to large-scale production of biomass and secondary metabolites in that species.     

Growth substances in roots of tomato (Lycopersicon esculentum Mill.) infected with root-knot nematodes (Meloidogyne spp.)

Roots of tomato plants with galls caused by larvae of Meloidogyne spp. contained a similar concentration of auxin as uninfected roots, but a larger total amount because the roots of infected plants were heavier. The body contents and saliva or excretions of M. incognita larvae contained too little auxin to account for the increased amounts in infected roots. Roots with galls contained more bound auxin, released by alkaline hydrolysis or incubation after maceration, and more tryptophan and other amino acids, than uninfected roots. The larvae may hydrolyse the plant proteins to yield tryptophan, which may then react with the endogenous phenolic acids to produce auxin.     

REGULATORY ROLE OF INDOLE-3-ACETIC ACID AND GIBBERELLIC ACID IN VEGETATIVE DEVELOPMENT OF XANTHIUM PENNSYLVANICUM

A single application of gibberellic acid to young internodes significantly accelerated the rate of internode growth and the rate of leaf production in shoots of Xanthium pennsylvanicum Wallr. The average duration of one plastochron in treated plants was reduced to 43% of control levels. Gibberellic acid also had a pronounced morphogenetic effect on leaves so that the area and leaf length of treated plants were both significantly reduced. Depending upon concentration, auxin had both inhibitory and promotive effects on Xanthium shoots. Indole-3-acetic acid markedly altered the response of the gibberellic acid-treated internodes and those located above and below the site of application. In addition, high auxin concentrations induced the formation of adventitious roots in treated internodes. Auxin also brought about significant reductions in the length and area of leaves developed under the influence of this hormone.     

A New Tomato Mutant Inefficient in the Transport of Iron

An Fe-inefficient tomato mutant, T3238fe (Lycopersicon esculentum) was identified by growing the plants in solution cultures containing different concentrations of FeHEDTA. Approach grafts of T3238Fe (Fe-efficient) top on T3238fe rootstock and vice versa, located the cause of Fe inefficiency in T3238fe roots. The T3238Fe tomato takes up more Fe than T3238fe and it responds favorably to Fe-stress by releasing hydrogen ions from its roots, increasing reduction of Fe³⁺ to Fe²⁺ at its roots, and increasing the citrate concentration in its roots. T3238fe showed very little response to Fe stress; it was unable to absorb and transport adequate Fe from PeEDDHA to support growth.     

Characterization of the growth and auxin physiology of roots of the tomato mutant,diageotropica

Roots of the tomato (Lycopersicon esculentum, Mill.) mutant diageotropica (dgt) exhibit an altered phenotype. These roots are agravitropic and lack lateral roots. Relative to wild-type (VFN8) roots, dgt roots are less sensitive to growth inhibition by exogenously applied IAA and auxin transport inhibitors (phytotropins), and the roots exhibit a reduction in maximal growth inhibition in response to ethylene. However, IAA transport through roots, binding of the phytotropin, tritiated naphthylphthalamic acid ([³H]NPA), to root microsomal membranes, NPA-sensitive IAA uptake by root segments, and uptake of [³H]NPA into root segments are all similar in mutant and wild-type roots. We speculate that the reduced sensitivity of dgt root growth to auxin-transport inhibitors and ethylene is an indirect result of the reduction in sensitivity to auxin in this single gene, recessive mutant. We conclude that dgt roots, like dgt shoots, exhibit abnormalities indicating they have a defect associated with or affecting a primary site of auxin perception or action.Abbreviations BCA bicinchoninic acid - IAA indole 3-acetic acid - dgt diageotropica - IC₅₀ concentration for 50% inhibition of growth - NPA N-1-naphthylphthalamic acid - SCB-1 semicarbazone 1 This research was supported by grants from Sandoz Agro, Inc. (G.K.M), the National Aeronautics and Space Administration (NASA) and the National Science Foundation (T.L.L), and NASA (D.L.R.).     

Glutathione and phytochelatin contents in tomato plants exposed to cadmium

The effect of cadmium on growth and contents of glutathione (GSH) and phytochelatins (PCs) were investigated in roots and leaves of tomato plants (Lycopersicon esculentum Mill. cv. 63/5 F1). The accumulation of Cd increased with external Cd concentrations and was considerably higher in roots than in leaves. Dry mass production decreased under Cd treatment especially in leaves. In both roots and leaves, exposure to Cd caused an appreciable decline in GSH contents and increase in PCs synthesis proportional to Cd concentrations in the growth medium. At the same Cd concentration, PCs production was higher in roots than in leaves. The implication of glutathione in PC synthesis was strongly suggested by the use of buthionine sulfoximine (BSO). The major fraction of Cd accumulated by tomato roots was in the form of a Cd-PCs complex.     

SOME EFFECTS OF KINETIN ON THE GROWTH AND FLOWERING OF INTACT GREEN PLANTS

Wittwer , S. H., and R. R. Dedolph . (Michigan State U., E. Lansing.) Some effects of kinotin on the growth and flowering of intact green plants. Amer. Jour. Bot. 50(4): 330–336. Illus. 1963.—Dry matter accumulation of aerial parts, and heights of tomato, cucumber, and pea plants were markedly reduced when kinetin was incorporated into the culture solution root medium in concentrations ranging from 10^–5 to 10^–7 M. Concentrations which suppressed top growth (height, dry weight) generally had lesser effects on root growth and, in some instances, enhanced it. Thus top/root ratios were greatly reduced and approached unity in kinetin-treated peas and tomatoes. Flowering was inhibited in tomatoes and accelerated in peas. There were marked changes in root morphology, including the formation of pseudonodules. Kinetin had an effect which was opposite to that of gibberellin on internode elongation, root extension, top/root ratios and flowering of dwarf peas. N⁶-benzyladenine was more active than kinetin in suppressing the growth of intact green plants. The data show that kinetin can markedly alter the behavior of intact plants when absorbed by the roots from culture solutions in which the concentrations are comparable to those which are biologically active on explants.     

Metabolic responses of Lemna minor to lead ions I. Growth, chlorophyll level and activity of fermentative enzymes

Duckweed Lemna minor L. was grown on Wang culture medium supplemented with lead ions for 24 hours. Metal was tested at 1.5, 3 and 6 mg·dm⁻³ concentrations. The growth of Lemna minor was inhibited by lead ions, but the dry to fresh weight ratio increased as the concentration of Pb²⁺ in the medium increased. With increased concentrations of Pb ions, the contents of chlorophyll a and chlorophyll b in roots and fronds were correspondingly lower in comparision with the control. The effect of lead upon activities of some glycolitic and fermentative enzymes in roots of duckweed was examined. The activity of pyruvate kinase decreased with increasing lead concentrations, but cytosolic malate dehydrogenase behaved in an opposite manner. The lowest concentration of Pb stimulated alcohol dehydrogenase; phosphoenolopyruvate carboxylase activity was maintained at relatively constant values at all tested lead concentrations.     

EFFECTS OF AUXIN ON CELL ENLARGEMENT IN FERN GAMETOPHYTES: DEVELOPMENTAL STAGE OF THE CELL AND RESPONSE TO AUXIN

When gametophytes of Onoclea sensibilis are placed on an auxin-containing medium in darkness, the cells of the plant increase in length and width. Measurements were made to determine the effects of cell age and auxin concentration on the magnitude of the cells’ response. When comparing final size with size before auxin treatment, the youngest cells have the greatest response. However, they also have the greatest endogenous growth. The optimum auxin concentration for increase in length changes with the age of the cells. The greatest length is attained in young cells with an auxin concentration of 10^−-6–10^−-7 m; 10^−-5 m auxin is supraoptimal. The greatest increase in width of the cells is produced by 10^−-5 m auxin, regardless of cell age. The data are believed best to be interpreted as showing an age-dependent change in the capacity of the cells to respond to auxin.     

Effects of heavy metal (Pb) on arbuscular mycorrhizal fungi in vitro

The responses of Ri-TDNA-transformed roots and arbuscular mycorrhizal fungi established on Ri-TDNA-transformed roots to lead-amended media was investigated in vitro. At exposure to increasing concentrations of lead (2–10 mg/l[ppm]), three Ri-TDNA-transformed root clones viz., Swa, Swb and Swc, exhibited profuse growth. At exposure to increasing concentrations of lead (0.1–5 ppm), the dual cultures of Ri-TDNA-transformed roots and arbuscular mycorrhizal fungi., Glomus lamellosum/Swa, Glomus intraradices/Swb and Glomus proliferum/Swc, exhibited tolerance to 5 ppm of lead. When subjected to one physiological stress, either exposure to Pb or inoculation with AM fungi, Ri-TDNA-transformed root clones exuded more phenols in the growth medium than retained in the roots. When subjected to dual physiological stress, mycorrhizal Ri-TDNA-transformed roots growing on Pb-enriched medium, the total phenol content increased in the roots and exudation into the medium decreased.