The Nature of Root-Promoting Substances in Lycopersicon esculentum Seedlings

Determination of the organ sites and chemical nature of root-promoting substances in Lycopersicon esculentum seedlings was made. Results of organ excision indicated that the young cotyledons were the primary site of root-promoting substances. As the cotyledon matured, its root-promoting activity decreased while that of the developing plumular leaves increased. Application of 2,3,5-triiodobenzoic acid (TIBA) at 10^?3 M in lanolin to the hypocotyl below the cotyledonary node significantly prevented root formation. Bioassay, using a new tomato rooting test, of the basic, acidic and bound fractions of the cotyledon extracts after paper chromatography showed biological activities in all three fractions. Gas-liquid chromatography of selected active regions of the paper chromatogram resulted in a partial tentative identification of indolepropionic acid, 5-methylindole, 5-hydroxy-indole and 3-indoleacetonitrile. The combined evidence indicated that the root-promoting substances in tomato seedlings resemble auxin compounds.     

Micropropagation of Capparis decidua through In Vitro Shoot Proliferation on Nodal Explants of Mature Tree and Seedling Explants

In vitro clonal propagation of Capparis decidua was achieved using nodal explants from mature trees, and cotyledonary node, cotyledon and hypocotyl explants taken from the seedlings. Explants cultured on MS medium supplemented with BAP showed differentiation of multiple shoots and shoot buds in 4–5 weeks in the primary cultures. The medium with BAP (5 mg/l) was the best for shoot bud proliferation from the nodal as well as seedling explant. Shoot multiplication was best on cotyledonary node. In the nodal explants shoot multiplication was best on medium supplemented with 5 mg/l BAP and after second subculturing further multiplication of shoot buds was highest on the medium containing 3 mg/l BAP. Shoots were separated from mother cultures in each subculturing for rooting. Rooting was best achieved using 1 mg/l IBA in the medium. Rooted plantlets were transferred td earthen pots with garden soil and peat moss mixture.     

The role of endogenous cytokinins in correlation between cotyledon and its axillary bud and in hypocotyl regeneration of flax

When flax seedlings are decapitated above cotyledons and three days later one of the two cotyledons is removed then the remaining cotyledon stimulates in four to five days growth of its axillary bud. It has been found that content of endogenous cytokinins was higher in the stimulated bud as compared with the other one already 12 h after the cotyledon removal. Flax seedlings decapitated under cotyledons regenerate adventitious buds on thy hypocotyl stump during 5–6 days. The endogenous fytohormonal preparation of this regeneration was investigated in the 20 mm apical part of the hypocotyl stump. Decrease in auxin and increase in gibberellins was already found during the first day after decapitation while the level of cytokinins increased as late as three days after the apex removal.     

Phenylacetic acid improves bud elongation and in vitro plant regeneration efficiency in Helianthus annuus L.

We have developed a highly efficient three-stage protocol for plant regeneration in sunflower (Helianthus annuus L.) from embryonal cotyledons. This protocol uses phenylacetic acid (PAA) for both shoot-bud induction and the elongation of smaller buds. The medium used for inducing bud formation from the cotyledons was modified MS medium supplemented with 3 mg/l 6-benzylaminopurine (BAP) and 0.5 mg/l PAA. Buds were elongated on MS medium supplemented either with only 0.2 mg/l gibberellic acid (GA₃) or with 0.2 mg/l GA₃ + 0.1 mg/l PAA + 0.3 mg/l BAP. The elongated shoots were then transferred onto rooting medium containing 1 mg/l PAA. The complete plantlets with well-developed roots were transferred to field conditions where they survived and set normal seeds. The induction of shoot buds from embryonal cotyledons was also observed on modified MS medium supplemented with 0.5-5 mg/l BAP in combination with 0.5-5 mg/l !-naphthaleneacetic acid (NAA). In this case, the formation of callus took place along with shoot-bud formation, which hindered further development of the latter. The presence of PAA with BAP in the primary bud induction medium promoted normal development and elongation of shoot buds.     

Effects of Plant Growth Regulators and Nutrient Supply on Tiller Bud Outgrowth in Barley (Hordeum distichum L.)

Seedlings of spring barley were raised in 100 and 20% nutrientsolution and treated with a foliar application of Terpal, Cerone,TIBA, GA₃ or BAP. The growth of individual tiller buds and tillers,the main shoot and the root system was recorded over the following15 d. Terpal and Cerone stimulated tiller bud elongation within5 d at both nutrient levels and after 15 d the number of emergedtillers was increased at the higher nutrient level. Terpal characteristicallypromoted the growth of secondary tiller buds whereas Ceronepromoted the emergence of the coleoptile tiller; both thesePGRs also retarded the development of the main shoot. TIBA increasedthe number of elongating tiller buds but this did not resultin greater tillering. GA₃ reduced the number of elongating tillerbuds and restricted their growth, especially in the high nutrientregime; this was accompanied by an increase in main shoot elongation.The growth and development of tiller buds was reduced by BAPand the number of emerged tillers was reduced at 15 d in bothnutrient levels; main shoot dry weight and root elongation werealso reduced. The results are considered in relation to theoverall influence of hormonal factors and mineral supply ontiller bud outgrowth. Hordeum distichum, spring barley, tiller bud outgrowth, plant growth regulators, Terpal, Cerone, GA₃, BAP, nutrient supply, apical dominance, TIBA     

Plant regeneration in tissue cultures of pepper (Capsicum annuum L. cv. mathania)

Leaf, stem, hypocotyl, cotyledon, root, shoot tip and embryo explants of Capsicum annuum L. cv. mathania were cultured on Murashige and Skoog (MS) medium supplemented with 6-benzylaminopurine (BAP) or kinetin (Kin) alone or in combination with 3-indoleacetic acid (IAA), 3-indolebutyric acid (IBA), α-naphthaleneacetic acid (NAA) or 2,4-dichlorophenoxyacetic acid (2,4-D). BAP (5.0 mgl⁻¹) in the medium was found to be the best growth regulator for shoot bud differentiation. Shoot buds cultured on 5.0 mgl⁻¹ BAP increased in number but did not elongate. For obtaining complete plantlets, shoot buds were placed on a medium with IBA or NAA (0.1 mgl⁻¹). Histological evidence revealed direct differentiation of buds from cotyledons. Regenerated plants were normal diploids. Unorganized callus could not be induced to differentiate shoot buds.     

Comparative anatomical analysis of the cotyledonary region in three Mediterranean Basin Quercus (Fagaceae)

Anatomical changes at the cotyledonary node from the embryo to the seedling stage in Quercus coccifera, Q. ilex, and Q. humilis were investigated by light and scanning electron microscopy techniques. Mature embryos of Q. humilis possess 2-3 pairs of leaf primordia and a pair of cotyledonary buds, whereas in Q. coccifera and Q. ilex there are two incipient primordia, and cotyledonary buds are not observed until 1 wk after germination. In all three species the cotyledonary buds multiply, forming bud clusters, and a vascular connection is well established within 5-6 wk after germination. As development proceeds, the cotyledonary region becomes woody, but buds, which are exogenous in origin, never become embedded in the periderm. In comparison with Q. suber, another native Mediterranean Basin oak, the cotyledonary node is short and axillary buds are not present below the insertion of cotyledons. In addition, starch accumulation in the cotyledonary region is not observed from histological analysis in the three oaks. Therefore, in Q. coccifera, Q. ilex, and Q. humilis seedlings the cotyledonary node can be considered to be an important regenerative structure enabling them to resprout after the elimination of the shoot above the cotyledons, despite the absence of a lignotuberous structure.     

Role of indoleacetic Acid and abscisic Acid in the correlative control by fruits of axillary bud development and leaf senescence

When fully filled pods of bean plants were deseeded, the rate of axillary bud growth and the chlorophyll content of leaves were increased. Application of 0.1% indoleacetic acid (IAA) in lanolin on the deseeded pods caused abscission of axillary buds, inhibited growth of the remaining buds, and decreased leaf chlorophyll content. The response of bud development to fruit-applied IAA was concentration dependent between 0.001 and 0.1% IAA (representing from 2 to 200 micrograms IAA per fruit) resulting in greater growth inhibition at higher IAA concentrations.     

Correlative inhibition of lateral bud growth in Phaseolus vulgaris L. timing of bud growth following decapitation

Summary On intact, 3-week-old plants of Phaseolus the larger bud in the axils of the primary leaves shows slow, continuous elongation growth. Release from correlative inhibition can be detected within 30 min following decapitation. When 0.1% indoleacetic acid in lanolin is applied to the decapitated stem stump, the lateral bud shows slow growth during the first 7 h, then stops completely for a further 15 h but after 2 days a further gradual increase in length is observed.The movement of ¹⁴C-labelled assimilates from the subtending primary leaf into the lateral bud increases following removal of the shoot apex. When indole acetic acid is applied to decapitated plants the ability of the buds to import ¹⁴C increases for 5–7 h and then declines to a negligible amount. Little or no radioactivity from tritiated indoleacetic acid is transported into the lateral buds of decapitated plants during the first 48 h following removal of the apex and it appears that rapid metabolism of the compound occurs in the stem tissues.     

Changes in organ growth ofChenopodium rubrum due to suboptimal and multiple photoperiodic cycles with and without flowering effect

The growth changes of cotyledons, leaves, hypocotyls and roots due to photoperiodic induction in short day plantChenopodium rubrum were investigated in relation to flowering. Six-day old plants were induced by photoperiods with a different number of dark hours. We found that the degree of inhibition which occurred during induction in the growth of leaves, cotyledons and roots similarly as the stimulation of hypocotyl is proportional to the length of dark period. The photoperiods with 12, 16 and 20 dark hours bring about marked inhibition of growth and at the same time induce flowering in terminal and axillary meristems. The inhibitory effect of critical period for flowering,i.e. 8 dark hours, is not apparent in all criteria used and even the flower differentiation is retarded. The photoperiods of 4 and 6 dark hours did not affect growth and were ineffective in inducing flowering even if their number has been increased. The experiments with inductive photoperiod interrupted by light break have clearly shown that growth pattern characteristic for induced plants can be evoked in purely vegetative ones. Such statement did not exclude the possible importance of growth inhibition as a modifying factor of flower differentiation. We demonstrated that the early events of flower bud differentiation are accompanied by stimulation of leaf growth. The evaluation of growth and development of axillary buds at different nodes of insertion enabled us to quantify the photoperiodic effect and to detect the effects due to differences in dark period length not exceeding 2 hours.     

Adventitious rooting in hypocotyls of sunflower (Helianthus annuus) seedlings

Removal of the main root system of sunflower ( Helianthus annuus ) initiates adventitious root development on the lower portion of the hypocotyl. The first cytological changes (enlarged nuclei in the interfascicular parenchymatous cells adjacent to the phloem and some cell divisions) are observed 24 h after root excision. On the basis of experiments in which (a) roots, apical buds and various amounts of cotyledonary tissue were removed, (b) cuttings were subjected to various light regimes, (c) benzyladenine oas applied to cotyledons to create an artificial sink, it was concluded that the roots normally produce factors inhibiting to adventitious rooting and might be a sink for stimulatory substances produced in the shoots. The cotyledons seem to be the major source of these stimulators. Application of aqueous and ethanolic extracts of cotyledons and hypocotyls to cuttings promoted adventitious rooting.     

Trijodbenzoesäure und die Stoffleitung bei höheren Pflanzen

Summary The effect of 2,3,5-triiodobenzoic acid (TIBA) on the translocation of various substances within etiolated pea plants was tested by applying the substances to different places on the decapitated plants and measuring the effect of the substances on the growth of lateral buds after placing a lanolin ring containing TIBA around the stem between the place of application of the substance and the buds. In control experiments the TIBA-ring was placed in such a way, that TIBA and the other substance reached the bud from opposite directions.TIBA blocked the basipetal translocation of indole-3-acetic acid, -4-chlorophenoxyisobutyric acid and -(1-naphthylmethylsulfid) propionic acid, it did not block the acropetal translocation of sucrose, potassium nitrate and indole-3-acetic acid. It did howevers block the acropetal translocation of native inhibitors (correlation inhibitors) extracted from pea plants. It is concluded that TIBA is a general blocker of the energy requiring translocation of many substances in plants. Moreover TIBA produces various different effects.Intensity of translocation of TIBA was equal in both directions, acropetal and basipetal. Application of TIBA to more distal points of the stem may cause greater effects because of a faster migration through younger tissues into the stem.Mit 2 Textabbildungen.     

HISTOLOGICAL ANALYSIS OF ADVENTITIOUS BUD FORMATION IN CULTURED DOUGLAS FIR COTYLEDON

Initiation of adventitious bud formation in vitro from Douglas fir cotyledons required both cytokinin and auxin at concentrations of 5 μM BAP and 5 nM NAA. Histological observations showed that these adventitious buds arose de novo from cells residing in hypodermal layers. Development of adventitious buds in culture was characterized by the sequential appearance of four anatomically distinguishable structures: 1) meristemoid, 2) bud primordium, 3) shoot apex with needle primordia, and 4) adventitious bud. The anatomical structure of tissue culture-produced buds was similar to that of vegetative buds produced on intact plants. Cultured cotyledons capable of producing adventitious buds (bud culture) were compared with bud-callus and callus cultures initiated by 5 μM BAP plus 5 μM NAA and 5μM NAA alone without BAP, respectively. Results showed that, during early stages of the culture period (i.e., prior to the appearance of meristemoid structure), cell division of bud culture was mainly located in hypodermal layers, whereas for the other culture types, bud-callus and callus cultures, cell division occurred randomly in all tissues.     

Obtention d'épinastie des cotylédons de Sinapis alba en éclairement rouge Iointain continu.

Obtention of epinasty in the cotyledons of Sinapis alba under continuous far-red illumination. Relation to the development of hypocotyl and cotyledons. Treatment by far red light induces epinasty of the cotyledonary leaf. The effects of light treatments of different intensities were recorded for hypocotyl length, percentage of epinasty and the cotyledon leaf area. The percentage of epinasty increases as a function of treatment duration and light intensity. As from the second day of treatment a correlation is obtained between the percentage of epinasty and hypocotyl length when the seedlings are given far-red light treatment of different durations.     

LIGNOTUBER ONTOGENY IN THE CORK-OAK (QUERCUS SUBER; FAGACEAE) I. LATE EMBRYO

Changes at the cotyledonary node of the cork-oak (Quercus suber L.) were examined during the embryo maturation phase using light microscopy and scanning electron microscopy techniques. During the maturation phase the embryo axis elongates by diffuse growth, the apical meristem forms the first leaf primordia, and the radicle meristem remains inactive. The primary axis of the embryo bears, axillary to the cotyledons, in the range of five to seven pairs of lateral buds at differing stages of development. Two or three pairs of these buds are visible, occurring on the upper unfused portion of the embryonic axis, while the remaining buds are hidden by the fused cotyledonary tissues. Lateral buds develop from clusters of cells in the peripheral meristem forming a shell zone delimiting the bud meristem. Lateral buds do not undergo much development until germination begins. The results are discussed with reference to the possible role of the cotyledonary node as the source of the lignotuber in the cork-oak.     

Micropropagation of Crataeva nurvala

A simple protocol for mass multiplication of Crataeva nurvala, a medicinal tree, from seedling-derived explants is described. Six different types of explants (cotyledonary nodes, epicotyl nodes, hypocotyl segments, first pair of leaves, cotyledons, and root segments) developed shoots on Murashige and Skoog's (MS) basal medium or the same supplemented with different concentrations of 6-benzylaminopurine (BAP). Among the explants tested for caulogenic potential, only the epicotyl and cotyledonary nodal explants developed shoots on MS basal medium, while on BAP (0 – 2.0 mg dm⁻³) adjuvated media all the explants exhibited caulogenesis. The optimum concentration of BAP varied for these explants. The shoots could be rooted on half strength MS with 0.02 mg dm⁻³ α-naphthalene acetic acid to get plants, which have been transferred to soil. The explants from in vitro regenerated shoots also possessed a similar caulogenic potential. This revised version was published online in July 2006 with corrections to the Cover Date.     

Arrest of somatic embryo development in grapevine: histological characterization and the effect of ABA,BAP and zeatin in stimulating plantlet development

In an effort to understand the causes of arrest of somatic embryo development, generally observed in grapevine (Vitis sp.), histological studies were undertaken, using two cultivars (CH76 and 41B) which differ in their ability to develop into plants. Embryos with a high conversion rate (70%; CH76) formed a well-structured and functional shoot apex between two thread-like cotyledons. In contrast, embryos with a low conversion rate (10%; 41B) formed a normal root apex but lacked a well-structured shoot apex and developed a wide range of aberrant forms in the intercotyledonary area: uncontrolled cellular proliferation, formation of adventitious buds, over-growth of cotyledonary or leaf meristems. ABA increased the conversion rate of 41B embryos from 10% to 20%, but failed to improve embryo morphology. Zeatin and BAP promoted growth of 41B somatic embryos, but generated a high level of abnormalities and failed to improve conversion rate. Applied in combination with ABA, these PGRs increased the frequency of cotyledonary embryos, but decreased the conversion rate.     

Role of Amino Acids in Evolution of Ethylene and Methane, and Development of Microshoots in Cajanus Cajan

In pigeonpea (Cajanus cajan L.) shoot buds were induced when cotyledonary node explants were supplemented with benzylaminopurine (BAP; 2 mg dm^–3). When 0.1 mg dm^-3 BAP and 0.01 mg dm^-3 naphtahalene acetic acid were supplemented to the medium, the 34 – 35 % of induced buds developed to microshoots. By supplementing amino acids like proline, glutamine, asparagine and L-cysteine, shoot bud development to microshoots was enhanced at least by two fold. Amongst the amino acids proline gave maximum number of microshoots per explant. With increase in concentration of amino acids, fresh mass increased but microshoot number decreased. Also methane evolution was increased by addition of amino acids, and also in medium containing more of its nitrogen in the form of ammonia. Increased evolution of methane was accompanied by reduction in evolution of ethylene, and enhancement of efficiency of microshoot development.     

Hormonal control of the outgrowth of axillary buds in <Emphasis Type="Italic">Alstroemeria</Emphasis> cultured <Emphasis Type="Italic">in vitro</Emphasis>

We study apical dominance in Alstroemeria, a plant with an architecture very different from the model species used in research on apical dominance. The standard explant was a rhizome with a tip and two vertically growing shoots from which the larger part had been excised leaving ca. 1 cm stem. The axillary buds that resumed growth were located at this 1-cm stem just above the rhizome. They were released by removal of the rhizome tip and the shoot tips. Replacement of excised tips by lanolin with indole-3-butyric acid (IBA) restored apical dominance. The auxin transport inhibitors 2,3,5-triiodobenzoic acid (TIBA) and N-1-napthylphthalamic acid (NPA) reduced apical dominance. 6-Benzylaminopurine (BAP) enhanced axillary bud outgrowth but the highest concentrations (> 9 μM) caused fasciation. Thidiazuron (TDZ) did not show improvement relative to BAP. Even though the architecture of Alstroemeria and the model species are very different, their hormonal mechanisms in apical dominance are for the greater part very similar.     

Preliminary Studies of Root-Stem Transition in Brassica napus L.

Seedlings of Brassica napus L. 2–11 days after germination were used. However, the most investigation was concentrated on the 6-day old seedlings. The primary root has a diarch protostele, the two groups of primary phloem alternate with the primary xylem. At higher level, the metaxylem is gradually differentiated in a lateral direction. Being coincident with this changes of the metaxylem, the groups of phloem cell are extended. The stele of the lower hypocotyl is root-like and has no pith. In the middle hypocotyl, there is a further lateral differentiation of the metaxylem. At the higher level, four metaxylem arms appear and the groups of phloem are extended circumferentially to form two crescent shaped sectors. In the upper hypocotyl below 0.2 cm of the cotyledonary node, a central pith has been formed which separates the differentiating primary xylem into two distinct units. At a slightly higher level, each primary phloem divides into two small groups, at this time, each xylem unit and the two adjacent groups of phloem constitute a cotyledonary trace. The foliar traces of the first two foliage leaves appear in the inter-cotyledonary plane between the vascular elements of the cotyledonary traces. At this level, the vascular tissue of the hypocotyl forms a siphonostele made up of two cotyledonary traces and the two foliage leaves, where the root-stem transition has nearly been completed, while the endarch condition is not attained in the hypocotyl. At incresing distances from the cotyledonary node upwards, in the cotyledonary petiole, the protoxylem occupies a more and more adaxial position and the metaxylem a more and more abaxial direction and, thus, the endarch condition is attained. The primary system of the root, hypocotyl, and cotyledons forms a complete circular system, the plumular vascular elements are directly connected by secondary elements formed by the cambium in the region of the hypocotyl. As for the results mentioned above, the authers have not detected that the primary xylem has a rotation of 180˚, as described by Van Tieghem.