Microcutting leaf area,weight and position on the stock shoot influence root vigour,shoot growth and incidence of shoot tip necrosis in grape plantlets in vitro

The physiological parameters of microcuttings, namely leaf area, weight (wt) and position on the stock shoot, had significant effects on root vigour, microshoot growth and incidence of shoot tip necrosis (STN) in cultures of grape (Vitis vinifera L.) ‘Arka Neelamani’. Single-node leafy cuttings cultured in MS medium containing 1 μM IAA and 0.1 μM GA₃ generally rooted first and subsequently sprouted into a single shoot. Small leafed cuttings exhibited slow root emergence, poor quality roots, early sprouting and weak shoot growth. Large leafed cuttings on the other hand, showed early rooting, vigorous roots, delayed sprouting and healthier shoots. Significant correlations were observed between fresh root wt per plantlet at 1 month in culture and wt of lamina, total wt and leaf area of the cuttings in that order. A significant correlation also existed between wt of roots and height or wt of the sprout that developed. The study suggests that the weight or area of the leaf governed the root growth in a microcutting. STN was observed in some plantlets particularly those derived from large leafed cuttings. Such cuttings showed vigorous roots and delayed but fast sprout growth that ended in STN. Plantlets showing STN had less Ca⁺⁺ and Mg⁺⁺ in the shoot tissue than in the shoots of normal plantlets while the roots showed similar Ca⁺⁺ or higher Mg⁺⁺ contents. Both had comparable amounts of cytokinins in shoot and root tissues. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of shoot tip and leaf removal on gravitropism in pea

Intact, light-grown pea (Pisum sativum L. cv. Alaska) seedlings were subjected to continuous horizontal gravistimulation and their growth and bending response compared with seedlings whose shoot tip and youngest leaf had been excised and with seedlings to which a counterweight to replace the mass of the decapitated tissue was added. While all seedlings achieved vertical orientation in 2 to 3 h, seedlings that were counterweighted bent upward at a significantly slower rate than the non-counterweighted, decapitated plants. In addition to this effect of mass on the rate of bending, decapitation also removed a major supply of auxin to cells in the bending zone which resulted in the slower bending of treated plants. Thus when using decapitation both the loss of mass and the time course of the response must be considered to understand its effect on gravitropism.     

Effects of gentamicin on growth of shoot initiation from cultured tobacco callus and salpiglossis leaf discs

Summary Tobacco (Nicotiana tabacum L. ‘Wisconsin 38’) callus growth was inhibited progressively by gentamicin sulfate at all concentrations tested. Gentamicin inhibited shoot initiation from tobacco callus and salpiglossis [Salpiglossis sinuata (Ruiz and Pav.) ‘Bolero’] leaf discs at concentrations above 25 mg/l. At 100 mg/l the antibiotic suppressed completely organogenesis from explants of both tobacco and salpiglossis. Journal paper 8410 of the Purdue University Agriculture Experiment Station. An erratum to this article is available at .     

Effect of inhibitors of ethylene biosynthesis and action, as well as calcium and magnesium on rose shoot rooting, shoot-tip necrosis and leaf senescence in vitro

Microcuttings of easy-to-root dwarf rose cv. Starina, showing early symptoms of leaf senescence and shoot-tip necrosis in rooting stage, were chosen for the study. The effects of inhibitors of ethylene biosynthesis (AOA, AIB) and action (AgNO₃), and Ca²⁺ and Mg²⁺ were studied in relation to rooting, leaf senescence and shoot-tip necrosis. The effects of these substances were examined with respect to IAA presence in a medium, which stimulated leaf yellowing and shoot-tip necrosis. AOA strongly inhibited rooting of microcuttings, but did not affect ethylene biosynthesis. AIB at 250 mg·l⁻¹ and AgNO₃ 2.5 mg·l⁻¹ in the presence of IAA did not affect rooting but effectively prevented leaf senescence. Ca²⁺ alone or combined with Mg²⁺ at raised concentration, or an ethylene action inhibitor Ag⁺, reduced shoot-tip necrosis in microcuttings treated with IAA. Addition of Ag⁺ to IAA medium drastically increased ethylene production by the shoots. Interaction between endogenous levels of auxin, ethylene and calcium in relation to rooting, shoot-tip necrosis and leaf senescence was discussed. Ethylene could enhance tissue sensitivity to auxin. Moreover, the tissue of rose shoots is very sensitive in the in vitro condition on standard medium because of the calcium deficiency. Thus, the raised Ca/Mg level counteracted shoot-tip necrosis through enhancing cell membrane and wall resistance to ethylene and IAA.     

Root and shoot initiation by leaf,stem, and storage root explants of sweet potato

Explants from stem, leaf, and storage root tissue of sweet potato (Ipomoea batatas L.) cv. Jewel, were placed on media conaining 0.1, 1.0, and 10 mg/1NAA with 0.1, 1.0, or 10 mg/1BA in a factorial experiment. Some callus formed in every treatment, but the best callus growth was on media containing 1.0 mg/1NAA and 10 mg/1BA. Roots formed over a range of treatments but were most prolific on the medium containing 1.0 mg/1NAA and 0.1 mg/1BA. Some de novo formed roots subsequently produced shoot buds in culture. Shoot formation increased the longer the original explants remained in culture without subculture. Roots could be subcultured indefinitely on agar solidified medium, but shoot regeneration did not occur after two subcultures. Shoot formation was greatest when the roots were subcultured on medium containing 1.0 mg/NAA and 0.1 mg/1BA. The cultivar Caromex followed the same regeneration pathway, but the number of shoots formed was considerably less. Regeneration in both Jewel and Caromex explants was enhanced by light.Paper No. 8292 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of products named, nor criticism of similar ones not mentioned.This work was done as a partial requirement for the M.S. degree at North Carolina State University.     

The control of shoot tip necrosis in Pistacia vera L. in vitro

The effect of increased concentrations of calcium (Ca) (3–24 mM) and boron (B) (100–800 M) in the medium was studied on the occurrence of shoot tip necrosis (STN) in cultures of Pistacia vera L. STN was significantly reduced by application of Ca or B, however media with more than 200 M boron had reduced shoot multiplication. Ca (12–24 mM) supplied as calcium chloride reduced STN without any adverse effect on shoot multiplication or elongation, whereas calcium acetate reduced elongation. It is concluded that STN is a physiological mineral disorder associated with Ca and/or B deficiency in the meristematic regions of actively growing shoots. Application of Ca (up to 24 mM) as calcium chloride to the medium was the best treatment for the control of STN. Reduction of humidity or increased aeration in the culture jars did not have any significant effect on the occurrence of STN.Abbreviations MS Murashige and Skoog medium - STN Shoot tip necrosis     

Role of ethylene and cytokinins in the initiation of lateral shoot growth in bromeliads

Aechmea victoriana var discolor L. B. Foster and Aechmea dactylina Bal. are commercially propagated in vitro through lateral shoot growth. A modified Murashige and Skoog medium is used which contains both BA and IAA. These growth substances were shown in the present study to synergistically stimulate the production of ethylene by the cultured plants. The stimulation of ethylene production is correlated with the outgrowth of the lateral buds. The rise in ethylene production was concluded to induce lateral shoot growth, because: (a) outgrowth of the shoots was blocked by preventing an increase in ethylene production, (b) 1-aminocyclopropane-1-carboxylic acid (ACC), the natural precursor of ethylene biosynthesis, substituted for IAA in the promotion of ethylene production and lateral bud outgrowth. Although ACC could substitute for IAA, it could not substitute for BA; therefore, cytokinins are concluded to be essential for lateral bud outgrowth in vitro in Aechmea. These results suggest that cytokinins and ethylene both play roles in natural lateral bud initiation and that the cytokinin function involves two stages of the process.     

Effects of exogenous ethylene on ethylene production in citrus leaf tissue

Exogenous ethylene stimulated ethylene production in intact citrus (Citrus sinensis L. Osbeck cv. “Washington Navel”) leaves and leaf discs following a 24-hour exposure. Studies with leaf discs showed that ethylene production decreased when ethylene was removed by aeration. The extent of stimulation was dependent upon the concentration of exogenous ethylene (1-10 microliters per liter). Silver ion blocked the autocatalytic effect of ethylene at concentrations of 0.5 millimolar and lower, but increased ethylene production at higher concentrations. The stimulating effect of ethylene resulted from the enhancement of both 1-aminocyclopropane-1-carboxylic acid (ACC) formation and the conversion of ACC to ethylene. Whereas autocatalysis was evident following 24 hours incubation, autoinhibition of wound- and mannitol-induced ethylene production was observed during the first 24-hour incubation. Ethylene treatment during this period resulted in a marked decrease in ACC levels and ethylene production rates. Furthermore, in leaf discs treated for 24 hours with ethylene, ethylene production rates increased greatly during the first 2 hours after removal of exogenous ethylene by aeration. This increase was eliminated if the discs were transferred to propylene instead of air, indicating that the autocatalytic effect of ethylene is counteracted by its autoinhibitory effect. It is suggested that autocatalysis involves increased synthesis of ACC synthase and the enzyme responsible for the conversion of ACC to ethylene, whereas autoinhibition involves suppression of the activity of these two enzymes.     

Influence of petiole and lamina on adventitious shoot initiation from leaf explants of Paulownia fortunei

Adventitious shoot bud differentiation occurred preferentially from the petiolar cut ends of leaf explants of Paulownia fortunei cultured on Murashige and Skoog medium supplemented with 4 μmα-naphthaleneacetic acid and 20 μm benzyladenine. The details of plantlet regeneration and successful transplantation to soil have been reported earlier. We now show that besides medium supplementation with auxin and cytokinin, the presence of lamina and petiole in the explant influence shoot bud induction. Explants with the basal half of the lamina and the entire petiole were much more responsive than those with whole lamina and petiole. A dual-culture-medium technique which permitted incubation of the two ends of excised petioles under two different phytohormone regimes was devised. Our data suggest that some of the diffusible factors from the lamina may be phytohormones, and that the establishment of an endogenous phytohormone gradient in the explants may affect shoot bud differentiation in this culture system. Received: 7 April 1998 / Revision received: 8 April 1998 / Accepted: 17 April 1998     

The quantitative ultrastructure of the pea shoot apex in relation to leaf initiation

Summary The ultrastructure of the pea shoot apical meristem was examined quantitatively in longitudinal sections. Photographs were taken at eleven defined positions in the apex, at six developmental stages within a single plastochron. The only change in ultrastructure during the period of a single plastochron was the increase in the proportion of plastids with starch in the central regions of the apex and in the young leaf axils. This increase occurred midway in time between the emergence of successive leaves, at precisely the time that the orientation of growth changes in the region where a new leaf is to emerge. There were quantitative changes in ultrastructure associated with cell differentiation. In the sequence of cell development from the summit of the apex (central zone) to the incipient pith, cell enlargement was accompanied by an increase in the volume of endoplasmic reticulum, dictyosomes, microbodies and vacuoles per cell, an increase in the number of mitochondria, microbodies and vacuoles per cell, and an increase in the volume, but not the number, of plastids per cell. In the sequence of axillary development (before the axillary bud begins to grow) the number of mitochondria per cell decreased as cell volume decreased but the number of plastids per cell remained constant. The number of plastids per cell increased only in the developmental sequence leading to leaf development, in which the number of mitochondria and dictyosomes per cell also increased. There appeared to be no features of ultrastructure, qualitative or quantitative, which could be correlated with the different rates of cell division in different regions of the meristem. The differences in ultrastructure throughout the apex were mainly quantitative and seemed to be associated with cellular differentiation rather than with the plastochronic functioning of the apex during leaf initiation.     

Effects of shoot bending on ACC content,ethylene production,growth and flowering of bougainvillea

Several factors, such as environmental conditions, pruning, and plant growth regulators, affect the flowering of bougainvillea. However, information on the effect of shoot bending on growth and flowering of bougainvillea is scarce. In the natural environment, most of the bougainvillea flowering shoots are inclining whereas vertical shoots are not flowering shoots. Bougainvillea shoots are artificially grown vertically, horizontally and at an inclined orientation, to investigate the effect of these orientations on plant growth and the development of flower buds. The results of this indicate an effect of shoot bending on the growth rate of bougainvillea and the rate of flower bud formation. Additionally, our results suggest that vertical shoots have a higher growth rate, more prolific vegetation growth, and longer plastochrons (which are the intervals between the initiations of successive leaves). In contrast, horizontal and inclined shoots exhibited slower growth, a shorter time to reach flowering, and more flower buds. Inclined shoots had a higher endogenous ACC (1-aminocyclopropene-1-carboxylate) content and produced more ethylene than either horizontal or vertical shoots, indicating that more ACC in the inclined shoot is converted into ethylene, and the higher ethylene concentration in the inclined shoot causes it to mature earlier and flower sooner.     

Effects of fungicides and bactericides on orchid seed germination and shoot tip cultures in vitro

Amphotericin B, benomyl, gentamycin, nystatin, quintozene penicillin G, sodium omadine, and vancomycin singly and in several combinations have no deleterious effects on the germination of orchid seeds, but inhibit the growth in vitro of shoot tip explants.     

The influence of ethylene and ethylene modulators on shoot organogenesis in tomato

The influence of ethylene and ethylene modulators on the in vitro organogenesis of tomato was studied using a highly regenerating accession of the wild tomato Solanum pennellii and an F1 plant resulting from a cross between Solanum pennellii and Solanum lycopersicum cv. Anl27, which is known to have a low regeneration frequency. Four ethylene-modulating compounds, each at four levels, were used, namely: cobalt chloride (CoCl₂), which inhibits the production of ethylene; AgNO₃ (SN), which inhibits ethylene action; and Ethephon and the precursor 1-aminocyclopropane-1-carboxylic acid (ACC), which both promote ethylene synthesis. Leaf explants of each genotype were incubated on shoot induction medium supplemented with each of these compounds at 0, 10 or 15 days following bud induction. The results obtained in our assays indicate that ethylene has a significant influence on tomato organogenesis. Concentrations of ethylene lower than the optimum (according to genotype) at the beginning of the culture may decrease the percentage of explants with buds (B), produce a delay in their appearance, or indeed inhibit bud formation. This was observed in S. pennellii and the F1 explants cultured on media with SN (5.8–58.0 μM) as well as in the F1 explants cultured on medium with 21.0 μM CoCl₂. The percentage of explants with shoots (R) and the mean number of shoots per explant with shoots (PR) also diminished in media that contained SN. Shoots isolated from these explants were less developed compared to those isolated from control explants. On the other hand, ethylene supplementation may contribute to enhancing shoot development. The number of isolable shoots from S. pennellii explants doubled in media with ACC (9.8–98.0 μM). Shoots isolated from explants treated with ethylene releasing compounds showed a higher number of nodes when ACC and Ethephon were added at 10 days (in F1 explants) or at 15 days (in S. pennellii) after the beginning of culture. Thus, the importance of studying not only the concentration but also the timing of the application of regulators when developing regeneration protocols has been made manifest. An excess of ethylene supplementation may produce an inhibitory effect, as was observed when using Ethephon (17.2–69.0 μM). These results show the involvement of ethylene in tomato organogenesis and lead us to believe that ethylene supplementation may contribute to enhancing regeneration and shoot development in tomato.     

杜衡离体繁殖的研究

以马兜铃科植物杜衡为研究材料,试图通过茎尖培养来获得愈伤组织,继而诱导愈伤组织分化形成杜衡小植株。试验证明：杜衡茎尖在MS基本培养基附加6-BA 0.6mg/l和NAA0.1mg/;这一激素组合上可诱导茎尖基部形成愈伤组织;将愈伤组织分割转接到附加6-BA0.2mg/l和NAA0.01mg/l 的MS基本幅度基上可使愈伤组织分化形成小芽;分化形成的芽置于1/8-1/4MS(大量元素减少,其余成分不变)附加6-BA0.1mg/l和GA1mg/l的培养基上,可促使芽的正常生长;新生芽转接在1/4MS附加IBA0.5mg/l培养基上促使其生根。     

Effects of picloram and ethylene on leaf movement in huisache and mesquite seedlings

Application of 4-amino-3,5,6-trichloropicolinic acid (picloram) to roots stimulated the production of ethylene in both mesquite [Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell] and huisache [Acacia farnesiana (L.) Willd.] seedlings. Herbicide levels rose in tissues before we detected increased ethylene production. Rates of ethylene production by various parts of the plant paralleled herbicide concentrations. In both species, picloram caused loss of leaf movement and epinastic curvature of leaves and stems. Only huisache was defoliated by picloram. Rates of ethylene production increased before we observed any leaf movement or defoliation responses. Fumigation of plants with levels of ethylene, calculated to approximate those in herbicide-treated plants at the initial loss of leaf movement, caused the same symptoms as picloram treatment. The time sequence of ethylene fumigation and loss of the ability for leaf movement is compatible with the hypothesis that there is a causal relationship between picloram and ethylene production and loss of leaf movement.     

Shoot organization genes regulate shoot apical meristem organization and the pattern of leaf primordium initiation in rice

The mechanism regulating the pattern of leaf initiation was analyzed by using shoot organization (sho) mutants derived from three loci (SHO1, SHO2, and SHO3). In the early vegetative phase, sho mutants show an increased rate of leaf production with random phyllotaxy. The resulting leaves are malformed, threadlike, or short and narrow. Their shoot apical meristems are relatively low and wide, that is, flat shaped, although their shape and size are highly variable among plants of the same genotype. Statistical analysis reveals that the shape of the shoot meristem rather than its size is closely correlated with the variations of plastochron and phyllotaxy. Rapid and random leaf production in sho mutants is correlated with the frequent and disorganized cell divisions in the shoot meristem and with a reduction of expression domain of a rice homeobox gene, OSH1. These changes in the organization and behavior of the shoot apical meristems suggest that sho mutants have fewer indeterminate cells and more determinate cells than wild type, with many cells acting as leaf founder cells. Thus, the SHO genes have an important role in maintaining the proper organization of the shoot apical meristem, which is essential for the normal initiation pattern of leaf primordia.     

Effects of shoot position on shoot and leaf morphology of Avicennia marina in the hyperarid Red Sea coastal region of Egypt

We examined the effects of shoot position on shoot growth and morphology of Avicennia marina (Forssk.) Vierh. in the Red Sea coastal region of Egypt. To determine differences in morphological characteristics, we collected shoots from the upper and lower canopies of A. marina individuals in the wild and compared the morphological characteristics of these shoots. The study plot was established in an A. marina mangrove forest. Heights and diameters of individual trunks (n = 14) in the plot were measured at ground level. Then, five shoots with young but fully expanded leaves were collected from the upper and lower canopies of the individuals. We measured shoot length, and dry weight and also area, dry weight, thickness, and Soil Plant Analysis Development (SPAD) value of collected leaves. Our measurements showed that leaf area, dry weight, specific leaf area, and SPAD value of leaves from the upper canopy were smaller than those of lower-canopy leaves in most individuals. From the differences in traits between upper and lower leaves, we concluded that leaves in the upper canopy are typically adapted to high light levels, whereas leaves in the lower canopy exhibit adaptations to low light conditions. In addition, soil-water salinity at the study site was far higher than the optimum salinity for A. marina. Hence, it is also suggested the salinity level at this site may have influenced the reduced leaf size in the upper canopy.     

Effects of simulated shoot and leaf herbivory on vegetative growth and plant defense in Acacia drepanolobium

Plants have considerable ability to respond to herbivory, both with (above-ground) regrowth and with increased defense. We simulated both leaf and shoot herbivory in controlled, replicated experiments on individuals of Acacia drepanolobium in Laikipia, Kenya. These experiments were carried out on individuals that had experienced different, experimentally controlled histories of large mammalian herbivory. Both forms of simulated herbivory were associated with compensatory regrowth. Branches whose shoots had been removed grew significantly more over the next year than paired control branches, fully compensating for the lost shoot length. Branches whose leaves were removed both grew faster and had more leaves one year later than did control branches. Shoot removal, but not leaf removal, increased the production of side shoots. However, because past herbivore pressure was negatively associated with net shoot growth, there may be a long-term cost of herbivory even when plants appear to fully compensate for herbivory in the short term. In contrast to the effects on growth, simulated herbivory did not significantly increase physical (spines) or chemical (tannins) defenses, and there were no significant negative correlations between compensatory growth and plant defense.     

High frequency shoot regeneration from nodal and shoot tip explants in Holarrhena antidysenterica L

Shoot tip and nodal segment explants of Holarrhena antidysenterica when cultured on MS medium containing BAP (1.0-3.0 mg/l) with NAA (0.2-1.0 mg/l) and BAP (1.0-3.0 mg/l) with Kn. (0.2-1.0 mg/l) produced multiple shoots. Maximum multiple shoots was found in MS medium supplemented with BAP (2.0 mg/l) and NAA (0.5 mg/l). Subculture on the same medium resulted in rapid shoot multiplication at an average rate of 16 new shoots per subculture. Addition of urea (100 mg/l) in the medium increased the number of shoots up to 22 per culture. For best rooting, the shoots were excised from the culture flask and implanted individually on half strength MS medium with 0.5 mg/l each of IBA, IAA and NAA. After 20 days of transfer on root induction medium 95% rooting was achieved. Regenerated plantlets were successfully acclimatized and established in soil. About 90% of plantlets survived under open field conditions.