Plantlet regeneration from mature zygotic embryos and embryonic explants of masson pine （Pinus massoniana Lamb.）

Excised zygotic embryos,cotyledons and hypocotyls of juvenile seedlings of masson pine were grown on DCR medium supplemented with several concentrations of various plant phytohormones.BA(1.0mg/L) in combination with NAA(0.05mg/L) in DCR medium was found to increase the formation of adventitious buds from mature zygotic embryos,but most of them were formed at the tips of embryonic cotyledons.Adventitious buds were obtained from cotyledons and hypocotyls from juvenile seedlings when they were cultured on DCR medium containing BA 3-5 mg/L and NAA 0.1-0.2 mg/L.Elongation of buds were observed on hormone-free DCR medium with or without activated charcoal(0.5%).Root initiation was achieved with full or half strength DCR medium supplemented with IBA 1.0 mg/L and NAA 0.25-0.5 mg/L.Approximately 11-20 axillary buds formed on each explant when juvenile seedling explants were treated(3-20h) with BA 50-100 mg/L,followed by transfer to hormone-free DCR medium.The maximum number of shoots obtained per explant within six months was 33.     

Ethylene Evolution Changes in Tilted Fraxinus mandshurica Rupr. var. japonica Maxim. Seedlings in Relation to Tension Wood Formation

The effects of ethylene on tension wood formation were studied in 3-year-old Fraxinus mandshurica Rupr. var. japonica Maxim. seedlings in two separate experiments. In experiment 1, ethylene evolution of buds and stems was measured using gas chromatography after 0, 2, 4, 7, 14, and 21 d of treatment; in experiment 2, both aminoethoxyvinylglycine （AVG） and AgNO3 were applied to the horizontally-placed stems, and the cell numbers on sites of applications were measured after 40 d. Ethylene evolution from buds was found to be much greater in tilted seedlings than in upright ones. The cell numbers of wood fibers in shoots and 1-year-old stems were reduced in treatments with 12.5×10^-7μmol/L AVG, 12.5×10^-8μmol/L AVG, and 11.8×10^-8μmol/Lmol/L AgNO3; whereas the horizontal and vertical diameters were reduced by treatment of 12.5×10^-7μmol/L AVG. Ethylene evolutions of shoots and 1-year-old stems were inhibited greatly in comparison with the control by applying 12.5×10^-7μmol/L AVG. The formation of a gelatinous layer of wood fibers was affected by neither AVG nor AgNO3 application. These results suggest that ethylene regulates the quantity of wood production, but does not affect G-layer formation in F. mandshurica Rupr. var.japonica Maxim. seedlings.     

Factors Influencing Formation of Sclerotia in Grifola umbellate （Pers.） Pilaet Under Artificial Conditions

The effects of substrate composition and temperature on myceilal growth and sclerotium production in Grlfola umbellate （Pers.） Pilaet were Investigated In the present study. The Induction of sclerotla of G. umbellate was affected greatly by the type of medium, as well as the type of carbon source. Malt-extract agar was able to induce the production of sclerotia. The production of sclerotia was also observed when the carbon source in the GPC agar medium （glucose 20 g/L, peptone 6 g/L, corn steep liquor 10 g/L, and agar 15 g/L） was replaced with glycerol or mannitol. Altering the composition of the GPC medium with milk powder, thiamine hydrochlorlde, extract of Armlllarla mellea, active clay, dlatomite, kaolin, or arginlne did not induce the production of sclerotla. A temperature range of 18-25 ℃ was suitable for both mycellai growth and sclerotium formation. Glycerol significantly Induced slerotium formation on nutrient supplemented with sawdust substrates In bottle culture. 24S-Polyporusterone A and polyporusterone B were assayed In samples of natural and cultured sclerotla. Both natural and cultured sclerotla contained 24S- polyporusterone A and polyporusterone B.     

Direct differentiation of ears and tassels from cultured shoot apices of maize

In vitro morphogenesis of inflorescences from the cultured corn seedling shoot tips was obtained on modified Murashige and Skoog (MS) medium in complete darkness. Some shoot tip meristems excised from seedlings of inbred line 515, inbred line 8112 and their filial generations would directly give rise to florets on modified MS medium supplemented with 2.0 mg/L N6-bezyladenine (6-BA) in five or six weeks. On the medium with 1.0 mg/L 6-BA and 0. 2 mg/L 2, 4-dichlorophenoxy acetic acid (2, 4-D), the explants swelled first, and produced multiple shoot clumps, then the culture of the shoot tips from all of the six inbred lines in experiment would ultimately initiate to develop ears and tassels accompanied by multiple shoot clumps developing on the medium with 1.0 mg/L 6-BA and 0. 2 mg/Lin-dole-3-butyric acid (IBA). The developmental patterns of the corn inflorescences were similar to the controls of normal plants in the field, but the number of the ears was much more than that of the tassels in vitro. It seem     

Biology and life table studies of the oriental tobacco budworm,Helicoverpa assulta （Lepidoptera： Noctuidae）, influenced by different larval diets

Development, survivorship, pupal weight, oviposition, and life table parameters of the oriental tobacco budworm, Helicoverpa assulta Guenée, were evaluated in the laboratory on an artificial diet, pepper （Capsicumfrutescens L.）, and tobacco （Nicotiana tobacum L.）. We found that the average developmental time of immature stages was longest on tobacco （36.2 d）, intermediate on pepper （34.4 d）, and shortest on artificial diet （33.5 d）. Immature survival from egg to pupa varied from 31% on tobacco, 43% on pepper, and 74% on artificial diet. Pupal weight ranged from 197.4 mg/pupa on tobacco, 233.1 mg/pupa on pepper and 253.4 mg/pupa on artificial diet. The average numbers of eggs laid by adults reared as larvae on the artificial diet, pepper, or tobacco were 614, 421 and 334 eggs/female, respectively. Numbers of remaining eggs in ovaries of the adult females reared as larvae on the artificial diet, pepper, or tobacco were 16, 26, and 42 eggs/female, respectively. The longevity of adult females developed from larvae reared on the three diets was not significantly different, whereas the longevity of male adults from the larvae reared on artificial diet was longer （16.8 d） than that for males reared on tobacco （13.8 d） and pepper （13.3 d）. The intrinsic, finite, gross, and net rates of increase were highest for females reared as larvae on artificial diet, lowest for females emerging from larvae reared on tobacco, and intermediate for females emerging from larvae reared on pepper. Generation times and doubling time of H. assulta were shortest for larvae fed artificial diet, intermediate from larvae reared on pepper, and longest from larvae reared on tobacco. We concluded that the artificial diet was the most suitable larval diet ofH. assulta followed by pepper, and tobacco.     

Comparison of fatty acid composition in total lipid of diapause and non-diapause larvae of Cydia pomonella （Lepidoptera： Tortricidae）

Seasonal changes in the fatty acid composition of the total lipid extracted from the whole body of Cydia pomonella L. larvae were determined by gas chromatography. The six most abundant fatty acids in both non-diapause and diapause larvae of codling moth were oleic （35%-39%）, palmitic （23%-33%）, linoleic （16%-30%）, palmitoleic （5%-10%）, stearic （1.5%-3.0%） and linolenic acids （1.0%-2.5%）. This represents a typical complement of Lepidopteran fatty acids. The fatty acid composition of total lipid of C. pomonella larvae was related to diapause. In similarity to most other reports, the proportion of unsaturated fatty acids increased in diapause initiation state. The total lipid of diapause larvae contained more linoleic acid （25.8% vs. 16.1%） and less palmitic acid （24.7% vs. 33.4%）, than that of non-diapause larvae. The weight percentage of linoleic acid （C 18：2） increased from 16% to 26% from early-August through early-September during transition to diapause, while palmitic acid （C16：0） decreased from 33% to 25% at the same time. These changes resulted in an increase in the ratio of unsaturated to saturated fatty acids （UFA/SFA） from 1.72 in non-diapause larvae to 2.63 in diapause larvae.     

Effects of Salt Stress on Carbohydrate Metabolism in Desert Soil Alga Microcoleus vaginatus Gom.

The effects of salt stress on carbohydrate metabolism in Microcoleus vaginatus Gom., a cyanobacterium isolated from desert algal crusts, were investigated in the present study. Extracellular total carbohydrates and exopolysaccharides （EPS） in the culture medium produced by M. vaginatus increased significantly during the growth phase and reached a maximum during the stationary phase. The production of extracellular carbohydrates also significantly increased under higher salt concentrations, which was attributed to an increase in low molecular weight carbohydrates. In the presence of NaCI, the production of cellular total carbohydrates decreased and photosynthetic activity was impaired, whereas cellular reducing sugars, water-soluble sugars and sucrose content and sucrose phosphate synthase activity increased, reaching a maximum in the presence of 200 mmol/L NaCI. These parameters were restored to original levels when the algae were transferred to a non-saline medium. Sodium and K＋ concentrations of stressed cells decreased significantly and H＋-ATPase activity increased after the addition of exogenous sucrose or EPS. The results suggest that EPS and sucrose are synthesized to maintain the cellular osmOtic equilibrium between the intra-and extracellular environment, thus protecting algal cells from osmotic damage, which was attributed to the selective exclusion of cellular Na＋ and K＋ by H＋-ATPase.     

Effect of phytohormones on plant regeneration from callus ofGladiolus cultivar “Jenny Lee”

Summary Callus capable of plant regeneration was initiated at a higher frequency from the basal leaves of in vitro plants (70% explants) as compared to cormel slices (30% explants) when cultured on medium containing various concentrations of auxin. The greatest number of plants were regenerated from 4-mo.-old callus (112 plants/g fresh weight callus) cultured on medium containing 10 mg/liter (53.8μM) 1-napthaleneacetic acid. The addition of 2 mg/liter (9.3μM) kinetin to a Murashige and Skoog’s basal salts regeneration medium resulted in an average two- to three-fold increase in the number of plants regenerated compared to regeneration on medium without hormones. Ten months after callus initiation, all callus maintained on auxin-supplemented media showed a drastic reduction in its capacity to regenerate plants. Ten-month-old callus maintained on dicamba regenerated the greatest number of plants (14 to 23 plants regenerated per gram fresh weight callus) as compared to callus maintained 10 mo. on medium containing 1-napthaleneacetic acid or 2,4-dichlorophenoxyacetic acid. Cormel slices cultured on cytokinin-supplemented media formed small amounts of callus which regenerated up to 19 plants per cormel slice within 1 to 2 mo. after the cormel slice had been placed on either 10 mg/liter (49.2μM) N⁶-2-isopentenyladenosine or 1 mg/liter (4.4μM) 6-benzylaminopurine.     

Survival of boll weevil （Coleoptera： Curculionidae） adults after feeding on pollens from various sources

The survival of overwintering boll weevil, Anthonomus grandis grandis （Boheman）, adults on non-cotton hosts in the Lower Rio Grande Valley （LRGV） of Texas was examined from 2001 to 2006. The success of the Boll Weevil Eradication Program, which was reintroduced into the LRGV in 2005, depends on controlling overwintering boll weevil populations. Laboratory studies were conducted using boll weevil adults that were captured in pheromone traps from September through March. The number of adults captured per trap declined significantly in the field from fall to the beginning of spring （3.5-7.0-fold）. The proportion of trapped males and females did not differ significantly. The mean weight of boll weevil adults captured in September was 13.3 mg, while those of captured adults from November to February were significantly lower and ranged from 6.7 to 7.8 mg. Our results show that boll weevil adults can feed on different plant pollens. The highest longevity occurred when adults were fed almond pollen or mixed pollens （72.6 days and 69.2 days, respectively） and the lowest when they fed on citrus pollen or a non-food source （9.7 days or 7.4 days, respectively）. The highest adult survival occurred on almond and mixed pollens [88.0%-97. 6% after 1st feeding period （10 days）, 78.0%-90.8% after 3rd feeding period （10 days）, 55. 0%-83.6% after 5th feeding period （10 days）, and 15.2%-32.4% after lOth feeding period （10 days）]. The lowest adult survival occurred on citrus pollen [52.0%-56.0% after 1st feeding period （10 days）, 13.3% after 3rd and 5th feeding periods （10 days）, and 0 after 6th feeding period （10 days）]. Pollen feeding is not a behavior restricted to adult boll weevils of a specific sex or physiological state. Understanding how boll weevil adults survive in the absence of cotton is important to ensure ultimate success of eradicating this pest in the subtropics.     

Comparative genetic analysis of,Arabidopsis purple acid phosphatases AtPAP10, AtPAP12, and AtPAP26 provides new insights into their roles in plant adaptation to phosphate deprivation

Induction and secretion of acid phosphatases （APases） is thought to be an adaptive mechanism that helps plants survive and grow under phosphate （Pi） deprivation, in Arabidopsis, there are 29 purple acid phosphatase （AtPAP） genes. To systematically investigate the roles of different AtPAPs, we first identified knockout or knock-down T-DNA lines for all 29 AtPAP genes. Using these atpap mutants combined with in-gel and quantitative APase enzyme assays, we demonstrated that AtPAP12 and AtPAP26 are two major intracellular and secreted APases in Arabidopsis while AtPAPlo is mainly a secreted APase. On Pi-deficient （P-） medium or P- medium supplemented with the organophosphates ADP and fructose-6-phosphate （Fru-6-P）, growth of atpaplo was significantly reduced whereas growth of atpap12 was only moderately reduced, and growth of atpap26 was nearly equal to that of the wild type （WT）. Overexpression of the AtPAP12 or AtPAP26 gene, however, caused plants to grow better on P- or P- medium supplemented with ADP or Fru-6-P. Interest-ingly, Pi levels are essentially the same for the WT and overexpressing lines, although these two types of plants have significantly different growth phenotypes. These results suggest that the APases may have other roles besides enhancing internal Pi recycling or releasing Pi from external organophosphates for plant uptake.     

Cryopreservation of hybrid Cymbidium protocorm-like bodies by encapsulation–dehydration and vitrification

Cryopreservation can be a stable, long-term method of germplasm conservation, but successful application can be challenging for tropical material. To optimize survival and re-growth from cryopreserved tissues derived from protocorm-like bodies (PLBs) of hybrid Cymbidium Twilight Moon ‘Day Light’, the effects of explant type (intact PLBs, half-PLBs, or PLB longitudinal thin cell layers) and various explant treatments were studied. Encapsulation in alginate beads was essential, and intact PLBs were best for cryopreservation, based on survival and ability to form neo-PLBs and/or percentage re-growth. Osmotic hydration of intact PLBs in 2% sucrose for 24 h increased neo-PLB formation and re-growth, with the best responses seen when PLBs were excised from alginate beads prior to re-growth after cryopreservation. Both non-transgenic and transgenic PLBs were amenable to cryopreservation for up to 1 year using these methods. This optimized protocol will improve the viability of hybrid Cymbidium germplasm after long-term cryopreservation.     

Successful storage of protocorm-like bodies of hybrid Cymbidium (Orchidaceae) under low temperature conditions

Low temperatures result in lower metabolic cellular activity, thus slowing down cell division and growth. This is advantageous where a plant scientist might seek to store important germplasm without the risks associated with low temperature storage. In this study, two cold temperatures above freezing, namely 4 and 10 °C, were tested to assess for how long PLBs could be preserved without a significant loss in regeneration ability (i.e., the ability to form neo-PLBs). Control treatments were cultured at 25 °C on Teixeira Cymbidium (TC) medium at a 16-h photoperiod at a photosynthetic photon flux density (PPFD) of 45 μmol m⁻² s⁻¹. For the cold treatments, each was replicated in the dark and at low light intensity (12-h photoperiod and a PPFD of 10 μmol m⁻² s⁻¹). All cultures were sub-cultured six times onto fresh medium every 60 days, for approximately 1 year. On the 7th subculture, all neo-PLBs were prepared uniformly and replated onto standard TC medium under light conditions described above for the control. 45 days after the 7th subculture and just before subcultures 1–6, the number of neo-PLBs per half-PLB was measured. The number of neo-PLBs that formed under different treatments depended strongly on the temperature and light conditions with most neo-PLBs forming under control conditions, although that number dropped significantly as the temperature was dropped to 10 °C and then even more to 4 °C, the same trend being observed when explants were cultured and subcultured under dim light, with organogenesis being more strongly negatively influenced in darkness. For all low-temperature treatments, as well as the dimmed light and darkness treatments, the number of neo-PLBs increased significantly when recultured, on the 7th subculture, onto control TC medium under control environmental conditions, almost as high as the control values. In contrast, the control values decreased, with significantly fewer neo-PLBs by the 7th subculture relative to the control, indicating that new PLBs should be induced from shoot cultures at least once a year to maintain their vitality.     

Synergistic effect of ethylene inhibitors and putrescine on shoot regeneration from hypocotyl explants of Chinese radish (Raphanus sativus L. var. longipinnatus Bailey) in vitro

Summary The role of ethylene and putrescine on shoot regeneration from hypocotyl explants of Chinese radish (Raphanus sativus L. var. longipinnatus Bailey cv. Red Coat) was investigated. Explants were recalcitrant in culture, but exogenous application of ethylene inhibitor [20–30 M aminoethoxyvinylglycine (AVG) or AgNO₃] enhanced shoot regeneration of explants grown on medium supplemented with 2 mg/l N⁶-benzyladenine and 1 mg/l 1-naphthaleneacetic acid. The best regeneration occurred in the medium containing AgNO₃ in combination with AVG. Culture medium solidified with agarose in the presence of AgNO₃ but not AVG was also beneficial to shoot regeneration. Exogenous putrescine, 2-chloroethylphosphonic acid and 1-aminocyclopropane-1-carboxylate had no effect on shoot regeneration. However, regeneration was greatly promoted by 10–25 mM putrescine in combination with 30 M AgNO₃ or AVG. Explants with high regenerability grown in the presence of AgNO₃ or in combination with putrescine emanated high levels of ethylene throughout the 21-d culture period. By contrast, AVG or putrescine alone resulted in a decrease in ethylene production. For rooting of shoot cuttings, IAA and IBA at 1–5 mg/l were more effective than NAA.Abbreviations ACC 1-aminocyclopropane-1-carboxylate - AVG aminoethoxyvinylglycine - BA N⁶-benzyladenine - CEPA 2-chloroethylphosphonic acid - IAA indole-3-acetic acid - IBA indole-3-butyric acid - MS Murashige and Skoog (1962) medium - NAA 1-naphthaleneacetic acid - PAs polyamines - SAM S-adenosyl-L-methionine     

Multiple Regeneration Pathways via Thin Cell Layers in Hybrid Cymbidium (Orchidaceae)

Protocorm-like body (PLB) and subsequent shoot development in hybrid Cymbidium Twilight Moon ‘Day Light’ can be established in vitro via 3 pathways: PLBs, PLB thin cell layers (TCLs), or embryogenic callus (EC). Traditionally Cymbidium hybrids are mass-produced commercially through the neo-formation of secondary PLBs (2° PLB) from initial or primary PLBs (1° PLB) or PLB segments, or from PLB TCLs, resulting in a moderate number of 2° PLBs (average 4.46 2° PLBs/1° bisected PLB, or 1.12 2° PLBs/ PLB TCL). This study shows that EC can be induced from 1° PLBs or PLB TCLs. Thereafter, resulting 2° PLBs (average 22.1 2° PLBs/EC cluster derived from 1° PLB) form directly from the EC on the same medium or following the transfer of EC onto PGR-free medium. By flow cytometry and PCR-RAPD analysis, the cytogenetic stability of 1° PLBs, of resulting 2° PLBs and EC, and plants derived therefrom was demonstrated.     

Promotion ofin vitro shoot formation from excised roots of silktree (Albizzia julibrissin) by an oxime ether derivative and other ethylene inhibitors

Summary This report describes the regeneration response of excised seedling roots of silktree (Albizzia julibrissin) to added ethylene precursors/generators (1-amino-cyclopropane-1-carboxylic acid [ACC], 2-chloroethylphosphonic acid [CEPA]), biosynthesis inhibitors (aminoethoxyvinylglycine [AVG], an oxime ether derivative [OED={[(ispropylidene)-amino]oxy}-acetic acid-2-(methoxy)-2-oxoethyl ester], CoCl² [Co⁺⁺]), and an ethylene action inhibitor (AgNO₃ [Ag⁺]). When placed on B5 medium, about 50% of the control explants formed shoot buds within 15 days. Addition of ACC or CEPA (1–10 µM) to the culture medium decreased both the percentage of cultures forming shoots and the number of shoots formed per culture. In contrast, AVG and OED (1–10 µM) increased shoot formation to almost 100% and increased the number of shoots formed per culture. Likewise, both Co⁺⁺ and Ag⁺ (1–10 µM) increased shoot regeneration, but the number of shoots produced after 30 days was less than with AVG or OED. The inhibitors of ethylene biosynthesis were partially effective in counteracting the inhibitory effect of ACC on shoot formation. These results suggest that modulation of ethylene biosynthesis and/or action can strongly influence the formation of adventitious shoots from excised roots of silktree.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AVG aminoethoxyvinylglycine - CEPA 2-chloroethylphosphonic acid - OED oxime ether derivative     

Role of Ethylene on de Novo Shoot Regeneration from Cotyledonary Explants of Brassica campestris ssp. pekinensis (Lour) Olsson in Vitro

The promotive effect of AgNO₃ and aminoethoxyvinylglycine (AVG) on in vitro shoot regeneration from cotyledons of Brassica campestris ssp. pekinensis in relation to endogenous 1-amino-cyclopropane-1-carboxylic acid (ACC) synthase, ACC, and ethylene production was investigated. AgNO₃ enhanced ACC synthase activity and ACC accumulation, which reached a maximum after 3 to 7 days of culture. ACC accumulation was concomitant with increased emanation of ethylene which peaked after 14 days. In contrast, AVG was inhibitory to endogenous ACC synthase activity and reduced ACC and ethylene production. The promotive effect of AVG on shoot regeneration was reversed by 2-chloroethylphosphonic acid at 50 micromolar or higher concentrations, whereas explants grown on AgNO₃ medium were less affected by 2-chloroethylphosphonic acid. The distinctive effect of AgNO₃ and AVG on endogenous ACC synthase, ACC, and ethylene production and its possible mechanisms are discussed.     

Deferral of senescence and abscission by chemical inhibition of ethylene synthesis and action in bean explants

Three compounds known to inhibit ethylene synthesis and/or action were compared for their ability to delay senescence and abscission of bean explants (Phaseolus vulgaris L. cv Contender). Aminoethoxyvinyl-glycine (AVG), AgNO₃, and sodium benzoate were infiltrated into the petiole explants. Their effect on abscission was monitored by measuring the force required to break the abscission zone, and their effect on senescence was followed by measuring chlorophyll and soluble protein in the distal (pulvinus) sections. AVG at concentrations between 1 and 100 micromolar inhibited ethylene synthesis by about 80 to 90% compared to the control during sampling periods of 24 and 48 hours after treatment. This compound also delayed the development of abscission and senescence. Treatment with AgNO₃ at concentrations between 1 and 100 micromolar progressively reduced ethylene production, but to a lesser extent than AVG. The effects of AgNO₃ on senescence and abscission were quite similar to those of AVG. Sodium benzoate at 50 micromolar to 5 millimolar did not inhibit ethylene synthesis during the first 24 hours, but appreciably inhibited ethylene synthesis 48 hours after treatment. It also delayed the development of abscission and senescence. The effects of AVG, Ag⁺, and sodium benzoate suggest that ethylene could play a major role in both the senescence induction phase and the separation phase in bean explants.     

Impact of paper bridges, activated charcoal, and antioxidants on growth and development of protocorm-like bodies of hybrid Cymbidium

This study aimed to establish whether protocorm-like bodies (PLBs) of hybrid Cymbidium Twilight Moon ‘Day Light’ could be cultured on paper bridges to remove tissue and medium browning and enhance growth. In addition, the effects of two antioxidants (ascorbic acid [AA] and α-tocopherol [AT]) and activated charcoal (AC) on tissue and medium browning were evaluated. Half-PLBs were cultured on Whatman No. 1 paper bridges in 10 ml of medium containing AC, AA, or AT. The production and development of new PLBs was inferior to that on standard agar-based solid medium when half-PLBs were used. The addition of 1 g/l AC, 10 mg/l AA, or 25 mg/l AT did not affect the formation of new PLBs from half-PLBs, but tissue or medium browning was also not observed. Encapsulated PLBs developed from half-PLBs germinated on medium containing AC or antioxidants. This research provides a simple but effective chemical means, through the use of AC or antioxidants, of avoiding tissue or medium browning without negatively impacting the growth and productivity of orchid PLBs. The use of paper bridges, however, significantly reduced PLB-related growth and development parameters relative to agar-based medium.     

Ethylene inhibitors enhance in vitro root formation from apple shoot cultures

Effects of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) and three ethylene inhibitors, AgNO₃, aminoethoxyvinyglycine (AVG) and CoCl₂, on root formation were tested in vitro using shoot cultures of the apple (Malus×domestica Borkh.) cultivar Royal Gala. ACC inhibited root formation by delaying root emergence and increasing callus formation at the bases of shoots. In contrast, ethylene inhibitors promoted root formation. Both AgNO₃ and AVG at the appropriate concentrations increased the percentage of shoots producing roots and reduced callus formation at the base of these shoots. AgNO₃ stimulated root emergence and enhanced root growth, while AVG increased the number of roots per shoot. CoCl₂ slightly increased root number and rooting efficiency. These promotive effects may result from a reduction in ethylene concentration or inhibition of ethylene action. The results found in this study may be used to improve the rooting efficiency of other apple cultivars and rootstocks, and possibly of other plant species. Received: 2 March 1997 / Revision received: 1 July 1997 / Accepted: 18 July 1997     

Ethylene as an effector of wound-induced resistance to cellulase in oat leaves

Peeling the abaxial epidermis from oat leaves (Avena sativa var. Victory) induces the formation of wound ethylene and the development of resistance to cellulolytic digestion of mesophyll cell walls. Ethylene release begins between 1 and 2 hours after peeling in the light or dark. Aminoethoxyvinylglycine (AVG, 0.1 millimolar), CoCl₂ (1.0 millimolar), propyl gallate (PG, 1.0 millimolar) or aminooxyacetic acid (AOA, 1.0 millimolar) inhibits, whereas AgNO₃ stimulates wound ethylene formation. Incubation on inhibitors of ethylene biosynthesis (AVG, CoCl₂, PG, AOA) or action (AgNO₃, hypobaric pressure or the trapping of ethylene with HgClO₄) also prevents the development of wound-induced resistance to enzymic cell wall digestion. 1-Aminocyclopropane-1-carboxylic acid (ACC, 1.0 millimolar) reverses AVG (0.1 millimolar) inhibition of the development of resistance. Exogenous ethylene partially induces the development of resistance in unwounded oat leaves.

These results suggest that peeling of oat leaves induces ethylene biosynthesis, which in turn effects changes in the mesophyll cells resulting in the development of resistance to cellulolytic digestion.