Moist Vermiculite Research Articles

Seed Hydration Treatments For Improved Sweet Corn Germination and Stand Establishment

Abstract This research examines the potential of seed hydration for improving sweet corn (Zea mays L.) seed performance, especially for plantings in cool (10°–15°C) soils. In addition to the effect of hydration treatments, the influence of seed quality and cultivar was evaluated using electrolyte leakage tests and seedling growth cold tests. Seed hydration treatments included seed hardening (a wetting/drying cycle), seed moisturizing (placing seed in moist vermiculite), and osmoconditioning, which were compared to a dry seed control. Hardening and moisturizing treatments improved early emergence by as much as 20%, while osmoconditioning significantly lowered field emergence. Seed moisturizing and hardening also improved uniformity of emergence, and reduced the number of days required to attain 50% or 75% emergence. Seed hydration treatments were effective with the three levels (high, medium, and low) of seed quality and the three cultivars (‘Jubilee’, ‘Midway’, and ‘Reward’) studied.

Carpogenic Germination of Sclerotia of Sclerotinia sclerotiorum after Periods of Conditioning in Soil

AbstractPeriods of conditioning in soil reduced the length of the resting period needed before sclerotia of Sclerotinia sclerotiorum could germinate to form apothecia. Curves for germination of sclerotia were fitted by a form of the log‐logistic equation and from this equation the time taken for 50% germination (x50) was calculated. These x50 values were used as the basis for comparing germinability of sclerotia collected from infected sunflower plants and others conditioned in soil, or moist vermiculite for various times. Sclerotia from sunflower roots germinated sooner than those from the stem cavities. Germinability increased with the length of the conditioning period. Conditioning in soil was more effective than in moist vermiculite.

Sterilization of Adult Male Field Crickets Gryllus integer (Orthoptera: Gryllidae) by Gamma Radiation

In this paper I report a dose of gamma radiation that will induce sterility in adult male field crickets. This work was undertaken as part of a larger study on sperm competition in the field cricket Gryllus integer (Backus, 1985). The methods used in this study are outlined in Backus (1985). Fifteen virgin adult female G. integer were each mated twice to 1 of 15 adult male crickets within 24 hr of the male's exposure to 7,000 roentgens of gamma radiation (R males). Following mating females were allowed 11 days for oviposition in a container filled with 250 ml moist vermiculite. Oviposition dishes were examined daily for the presence of nymphs; any nymphs found were mouth-aspirated and counted. A control group consisted of 5 females mated with unirradiated (N) males and were treated similarly to females mated with R males. Following 8 weeks, the soil in each oviposition dish was dried and examined under a dissecting microscope for the presence of unhatched eggs. All unhatched eggs were counted; any nymphs that had hatched and were remaining in the soil were counted and added to the number of emerged nymphs. Productivity, the total number of eggs laid by a female, was determined by summing the number of nymphs emerged with the number of unhatched eggs. Mean productivity for females mated with R males was 337.5 (SD 201.4, Range 65-733), whereas mean productivity for females mated with N males was 291.2 (SD 128.3, Range 153-500). A Mann-Whitney U test revealed no significant difference in mean productivity between the 2 groups (U = 35.5, p > 0.05). The mean proportion of eggs hatched for females mated with R males was 0.01 (SD 0.02, Range 0-0.04); for females mated with N males was 0.67 (SD 0.27, Range 0.190.86). There was a significant difference between these values (U = 0, p < 0.05; onetailed). The mean age of death for males in the R group was 22.8 days (SD 30, Range 16-28); for males in the N group was 59.2 days (SD 19.0, Range 27-77). There was a significant difference between the 2 groups of males for age of death (U = 1, p < 0.05, two-tailed). The proportion of eggs hatched for females mated with N males was much greater than for females mated with males exposed to 7,000 roentgens of gamma radiation. The proportion of eggs hatched by females in the R group was so low that 7,000 roentgens was apparently sufficient to sterilize adult male G. integer. A second effect of this dosage appears to be a significantly shortened lifespan in R group males. The dosage of radiation used did not appear to affect male courtship or mating behavior (Backus, 1985). This was the only dosage of radiation tested and may be considered as a minimum as 1% of the eggs laid by females mated with R group males hatched. Support for this work was provided by a Natural Sciences and Engineering Council of Canada grant to Dr. W. H. Cade.

Toxic effects of two organophosphate insecticides, monocrotophos and dichlorvos to common earthworm Lampito Mauritii (Kinberg)

The lethal concentrations (LC50 96 h−1) were measured experimentally by exposing the earthworms (Lampito mauritii) in moist vermiculite and in water. The morphological changes observed during the exposure of animals to the monocrotophos and dichlorvos were outlined. The mortality rate was higher in the water medium than in moist vermiculite. The hyperactivity at low pesticide concentrations is found to influence the size of the population.

Candidate Fumigants for Control of Caribbean Fruit Fly, 1983-1984

Abstract The chemical compounds listed below were tested for effectiveness as fumigants against laboratory-reared, mature fruit fly larvae. Ethylene dibromide was used as the standard for comparison. All compounds were reagent grade (99% pure) or better. Fumigation containers were 3.8-liter widemouth glass jars with teflon-lined, screw-cap lids. An open petri dish containing 100 naked larvae was placed on a wire rack in each jar. Test chemicals were then pipetted onto 11-cm filter papers which were placed in the jars under the rack, and the lids were fastened in place. Jars were placed on their sides to minimize settling effects. All tests were conducted at 24°C and 50% RH. After exposure, larvae were placed in moist vermiculite, held at 27°C, and allowed to complete development. Survival was based on the number of insects that reached the adult stage. A two-phase testing procedure was used to evaluate the chemicals. The first phase was designed to eliminate compounds that were not effective at high dosage-time combinations, and involved exposure of larvae to 16, 32, and 64 g/m3 for 4 h (1 replicate). High mortality in the initial tests qualified compounds for second-phase testing. This involved exposing larvae to a series of lower dosages (2 replicates) for only 2 h, so LD values could be determined. Data were first corrected for natural mortality in the controls by Abbott’s formula. Then probit mortality was plotted against the logarithm of dosage and examined by eye to determine that linear regression was appropriate. Data were subjected to a computer programmed probit analysis to estimate the LD50, LD95, and LD99 dosages.

A MODEL SYSTEM FOR THE STUDY OF 2,4-D TRANSLOCATION IN LEAFY SPURGE

A model system was devised to study the translocation of 2,4-D in leafy spurge (Euphorbia esula L.). The effects of rate of 2,4-D application, decapitation, and rate and pretreatment with ethephon on 14C-2,4-D translocation were studied. Rooted cuttings were obtained by rooting newly-developed axillary shoots in moist vermiculite for 4 wk. These cuttings were then placed in liquid nutrient medium for translocation experiments. Seven days after application, 50–60% of the 14C translocated from 14C-2,4-D treated leaves was found in the stem. The percentage of 14C that accumulated in the stem increased with increasing rate of 2,4-D application to 1 kg/ha. Up to 85% of 14C translocated to the root was released into the nutrient medium. Shoot decapitation 5 mm below the apex up to 4 days before 2,4-D application decreased 14C percentage in leaf tissue and increased 14C in stem and root. Foliar application of ethephon at 1 kg/ha resulted in a transient increase in the rate of ethylene evolution from shoot and root tissues, decreased the amount of 14C translocated to the root zone and increased the 14C in the leaves. Ethephon treatment of larger, vermiculite-grown plants also decreased 14C accumulation in the roots. These results indicate that the use of root cuttings is a convenient and reliable method for the study of herbicide translocation and plant growth regulator/herbicide interactions in leafy spurge.Key words: Translocation, 2,4-D, leafy spurge, Euphorbia esula L., plant growth regulator, ethephon

Candidate Fumigants for Control of Caribbean Fruit Fly, 1981-1982

Abstract The chemical compounds listed below were tested for effectiveness as fumigants against mature fruit fly larvae. Ethylene dibromide was used as the standard for comparison. All compounds were reagent grade (99% pure) or better. Fumigation containers were 3.8 liter widemouth glass jars with teflon-lined, screw-cap lids. An open petri dish containing 200 naked larvae was placed in each jar. Test chemicals were then pipetted onto 11-cm filter papers, placed in the jars with the insects. The lids were fastened in place. Jars were placed on their sides to minimize settling effects. All tests were conducted at 24°C and 50% RH. After exposure, larvae were placed in moist vermiculite, held at 27°C, and allowed to complete development. Survival was based on the number of insects that reached the adult stage. A two-phase testing procedure was used to evaluate the chemicals. The first phase was designed to eliminate compounds that were not effective at high dosage-time combinations, and involved exposure of larvae to 16, 32, and 64 g/m3 for 4 h. High mortality in the initial tests qualified compounds for second-phase testing. This involved exposing larvae to a series of lower dosages for only 2 h, so LD values could be determined. Data were first corrected for natural mortality in the controls by Abbott’s formula. Then probit mortality was plotted against the logarithm of dosage and examined by eye to determine that linear regression was appropriate. Data were subjected to a computer programmed probit analysis to estimate LD50, LD95, and LD99 dosages.

Effect of morphactin on certain plant growth substances in bean roots

AbstractThe effect of morphactin (methyl‐2‐chloro‐9‐hydroxyfluorene‐9‐carboxylate) on the content of several plant growth substances in bean roots was determined. Beans (Phaseolus vulgaris L. cv. Spartan) were soaked in aqueous solutions of morphactin, 1 x 10‐4, 1 x 10‐5, and 1 x 10‐6M and grown in moist vermiculite. As controls were used beans grown in water‐moistened vermiculite either intact or having the root tips removed (decapped). The roots, morphactin‐treated, controls, and the decapped ones were analyzed for indol‐3‐yl acetic acid (IAA), indol‐3‐yl acrylic acid (IAcA), indol‐3‐yl pyruvic acid (IPyA), indol‐3‐yl lactic acid (1LA), abscisic acid (ABA), gibberellins GA1, GA3, GA4, and GA9 using gas‐liquid chromatographic methods. Morphactin, while affecting the geotropical responses, changed also the growth substance content of roots. IAA, ABA, GA1, and GA9 contents decreased, IPyA, IAeA, GA3, and GA4 contents were not affected and ILA content increased slightly with increasing dosages of morphactin. Growth substance pattern of decapped roots resembled that of the roots treated with the highest dose, 1 x 10‐4M, of morphactin.

The Development of Plantlets from Strobilus Branches in Lycopodium phlegmaria

Lycopodium phlegmaria L. is an epiphyte commonly found growing on the trunks and branches of forest trees in Singapore. It is a widely distributed species in the Old World tropics, ranging from Africa to Polynesia. Its pendulous stems are covered with spirally arranged, stiff, ovate-lanceolate leaves (Fig. 1). Both the sterile portions of the stems and the strobili branch dichotomously (Figs. I and 2). The sporophylls are smaller than the foliage leaves and are arranged more compactly along the branches. In most cases, the sporophylls are grouped terminally on determinate stems. However, instances of foliage leaves appearing along the strobilus branches have been observed (Fig. 2). This is reminiscent of the condition seen in L. selago L., where the fertile zones alternate with the sterile and the foliage leaves are not much different from the sporophylls (Bower, 1935, p. 200). Recently, a portion of L. phlegmaria detached from the parent plant was found lying on damp ground on the secondary forest at the MacRitchie Catchment area in Singapore. It was still green, and the ends of the fertile branches showed growth following detachment. Under the humid conditions of the forest floor, the ends of the branches had reverted to vegetative growth and had produced one or two young plants each (Fig. 4). Roots had grown from the base of some of these young plants. In one instance, the extension of a strobilus branch was an elongate stem with long internodes (Fig. 3). At the nodes were leafy structures similar to the sporophylls. In the axils of these structures were obviously vegetative buds, some of which had developed into vegetative shoots (Fig. 3). Longitudinal sections of the strobilus branches revealed the gradual transformation of the sporangia from fertile to sterile in the acropetal direction. The fertile, spore-containing sporangia had thickened outer cells along the inner and radial walls. Sterile sporangia lacked these characteristically thickened outer cells. Sporangia along the vegetative outgrowths were mere protuberances, without any differentiation whatsoever. As in ferns, root development was endogenous and very close to the vascular strand. Placing the ends of strobilus branches from cultivated L. phlegmaria on moist vermiculite similarly stimulated development of vegetative shoots after about four months. The new growths had excessively elongate interodes, the sporophylls were smaller until foliage leaves were produced when the axis turned upwards. Roots formed at the points of turning after a further period of two to four months. These shoots could then be removed as plantlets. These observations give support to Bower's (1908, p. 164) theory that foliage leaves essentially are sporophylls with the sporangia completely suppressed. In this respect, it should be noted that the strobili of L. obscurum L. and L. flabel-

Ribonucleic Acid Synthesis in Germinating Castor Bean Endosperm

Ribonucleic Acid Synthesis in Germinating Castor Bean Endosperm

Plant regeneration from shoot tips and callus of papaya.

Two methods of in vitro culture were employed to regenerate papaya plants. One involved regeneration of plants from callus and the other, production of multiple plants from single shoot-tip explants. Callus was induced from stem sections of papaya seedlings in a medium containing 1 mg per 1 NAA and 0.1 mg per 1 kinetin. The callus regenerated shoots and/or embryoids when transferred to a medium of lower auxin, 0 to 0.05 mg per 1 IAA, and higher cytokinin, 1 to 2 mg per 1 kinetin. Multiple shoots were produced when the excised shoot-tip explants were cultured in a medium supplemented with 0.05 mg per 1 IAA and either 5 mg per 1 kinetin or 0.5 to 1.0 mg per 1 benzyladenine. Root formation of the shoots or embryoids that derived from callus or shoot tips occurred in a medium containing 5 mg per 1 IAA and in a light intensity of 3000 to 4000 lx. The rooted plants could be established in soil and under standard greenhouse conditions after they had been acclimated by initially growing them in moist vermiculite contained in polyethylene-covered pots.

Apical dominance in the rhizome of Agropyron repens: the influence of water stress on bud activity

Experiments conducted under both field and growth-chamber conditions showed that buds on the rhizome of Agropyron repens L. Beauv. could be released from inhibition by a localized reduction of water stress, e.g. by enclosing the rhizomes in moist vermiculite. This response was obtained even at low N levels, a fact which may be due partly to the relatively low N requirement of buds developing as rhizomes as compared with those developing as shoots. The induced growth of the lateral buds was correlated with a reduction or complete inhibition of apical growth of the parent rhizome or with its transition from rhizome to shoot development. Continuous root removal reduced the bud response to high humidity in N-deficient plants but had relatively little effect at a higher N level. In water-stressed rhizomes the apparent increase of bud inhibition with distance from the apex, a characteristic feature of apical dominance, was correlated with the water content of the rhizome, which was greatest at the apex and decreased basipetally. It is postulated that this gradient of decreasing rhizome water content may be causally related to the increasing inhibition of bud activity.

A comparison of the infectivity of Trichuris suis ova embryonated by four different methods

Abstract Four methods for embryonating the eggs of Trichuris suis in the laboratory were compared. Eggs were mixed with moist vermiculite (method 1) or were suspended in a 0.2% potassium dichromate solution that was either aerated (2), non-aerated (3) or deoxygenated (4). It was shown that differences in the method of culture profoundly affected the ability of the fully developed eggs to hatch and the parasites to become established in pigs. Of the four methods compared, ova of highest infectivity were produced after culture in moist vermiculite.

Genetic Similarity Between Gaura longiflora and Its Obligately Outcrossing Derivative G. demareei

Genetic Similarity Between Gaura longiflora and Its Obligately Outcrossing Derivative G. demareei

Developmental Changes in Endosperm of Germinating Castor Bean Independent of Embryonic Axis

Dry castor bean (Ricinus communis) seeds were cut transversely into halves and the half without the embryonic axis was placed in moist vermiculite at 30 C for 5 days. The development of the endosperm in the half-bean was found to be qualitatively similar to that in the whole seedling in the appearance of various enzymes of gluconeogenesis, the accumulation of glucose and sucrose as the end products of fat utilization, and the development of subcellular structure. It is concluded that during germination of castor bean, the embryonic axis does not directly control the developmental changes in the endosperm.

THE EFFECTS OF IMBIBITION DRYING TREATMENTS ON WHEAT SEEDS

SUMMARYWheat seeds were imbibed and re‐dried under conditions that did not give rise to radicle protrusion through the seed coat. When seeds pre‐treated in this way were planted in moist vermiculite, coleoptile emergence was faster than from untreated seeds. This advancing effect on coleoptile emergence (‘seed invigoration’) was most marked when the seedlings were grown at low temperature or under osmotic stress (i.e. under unfavourable conditions). The seed‐borne pathogen Septoria nodorum was not affected by an imbibing‐drying treatment.Conditions of imbibition and drying giving optimal invigoration are described and data on the metabolism of untreated and invigorated seeds are presented. Oxygen uptake and [14C]‐leucine incorporation into protein were more enhanced in aleurone layers than in embryos isolated from invigorated seeds. Both untreated and invigorated seeds showed very low α‐amylase levels when dry, although a‐amylase activity developed more rapidly in invigorated seeds during germination. Gibberellic acid alone was not able to replace an imbibing‐drying treatment.

Ricerche Sul Meristema Apicale della Radice. VII L'attività di Alcuni Enzimi Della Glicolisi, del Ciclo di Krebs e di Quello dei Pentoso Fosfati

Abstract Studies on root apical meristem. VII. Activities of some enzymes of glycolysis, of the Krebs cycle and of the pentose phosphate cycle. — The enzymes assayed are: aldolase, glyceraldheyde-3-phosphate: NAD oxidoreductase, triosephosphate isomerase, fumarate hydratase, aconitate hydratase, glucose-6-phosphate: NADP oxidoreductase, 6-phosphogluconate: NADP oxidoreductase. The determinations were made on pea roots (Pisum sativum cv. Alaska) which were obtained by germinating seeds on moist vermiculite, in the dark, at 25° C, either for 2 or 7 days. In both cases samples were collected from the meristematic zone (0-2 mm from the apex) and from the extending zone (2-4 mm from the apex). All the enzymes determined are present both in the meristematic and in the extending zone of the root. If referred to a fresh weight basis, their activities are always greater in the meristem; if referred to a dry weight or to a protein basis, the values in the meristematic zone are nearly equal to, or higher than those in the extending zone. With respect to the development of the cell in the root from the meristematic to the vacuolated state, the present results indicate that the change in volume is accompanied by increases is the enzymes tested.

ASSOCIATION BETWEEN ASCORBIC ACID CONCENTRATION AND COLD HARDENING IN YOUNG WINTER WHEAT SEEDLINGS

The ascorbic acid content of winter wheat varieties, germinated in the dark at various temperatures on the surface of moist vermiculite, was much higher at a hardening temperature of 1.5 °C than at higher temperatures of 5°, 10°, or 20 °C. There were no differences between the ascorbic acid contents of wheat grown at the three higher temperatures. Ascorbic acid content was dependent on the stage of development at all temperatures. At 1.5 °C, the ascorbic acid content increased during the first 6 weeks of growth (shoots about 15 mm) and then decreased rapidly. This variation in ascorbic acid content was closely associated with the increase and decrease in cold hardiness of wheat grown under similar conditions.Ascorbic acid content was highest in shoots, intermediate in roots, and lowest in the endosperm of wheat grown for 6 weeks at 1.5 °C.At hardening temperatures (1.5° and 3 °C) the more cold hardy winter wheat varieties had higher contents of ascorbic acid. At higher temperatures the differences between varieties were small. The ranking of varieties by ascorbic acid content could be influenced by relative stages of growth.Artificial cold hardiness was imparted to winter wheat seedlings by feeding them aqueous ascorbic acid solutions of adequate concentration. The ascorbic acid content of leaves required for artificial hardening appeared to be similar to that accumulated in sprouts hardened fully by growth at low temperature.

Response of Stomata to Wounding

1. The present paper reports the results of an exploratory investigation of the degree of lability of differentiation of a physiologically specialized, apparently late-determined, ubiquitous plant cell type, the guard cell. 2. To determine whether guard cells could be stimulated to divide, mature foliage leaves of Begonia aridicaulis Zies. were subjected to three types of wounds: (a) a 5-7 mm. razor-blade incision through the leaf, which was allowed to remain on the plant (non-excised), (b) the same type and position of incision, but with the leaf excised at juncture of petiole and lamina and placed abaxial side down on moist vermiculite in a partially covered glass dish (excised), and (c) leaves cut in half perpendicular to their long axis and the apical half inserted vertically, cut edge down, into moist vermiculite in a partially covered glass dish (leaf fragments). 3. Comparing the three wound methods, uniform results were as follows: (a) Guard-cell division was not observed; (b) the wound-induced division walls in epidermal cells were oriented parallel to the long axis of the wound; (c) the wound-induced division walls proceeded as a wave away from the wound; (d) guard cells degenerated at variable distances from the wound, and this degeneration involved shrinkage of the guard cells parallel to their long axis as well as unequal, and often extensive, deposition of additional wall material and "fragmentation" of the chloroplasts, resulting in their numerical increase, assumption of irregular form, and reduced size; and (e) guard-cell degeneration in both the excised leaves and leaf fragments occurred within approximately the same distance distal from the outermost extent of the wound-induced divisions in the same time interval following wounding. 4. Individually unique results were as follows. In non-excised leaves guard-cell degeneration was conspicuous and occurred at relatively great distances from the wound region. Apparently normal stomata, however, occurred within the region of active division. Although the three subsidiary cells adjacent to the guard cells eventually divided, they did so noticeably later than did regular epidermal cells. In excised leaves guard-cell degeneration was relatively infrequent. The three subsidiary cells next to the guard cells did not divide. In leaf fragments guard-cell degeneration occurred outside the wound-induced division region with intermediate frequency. The three subsidiary cells adjacent to the guard cells divided as actively as surrounding cells with no time lag. 5. It is stressed that (a) the potency of the guard cell and any derivative cells probably can be only elucidated if the guard cell itself can be released from the physical and chemical correlations serving to keep cells in a normal plant morphogenetically stable at functional maturity and that (b) such a problem is simply one facet of a much larger one dealing with potency of idioblastic cells in general.

MODIFICATION OF FLORAL INITIATION WITH AUXINS AND TEMPERATURES

THE FACT that auxins are capable of modifying floral initiation has been known since 1937 when Dostal and Hosek demonstrated an inhibition of flowering in Circaea. It appears from the experiments of Cholodny (1936) and Thimann and Lane (1938) that auxins may have an effect on flowering as a function of vernalization, and the work of Leopold and Thimann (1948) and Bonner and Thurlow (1949) indicate that auxins can modify flowering as a function of photoperiodism. Up to the present time promotive effects of auxins upon photoperiodic induction have been reported only for long-day plants (Leopold and Thimann, 1948; Leopold and Thimann, 1949; Klein, 1951; Claes, 1952; Liverman and Lang, 1952) . Studies of floral initiation in this laboratory have indicated a strong interaction between auxin effects and temperatures experienced by pea plants (Leop6ld and Guernsey, 1953a). A similar interaction has been found between auxin and vernalization of barley (Leopold, 1952). These results suggest the possibility that an auxin-temperature interaction might be general among plants, and might offer a new method of altering floral initiation. Knowledge of such a phenomenon would be of considerable interest both physiologically and agriculturally. METHODS.-Seeds of diverse types of plants were soaked in solutions of auxin (naphthaleneacetic acid) for 24 hr. at room temperature. After removal from the solution, the seeds were placed in moist vermiculite and transferred to dark controlled temperature rooms where they remained for a period of 2 wk. At the end of the temperature treatment they were transplanted into gravel beds in the greenhouse and permitted to develop under photoperiods which were favorable for flowering. Ten plants from each treatment were then dissected under a microscope and the numbers of flower primordia, their location and stage of development were recorded. This procedure is essentially the same as that described by Leopold and Guernsey (1953a) for peas, with the exception that a longer temperature control period was used. Long photoperiods were obtained by extension of natural daylight hours with 100 ft.-c. of incandescent light. Short photoperiods were obtained by use of black cloth curtains. The stage of development of the various grain species was recorded in each experiment upon dissection. A simple scoring method was used as follows: 0 vegetative; 1 simple spikelet primordia; 2 floret parts differentiated; 3 pre-boot stage; 4 boot stage; 5 flag stage; 6 heading out.