Delayed Seedling Emergence Research Articles

Standardization of an Effective Scarification and Germination Protocol for Strawberry Seeds That Is Useful for Gamic Propagation

In strawberry (Fragaria × ananassa Duch.) breeding programs, seed dormancy adversely affects germination, resulting in delayed seedling emergence and low germination rates. This study investigated the best solution to enhance strawberry seed germination both in terms of efficiency and timing by evaluating the effect of three key factors: genotype, pre-sowing treatment, and germination medium. Chemical scarification treatment with the sulfuric acid of seeds from three different genotypes was optimized; treated seeds were placed to germinate on three germination media (Murashige and Skoog medium, peat, and filter paper) in a growth chamber. Seedlings obtained were acclimatized for evaluating post-acclimatization survival rate and possible phenotypic differences regarding seedling development. Chemical scarification treatment produced the best results, with germination rates of around 100% and the highest speed of germination compared to the not-treated controls. Indeed, more than 90% of the seeds germinated 14 days after sowing, regardless of the genotype or germination medium tested. Seedlings germinated on filter paper gave the poorest performances in terms of post-acclimatization survival rate and showed lower average plant height. In conclusion, it was demonstrated that excellent germination rates can be achieved through proper seed scarification, which is not genotype dependent; furthermore, when this method is combined with the correct germination medium, excellent seedling quality can be achieved.

Germination traits explain the success of direct seeding restoration in the seasonal tropics of Brazil

Direct seeding is a major method for active restoration of tropical forests and savannas. Although seed traits such as large and rounded seeds are proxies for successful establishment, the effects of germination traits have not been investigated. The study of germination traits allows understanding how to manipulate seed and germination traits to improve the success of seedling establishment. In this study, we evaluated how germination traits are related to success of seedling emergence after direct seeding for forest and savanna trees of the Cerrado, as well as how dormancy breaking treatments modify germination traits and the success of seedling emergence. Twenty-three trees and three shrubs species from forest and savanna in the Cerrado biome were studied in the laboratory. To evaluate how dormancy breaking treatments modify germination traits, intact and pretreated seeds were sowed in a greenhouse. Data on direct seeding success of pretreated and untreated seeds were taken from the literature. Time to start imbibition had a positive effect, and seed shape (variance of seed dimensions) had a negative contribution to direct seeding success. Seed size was not significant in the presence of these variables. In the greenhouse, pretreated seeds anticipated emergence from 40 to 24 days. In field direct seeding, seedling emergence decreased from 30 % for untreated seeds to 18 % for pretreated seeds. Delayed seedling emergence is a positive strategy for direct seeding. Seed technology should target mechanisms and structures to avoid fast and synchronic emergence for direct seeding in the seasonal tropics.

Physiology in Talisia esculenta seedlings under irrigation with saline water on substrate with hydrogel

Salinity interferes in the physiology of seedlings from germination and seedling emergence, so it is necessary to adopt measures to mitigate its effects. The objectives of this research were to evaluate irrigation frequency, saline water, polymer, and container volume in the emergence and physiology of Talisia esculenta (A. St.-Hil.) Radlk. The treatments were obtained from the combination of polymer doses (0.0; 0.2; 0.6; 1.0; and 1.2 g dm-3), electrical conductivities of the irrigation water (0.3; 1, 1; 2.7; 4.3; and 5.0 dS m-1), and irrigation frequencies (daily and alternate), plus two additional treatments to assess the volume of the container. A randomized block design was used. Emergence and leaf indices of chlorophyll, fluorescence, and gas exchange were analyzed 100 days after sowing. The increase in electrical conductivity reduced and delayed seedling emergence. Decreasing irrigation frequency reduced the chlorophyll b index, stomatal conductance, transpiration, net CO2 assimilation, and carboxylation efficiency. The magnitude of the effects of electrical conductivity of water and polymer were associated with the frequency of irrigation. However, both salinity and polymer reduced practically all physiological variables. The reduction in container volume also affected the physiology of the seedlings, with more effects when irrigated on alternate days. The T. esculenta seedlings are considered sensitive to salinity, should be irrigated daily with water with less electrical conductivity than 1.0 dS m-1, as well as higher capacity containers used (0.75 vs 1.30 dm3).

ModellingChloris virgatagermination and emergence under different temperature and light quality conditions

AbstractChloris virgatais a problematic weed around the world. Prediction of weed germination rates could be a useful strategy to optimise timing of weed control actions. We studied the germination and emergence ofC. virgatacollected seeds under different after‐ripening treatments and different exhumation dates after seed dispersal, to estimate seed dormancy level and predict weed emergence dynamics under field conditions. Three experiments were conducted under controlled conditions to determine base, optimum and maximum germination temperatures (Tb,ToandTmrespectively) and comprised: (a) exposure of seeds to gradually increasing and decreasing temperatures between 5 and 35°C; (b) exposure of seeds to different constant temperatures; and (c) exposure of seeds to different light quality conditions (red – far red ratio) and temperature regimes (constant and alternating temperatures). To explore genuine environmental conditions, a field experiment was performed to determine weed emergence under different shading levels. Finally, with the data obtained, a thermal time model for dormancy release was used to predictC. virgataseedling emergence in the Argentine Pampas region. Seeds after‐ripened in cold and wet conditions and constant 25°C showed the highest germination percentages. The values ofTb(7°C),To(28°C) andTm(40°C) remained constant at all exhumation dates. Neither light quality nor thermal regime modified the final germination percentages. However, shading delayed seedling emergence under field conditions, even when it was adjusted by thermal time. These results may allow predictingC. virgataemergence in temperate regions and help to improve weed control in integrated weed management strategies.

Cadmium toxicity in African yam bean (Sphenostylis stenocarpa (HOCHST. EX A.RICH.) HARMS genotypes

The aim of the study was to investigate the growth responses of African yam bean (Sphenostylis sternocarpa (Hochst. ex A. Rich.) Harms (AYB) to cadmium pollution. Top garden soil (0 – 10 cm) was obtained as pooled and polluted with cadmium (as CdCl2) at the rate of 12 mg kg-1, which is equivalent to 3 times the ecotoxicological screening value of Cd. The polluted soils were made ready for use 3 days later. Nine selected AYB accessions (TSs-87, TSs-89, TSs-90, TSs-91, TSs-92, TSs-93, TSs-94, TSs-95, and TSs-96) were pre-soaked for 30 minutes and then sown in the polluted and unpolluted soils. Data collected were subjected to ANOVA, and means were separated at 95 % confidence interval. Results showed that incidence of cadmium pollution significantly delayed seedling emergence in all tested AYB accessions by at least one day (p < 0.05). Despite exposure to Cd, TSs-96 attained 50 % emergence faster than other accessions. Although there were general reductions in yield due to exposure to Cd, TSs-92 showed the least percentage yield reduction (50 %), compared to 74 % yield reduction in TSs-93, thereby suggesting a comparatively better yield capacity compared to the other test accessions. Overall, decrease in total chlorophyll content seems to be the major reason of injury in Cd-exposed plants.

Biodegradation of chlorpyrifos by bacterial genus Pseudomonas.

Chlorpyrifos is an organophosphorus pesticide commonly used in agriculture. It is noxious to a variety of organisms that include living soil biota along with beneficial arthropods, fish, birds, humans, animals, and plants. Exposure to chlorpyrifos may cause detrimental effects as delayed seedling emergence, fruit deformities, and abnormal cell division. Contamination of chlorpyrifos has been found about 24 km from the site of its application. There are many physico-chemical and biological approaches to remove organophosphorus pesticides from the ecosystem, among them most promising is biodegradation. The 3,5,6-trichloro-2-pyridinol (TCP) and diethylthiophosphate (DETP) as primary products are made when chlorpyrifos is degraded by soil microorganisms which further break into nontoxic metabolites as CO(2), H(2)O, and NH(3). Pseudomonas is a diversified genus possessing a series of catabolic pathways and enzymes involved in pesticide degradation. Pseudomonas putida MAS-1 is reported to be more efficient in chlorpyrifos degradation by a rate of 90% in 24 h among Pseudomonas genus. The current review analyzed the comparative potential of bacterial species in Pseudomonas genus for degradation of chlorpyrifos thus, expressing an ecofriendly approach for the treatment of environmental contaminants like pesticides.

Phytotoxicity of three plant-based biodiesels, unmodified castor oil, and Diesel fuel to alfalfa (Medicago sativa L.), lettuce (Lactuca sativa L.), radish (Raphanus sativus), and wheatgrass (Triticum aestivum)

The wide use of plant-based oils and their derivatives, in particular biodiesel, have increased extensively over the past decade to help alleviate demand for petroleum products and improve the greenhouse gas emissions profile of the transportation sector. Biodiesel is regarded as a clean burning alternative fuel produced from livestock feeds and various vegetable oils. Although in theory these animal and/or plant derived fuels should have less environmental impact in soil based on their simplified composition relative to Diesel, they pose an environmental risk like Diesel at high concentrations when disposed. The aim of the present study was to ascertain the phytotoxicity of three different plant-derived biodiesels relative to conventional Diesel. For phytotoxicological analysis, we used seeds of four crop plants, Medicago sativa, Lactuca sativa, Raphanus sativus, and Triticum aestivum to analyze the germination of seeds in contaminated soil samples. The toxicological experiment was conducted with two different soil textures: sandy loam soil and silt loam soil. The studied plant-based biodiesels were safflower methyl-ester, castor methyl ester, and castor ethyl-ester. Biodiesel toxicity was more evident at high concentrations, affecting the germination and survival of small-seeded plants to a greater extent. Tolerance of plants to the biodiesels varied between plant species and soil textures. With the exception of R. sativus, all plant species were affected and exhibited some sensitivity to the fuels, such as delayed seedling emergence and slow germination (average=10 days) at high soil concentrations (0.85% for Diesel and 1.76% for the biodiesels). Tolerance of plants to soil contamination had a species-specific nature, and on average, decreased in the following order: Raphanus sativus (0–20%)>Triticum aestivum (10–40%)≥Medicago sativa> Lactuca sativa (80–100%). Thus, we conclude that there is some phytotoxicity associated with plant-based biodiesels. Further, the findings of this study can be useful for selecting the least fuel-tolerant species as a soil contamination bio-indicator and for determining the risks of biodiesel contamination.

Substitution of a Soilless Medium with Yard Waste Compost for Basil Transplant Production

Four experiments were conducted under greenhouse conditions in Oklahoma. Pelleted ‘Genovese’ basil (Ocimum basilicum) seeds were sown in polystyrene flats with six different blends of a peat-lite mix (PL0) and yard waste compost [YWC (this batch designated C0)] in 2012 for the first two experiments. The proportions by volume of PL0:C0 included 100%:0%, 80%:20%, 60%:40%, 40%:60%, 20%:80%, and 0%:100%. Seedling establishment was unaffected consistently, but there was a distinct decline in seedling height and dry weight between 100% PL0 and 80% PL0:20% C0, followed by smaller decreases as the percentage of compost increased in the blends. A third experiment was conducted in 2013 with a different batch of peat-lite (PL1) after the compost had aged 17 months (now designated C1). Treatments were 100% PL1, 80% PL1:20% C1, and 80% PL1:20% C1 mixed with sulfur (S) at 1, 2, or 3 lb/yard3 of blend to acidify the media. The 100% PL1 treatment delayed seedling emergence and suppressed height and dry weight relative to seedlings grown in 80% PL1:20% C1 blends. The PL1 subsequently was found to have been produced in 2010, and the wetting agent had apparently degraded. The aged 2012 compost (C1) was not inhibitory to basil seedling growth when blended at 20% with the PL1, and in fact restored utility to the PL1. The carbon:nitrogen ratio of the original 2012 compost (C0) was 10.8:1, suggesting stability. It appeared that the main reason the C0 compost was inhibitory was that mineralization was slow or immobilization occurred, causing a lack of plant-available nitrogen, especially nitrate. Treatments with S lowered pH of the media, but there were no differences in basil seedling growth between the unamended 80% PL1:20% C1 blend and blends with added S. A fourth experiment compared three peat-lite media: PL1; a batch of the same medium as PL1 that was produced in 2013 (PL2); and a different medium also produced in 2013 (PL3). Peat-lite media were either used unblended, or blended with 20% C1 or 20% C2 (a fresh batch of YWC obtained from the same facility that had produced the original C0). The unamended PL1 was again inhibitory to basil seedling establishment and development. The two “fresh” peat-lite media (PL2 and PL3) were not inhibitory and were similar to each other in performance. A blend of 80% PL2 or 80% PL3 with 20% compost produced similar (C2) or somewhat better (C1) results than were obtained with the unamended peat. We conclude that a blend of 80% peat-lite medium and 20% YWC can be used to produce basil transplants. However, producers must consider the quality of the peat-lite medium and the compost based on the age and composition of the components.

Facilitative and inhibitory effect of litter on seedling emergence and early growth of six herbaceous species in an early successional old field ecosystem.

In the current study, a field experiment was conducted to examine effects of litter on seedling emergence and early growth of four dominant weed species from the early successional stages of old field ecosystem and two perennial grassland species in late successional stages. Our results showed that increased litter cover decreased soil temperature and temperature variability over time and improved soil moisture status. Surface soil electrical conductivity increased as litter increased. The increased litter delayed seedling emergence time and rate. The emergence percentage of seedlings and establishment success rate firstly increased then decreased as litter cover increased. When litter biomass was below 600 g m−2, litter increased seedlings emergence and establishment success in all species. With litter increasing, the basal diameter of seedling decreased, but seedling height increased. Increasing amounts of litter tended to increase seedling dry weight and stem leaf ratio. Different species responded differently to the increase of litter. Puccinellia tenuiflora and Chloris virgata will acquire more emergence benefits under high litter amount. It is predicted that Chloris virgata will dominate further in this natural succession old field ecosystem with litter accumulation. Artificial P. tenuiflora seeds addition may be required to accelerate old field succession toward matured grassland.

Plant growth-promoting rhizobacteria affect the growth and nutrient uptake of Fraxinus americana container seedlings

Plant growth-promoting rhizobacteria (PGPR) are important catalysts that regulate the functional properties of agricultural systems. However, there is little information on the effect of PGPR inoculation on the growth and nutrient accumulation of forest container seedlings. This study determined the effects of a growth medium inoculated with PGPR on the nutrient uptake, nutrient accumulation, and growth of Fraxinus americana container seedlings. PGPR inoculation with fertilizer increased the dry matter accumulation of the F. americana aerial parts with delayed seedling emergence time. Under fertilized conditions, the accumulation time of phosphorous (P) and potassium (K) in the F. americana aerial parts was 13 days longer due to PGPR inoculation. PGPR increased the maximum daily P and K accumulations in fertilized seedlings by 9.31 and 10.44 %, respectively, but had little impact on unfertilized ones. Regardless of fertilizer application, the root exudates, namely sugars, amino acids, and organic acids significantly increased because of PGPR inoculation. PGPR inoculation with fertilizer increased the root, shoot, and leaf yields by 19.65, 22.94, and 19.44 %, respectively, as well as the P and K contents by 8.33 and 10.60 %, respectively. Consequently, the N, P, and K uptakes increased by 19.85, 31.97, and 33.95 %, respectively. Hence, PGPR inoculation with fertilizer can be used as a bioenhancer for plant growth and nutrient uptake in forest container seedling nurseries.

Tillage and crop residue effects on rainfed wheat and maize production in northern China

Dryland farming in the dry semi-humid regions of northern China is dominated by mono-cropping systems with mainly maize (Zea mays L.) or wheat (Triticum aestivum), constrained by low and variable rainfall, and by improper management practices. Addressing these problems, field studies on tillage and residue management for winter wheat and spring maize were conducted at 4 sites in Linfen, Tunliu and Shouyang (Shanxi province) and Luoyang (Henan province). These studies (a.o.) explored the impacts of different tillage and residue application methods on soil physical conditions, water storage, water use, water use efficiency (WUE) and crop yields of wheat and maize. An analysis of the results of these studies is presented. Conservation tillage, comprising no-till as well as reduced tillage practices (subsoiling, deep ploughing) showed benefits which were more prominent in combination with residue application. Benefits compared to conventional tillage were found in the form of improved soil physical conditions, such as higher topsoil bulk densities but lower subsoil bulk densities. This resulted in a better water storage during the summer fallow or rainy season in winter wheat fields, and a better water conservation and soil protection in spring maize fields. Compared to conventional methods, reduced tillage gave yields around 13–16% higher in spring maize and round 9–37% higher in winter wheat. Yields under no-till were very close to those from conventional methods. Surface application of crop residue for maize was found to increase the risk for delayed seedling emergence, because of low temperatures, leading to a recommendation for incorporation of residue in combination with reduced tillage. For winter wheat, subsoiling in combination with straw mulching after harvest in summer every other two or three year, and no-till seeding is a promising practice for sandier soils and low rainfall conditions. For heavier clay loam soils, deep ploughing with straw mulching after wheat harvest in summer every other two or three year, and no-till seeding practice is recommended. For spring maize, deep ploughing with straw and fertilizers incorporation after harvest in fall, and no-till seeding practices are recommended. Subsoiling or no-till with residue mulching after harvest in fall, and no-till seeding practices in spring are also promising practices, the latter only in situations where low spring temperatures are not a problem. Continuous no-till is not recommended.

Selection of shade-adapted subterranean clover species for cover cropping in orchards

The environmental side effects of intensive agriculture have underlined the need to develop sustainable farming systems. In particular, the use of cover cropping in orchards is a means of improving cash crop yield and of reducing the quantity of applied fertilisers. In the Mediterranean environment, subterranean clover species could be the best choice for cover cropping, but they are only poorly adapted to the heavily shaded conditions characteristic of modern high-density orchards. The plant traits needed to improve adaptation of subterranean clover are not well understood. Therefore, in a two-year experiment we studied the effects of four shading levels, of 0%, 40%, 60% and 90% reduction of photosynthetic active radiation, on phenology, growth and development of two subterranean clover species: Trifolium brachycalycinum cv. ‘Clare’ and T. Subterraneum ecotype ‘Ragalna’. Our results show that shading progressively delayed seedling emergence by up to 21 days, the initiation of flowering by up to 27 days, and the end of flowering by up to 25 days. Shading also lengthened the life cycle from 237 to 267 days. Shading reduced both soil cover by up to 38.2% and cover crop density by up to 39.7%. Shading lowered both the quantity of above-ground dry biomass by up to 820 g m−2 and photosynthetically active surface area by up to 213 cm2 plant−1. Trifolium brachycalycinum ‘Clare’ was more productive in terms of above-ground dry biomass yield, but T. Subterraneum ‘Ragalna’ was better adapted to shading in terms of rapid emergence, earliness and the time taken to achieve soil cover. These species differences suggest that the breeding targets for improving the adaptation of subterranean clover to heavy shading are the ability to maintain earliness and the capacity to quickly break down hard-seededness under conditions of partial shade. A rapid initial increase in photosynthetically active surface area is particularly needed for maximising light harvesting during the early growth period.

Performance of genotypes in crosses of egusimelon (<i>Colocynthis citrullus</i> L ).

Crosses were made among seven inbred lines of Egusi melon (Colocynthis citrullus L.), White, Blue, Elongated, Sewere, OV-I, W.SE and B.SE. The parents and the progenies (F1, F2 and BCs) were evaluated for some growth and yield attributes. The white inbred parent was found to have the highest seed yield among the parents. The F1s were also found to perform better than their parents in the yield attributes. The hybrid (OV-I x W.SE) had the highest seed yield/plant. Delayed seedling emergence and flowering influenced seed yield negatively while large number of branches/plant and vine length enhanced seed yield/plant. All other yield attributes correlated positively with seed yield/plant, an indication that any of them can be used as an index for selection for seed yield in the crop. Keywords: Egusi melon, (Colocynthis citrullus, hybrid. > Agro-Science Vol. 6 (1) 2007: pp. 17-24

Arsenic mitigation strategy for rice, using water regime management

The response of two varieties of rice plant (BR-28 and BR-29) to arsenic accumulation added from two sources (As III and As V ) under two different water regimes (100 and 75% of field capacity) were examined. Treatments added to soil were 0, 10, 20 and 40 mg As/kg soil. Plant samples were collected after 120 and 140 days from seed sowing, for BR-28 and BR-29 respectively. Delayed seedling emergence; reduced plant growth; yellowing and wilting of leaves; brown necrotic spots on old leaves; and, finally, reduced grain yield of the two varieties, confirmed the symptoms of As toxicity. Arsenic accumulation by plants growing with either As III or As V increased with increasing As treatment, irrespective of water regimes. However, the accumulation was greater in the arsenite-treated soil than that in the arsenate-treated one, indicating the higher phytoavailability of As III . Most of the As taken up by plants was sequestered in the root, followed by straw and grain. In roots of BR-28, the maximum As accumulation from arsenite-treated soil was 17.6 mg/kg dry weight (d.w.) at 100% field capacity (f.c.), whereas at 75% f.c. it was 15.4 mg/kg d.w. and for the roots of BR-29 the values were 31.04 mg/kg d.w and 22.65 mg/kg d.w. at 100 and 75% of f.c. respectively. Arsenic in straw and grain was lower for plants of both varieties at 75% of f.c. However, there have been some varietal differences in the response to As III or As V . The paper discusses the possible management of moisture regimes to reduce the phytoavailability of arsenic, thereby mitigating its toxicity in the rice crop.

Longer coleoptiles improve emergence through crop residues to increase seedling number and biomass in wheat (Triticum aestivum L.)

Crop residues protect soils from erosion, reduce soil water evaporation and increase soil organic matter. Yet management of stubbles for cropping can be difficult. Surface-retained residue can act as a mechanical barrier to slow emergence and reduce seedling biomass. Longer coleoptiles improve seedling emergence with deep sowing and may assist where stubble load is large. In a glasshouse study, six wheat and barley genotypes were sown at 30 and 50 mm depth into pots containing pasteurised soil. Unweathered sorghum, canola and wheat stubble were added at 0, 3 and 6 t/ha equivalents to the soil surface and pots watered above or below the stubble. Stubble species and watering regime had little effect on seedling growth. However, deeper sowing and increased stubble mass adversely affected most seedling characteristics particularly slowing seedling emergence and reducing tiller number to decrease plant biomass (environmental correlations (re) of −0.98** and 0.88**, respectively). Shorter coleoptile Rht-B1b wheats ‘Banks’ and ‘Janz’, and barley ‘Beecher’ emerged slower and abnormally with thicker stubble, and had more sterile tillers to reduce total tiller number and biomass. Deeper crowns for these genotypes also resulted in proportionally less biomass located above the stubble. The converse was true of long coleoptile ‘Vigour 18’, ‘Halberd’, and its Rht8 progeny, ‘HM14bS’ which were less affected by stubble mass and sowing depth. In a corresponding field study, increasing wheat stubble mass from 0 to 3 and 6 t/ha delayed seedling emergence and decreased plant number to reduce biomass. Short coleoptile wheat genotypes ‘Hartog’ and ‘Janz’ emerged slower and produced less biomass at 3 and 6 t/ha of stubble than long coleoptile wheat genotypes ‘Halberd’ and ‘HM14bS’. Emergence of seedlings sown at 50 mm depth with 6 t/ha overlying stubble was similar to that sown at 120 mm with no stubble, reflecting the similar impact of retained residues to deep sowing. Genetic variation for coleoptile length and availability of gibberellin-responsive dwarfing genes such as Rht8 will allow development of long coleoptile wheats for deep sowing or where stubble retention is practiced.

Influence of temperature on plant–rhizobacteria interactions related to biocontrol potential for suppression of fusarium wilt of chickpea

Seed and soil treatment with Pseudomonas fluorescens RGAF 19, P. fluorescens RG 26, Bacillus megaterium RGAF 51 and Paenibacillus macerans RGAF 101 can suppress fusarium wilt of chickpea (Cicer arietinum), but the extent of disease suppression by these rhizobacteria is modulated by soil temperature. In this work, the effect of temperature on plant–rhizobacteria interactions was assessed in relation to biocontrol potential for suppression of fusarium wilt of chickpea. Seed and soil treatment with those rhizobacteria delayed seedling emergence compared with nontreated controls, and either increased or had no deleterious effect on chickpea growth. Pseudomonas fluorescens isolates significantly increased chickpea shoot dry weight at 20°C and root dry weight at 25 and 30°C. All bacterial isolates colonized the chickpea rhizosphere and internal stem tissues at 20, 25 and 30°C, and there was a positive linear trend between bacterial population size in the rhizosphere and temperature increase. The maximum inhibition of mycelial growth and conidial germination of Fusarium oxysporum f. sp. ciceris race 5 in vitro occurred at a temperature range optimal for bacterial growth and production of inhibitory metabolites. These results demonstrate the need to understand the effects of environmental factors on the biological activities of introduced rhizobacteria of significant importance for plant disease suppression.

STAND ESTABLISHMENT TECHNOLOGIES FOR PROCESSING CARROTS

STAND ESTABLISHMENT TECHNOLOGIES FOR PROCESSING CARROTS

Physical and chemical factors associated with the reduction or delay of seed germination and seedling emergence of bull thistle, Cirsium vulgare (Savi) Ten. under leaf litter1

Leaf litter can affect seed germination and seedling emergence by altering both the physical and chemical environment. A series of experiments were conducted to investigate litter effects on germination and emergence of Cirsium vulgare seeds and seedlings. Thin (2 layers) and thick (5 layers) of leaf litter of Acer saccharum, Quercus alba, and Juglans nigra reduced and delayed seedling emergence of bull thistle (C. vulgare) in two greenhouse experiments. Leaves of J. nigra were less effective than those of the other two species. In one experiment, removal of the litter after seedling emergence had ceased was followed by a second flush of emergence, but no further emergence occurred in the non-litter control. However, in a second experiment no further emergence was recorded after litter removal. Artificial litter, chemical-free cotton paper cut in leaf shapes, reduced and delayed seedling emergence but to a lesser extent than natural leaf litter. Germination in distilled water in Petri dishes was not affected within a pH range of 3-10. However, black walnut leaf extract reduced seed germination, and extracts of all three species slowed germination rates. There was no effect of leaf extracts on rates or percent emergence from soil in the greenhouse. We concluded that leaf litter can have an important role in determining patterns of seedling emergence of C. vulgare, possibly because of physical effects on the dormancy status of its seeds.

Effects of acorn storage duration and parental tree on emergence and physiological status of Cork oak (Quercus suber L.) seedlings

This study was conducted to evaluate how parental trees and seed storage duration influenced subsequent seedling physiolo- gical status and growth. Seedling emergence rate was higher than 90% independently of the duration of seed storage or parental trees. Seed storage shortened significantly the time and increased the uniformity of seedling emergence. Consequently, the delayed seedling emergence from fresh seeds could be explained by epicotyl dormancy. Seed size varied with parental tree. Seedling growth rate was greatly affected by seed size, independently of storage treatment. Seedlings originating from large seeds (>5 g) had the fastest growth ra- tes and seedlings from the smallest seeds (<4 g) had the slowest. Final shoot height, however, depended on the duration of seed storage. The seed size and the duration of storage had a great effect on the initial rate of leaf production, but did not affect the final number of lea- ves. Leaf chlorophyll concentration was reduced as the duration of seed storage increased but was independent of parental tree (i.e., seed size). Seedling biomass was positively related to seed size. The duration of seed storage reduced the shoot/root ratio, but no significant effect was observed among parental trees. The shoot/root value of seedlings from stored seed was about 1.5 and the one of seedlings from fresh seed was about 2.

RICE GROWTH AND NUTRIENT UPTAKE AS AFFECTED BY LIVESTOCK MANURE IN FOUR JAPANESE SOILS

One of the measures being adopted for relieving environmental problems arising from agricultural production is to recycle animal manure and other organic products as fertilizers and soil amendment. In Japan, this is a usual practice among farmers. In this study, we evaluated the effects of chicken manure (PM), cattle manure (CM), swine manure (SM) and mixed manure (MM = PM + CM + SM) on the growth, dry matter yield, and nutrient [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] uptake of rice (Oryza sativa Var. koshihikari). Four naturally infertile soils, andosol (A), red-yellow soil (RY), sandune soil (SD), and masatsuchi (M), were amended with 100 Mg ha−1 (dry weight) of each of the manure and allowed to stabilize for 4 weeks before rice was seeded. Changes in rice growth as indicated by plant height and number of leaves and tillers were monitored for 6 weeks, and the biomass yield was determined. Shoot samples were also analyzed for nutrient uptake. The amended A and RY soils produced the best effects on all the rice parameters studied. However, the number of rice leaves were significantly higher in RY than A. The manure effects on rice growth and biomass yield were ranked as CM > MM > SM > PM. Amending the soils with manure significantly delayed seedling emergence. Andosol amended with CM and MM produced significantly greater roots than with other manures. Masatsuchi amended with PM had lower shoot and root biomass than even the control. Among the manures, the uptake of all nutrients was highest in CM. The higher dry matter yield of rice in soils amended with CM and MM may be due to better nutrient balance and relatively lower levels of toxic factors in the material.