The effect of sodium fluoride on cereal seed germination and seedling growth

Abstract. Fluoride has been shown to inhibit germination and seedling establishment in barley cv. Natasha, wheat cv. Axona and rice cv. Ishikari. The concentrations of fluoride were selected so as to give a satisfactory dose-response relationship and also to relate to levels of fluoride present under natural conditions. Concentrations used were zero, 0.5, 1.0, 10 and 40 mol m⁻³ sodium fluoride. In germination studies, barley was found to be least tolerant and rice most tolerant of fluoride. The inhibition was found to be a response to fluoride itself and the observed effects were not due to pH, sodium or an unspecific effect of halide ion. Phosphate, applied at two concentration levels, was unable to overcome the inhibition. Fluoride was also shown to inhibit seedling growth. The inhibitory effects of fluoride may be accounted for by a wide range of metabolic effects including inhibition of gibberellic acid–triggered alpha amylase activity during germination, and later on to inhibition of chlorophyll synthesis in the developing leaves.     

城市污泥对作物种子发芽及幼苗生长影响的初步研究

不同类型污泥及其堆肥对通菜、菜心种子发芽和幼苗生长影响的研究表明 ,深圳生污泥、佛山生污泥和广州生污泥及其堆肥对通菜种子的发芽率有明显的影响 ,前者仅为73% ,其余的在 85%左右 ,均低于对照处理 ( 93% ) .而它们对菜心种子的发芽率 ,除了深圳生污泥有抑制作用外 ( 75% ) ,其余均表现为促进作用 ( 90 % ) ,均高于对照处理 ( 85% ) .它们对于两种作物幼苗的生长则均表现为不同程度的抑制作用甚至是损害作用 .污泥及其堆肥中抑制作物种子发芽和幼苗生长的物质主要是有机酸和醛类等有机物 .生污泥经过消化作用或适当的堆沤作用可降解这些有机物 ,从而减弱或消除这种抑制作用 .因此 ,生污泥经过消化作用或适当的堆沤作用后用于农业生产更为安全 .但对刚施用污泥或污泥堆肥的耕地最好不要直接播种 .     

Identification and mode of action of quantitative trait loci affecting seedling height and leaf area in Eucalyptus nitens

 Regions of the genome influencing height and leaf area in seedlings of a three-generation outbred pedigree of Eucalyptus nitens have been identified. Three QTLs affecting height and two QTLs affecting leaf area were located using single-factor analysis of variance. The three QTLs affecting height each explained between 10.3 and 14.7% of the phenotypic variance, while the two QTLs for leaf area each explained between 9.8 and 11.6% of the phenotypic variation. Analysis of fully informative marker loci linked to the QTLs enabled the mode of action of the QTLs to be investigated. For three loci the QTL effect segregated from only one parent, while for two loci the QTL showed multiple alleles and the effect segregated from both parents in the pedigree. The two QTLs affecting leaf area were located in the same regions as two of the QTLs affecting height. Analysis of these regions with fully informative markers showed that both QTLs were linked to the same markers, but one had a similar size of effects and a similar mode of action for both height and leaf area, whilst the other showed a different mode of action for the two traits. These regions may contain two closely linked genes or may involve a single gene with a pleiotrophic effect on both height and leaf area. The QTL with the greatest effect showed multiple alleles and an intra-locus interaction that reduced the size of the effect. Assessment for two of the QTLs in a second related family did not show an effect associated with the marker loci; however, this was consistent with the mode of action of these QTLs and the pattern of inheritance in the second family. Received: 1 August 1996 / Accepted: 25 October 1996     

Quantitative genetic analysis of seed vigour and pre-emergence seedling growth traits in Brassica oleracea

The ability of seeds to germinate and establish seedlings in a predictable manner under a range of conditions has a direct contribution to the economic success of commercial crops, and should therefore be considered in crop improvement. We measured traits associated with seed vigour and pre-emergence seedling growth in a segregating population of 105 doubled haploid Brassica oleracea lines. The germination traits measured were: mean germination times for unstressed germination; germination under water stress or germination after a heat treatment; and conductivity of seed leachate. The seedling growth traits measured were: seed weight; seedling growth rate; and seedling size at the end of the exponential growth phase. There were some correlations, notably among germination traits, and between seed weight and pre-emergence seedling growth. Heritability of the various traits was typically in the 10–15% range, with heritability of conductivity and mean germination time under water stress 25 and 24% respectively. Collectively the results indicate that germination and pre-emergence seedling growth are under separate genetic control. Quantitative trait loci analyses were carried out on all measurements and revealed significant loci on linkage groups O1, O3, O6, O7 and O9. We suggest that genes at these loci are important in determining predictable seed germination and seedling establishment in practice.     

The effect of Drechslera teres seed infection on spring barley seedling growth

Barley seedlings (cv. Beatrice) emerging from seed infected with Drechslera teres were sorted into healthy seedlings, those with leaf sheath lesions and those with leaf blade lesions. Leaf area, plant height and total weight were reduced relative to healthy plants; leaf emergence also appeared to be delayed.     

Smoke and heat: influence on seedling emergence from the germinable soil seed bank of mesic grassland in South Africa

We examined if germination and seedling emergence of species from the soil seed bank of mesic grassland in South Africa differed in their response to smoke or heat treatments alone or combined. Soil seed bank samples taken from 0 to 5 cm depth of the topsoil were treated with smoke-water solution, heat and heat + smoke-water combined and subsequent emergence of seedlings monitored over 90 days. In total, 790 individuals from 11 different plant families representing 37 graminoid (Poaceae) and non-graminoid species of flowering plants were identified. The most abundant plant families that emerged were Poaceae followed by Asteraceae. Grasses contributed 18% of the germinable seed bank, while non-grass (forbs and trees) species contributed >80%. The most abundant grass species that emerged was Themeda triandra and the most common forb species was Centella asiatica. Compared to the control, smoke-water (SW) and/or smoke-water + heat (H + SW) treatment resulted in a 1.6-fold increase in mean number of seedling emergence. SW and H + SW treatment of soil seed bank also resulted in fourfold to fivefold greater biomass production. These results suggest that emergence of some smoke-responsive perennial grasses (e.g. Themeda triandra) from the soil seed bank can be enhanced using smoke techniques. Moreover, plant-derived smoke could potentially have a significant role in the restoration of degraded grasslands in South Africa and elsewhere.     

Comparing the effect of modeled climatic variables on the distribution of African horse sickness in South Africa and Namibia

Africa horse sickness (AHS) is a lethal disease of horses with a seasonal occurrence that is influenced by environmental conditions that favor the development of Culicoides midges (Diptera: Ceratopogonidae). This study compared and evaluated the relationship of various modeled climatic variables with the distribution and abundance of AHS in South Africa and Namibia. A comprehensive literature review of the historical AHS reported data collected from the Windhoek archives as well as annual reports from the Directorate of Veterinary services in Namibia were conducted. South African AHS reported data were collected from the South African Department of Agriculture, Forestry, and Fisheries. Daily climatic data were extracted for the time period 1993–2011 from the ERA‐interim re‐analysis dataset. The principal component analysis of the complete dataset indicated a significant statistical difference between Namibia and South Africa for the various climate variables and the outbreaks of AHS. The most influential parameters in the distribution of AHS included humidity, precipitation, evaporation, and minimum temperature. In South Africa, temperature had the most significant effect on the outbreaks of AHS, whereas in Namibia, humidity and precipitation were the main drivers. The maximum AHS cases in South Africa occurred at temperatures of 20–22° C and relative humidity between 50–70%. Furthermore, anthropogenic effects must be taken into account when trying to understand the distribution of AHS.     

Effects of salicylhydroxamate on respiration, seed germination and seedling growth in Avena fatua

The effects of inhibitors of alternative respiration [salicylhydroxamate (SHAM) and propyl gallate (PG)] on germination, seedling growth and O₂ uptake in Avena fatua L. (wild oats) were studied. SHAM did not inhibit germination or O₂ uptake prior to germination. SHAM-sensitive (alternative) respiration, therefore, cannot be a pre-requisite for germination. Following germination, both chemicals inhibited seedling growth with the root being more susceptible than the shoot. SHAM concentrations that inhibited root growth by 90 to 95%, inhibited O₂ uptake of 1 cm root apices by less than 15%. While sodium azide (a cytochrome-oxidase inhibitor; 1 m M ) alone inhibited O₂ uptake by only 40 to 50%, in the simultaneous presence of SHAM (or PG), O₂ uptake was inhibited by 90 to 99%. Thus: 1) respiration of wild oat seedling root apices is predominantly cytochrome-mediated and incomplete inhibition of O₂ uptake in the presence of azide alone is due to diversion of electrons to the alternative pathway and 2) even though these roots have little alternative respiration, they maintain the capacity to support a much greater flux of electrons via this path way. SHAM and PG at concentrations (0.05 to 0.4 m M ) which inhibited O₂ uptake significantly in the presence (but not in the absence) of azide had little effect on root growth suggesting that an effect(s) other than that on respiration is involved in the inhibition of root growth at higher concentrations. The effect of SHAM on wild oat root growth is not selective as it also inhibits growth of a number of crop species.     

Inhibitory effects of monoterpenes on seed germination and seedling growth

Monoterpenes, the chemical constituents of essential oils found in plants, are known biologically active compounds. The present study was conducted to investigate the inhibitory effects of 30 monoterpenes including monoterpene hydrocarbons and oxygenated monoterpenes on seed germination and seedling growth of Amaranthus retroflexus, Chenopodium album and Rumex crispus under laboratory conditions. The monoterpenes were applied at contents of 10 and 20 microl for liquid compounds and 10 and 20 microg for solid compounds. The results show that most of the monoterpenes significantly inhibited seed germination and seedling growth of the tested plants. Oxygenated monoterpenes including beta-citronellol, nerol and terpinen-4-ol completely inhibited seed germination and seedling growth of all tested plants. Their inhibitory effects were also stronger than that of the herbicide 2,4-D. In general, monoterpenes were less effective against seed germination and seedling growth of C. album as compared with R. crispus and A. retroflexus. Phytotoxic effects of monoterpene hydrocarbons were found to be lower than those of oxygenated monoterpenes. The alcohol derivatives of oxygenated monoterpenes were also found to be more phytotoxic as compared with their acetate derivatives. Based on the present results, it can be concluded that the oxygenated monoterpenes can be used as potential bio-herbicides.     

Isolation and identification of species of Alicyclobacillus from orchard soil in the Western Cape, South Africa

Alicyclobacilli were isolated from orchard soil collected from an apple and pear farm in Elgin, Western Cape, South Africa. Morphological, biochemical and physiological characteristics of the isolates were used to presumptively classify them as belonging to the genus Alicyclobacillus. Strains were identified to species level by polymerase chain reaction (PCR) with genus-specific primers, and 16S ribosomal RNA (rRNA) gene sequencing. To our knowledge this is the first report on the isolation of Alicyclobacillus acidoterrestris and Alicyclobacillus acidocaldarius from orchard soil. The presence of these organisms in the soil suggests a possible source of contamination for the final fruit juice, concentrate or pulp.     

森林凋落物对种子萌发与幼苗生长的影响

森林更新是森林生态系统维持自身稳定的重要环节,其早期阶段(种子萌发与幼苗生长)对气候变化十分敏感,同时显著地受到森林凋落物的影响。对这种影响机制的深入研究,有助于进一步认识和了解森林更新动态和群落演替方向。本文简要概述了近年来国内外森林凋落物研究动态,从森林凋落物影响种子萌发与幼苗生长的物理作用机制(凋落物对种子与幼苗产生的物理障碍与机械损伤,微环境的温度、湿度以及光照条件的变化等)、生物化学作用机制(产生化感物质、降解释放营养物质)以及通过改变土壤理化性质间接对其产生影响等3个方面进行了系统综述,并且就气候变化与森林凋落物的协同作用通过多种方式直接或间接地对树木种子萌发与幼苗生长产生影响的机理进行了初步探讨。在此基础上提出了这一领域未来研究趋势和需要加以重视的问题。     

The influence of drought on the relationship between leaf and conducting sapwood area in Eucalyptus globulus and Eucalyptus nitens

 Development of the relationship between leaf area (A _l ) and sapwood area (A _s ) was investigated in two important hardwoods, Eucalyptus globulus (Labill) and E. nitens (Deane and Maiden) Maiden, growing in an experimental plantation established in a low rainfall zone (approx. 515 mm year^–1) of Tasmania. The experiment compared irrigated controls and a rainfed treatment which was subjected to cyclical summer droughts from age 1 to 6 years old. Leaf area and sapwood area were determined by destructive sampling at ages 2, 3 and 6 years old. There was no effect of stand age on A _l :A _s when sapwood area was measured at crown break. At age 3 years old A _l :A _s was significantly greater in the rainfed than the irrigated trees. It was concluded that this difference was due to earlier canopy closure in the irrigated trees. When the plantation was 6 years old A _l :A _s was significantly greater in the irrigated than the rainfed treatment. An analysis based on an equation which links A _l :A _s with transpiration and volumetric flow rate (Whitehead et al. 1984) was used to infer a positive correlation between stem hydraulic conductivity (k _h ) and water availability. Independent of water availability E. globulus maintained a higher A _l :A _s than E. nitens at all ages. Received: 20 March 1997 / Accepted: 30 December 1997     

Vegetation and soil recovery following Eucalyptus grandis removal in Limpopo Province,South Africa

South African terrestrial ecosystems are invaded by hundreds of alien plant species, and large‐scale clearing based on the passive restoration assumption that cleared areas will recover unaided is underway. This study assessed the recovery of vegetation and soil properties, three years following Eucalyptus grandis clearing using fell‐and‐removal and fell‐and‐stackburn methods at Zvakanaka Farm in Limpopo Province, South Africa. The main aim was to ascertain the extent of vegetation and soil recovery, as well as determining which clearing methods facilitate passive vegetation and soil restoration. Results indicate significantly (p < 0.001) lower native species diversity, cover and composition in cleared than in uninvaded sites. However, the recorded low species diversity and composition in cleared sites were more pronounced in the fell‐and‐stackburn than in the fell‐and‐removal sites. Measured soil physical properties varied, with compaction being higher in fell‐and‐removal, whereas soils were more repellent in fell‐and‐stackburn sites. The study concludes that vegetation and soil recovery, following E. grandis clearing, is complex and involves several interacting factors, which are linked to invasion history and intensity. Therefore, for vegetation and soil properties to recover, following E. grandis removal, the clearing programme should consider active restoration techniques, for example soil manipulation and native plant seeding.     

Complex patterns of mating revealed in a Eucalyptus regnans seed orchard using allozyme markers and the neighbourhood model

The neighbourhood model apportions offspring of individual mother plants to self-fertilization, outcrossing to males within a circumscribed area around the mother plant (the neighbourhood), and outcrossing to males outside the neighbourhood. Formerly the model was applied only to haploid pollen gametes in the offspring of conifers, but is extended so that it can be used with genotypic data from diploid offspring of both angiosperms and gymnosperms. In addition, it is shown that the mating parameters can be estimated without independent estimates of allele frequencies in the pollen pools outside the neighbourhood; thus the model might be applied effectively to natural populations exposed to unknown external pollen sources. Parameters of the neighbourhood mating model were estimated for a 10-year-old seed orchard population of the insect-pollinated tree, Eucalyptus regnans, in southeast Australia, which contained a mixture of two geographical provenances (Victoria and Tasmania). The mating patterns revealed were complex. Crosses between trees of the same provenance occurred three times more often than crosses between trees of different provenances. Levels of self-fertilization and patterns of mating within neighbourhoods were influenced by provenance origin, crop fecundity and orchard position (central vs. edge) of mother trees. Gene dispersal, however, was extensive, with approximately 50% of effective pollen gametes coming from males more than 40 m away from mother trees (average distance between neighbouring trees was 7.4 m). Thus, insect pollinators are efficient promoters of cross-fertilization in this orchard, with the result that the effective number of males mating with each female is large.     

Impact of bio-nanogold on seed germination and seedling growth in Pennisetum glaucum

Nanotechnology is leading towards the development of low cost applications to improve the cultivation and growth of plants. The use of nanotechnology in agriculture will leads to a significant effect on food industry along with opening a new area of research in agroecosystem. In this paper gold nanoparticles were biosynthesized with Cassia auriculata leaf extract at room temperature and characterized by UV–vis spectroscopy, X-ray diffraction and transmission electron microscopy. The objective of this study was to investigate effect of synthesized bio-nanogold on an important food and biofuel producing plant Pennisetum glaucum. Positive effects were observed on percentage of seed germination and growth of seedlings. Improved germination and increased plant biomass have high economic importance in production of biofuel or raw materials, agriculture and horticulture. Although the impact of nanoparticles on plants depends on concentration, size and shape. The biological synthesized AuNPs can replace the chemically synthesized AuNPs used in gene transfer method. The study gives brief insight on nanoparticles effects on plants, brings attention on both positive and negative side of nanomaterial which can resolve phytopathological infections by stimulating nutrition and growth.     

The effects of seed production techniques on seed characteristics, seedling growth and crop performance of crisp lettuce

Seed crops of crisp lettuce were produced in three years with and without gibberellin 4 plus 7 (GA₄₊₇) application to the young seedlings. The effects on seed and seedling characters and field performance of harvesting seed at different times, either by shaking out mature seed or by ‘windrow’ harvests, were assessed. Differences between treatments in seed and seedling characters within any one year were relatively small although those treatments producing large seed gave large seedlings and those giving uniform seed gave uniform seedlings. There were no important effects of seed production treatments on field characters in any one year. However, when different years of seed production were compared directly there was a large effect of year of production on seedling establishment and the size and uniformity of seedlings. Application of GA₄₊₇ resulted in heavier and more uniform seedlings in two of the three years. The results suggest that major differences between commercial seedlots occur as a result of differences in the environment rather than in the technique of seed production.