沙埋对六种沙生植物种子萌发和幼苗出土的影响

研究了沙埋对科尔沁沙地6种优势植物的种子萌发和幼苗出土的影响．进行0．2、4、6、8、10和12cm等7个深度沙埋处理．结果表明,在不同沙埋处理时,沙蓬萌发差异显著。而差不嘎蒿2锄埋深与其他埋深的发芽差异显著,其他4种植物0cm埋深与其他埋深的发芽差异显著;沙埋对所有植物幼苗出土均有显著影响,埋深增加,出苗率减小;繁殖体大的物种与繁殖体小的物种相比,能从更深沙层中出苗,幼苗出土最大深度排序为苦参>东北木蓼≥沙蓬>山竹子>雾冰藜>差不嘎蒿．     

沙埋对西鄂尔多斯珍稀植物种子萌发和幼苗出土的影响

采用不同沙埋深度(0、1、2、3、5、7、10 cm埋深)处理,对内蒙古西鄂尔多斯4种珍稀植物霸王(Zygophyllum xanthoxylum)、沙冬青(Ammopiptanthus mongolica)、蒙古扁桃(Prunus mongolica)和长叶红砂(Reaumuria trigyna)种子萌发及幼苗出土情况进行研究,以揭示其种子萌发特性.结果表明:表层沙土(0 cm埋深)的种子几乎不萌发;除霸王外,其他3种植物在不同沙埋深度处理下的种子萌发率差异显著(P＜0.05);沙埋对4种珍稀植物的幼苗出土均有显著影响,出苗率随着沙埋深度的增加而降低,且遵循指数方程.霸王在2 cm沙埋深度的出苗率最高,其他物种在1 cm沙埋深度的出苗率最高.沙埋深度对幼苗生物量的影响不显著.     

Experiments on the mechanism of tree and shrub establishment in temperate grassy woodlands: Seedling emergence

Field experiments were designed to examine tree and shrub seedling emergence in temperate grassy woodlands on the New England Tablelands. The effects of study sites, intensity of previous grazing, removal of ground cover by fire or clearing, burial of seeds and ant seed theft on seedling emergence were tested in two field experiments. Six tree and seven shrub species were used in the experiments and their cumulative emergence was compared with laboratory germination studies. All species used in field experiments had lower cumulative emergence than those in laboratory germination studies despite prolonged periods of above average rainfall before and after seeds were sown. Eucalypt species emerged faster in the field than the shrub species and generally attained higher cumulative emergence than the shrubs. Spatial effects of sites and patches within sites, and of previous grazing history did not strongly influence patterns of seedling emergence in most species. Ground and litter cover generally did not enhance or suppress the emergence of seedlings, although the removal of cover in recently grazed areas enhanced the emergence of some species. Burning enhanced the emergence of some tree and shrub species where plots had more fuel and intense fires, but this effect was not strong. Compared with other treatments, seedbed manipulations produced the strongest effects. In the absence of both invertebrate and vertebrate predators, seedling emergence was lower for surface‐sown seed, compared with seed sown on scarified soil surfaces. Higher seedling emergence of buried seeds in the presence of invertebrate predators probably resulted from the combined effects of predator escape and enhanced moisture status of the germination environment. Some promotion of emergence was achieved for all species in most sown treatments probably as a result of a prolonged above average rainfall. In contrast, the natural recruitment of trees and shrubs was negligible in experimental plots, highlighting the importance of seed supply and dispersal as ultimate determinants of recruitment.     

Cell cycle activity during seed priming is not essential for germination advancement in tomato

Seed priming is a technique of controlled hydration and drying that results in more rapid gemination when the seeds are reimbibed. Advancement of radicle meristem cells into the S and G2 phases of the cell cycle, increasing the percentage of nuclei having a 4C DNA content, has been reported to occur during priming. It has been suggested that the efficiency of priming is related to the accumulation of 4C nuclei in the radicle meristem, but the extent of cell cycle activity varied among different treatments and seed lots. A wide range of priming treatments across temperatures, water potentials and durations can be compared on a common basis using the hydrothermal priming time model. Flow cytometry was used to monitor cell cycle activity in a number of tomato (Lycopersicon esculentum Mill.) seed lots during priming in relation to the accumulation of hydrothermal priming time and the subsequent germination rate response. In some seed lots, the percentage of 4C nuclei in the radicle meristems prior to emergence increased in proportion to accumulated hydrothermal priming time, while in other lots, no increase in nuclear DNA content was detected. All lots, however, demonstrated rapid radicle emergence following priming. Thus, replicative DNA synthesis in radicle meristem nuclei often occurred during seed priming, but an increase in the percentage of 4C nuclei was not essential for germination advancement.     

基于小麦种子发芽逆境抗逆指数的种子活力评价

以16个小麦品种的种子为材料,通过标准发芽、逆境发芽和田间出苗试验,测定不同基因型小麦品种的种子活力,以不同发芽条件下种子活力指数的抗逆指数和田间出苗率作为衡量抗逆性的指标,利用主成分分析、聚类分析对种子活力进行综合评价.结果表明: 干旱胁迫、人工老化和冷浸胁迫3种逆境对种子活力都有一定的影响.人工老化抗逆指数和冷浸胁迫抗逆指数与田间出苗率呈显著正相关,干旱胁迫抗逆指数与田间出苗率的相关性不显著.通过主成分分析和聚类分析将16个小麦品种划分为3类、豫农949、豫麦49-198、鲁原502、郑育麦9987、石麦21、山农23号、石新828为高活力品种;许农5号、豫农982、唐麦8号、济麦20、济麦22、济南17号、山农20为中活力品种;长4738和轮选061属低活力品种.     

Effects of osmotic priming and ageing on the germination and emergence of carrot and leek seed

Carrot and leek seed was osmotically primed in polyethylene glycol solution (273 g/kg water and 342 g/kg water respectively) for 10, 14 or 17 days before accelerated ageing for 0, 24, 48, 72 or 96 h. Priming reduced the germination time compared with non-primed seed. Accelerated ageing increased germination and emergence times and decreased percentage germination and emergence to a greater extent for the primed seeds than for non-primed seeds in both species. Primed and dried but non-aged seed from both species was stored at 10°C for 12 months. There was no loss of viability and improvements in germination time due to priming were maintained throughout the storage period for all the priming treatments in leek, and for the 10 and 14 day priming treatments in carrot. Carrot seed primed for 17 days lost some viability after 12 months storage compared with non-stored seed.     

Combining ability of tropical maize lines for seed quality and agronomic traits

Studies of genetic effects of early selection of maize based on seed quality traits are rare, especially those that use materials from different heterotic groups. These studies are also useful in tropical environments and for the advancement of sustainable agriculture with cropping during seasons not commonly used for cultivation. We estimated, through diallel crosses, the predominant genetic effects on the expression of agronomic traits and seed quality and on the general combining ability of nine maize lines from commercial hybrids and the specific combining ability of hybrid combinations among them. In the evaluation of seed quality, seven tests were used: first count and final count of seed germination, seedling vigor classification, cold tolerance, seedling emergence rate in a sand seedbed, speed of emergence in a sand seedbed, and speed of emergence index. Plant height, first ear height and grain yield were the estimated agronomic traits. In the diallel analysis, method 3 (model I) proposed by Griffing was used. There was a greater significance of non-additive genetic effects in the genetic control of seed quality of the various lines. The Flash, Dekalb 350 and P 30F80 lines combined high seed quality and high grain yield. For growth during the normal planting season, the combinations CD 3121-1 x P 30F80, Speed x CD 3121-2, Dow 8330 x AG 8080 and Dekalb 350 x CD 3121-2 were the most promising for both seed quality and agronomic traits.     

Genomic Prediction of Testcross Performance in Canola (Brassica napus)

Genomic selection (GS) is a modern breeding approach where genome-wide single-nucleotide polymorphism (SNP) marker profiles are simultaneously used to estimate performance of untested genotypes. In this study, the potential of genomic selection methods to predict testcross performance for hybrid canola breeding was applied for various agronomic traits based on genome-wide marker profiles. A total of 475 genetically diverse spring-type canola pollinator lines were genotyped at 24,403 single-copy, genome-wide SNP loci. In parallel, the 950 F1 testcross combinations between the pollinators and two representative testers were evaluated for a number of important agronomic traits including seedling emergence, days to flowering, lodging, oil yield and seed yield along with essential seed quality characters including seed oil content and seed glucosinolate content. A ridge-regression best linear unbiased prediction (RR-BLUP) model was applied in combination with 500 cross-validations for each trait to predict testcross performance, both across the whole population as well as within individual subpopulations or clusters, based solely on SNP profiles. Subpopulations were determined using multidimensional scaling and K-means clustering. Genomic prediction accuracy across the whole population was highest for seed oil content (0.81) followed by oil yield (0.75) and lowest for seedling emergence (0.29). For seed yieId, seed glucosinolate, lodging resistance and days to onset of flowering (DTF), prediction accuracies were 0.45, 0.61, 0.39 and 0.56, respectively. Prediction accuracies could be increased for some traits by treating subpopulations separately; a strategy which only led to moderate improvements for some traits with low heritability, like seedling emergence. No useful or consistent increase in accuracy was obtained by inclusion of a population substructure covariate in the model. Testcross performance prediction using genome-wide SNP markers shows considerable potential for pre-selection of promising hybrid combinations prior to resource-intensive field testing over multiple locations and years.     

Effects of the duration of cold stratification on early life stages of the Mediterranean alpine plant Silene ciliata

Cold stratification provided by snow cover is essential to break seed dormancy in many alpine plant species. The forecast reduction in snow precipitation and snow cover duration in most temperate mountains as a result of global warming could threaten alpine plant populations, especially those at the edge of their species distribution, by altering the dynamics of early life stages. We simulated some effects of a reduction in the snow cover period by manipulating the duration of cold stratification in seeds of Silene ciliata, a Mediterranean alpine specialist. Seeds from three populations distributed along an altitudinal gradient were exposed to different periods of cold stratification (2, 4 and 6 months) in the laboratory and then moved to common garden conditions in a greenhouse. The duration of the cold stratification treatment and population origin significantly affected seed emergence percentage, emergence rate and seedling size, but not the number of seedling leaves. The 6‐month and 4‐month cold stratification treatments produced higher emergence percentages and faster emergence rates than seeds without cold stratification treatment. No significant cold stratification duration x seed population origin interactions were found, thus differential sensitivity to cold stratification along elevation is not supported.     

Flooding and grazing promote germination and seedling establishment in the perennial grass Paspalum dilatatum

Seed germination and seedling emergence are key processes for population recruitment. Flooding and grazing are disturbances forming gaps that may strongly influence recruitment patterns in space and time, but their combined effects and action mechanisms have rarely been addressed. In this study we analysed the effects of microhabitat conditions associated with winter flooding and spring‐summer defoliation on seed germination and seedling establishment of Paspalum dilatatum, a dominant perennial C₄ grass in native grasslands of the Flooding Pampa, Argentina. The dynamics of seedling emergence from natural seed banks and buried seeds was studied in a factorial experiment with flooding and defoliation treatments applied to soil monoliths (mesocosms) collected from natural grassland. Additional laboratory experiments were applied to investigate seed germination under different combinations of temperature, light quality and simulated flooding. Seed germination and seedling emergence of P. dilatatum were promoted by flooding and high intensity defoliation. Gaps generated by flooding were maintained by high intensity defoliation exercising a synergistic effect on survival seedlings. Flooding resulted in the breaking of seed dormancy and higher germination rates associated with alternating temperature and the activation of the phytochrome system. Our results indicate that microhabitat conditions associated with the disturbances forming gaps, such as flooding and heavy grazing, synergistically promote the recruitment process of this dominant grass species.     

Antelope ingestion enhances germination of the marula (Sclerocarya birrea), an important African savannah tree

The marula (Sclerocarya birrea Hochst.) is an important forage and fruit tree in African savannahs. This study compared germination rate (days to germination) and success (percentage of stones that produced seedlings) among an intact control and four treatments, where fruits were (i) ingested by antelope (Cephalophinae and Neotragini), (ii) manually depulped, (iii) manually depulped and burnt and (iv) burnt intact. Measurements on three unrelated trees showed that whilst stone size differed significantly, germination success was comparable. Antelope regurgitated and expelled stones during rumination, within 16 h of ingestion. Seedling emergence commenced approximately 6 months after fruit drop when ambient temperature increased. Removal of fruit pulp increased germination rate and germination success, but moderate exposure to fire inhibited germination, especially following depulping. Germinated seeds were from significantly smaller stones than ungerminated seeds, suggesting that thicker‐walled endocarps inhibited seedling emergence. However, germination of the second seed in a stone was from larger stones in the germinated subset, possibly due to larger seed size. That antelope ingestion significantly enhanced germination over other treatments suggests that endozoochory is an important mode of seed dispersal in marulas. Appropriate fire management is therefore required in savannahs, as high‐intensity fires may limit germination and recruitment of marulas.     

以杜鹃红山茶为母本的优良种间杂交父本筛选

以杜鹃红山茶(Camellia azalea)为母本,‘绿带可娜’、‘红芙蓉’、‘迪朱丽亚’等13个观赏性较强的山茶花品种为父本,采用常规杂交育种方法,共配置13个杂交组合进行杂交试验。以坐果率、结实率、出苗率、单花成苗率作为评价亲和性的指标对杂交父本进行筛选,利用因子分析法对杂交组合亲和力进行综合评价,并采用形态鉴定法比较杂交子代与父母本主要性状差异。结果表明,‘绿带可娜’、‘玛丽费丝’、‘尼丽夫人’、‘花露珍’、‘娃丽娜深’为亲和性高的父本,杜鹃红山茶ב绿带可娜’、杜鹃红山茶ב玛丽费丝’为杂交亲和性较高的组合。杜鹃红山茶种间杂交后代花色、花型表现趋于父本,叶片更接近于母本杜鹃红山茶,杂交后代均遗传母本全年开花的特性。     

紫花苜蓿种子对逆境贮藏条件的反应

以陇东紫花苜蓿 (MedicagosativaL .cv .“Longdong”)种子为材料 ,在室温、35℃和 35℃ +10 %的种子含水量 (SMC) 3种贮藏、接种或不接种燕麦镰刀菌 (Fusariumavenaceum (Fr.)Sacc .)的条件下 ,1年贮藏期内对各逆境处理的种子每隔 6 0d进行 1次标准发芽试验 ,2 0℃恒温、第 10d统计种子的发芽率和死亡率 ,试验结束时计测种子幼苗的长度和感病率 ;在大田条件下观测各处理种子的出苗率 ,确定催腐 (CD)与各种贮藏条件下的苜蓿种带真菌种类和检出率 .结果表明 ,随着贮藏温度和种子含水量等逆境贮藏条件胁迫的加剧 ,苜蓿种带真菌检出率逐渐增高 ,从室温、35℃条件下的 10 %上升到CD +35℃ +10 %SMC条件下的 2 9% ;抗病性逐渐减弱 ,35℃ +10 %SMC条件下幼苗的感病率和种子死亡率显著 (P <0 .0 5 )高于室温和 35℃下的感病率和种子死亡率 ;室内种子发芽率和田间出苗率逐渐下降 ,35℃ +10 %SMC条件下的种子的发芽率和田间出苗率显著 (P <0 .0 5 )低于在室温和 35℃下的发芽率和田间出苗率 ;幼苗生长受到抑制 ,35℃ +10 %SMC条件下的苗长和根长显著 (P <0 .0 5 )低于在室温和 35℃下的幼苗长度 .随着贮藏时间的延长 ,种子真菌检出率和田间出苗率下降 ,幼苗感病率增加 .与未接种的对照相比 ,接种燕麦镰刀菌的种子     

Effects of chemical treatments for mildew control at different times on the growth and yield of spring barley

Experiments in 1973 and 1974 tested the effects of ethirimol seed treatment and the timing of single sprays of ethirimol or tridemorph, on mildew control and the growth and yield of spring barley. These treatments were compared with selected combinations of two treatments designed to give longer protection. In 1973, combinations of seed treatment and spray, or two sprays, did not yield better than the best component treatment applied alone or the most effective single spray of tridemorph applied on 1 June. In 1974, mildew developed usually early and yields were increased by applying ethirimol to the seed plus a tridemorph spray or two tridemorph sprays. However, barley sprayed once with tridemorph on 20 May, the expected best date, yielded more than barley receiving a seed treatment of ethirimol plus a tridemorph spray applied on either 3 or 12 June. Sprays of captafol and tridemorph, applied as separate treatments, successively to the same plots on three occasions, gave the best yields in both years. Treatments most affected ear number but they did have some effect on all components of yield. In 1974 there was a significant relationship between ear number and the variance of the number of grains per ear.     

Residual herbicide treatments reduce Andropogon gayanus (Gamba Grass) recruitment for mine site restoration in northern Australia

Weed invasion is a major threat to Australian tropical savannas, and controlling weeds is essential for successful re‐establishment of native species on disturbed sites. Gamba Grass (Andropogon gayanus) is an African grass which has invaded large areas of tropical savanna across northern Australia. Current management strategies in northern Australia focus on fire and glyphosate to effectively control mature plants; however, re‐establishment of infestations from the soil seed bank remains a major challenge to eradication efforts. This study focused on the effects of soil seed bank treatments on Gamba Grass recruitment on a mine site in northern Australia. Adult Gamba Grass plants within test plots were killed with glyphosate to exclude resource competition. Chemical, physical and biological treatments were then applied, and the treatment effects on subsequent Gamba Grass seedling emergence and survival quantified. Seedling emergence was significantly reduced by three of the four residual herbicide treatments tested. The most effective herbicide treatments, dalapon and sulfometuron, reduced emergence by 90% compared to the standard glyphosate treatment alone. This equated to a reduction in Gamba Grass seedling emergence from 1 seedling/m² to 1 seedling 10 m^?2, a major improvement for Gamba Grass management. These residual herbicide treatments significantly reduced the population density of Gamba Grass for at least 5 months after emergence. The physical and biological treatments did not have a significant effect on seedling emergence. This significant reduction in Gamba Grass seedling emergence and survival can substantially improve Gamba Grass management. Reducing re‐colonisation from the soil seed bank using residual herbicides provides a valuable management tool for land managers, integrating readily with established strategies for controlling the mature plants.     

Influence of fungal isolates on germination and growth of perennial ryegrass

Summary The influence of fungi isolated from perennial ryegrass roots on the germination and development of seedlings of perennial ryegrass was investigated. The basic procedure employed was to sterilise the seed surface and then inoculate with fungi and plant in non-sterile soil. It was realised that the fungal isolate inoculated on to the sterile seed surface would not remain dominant in the root region of the host and would have an influence on the host which would decline with time from when the seed germinated. This was because it would have to face antagonism from the normal components of the root microflora present in the non-sterile soil.Trichoderma viride delayed the emergence of the seedlings and reduced the production of herbage, an observation consistent with results of some other investigators. A sterile hyaline fungus stimulated the emergence of the seedlings, but subsequent tests showed that the presence of the microflora of the seed coat, or the soil microflora, or the sterile hyaline fungus was effective in promoting the rate of germination of seed that had been surface sterilised. Leaching seed in water brought about an increase in the rate of seed germination, and it is suggested that there might be a germination inhibitor soluble in water present in the seed coat, which might be inactivated by saprophytic micro-organisms.     

Performance of carrot and onion seed primed with beneficial microorganisms in glasshouse and field trials

Beneficial microorganisms (Clonostachys rosea IK726, Pseudomonas chlororaphis MA342, Pseudomonas fluorescens CHA0, Trichoderma harzianum T22 and Trichoderma viride S17a) were successfully applied to carrot and onion seed during a commercial drum priming process. Applied microorganisms were recovered above the target of at least 1 × 10⁵ cfu g⁻¹ seed following subsequent application of pesticides to the seed according to standard commercial practices of film-coating carrot and pelletting onion seed. Two glasshouse experiments consistently showed that priming improved emergence of carrot seed and that C. rosea IK726 further improved emergence time. Priming improved emergence of onion seed in one glasshouse experiment, but had an unexpected negative effect on emergence in the second experiment, possibly due to the proliferation of an unidentified indigenous microorganism during priming, becoming deleterious in high numbers. In this experiment, the application of beneficial microorganisms during priming negated this effect and significantly improved emergence. For each crop, a series of field trials was also carried out over three years, at two different sites each year. Although some positive effects of different seed treatments were seen on emergence or yield in individual field trials, no consistent effects were found for primed or microorganism-treated seed across all sites and years. However, a combined analysis of data for all years and sites indicated that pesticide application did consistently improve emergence and yield for both carrot and onion. This is the first comprehensive study assessing glasshouse and field performance of carrot and onion seed primed with beneficial microorganisms during a commercial process of drum priming in the UK.     

Potential for control of seedling blight of wheat caused by Fusarium graminearum and related species using the bacterial endophyte Bacillus mojavensis

Fusarium-infected wheat seed decreases germination, seedling emergence, and causes post emergence seedling death, and can contribute to wheat scab and ear rot of maize, with consequent production of mycotoxins such as deoxynivalenol and zearalenone. Current seed treatments have proved ineffective in controlling seedling blight and scab. A patented endophytic bacterial strain, Bacillus mojavensis RRC 101, and several other strains of this species were studied to determine in vitro antagonism to some Fusarium species and to assess the potential of this bacterium to serve as an endophytic biocontrol for seedling blight of wheat produced by species within the F. graminearum complex, as well as other species of Fusarium. Seedling emergence and seed germination were two tests used as indicators of seedling blight. These tests were conducted in growth rooms with two wheat cultivars highly susceptible to scab, Norm and Pioneer 2552, and other cultivars with varying resistance to scab. The results indicated that all strains of this bacterium were antagonistic in vitro to the strains of F. graminearum and its seven related species, as well as four strains of F. pseudograminearum and the two strains of F. verticillioides. Germination of the highly scab susceptible cultivar 2552 was increased from 77 to 97% when planted in soil containing a mixed inoculum of F. graminearum and related species. Seedling emergence in the very susceptible wheat cultivar Norm increased from 20 to 82% when treated with the bacterium. The data indicated that inoculating wheat kernels with B. mojavensis reduced seedling blight of wheat produced by F. graminearum and related Fusarium species indicating the potential for this bacterium as a biocontrol under field condition.     

Physiological Strategies to Improve the Performance of Spring Maize (Zea mays L.) Planted under Early and Optimum Sowing Conditions

Low temperature at stand establishment and high temperature at reproductive stage are involved in reduction of grain yield of spring maize. A field study was therefore conducted to evaluate different physiological strategies for improving performance of spring maize under temperature extremes. Seed priming and foliar spray with 3% moringa leaf extract (MLE) and 100 mg L^-1 kinetin solution alone or in all possible combinations with each other at three growth stages (knee height, tasseling and grain filling stage) and hydropriming was compared with control. Seed priming plus foliar spray of MLE and kinetin significantly improved stand establishment especially under early sown crop as indicated by reduced mean emergence time (MET), improved emergence index (EI) and final emergence percentage (FEP). Similarly increased chlorophyll contents, crop growth rate, leaf area index, photosynthetic rate, transpiration rate, relative water content and decreased membrane permeability were recorded in both early and optimum sowing conditions in MLE priming plus foliar spray treatment. All these improvements were harvested in the form of increased yield and harvest index compared with control treatment. Overall crop sown at optimum time performed best but exogenous application of MLE through seed priming and foliar spray maximally improved the performance of early sown maize crop which is attributed more likely due to improved stand establishment, chlorophyll and phenolic contents, increased leaf area duration and grain filling period. It can be concluded that seed priming with MLE along with its foliar spray could increase production of maize under temperature extremes.     

Endo-[beta]-Mannanase Activity from Individual Tomato Endosperm Caps and Radicle Tips in Relation to Germination Rates

Endo-[beta]-mannanase is hypothesized to be a rate-limiting enzyme in endosperm weakening, which is a prerequisite for radicle emergence from tomato (Lycopersicon esculentum Mill.) seeds. Using a sensitive, single-seed assay, we have measured mannanase activity diffusing from excised tomato endosperm caps following treatments that alter the rate or percentage of radicle emergence. Most striking was the 100- to more than 10,000-fold range of mannanase activity detected among individual seeds of highly inbred tomato lines, which would not be detected in pooled samples. In some cases a threshold-type relationship between mannanase activity and radicle emergence was observed. However, when radicle emergence was delayed or prevented by osmoticum or abscisic acid, the initial increase in mannanase activity was unaffected or even enhanced. Partially dormant seed lots displayed a bimodal distribution of activity, with low activity apparently associated with dormant seeds in the population. Gibberellin- and abscisic acid-deficient mutant seeds exhibited a wide range of mannanase activity, consistent with their variation in hormonal sensitivity. Although the presence of mannanase activity in the endosperm cap is consistently associated with radicle emergence, it is not the sole or limiting factor under all conditions.