The effect of nitrogenous compounds on in vitro germination of Orobanche crenata Forsk.

The effect of nitrogen (ammonium, urea and nitrate), applied during a conditioning or germination phase, on germination of Orobanche crenata Forsk, seeds was investigated in vitro. Ammonium sulphate (8 mM) applied during conditioning in combination with the nitrification inhibitor nitrapyrin, reduced germination of seeds from 46% to 26%. A lower concentration of 4 mM ammonium sulphate or supplying nitrogen as 8 mM urea or 16 mM nitrate did not inhibit germination. Applied after conditioning during the germination phase, 4 mM ammonium sulphate strongly inhibited germination, especially in combination with a nitrification inhibitor: germination was reduced to less than 5%. Urea (8 mM) reduced germination to only a limited extent (from 58% to 40%). When a urease inhibitor (carbon disulfide) was additionally applied, germination percentage was not affected. Nitrate had no effect. It is hypothesized that the inhibition by ammonium of O. crenata germination is connected with a reduced ability to detoxify ammonium, owing to the reduced activities of the enzymes GS and GOGAT. The inhibitory effect of urea may be indirect, occurring through conversion to ammonium. The effect of a short-term exposure to ammonium was largely reversible and no increase in mortality could be detected. The presence of 6 mM phosphate, Hepes or Mops buffer was found to intervene with the inhibition by ammonium.     

Factors affecting the seed germination and seedling emergence of muskweed (Myagrum perfoliatum)

Myagrum perfoliatum is a noxious broad‐leaved weed in western Iranian farming systems. A better understanding of the timing of seedling emergence would facilitate the development of better control strategies for this weed. Therefore, the objective of this study was to examine the effects of different factors on muskweed seed germination. Only 2.8% of the seeds of this species, which are encapsulated in siliques, germinated by, while the seeds that had been removed from the siliques had a 50% germination rate. The immersion of muskweed fruits in concentrated sulfuric acid for 110 min was the best treatment for promoting germination. Gibberellic acid stimulated the germination of the naked seeds by 29.1%, potassium nitrate (40 mmol L^‐1) increased the germination rate to 71%, while higher concentrations of potassium nitrate inhibited germination. The optimum germination temperature for the naked seeds was 20/10°C (day/night) and light was not required for germination. No seedling emerged when the seeds were buried 6 cm deep. The seeds were sensitive to both osmotic and salinity stress, but they germinated to 46–49% over a pH range of 4–10. The results of this study revealed that the seeds of M . perfoliatum have physiological dormancy and that it is slowly broken via after‐ripening. However, the fruit wall can prevent germination after physiological dormancy is broken. Thus, this species has the potential to form a persistent seed bank because of the presence of the fruit wall.     

Germination, emergence and seedling growth of Hypericum perforatum L.

Germination of new seeds (1–6 months old) of Hypericum perforation L. was restricted by high temperatures (16h/8h, 20/30°C), darkness and a chemical inhibitor in exudate from the capsule, whereas germination of old seeds (9 years) was only restricted by the inhibitor. The effect of the chemical inhibitor and high temperatures was overcome, respectively, by washing seeds in water and by reducing temperatures to constant 15°C. Calcium in solution from CaCO₃ and from three different soils did not prevent the germination of new or old seeds or of seeds collected from five different locations. There were differences in the germination characteristics and dormancy mechanisms of seeds collected from different localities, Restriction of the emergence of seedlings by a covering of > 2 mm of soil appeared to be due to lack of seedling vigour rather than to lack of light. Seedling growth was much slower than in other pasture species. Thus the requirements for germination of H. perforatum of low temperature and moisture to wash away the chemical inhibitor favour its establishment but the slow growth of its seedling restricts its emergence and renders it extremely susceptible to competition from other plants.     

THE EFFECTS OF LIGHT, POTASSIUM NITRATE AND TEMPERATURE ON THE GERMINATION OF CHENOPODIUM ALBUM L.

Summary. The influence of light, potassium nitrate and temperature on the germination of two samples of black seeds of Chenopodium albian L. was investigated. At constant temperature (23°C), light and nitrate together promoted germination of the younger (8–11-month-old) seed, which was insensitive to cither factor applied separately. Germination of older (32–35-month-old) seed was increased by both light and nitrate applied either separately or together, but there was no consistent interaction. While the older seed was generally indifferent to light, germination of the younger seed treated with nitrate was greatly promoted by relatively short periods of white light. Four minutes of light 36 hr after the initial moistening was as effective as 16 min and almost as effective as daily light exposure, in promoting germination of the younger seed. Long photoperiods slightly inhibited germination as compared with short photoperiods. Sensitivity of the younger seed to light varied with nitrate concentration, temperature, duration of imbibition in the dark prior to exposure, and time of nitrate application. Alternating temperatures (10–30°C daily) increased the sensitivity to light and to nitrate given either separately or together. Drying the younger seed for short periods after treatment with light and nitrate did not influence the response to either factor. Influence de la lumière, du nitrate de potassium et de la température sur la germination de Chenopodium album L. Résumé. L'influence de la lumiére, du nitrate de potassium et de la température sur la germination de deux lots de graines noires de Chenopodium album L. a étéétudiée. A température constante (23°C), la lumière et le nitrate appliqués ensemble provoquérent la germination des plus jeunes semences (agées de 8 à 11 mois), lesquelles ne réagirent pas à chacun des deux faeteurs appliqué séparément. La germination de semences plus âgées (32 à 35 mois) fut accrue par la lumière et par le nitrate, appliqués soit séparément, soit ensemble, mais il n'y eut pas d'interaction logique entre ces deux faeteurs. Alors que les semences les plus âgées furent généralement indifférentes à la lumiére, la germination des semences plus jeunes traitées par le nitrate fut fortement augmentée par des périodes relativement courtes d'éclairage en lumière blanche. Trente-six heures après l'humidification initiale, quatre minutes de lumiére furent aussi efficaces que seize minutes et presque aussi eflicaces que l'exposition à la lumiére du jour, pour provoquer la germination des jeunes semences. De longues photopériodes inhibérent légérement la germination par rapport á des photopériodes courtes. La sensibilite des jeunes semences à la lumière varia avec la teneur en nitrate, la concentration, la temperature, la durée de l'inhibition à l'obscurité avant l'exposition à la lumiére et l'epoque d'application du nitrate. Les variations de températures (entre 10 et 30°C dans la même journée) accrurent la senaibilitéà la lumière et au nitrate, appliquéés soit séparément soit ensemble. Le séchage des semences les plus jeunes pendant de courtes périodes après le traitement au nitrate et l'exposition à la lumière n'eut pas d'influence sur la résponse à I'un ou l'autre de ces facteurs. Einfluss von Licht, Kaliumnitrat und Temperatur auf die Keimung von Chenopodium album L. Zusammenfassung. Der Einfluss von Licht, Kaliumnitrat und Temperatur auf die Keimung zweier Proben schwarzer Samen von Chenopodium album wurde untersucht. Bei konstanter Temperatur (23°C) fordertcn Licht und Nitrat zusammen, nicht jedoch die beiden Faktoren fur sich allein, die Keimung der jüingeren Samen (8–11 Monatealt). Die Keimung älterer Samen (32–35 Monate alt) wurde durch Licht und Nitrat sowohl bei gemeinsamer als auch bei getrennter Anwendung erhiiht, wobei zwischen beiden Faktoren keine sichere Interaktion bestand. Während die ältercn Samen normalerweise gegenüber Licht indifferent waren, wurde die Keimung der jungeren mit Nitrat behandelten Samen durch verhaltnismässig kurze Perioden weissen Lichts stark gefördert. Eine Belichtungsdaucr von 4 Minuten, gegeben 36 Stunden nach Beginn des Einquellcns, fordcrtc die Keimung der jungeren Samen gleich stark wie eine solche von 16 Minuten und nahezu so stark wie eine tägliche Bclichtung. Lange Photoperioden hemmten die Keimung im Vergleich zu kurzen etwas. Die Reaktion der jungeren Samen aufdas Lieht hing von der Nitratkonzentration, der Temperatur, der Einquclldauer im Dunkeln vor der Bclichtung und dem Zeitpunkt der Nitratapplikation ab, Tamperaturweehsel (täiglicher Wechsel zwischen 10 und 30°C) erhohte die Empfindlichkeit gegenüber Licht und Nitrat sowohl bei gcmeinsamer als auch bei alleiniger Anwendung. Kurzzeitiges Rücklrocknen der Samen nach Licht- und Nitratapplikation beeinflusste die Reaktion der Samen auf diese beiden Faktoren nicht.     

STUDIES ON WEED SPECIES OF THE GENUS POLYGONUM L.

Summary. Seeds of Polygonum persicaria from several sources, or from plants subjected to in lain treatments, were chilled for varying periods and incubated for a 3-week germination test period. Populations differed widely in seed weight and to some extent in the response to different periods of chilling. No relationship between this response and the climate of the locality of origin could be found. There was much variation in seed weight and germination behaviour between individual plants within populations. A total of four polymorphic seed categories were observed. The proportions of seeds in the two main categories varied widely between and within populations, and were affected by certain environmental factors. These factors also appeared to affect the degree of inter-plant variation in seed shape and germination behaviour.
Travaux sur les espàes indésirables du genre Polygonum L. V. Variations dans le poids des semences, leur comportement à la germination et leur polymorphisme chez P. persicaria L.     

The Present Outlook for Pest Control

Abstract

Results of an experiment comparing six times of herbicidal application showed that an application of the amine salt of 2,4-D at the rate of 1.0 kg/ha at 50% flowering of the weeds had the most detrimental effect on viable seed production of both winter and rainy season weeds as judged from their germination tests. Delay in the application time of 2,4-D by one week increased seed viability by 150 and 55% in rainy and winter season respectively. Delay of each week in application tended to significantly increase viable seed production. Germination percentage of Triantherna portulacastrum, Digera arvensis, Amaranthus viridis, Amaranthus spinosus, Physalis minima, Phyllanthus niruri, Echinochloa colonum, Acalypha celiata, Flavaria contra-yerba and Cyperus rotundus growing in kharif season when treated at flowering stage was 0,0,0,0,2,0,16,0,14, and 0% respectively as against 44, 66, 76, 58, 82, 66, 90, 26, 92 and 61% respectively for untreated seeds.

In the case of winter weeds, germination percentage of Cornopus didymus, Anagallis arvensis, Melilotus indica, Chenopodium album, Chenopodium murale, Convolvulus arvensis, Spergula arvensis, Argemone mexicana, Asphodelus tenuifolius and Sonchus arvensis when treated at flowering stage was 0, 2.7, 0, 5.3, 2.7, 0, 0, 0, 0 and 0% respectively as against 8.0, 30.7, 40.0, 32.0, 33.3, 38.7, 16.3, 18.7, 25.3 and 12.7% respectively for untreated seeds.     

喜盐鸢尾种子休眠与萌发特性初步研究

喜盐鸢尾(Iris halophila）是一种干旱地区野生观赏花卉,种子萌发困难,限制了该种在园林绿化中的应用,也为育种工作带来难度。从吸水性和萌发性两个方面对喜盐鸢尾种子休眠原因和打破休眠的方法进行了探索。研究表明,在25/10 ℃（高温/低温）条件下,喜盐鸢尾种子萌发率最高,达到44.33%;胚乳中的萌发抑制物质是限制喜盐鸢尾种子萌发的主要原因;种皮可限制胚乳萌发抑制物质的释放。砂纸摩擦、切除部分胚乳和赤霉素(GA3)处理都能提高种子的萌发率。综合考虑经济费用和可操作性等因素,砂纸摩擦后蒸馏水浸种处理是打破喜盐鸢尾种子萌发行之有效的方法。     

Effects of some chemical factors,prechilling treatments and interactions on the seed dormancy‐breaking of two Papaver species

Seed dormancy is a common strategy of many plants to survive in natural and agricultural ecosystems. This study examined the effects of some chemical factors, including gibberellic acid and potassium nitrate, the prechilling temperature, duration and conditions and the light regimes on the seed dormancy‐breaking of Papaver rhoeas L. and Papaver dubium L. The results showed that all the tested seed dormancy‐breaking treatments significantly stimulated the germination of the two Papaver species. The seed germination was significantly influenced in relation to the seeds that were treated with 0–1250 p.p.m. of gibberellic acid. The maximum germination was observed in P. rhoeas L. at 750 p.p.m. and in Pa. dubium L. at 500 p.p.m. in the light/dark regime. There was a significant increase in the germination with an increase in the potassium nitrate concentration. The greatest germination was achieved at the lowest potassium nitrate concentration (0.5 g L^?1) in the light/dark regime. The wet prechilling was more effective than the dry prechilling in the dormancy‐breaking of both P. rhoeas L. and Pa. dubium L. The highest germination percentage was found in the wet prechilling condition after 45 days' prechilling duration. The combination of gibberellic acid and potassium nitrate was more successful than their separate application in the stimulation of germination in both Papaver species. Among the combined treatments of prechilling and gibberellic acid, the highest germination of P. rhoeas L. was recorded in the seeds that were treated with wet prechilling for 45 days with 750 p.p.m. gibberellic acid, while in Pa. dubium L., the maximum germination was recorded with wet prechilling for 45 days with 500 p.p.m. of gibberellic acid.     

黄顶菊种子萌发过程中DNA甲基化的MSAP分析

为明确入侵植物黄顶菊Flaveria bidentis生长发育与DNA甲基化之间的相互关系,采用甲基化敏感扩增多态性(methylation sensitive amplification polymorphism,MSAP)方法研究了黄顶菊种子萌发过程中DNA甲基化的动态变化。结果表明,DNA甲基化与去甲基化两者共同调控黄顶菊生命初期的生长发育,且去甲基化的变化在种子萌发过程中占主导。筛选出的12对引物共扩增出998条MSAP条带,其中多态性条带为951条,多态性百分比为95.37%。黄顶菊种子萌发过程中胞嘧啶发生甲基化主要以双链甲基化形式为主,位点数为94个,而单链甲基化位点数仅为50个;多态性位点数占总位点数比率为48.95%,表明有近一半的位点发生了DNA甲基化和去甲基化的变化;发生去甲基化变化的多态性片段有73个,而发生甲基化变化的有21个,说明黄顶菊种子萌发阶段DNA甲基化的变化主要以去甲基化形式为主,且在萌发第4天后去甲基化数目持续快速上升。     

叶甜菜种子发芽特性的研究

研究了不同化学药剂和植物激素浸种处理及种球色泽、粒径、储藏时间等对叶甜菜种子发芽的影响。研究表明,用一定浓度的双氧水、硼酸、磷酸二氢钾浸种处理叶甜菜种子,可提高种子发芽率、发芽势与发芽指数,其中以10g/kgH2O2、0.5g/kgH3BO3和5g/kgKH2PO4处理效果最好。赤霉素处理(10、30、50、70、100mg/L)叶甜菜种子,促进种子发芽的效果不明显。吸湿-回干处理对叶甜菜种子发芽有良好的促进作用。叶甜菜种球色泽、粒径大小与发芽的关系密切,黄色或黄褐色的种球比黑色或褐色种球及大、中粒种子比小粒种子发芽力显著;叶甜菜种子不耐贮藏,发芽力下降较快,使用年限仅为1a。     

Seed dormancy,germination, emergence and seed longevity in Galinsoga parviflora and G. quadriradiata

Galinsoga quadriradiata (hairy galinsoga) and Galinsoga parviflora (smallflower galinsoga, gallant soldier) are very troublesome weeds in many vegetable row crops in Europe. To optimise management strategies for Galinsoga spp. control, an in‐depth study of germination biology was performed. Germination experiments were conducted to evaluate the impact of light and alternating temperatures on germination of a large set of Galinsoga populations. Seedling emergence was investigated by burying seeds at different depths in a sandy and sandy loam soil. Dormancy of fresh seeds harvested in autumn was evaluated by studying germination response in light at 25/20°C with and without nitrate addition. Seed longevity was investigated in an accelerated ageing experiment by exposing seeds to 45°C and 100% relative humidity. Galinsoga spp. seeds required light for germination; light dependency varied among populations. Seedling emergence decreased drastically with increasing burial depth. Maximum depth of emergence varied between 4 and 10 mm depending on soil type and population. In a sandy soil, emergence percentages were higher and seedlings were able to emerge from greater depths than in a sandy loam soil. Freshly produced G. parviflora seeds, harvested in autumn, showed a varying but high degree of primary dormancy and were less persistent than G. quadriradiata seeds that lack primary dormancy. Lack of primary dormancy of freshly harvested G. quadriradiata seeds and light dependency for germination may be used to optimise and develop Galinsoga management strategies.     

玉米田两种阔叶杂草藜及苍耳对草甘膦的敏感性测定

苍耳Xanthium strumarium和藜Chenopodium album是常见的两种阔叶杂草,其在玉米田发生严重,影响了玉米的生长和产量.本文利用整株生物测定法对我国东北及黄淮海玉米产区采集到的苍耳及藜种群对草甘膦的敏感性进行了测定.种子室内培养至5～6叶期,喷施草甘膦后14 d称量鲜重,计算抑制杂草种群50％...     

反枝苋种子休眠解除方法研究

研究了光照和黑暗两种条件下氢氧化钠（NaoH）、盐酸（HC l）、赤霉素（GA3）和乙烯利（ETH）处理对反枝苋种子萌发的影响。结果表明,氢氧化钠、盐酸、赤霉素和乙烯利浸泡处理均可以明显提高反枝苋种子的发芽率,且随着试剂浓度的提高,发芽率表现出单峰变化曲线,浓度过低或过高均不利于种子的萌发。其中,赤霉素对解除反枝苋种子休眠最有效,且以200 mg/L浸泡处理24 h效果最好,发芽率可达90.8%,比对照提高了52.5百分点。其次为4%NaOH和6%HC l处理1 h,与800 mg/L ETH处理24 h的效果相当,发芽率在70%~75%之间。黑暗条件不利于反枝苋种子的萌发,发芽率略低于光照条件。     

Effects of the seed weight and burial depth on the seed behavior of common ragweed (Ambrosia artemisiifolia)

Common ragweed (Ambrosia artemisiifolia L.) is one of the annual plants that were described recently as invasive weeds in Europe. This species is described as an invasive plant that produces seeds that are highly variable. Its production of variably sized seeds is regarded as promoting its spread in different environments. Experiments were carried out to determine the influence of the seed weight and temperature on germination and the influence of the seed weight and burial depth on seedling emergence. The seeds were divided into a number of classes of weight and the seed weight effect on germination was evaluated by Petri dish assays. In another experiment, the seeds were buried at different depths in a clay soil/sand mix to estimate the burial effect on germination and seedling emergence. The germination level of A. artemisiifolia was high overall, between 76.8% and 94.2%. The seed germination was modified by temperature but it was not influenced by the seed weight. The amounts of germination and seedling emergence were greater for the seeds on the soil surface and decreased with an increasing burial depth, from 2 to 8 cm. No germination or emergence was observed for the seeds that were buried at 10 and 12 cm. The lightest seeds were more sensitive to burial. A greater level of seedling emergence for those seeds that were placed near the soil surface could explain the success of this species in open habitats, where the probability of deeper burial is low. After high seed production, the management of A. artemisiifolia in fields could be partly achieved through soil tillage, burying seeds below 10 cm, and not carrying out deep soil tillage the following year.     

Weed seedling emergence and seed survival: separating the effects of seed position and soil modification by tillage

Tillage causes both vertical redistribution of weed seeds and changes in soil physical properties. These two factors are rarely distinguished in studies of the impact of tillage on seedling emergence or seed survival. In this study, seeds of Chenopodium album L., Amaranthus retroflexus L., and Abutilon theophrasti Medik, were planted at particular depths in pots of undisturbed or stirred soil to separate these effects. Emergence and survival data were analysed by non-linear regression to determine the nature of significant differences between treatments. Emergence increased with slight burial and then decreased exponentially at greater depths. Average emergence over all depths was generally greater in tilled sou than in unfilled soil, particularly for C. album and A. retroflexus . Seed survival approached a maximum with increasing depth. Average survival of seeds that did not produce emerged seedlings was greater in tilled soil than in untilled soil for C. album and A. retroflexus . Thus, tillage affects emergence and seed survival of weeds through changes in soil conditions independently of effects resulting from redistribution of seeds in the soil profile.     

Study of seasonal variation in dormancy of Spergula arvensis L. seeds in a condensed annual temperature cycle

Changes in dormancy of Spergula arvensis seeds were studied during pre-incubation at constant temperatures and under a temperature regime that condensed the annual temperature cycle into 73 days. Each day in the regime represented the mean day and night temperatures and day lengths of 5 successive days of an average year in The Netherlands. Incubation occurred in water or loamy sand, in darkness. Germination of the seeds was tested in water or KNO₃ over a range of temperature. Seeds were irradiated with saturating doses of red light. In half of the treatments, pre-incubated seeds were dehydrated at the transfer to the conditions of the germination test. Breaking of dormancy occurred under conditions of 'spring'. It did not depend on exposure to low‘winter’temperatures, but was induced by rising 'spring’temperatures. Seeds developed secondary dormancy in late‘autumn'. The expression of the changes in dormancy that were induced during pre-incubation depended on the conditions of the germination test. Light, nitrate and dehydration stimulated germination. The experiments predicted that field emergence from nitrate-poor soils that have not been dehydrated will be restricted to a short period in autumn, whereas disturbance of nitrate-rich soils followed by a dry spell will stimulate germination of S. arvensis seeds from early spring to late autumn. The data presented good explanations for the cosmopolitan character and the serious weediness of this species. Its classification as a summer or winter annual is discussed.     

Seed dormancy and soil seedbank of the invasive weed Chenopodium hybridum in north‐western China

Seed dormancy and persistence in the soil seedbank play a key role in timing of germination and seedling emergence of weeds; thus, knowledge of these traits is required for effective weed management. We investigated seed dormancy and seed persistence on/in soil of Chenopodium hybridum, an annual invasive weed in north‐western China. Fresh seeds are physiologically dormant. Sulphuric acid scarification, mechanical scarification and cold stratification significantly increased germination percentages, whereas dry storage and treatments with plant growth regulators or nitrate had no effect. Dormancy was alleviated by piercing the seed coat but not the pericarp. Pre‐treatment of seeds collected in 2012 and 2013 with sulphuric acid for 30 min increased germination from 0% to 66% and 62% respectively. Effect of cold stratification on seed germination varied with soil moisture content (MC) and duration of treatment; seeds stratified in soil with 12% MC for 2 months germinated to 39%. Burial duration, burial depth and their interaction had significant effects on seed dormancy and seed viability. Dormancy in fresh seeds was released from October to February, and seeds re‐entered dormancy in April. Seed viability decreased with time for seeds on the soil surface and for those buried at a depth of 5 cm, and 39% and 10%, respectively, were viable after 22 months. Thus, C. hybridum can form at least a short‐lived persistent soil seedbank.     

Biology of Commelina benghalensis L. in south-eastern Queensland. 2. Seed dormancy, germination and emergence

Germination of freshly harvested seeds of Commelina benghalensis L. varied from 0–3% for small aerial seeds, 20–35% for large aerial seeds and from 33% for small underground seeds to 90% for large underground seeds. Innate dormancy of all seed types was completely overcome by clipping the seed coat. Exposure to 90°C dry heat for 2 h was also effective in increasing germination of the three strongly dormant seed types. Optimum temperature for germination varied with the different seed types. Periods of likely major weed infestation from the four seed types were predicted using soil temperature data. Exposure to light increased germination but was not essential and underground seeds responded more to light than aerial seeds. Optimum depth of emergence for the four seed types was from 0 to 50 mm and there was a positive correlation between maximum depth of emergence and seed weight.     

Seed viability determination in parasitic broomrapes (Orobanche and Phelipanche) using fluorescein diacetate staining

Fluorescein diacetate (FDA) was investigated as a potential viability stain for seeds of holoparasitic broomrapes Orobanche and Phelipanche (Orobanchaceae), using four weedy and two non-weedy taxa. FDA viabilities were compared with the currently used 2,3,5-triphenyl tetrazolium chloride (TTC) test, and in vitro germination induced by the strigolactone analogue GR-24. Viable FDA-stained seeds were characterised by bright yellow–green fluorescence under 450–490 nm blue light. These viable seeds could be discriminated from non-viable seeds, in which low levels of fluorescence, similar to non-stained control seeds were observed. FDA viabilities were not significantly different from those obtained using the TTC stain; however, viability values for both stains were consistently higher than levels of artificially induced germination. Positive TTC-staining showed continuous variation that was difficult to interpret. Nevertheless, the TTC test does not involve grinding seeds, and therefore probably remains a practical alternative to FDA for screening soil samples contaminated with Orobanche and Phelipanche seeds, which indicates different applications for the two viability tests. Interestingly, the strigolactone analogue GR-24 only induced germination in O. crenata , P. ramosa and O. minor , suggesting a high specificity towards this germination inducer among the species investigated. We suggest that FDA-staining provides a potential alternative to the currently used TTC test for seed viability assays for Orobanche and Phelipanche , and other parasitic weeds which are an obstacle to crop cultivation.     

Correlation between the soil seed bank and weed populations in maize fields

Annual weed populations establish every year from persistent seed banks in the soil. This 3 year study investigated the relationship between the number of weed seeds in the soil seed bank and the resultant populations of major broadleaf and grass weeds in 30 maize fields. After planting the crop, 1 m² areas were protected from the pre-emergence herbicide application. Soil samples were collected soon after spraying to a depth of 100 mm and the weed seeds therein were enumerated. The emerged weed seedlings in the field sampling areas were counted over the following 8 weeks. Up to 67 broadleaf species and five grass weeds were identified, although not all were found at every site and some were specific to a region or soil type. For the most abundant weeds in the field plots, on average 2.1–8.2% of the seeds of the broadleaf species and 6.2–11.9% of the seeds of the grass weeds in the soil seed bank emerged in any one year, depending on the species. Overall, the results showed a strong linear relationship between the seed numbers in the soil and the seedling numbers in the field for all the grasses and for most broadleaf weeds. For some species, like Trifolium repens , only a weak relationship was observed. In the case of Chenopodium album , which had the largest seed bank, there was evidence of asymptotic behavior, with seedling emergence leveling off at high seed numbers. An estimate of the soil seed bank combined with knowledge of the germination and behavior of specific weed species would thus have good potential for predicting future weed infestations in maize fields.