Stimulation of weed seed germination by 1–(3-chlorophthalirnido) cyclohexanecarboxamide (AC 94377)

The N-substituted phthalimide, AC 94377, promoted the germination of dry-stored seeds of 17 out of 24 weed species in Petri-dish tests maintained at 22°C. In a further test it was able to substitute for light and/or alternating temperatures in promoting the germination of some species. AC 94377 was more active than GA, in stimulating Solanum nigrum seed to germinate. When mixed with soil in the laboratory, AC 94377 again promoted germination of S. nigrum but the level and persistence of activity differed between soils. In the glasshouse, with soil containing a natural weed seed population, more seedlings emerged from treated than from untreated soil but this number represented fewer than half of the apparently viable seeds present. Field applications of AC 94377 promoted the germination of hand-sown seeds of certain weed species but did not increase the number of seedlings emerging from the natural weed seed bank.     

Plant‐driven changes in soil microbial communities influence seed germination through negative feedbacks

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Soil steaming effects on weed seedling emergence under the influence of soil type,soil moisture,soil structure and heat duration

Soil steaming applied in bands is a new technology with the potential to radically lower the burden of hand‐weeding intra‐row weeds in non‐herbicidal vegetable cropping. Preliminary studies with band‐steaming have shown effective control of viable weed seeds when the maximum soil temperatures reach 60–80°C. This temperature range has a particular agronomic interest, and the present study aimed at investigating the influence of soil factors and heat duration on weed seed mortality of soil steaming targeting 60–80°C. Two soil types (sand versus sandy loam) and two moisture levels (moist versus dry) were studied in one experiment (expt) while two levels of structure of a sandy loam (coarse versus fine) were included in a second experiment. A third experiment was focussing on the significance of heat duration expressed as the speed of cooling‐down after steaming had been stopped. Weed control efficacy was generally greater in sand than in sandy loam and soil irrigation further improved weed control. Steam application to the finely structured soil improved weed control efficacy relative to that obtained with the coarse soil of larger aggregate size. The rapidity of cooling from the maximum temperature did not affect the efficacy of the treatment on weed seed mortality. Based on these experiments, a maximum soil temperature of 80°C should ensure satisfactory weed control under moist soil conditions, especially if the soil is cultivated prior to steaming.     

储藏条件和时间对六种多年生湿地植物种子萌发的影响

研究了储藏条件和时间对 6种湿地植物种子萌发的影响 ,以便为采用种子恢复和重建湿地植被提供指导。将新鲜种子在浸泡 -冷、湿 -冷、湿 /干 -冷和干 -冷 4种条件下储藏 3个月后再进行种子萌发 ,结果表明 ,普通野生稻 (Oryza rufipogon)和野慈姑(Sagittaria trifolia)在 3种水胁迫冷藏条件下的种子萌发率显著高于干 -冷储藏时的萌发率 ;柳叶箬 (Isachne globosa)和水毛花(Scirpus triangulatus)种子发芽率最高的储藏条件分别是浸泡 -冷或湿 -冷储藏和干 /湿 -冷藏。小慈姑 (Sagittaria potam-ogetifolia)和野荸荠 (Eleocharisplantagineiformis)在 4种储藏条件下的发芽率没有显著差异。将种子在干 -冷条件下分别储藏1个月、6个月、18个月和 30个月后再进行萌发 ,结果显示储藏时间延长显著提高了普通野生稻、柳叶箬、野荸荠和小慈姑的发芽率。野慈姑的发芽率在前 3个储藏期随储藏时间延长而提高 ,但 30个月后发芽率开始下降。水毛花在所有储藏期间的发芽率均小于 2 %。结果建议采用种子恢复和重建湿地植被时 ,将种子水胁迫冷藏利于种子的萌发。同时 ,结果也表明干 -冷储藏 30个月的种子仍可作为湿地恢复的种质资源     

野豌豆属4种植物种子萌发的积温模型分析

以青藏高原野豌豆属窄叶野豌豆(Vicia angustifolia)、山野豌豆(V. amoena)、歪头菜(V. unijuga) 3种野生植物与一种当地栽培植物救荒野豌豆(箭筈豌豆) (V. sativa) ‘兰箭3号’种子为材料, 在5、10、15、20、25及30 ℃下进行萌发实验, 应用种子萌发的积温模型对上述4种植物萌发对温度的响应特征进行了比较分析。结果表明: 1)基于萌发速率(1/T_g)对种子萌发温度最低温T_b值的估计受萌发率(g)的影响较小; 与此不同, 除‘兰箭3号’种子外, 对萌发最高温T_c值的估计, 受到g的显著影响。 这表明种群内所有种子个体萌发的T_b值相对恒定, 但T_c值在有些物种中变异较大; 2)基于重复概率单位回归分析估计的种子萌发T_b值与基于萌发速率估计的值较为接近; 而由此方法估计的T_c值则与萌发率为50%时的估计值较为接近; 3)相比多年生豆科植物歪头菜和山野豌豆, 一年生豆科植物箭筈豌豆‘兰箭3号’与窄叶野豌豆具有相对较低的T_b与T_c值; 4)积温模型可准确地预测休眠破除后豆科植物种子在不同温度条件下的萌发进程。     

Response surfaces for the combined effects of heat shock and smoke on germination of 16 species forming soil seed banks in south‐east Australia

Abstract There is limited understanding of how fire‐related cues such as heat shock and smoke can combine to affect the germination response of seeds from fire‐prone vegetation because combinations of multiple levels of both cues have rarely been investigated. Germination response surfaces were determined for the combination of heat shock and smoke by applying factorial combinations of temperature (up to 100°C) and aerosol smoke (0–20 min) to 16 species that form soil seed banks in the Sydney region of south‐eastern Australia. Duplicate populations of three species were also examined to assess the constancy of a species response surface. Of the 19 populations examined, 16 showed a germination response to both the fire cues, which combined interactively in 14 populations, and independently in two. No population responded only to a single cue; however, seeds of 11 populations responded to heat in the absence of smoke, and nine responded to smoke in the absence of heat. Heat applied in the absence of smoke negatively affected germination in seven populations, either progressively as temperature increased, or above a set temperature. Negative germination responses over part of the temperature range were fully reversed at higher temperatures for unsmoked seeds of four populations (curvilinear heat response). Smoke effects were most frequently positive over all or part of the range of durations used, and when combined with heat frequently fully or partially reversed negative heat effects. Three populations required the obligatory combination of smoke and heat. A novel response to the cues was observed for three species, with smoke reversing negative heat effects at 75°C, being supplanted by a positive heat response of unsmoked seed at 100°C. The response surface for duplicate populations of two of the three species examined was variable. Heat shock and smoke frequently combined to affect germination, in both positive and negative ways. Consequently, to gain an accurate assessment of the response of seeds to fires, an experimental design that samples within the potential response zones of germination cues is essential.     

青藏高原东缘31种常见杂草种子萌发特性及其与种子大小的关系

以青藏高原东缘31种常见杂草(禾本科、菊科和紫草科)植物种子为对象,在野外实验条件下,观测了其萌发特性,并对其萌发模式以及种子大小和萌发特征的关系进行了分析,以期对当地的杂草防治提供理论依据.结果表明,这些植物种子的萌发模式可以分为以下4种类型:爆发型、过渡型、缓萌型和低萌型.其中过渡型和缓萌型所占比例最大(各占32.3%),爆发型次之(25.8%),低萌型最小(9.7%).高峰萌发率与种子大小呈显著负相关,萌发高峰时间与种子大小呈显著正相关,萌发率、萌发指数与种子大小呈较弱的负关联,萌发开始时间与种子大小呈较弱的正关联,萌发持续时间与种子大小几乎无相关关系.     

热激对大兴安岭三种松科树种种子萌发的影响

研究了热激对大兴安岭地区兴安落叶松、樟子松、红皮云杉种子萌发的影响,热激温度分别为80℃、100℃、120℃、150℃,每个温度下热激时间分别为1min、3min、5min、10min。研究结果表明:兴安落叶松种子在100℃热激10min,120℃热激5min,10min,150℃热激5min处理下萌发率较对照显著下降(P%0.05),除80℃热激1min、3min、5min、120℃热激1min、150℃热激1min外,其他处理萌发速率指数较对照均显著下降(P%0.05);樟子松种子在高于80℃的所有热激处理萌发率较对照均显著下降(P%0.05),甚至没有萌发,除80℃热激1min外,所有处理下萌发速率指数较对照均显著下降;红皮云杉种子萌发率在80℃热激5min和100℃热激1min处理下较对照显著提高(P%0.05),萌发速率指数在80℃热激1min、3min、5min,100℃热激1min处理下较对照显著提高(P%0.05)。兴安落叶松种子可以在短时间高强度(150℃)热激下维持萌发率,但不能承受长时间热激;樟子松种子对高于80℃的热激反应敏感,热激降低了樟子松种子的萌发能力;热激可以提高红皮云杉种子的萌发能力,短时间(1min、3min、5min)低强度(80℃)热激(包括100℃热激1min)提高红皮云杉种子萌发率和萌发速率指数,红皮云杉种子也可以承受高强度(150℃)瞬时(1min)热激。     

Smoke and heat effects on soil seed bank germination for the re‐establishment of a native forest community in New South Wales

The effects of plant‐derived smoke and of heat on the emergence of seedlings from seeds were assessed. Seeds had been stored in forest topsoil used for mine site rehabilitation. The study was carried out in a dry sclerophyll, spotted gum (Corymbia maculata), forest community at the Mount Owen open‐cut coal mine in the Hunter Valley region of New South Wales. Samples of the surface 2.5 cm of topsoil were either exposed to cool smoke from eucalypt foliage for 60 min, heated to 80°C, or left untreated. Seedling emergence from the seed bank in this soil was then monitored in a glasshouse. Within the first month, smoke alone promoted a 4.3‐fold increase in the density of seedlings relative to control. There were 540 emergents per m² in the control and 2309 per m² in the smoke treated topsoil. Many annual and perennial herbs emerged but grasses responded most strongly to smoke. Germination in seven of the 20 grass species was promoted by smoke. Smoke promoted the germination of some introduced species as well as native species, and accelerated the rate at which seedlings emerged, although these differences sometimes declined with time. Heat also stimulated germination but smoke and heat stimuli appeared to be complementary in their promotion of seedling emergence from the topsoil seed bank. Each treatment increased the density of different species, enhanced the species richness of different components of the seed bank, and had different effects on the rate of emergence. The results suggest that increased seed germination in the field immediately following a moderate intensity fire may sometimes be the result of smoke stimulation and sometimes the result of heat stimulation of the soil seed bank. These findings may have important implications for minesite revegetation programs where topsoils are replaced after mining and rapid germination of seeds stored in these soils is required during short periods when conditions are favourable for germination.     

The effect of parent plant nutrition on seed size, viability and vigour and on germination of wheat and triticale at different temperatures

Seed was obtained from two adjacent trials of wheat (cv. Avalon) and triticale (cv. Lasko) harvested in 1990. The treatments consisted of factorial combinations of five levels of spring nitrogen (50, 100, 150, 200 and 250 kg N ha^-1) with fungicide treatments designed to control foliar diseases. Seed was graded by size into different fractions. Application of foliar fungicides to the parent plant increased the proportion of large seed in wheat but not in triticale. Fungicide application had no effect on seed vigour (quantified as the value of K; after controlled deterioration), final germination, median germination time (t₅₀) or rate of germination. Parent plant nutrition altered the proportions of seed in different size categories in triticale and wheat. In laboratory germination tests, final germination of wheat increased with seed size. Large (> 3.0 mm diameter) wheat seed from plots receiving 50 kg N ha“¹ had a lower final germination than large seed from plots which had received greater amounts of nitrogen, but t₅₀ and K; were similar for all nitrogen levels. In triticale, the higher the seed weight, the higher the final germination, the faster the rate and the higher the Ki. Final germination, t₅₀ and K;, were all positively correlated with the amount of nitrogen received by the parent plants. Parent plant nutrition had no effect on the response to temperature of final germination, t₅₀, or rate of germination for large or small seeds of both wheat and triticale.     

Effect of lanthanum on aged seed germination of rice

Attempts were made to promote germination of natural aged rice seeds by treating them with lanthanum nitrate. In tests to measure the germination rate, germination index, and vigor index of natural aged rice seeds were found to be significantly increased by lanthanum. It is treating aged rice seed with lanthanum nitrate that enhanced the respiratory rate and activities of superoxide dismutase, catalase, and peroxidase, and decreased superoxide and malondidehyde contents, and therefore reduced plasma membrane permeability. It suggests that lanthanum may be used to pretreat seed before sowing.     

生物土壤结皮对荒漠土壤种子库和种子萌发的影响

研究了腾格里沙漠东南缘在不同自然条件（风、温度、水分）下,人工固沙植被区（24龄、41龄、50龄）和相邻天然植被区的两种生物土壤结皮对荒漠土壤种子库和种子萌发的影响。结果表明,荒漠土壤种子库在苔藓结皮上的储量显著高于藻类结皮。随着生物土壤结皮的发育,种子萌发量在苔藓结皮上增加,在藻类结皮上减少。生物土壤结皮层的含水量对种子萌发有显著的影响（p〈0.05）,植物种子在湿润处理的生物土壤结皮上的萌发量高于干燥处理的生物土壤结皮上的种子萌发量。生物土壤结皮表层温度和亚表层温度对荒漠植物种子萌发无显著影响（p〉0.05）,但总体而言,对于苔藓结皮,植物种子在较高温度下的萌发量略高于在较低温度下的萌发量,而对于藻类结皮,植物种子在较低温度下的萌发量略高。     

铝浸种对荞麦种子萌发和幼苗生理的影响

对2个荞麦(Fagopyrum esculentumMoench)品种(小白花叶和溪荞5号)在铝浸种后萌发特性和幼苗的生理变化进行了初步研究。结果表明,10~1000mg.L-1的铝浸种处理对2个荞麦品种的发芽率和发芽指数影响不明显,低浓度铝(≤100mg.L-1)处理可降低荞麦种子细胞膜透性,减少细胞内营养物质的外渗,促进种子的萌发。5000mg.L-1的铝处理降低了荞麦的发芽指数。种子萌发后,铝对荞麦根的伸长有抑制作用,并且随着铝浓度的增加,抑制作用增大。10~1000mg.L-1的铝浸种处理对荞麦叶片内MDA含量影响较小,但高浓度的铝处理(5000mg.L-1)明显增加了MDA的含量;POD、SS、Pro随着铝浓度增加都有先降低后增加的趋势;不同品种叶片内CAT活性变化趋势不同,小白花叶内CAT活性对铝的敏感性大于溪荞5号。试验结果可以看出,荞麦种子和幼苗对环境中的铝都有较强的耐受性,在铝胁迫下,荞麦可以通过升高POD活性以及增加SS和Pro含量来缓解铝毒害,不同荞麦的基因型对铝毒害的反应有一定的差异性。     

Interspecific variation in persistence of buried weed seeds follows trade‐offs among physiological,chemical, and physical seed defenses

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Mathematical description of the seed germination dependency on time and temperature

Abstract. A mathematical model which describes the germination percentage dependency on time and temperature of a seed population was derived from the experimental results with a seed population of Amaranthus patulus Bertol. under sub-optimal temperature conditions (Washitani & Takenaka, 1984). The equation of the model which is a modified thermal time model is where G is germination percentage at a certain time after the start of imbibition ( t ) at a certain temperature ( T ), μ _{T 1} and σ _{T 1} are the mean and standard deviation of lower limit temperature among the seeds belonging to the seed population, and Tb, m , and A are the parameters characterizing the linear relationship between the rate and temperature, namely, Tb is the base temperature, m , the median of the required thermal time and A , a parameter determining the pattern of the variation of the required thermal time within seed population, respectively. The equation yields time courses for germination which are very similar to those observed by experiment.     

Effect of seed passage through vertebrate frugivores'' guts on germination: a review

The capacity of seeds to germinate after ingestion by frugivores is important for the population dynamics of some plant species and significant for the evolution of plant-frugivore interactions. In this paper the effects of different vertebrates on seed germination of nearly 200 plant species are reviewed, searching for patterns that predict the circumstances in which germination of seeds is enhanced, inhibited, or unaffected by the passage through the digestive tract of a seed disperser. It was found that seed dispersers commonly have an effect on the germinability of seeds, or on the rate of germination, or both, in about 50% of the plants they consume, although the diversity of animal species tested so far is still rather low (42 bird species, 28 non-flying mammals, 10–15 bats, 12 reptiles, 2 fishes). Enhancement of germination occurred about twice as often as inhibition.

In spite of the morphological and physiological differences in their digestive tracts, the different animal groups tested have similar effects on seed germination, although non-flying mammals tend to influence germination slightly more often than the other groups. Data on fishes are still too scarce for any generalization. Seed retention time in the dispersers' digestive tract is one factor affecting germination, and helps to explain the variation in seed responses observed among plant species, and even within a species. However other factors are also important; for example, the type of food ingested along with the fruits may affect germination through its influence on chemical or mechanical abrasion of the seed coat. Seed traits such as coat structure or thickness may themselves be responsible for some of the variation in seed retention times. Seeds of different sizes, which usually have different transit times through frugivores, and seeds of either fleshy or dry fruits, show often similar germination response to gut passage.

Seeds of different plants species differ strongly in their germination response after ingestion, even by the same frugivore species. Congeneric plants often show little consistency in their response. Even within a species variation is found which can be related to factors such as the environmental conditions under which germination takes place, seed morphology, seed age, and the season when the seeds are produced.

The effect of gut passage on germination differs between tropical and temperate zones. Seed germination of both shrubs and trees (data on herbaceous species are still scarce) in the temperate zone is more frequently enhanced than in the tropics. This result supports the hypothesis that enhanced germination may be more advantageous in unpredictable or less constant environments. Significant differences in frugivore-mediated germination are also found among different life forms. In both tropical and temperate zones, trees appear to be consistently more affected than shrubs or herbs. This might be due to an overall higher thickness of the seed coats, or to a higher frequency of seed-coat dormancy in tree species.

The influence of frugivory upon the population dynamics of a species has to be evaluated relative to other factors that influence germination and seedling recruitment at a particular site. Whether seed ingestion by dispersers is really advantageous to a plant (as has commonly been assumed) can only be assessed if we also determine the fate of the ingested seeds under natural conditions, and compare it to the fate of seeds that have not been ingested.     

Interactive effects of heat shock and smoke on germination of nine species forming soil seed banks within the Sydney region

Abstract The germination response of seeds from fire‐prone vegetation to fire‐related cues such as heat shock and smoke has usually been studied by applying the cues singly. The few studies that have applied the cues in combination have shown that interactions between the cues are possible. Here, the response of seeds from a number of species to combined heat shock and smoke is reported. Heat shock (25, 50, 75 and 100°C) and aerosol smoke (0, 5, 10 and 20 min) were applied factorially to nine species that form soil seed banks in the Sydney region of south‐eastern Australia. These species were from Epacridaceae (four species), Myrtaceae (four species) and Cyperaceae (one species) and ranged from fire‐sensitive obligate seeders to fire‐tolerant facultative resprouters. Germination of Dracophyllum secundum R. Br and Sprengelia monticola (A. Cunn. ex DC.) Druce was low and did not respond to the germination cues. The positive response of Gahnia sieberiana Kunth and Kunzea ambigua (Sm.) Druce to heat shock and smoke was independent and additive. The positive response of Kunzea capitata Rchb. to the interaction between heat shock and smoke was synergistic, and the response of Baeckea diosmifolia Rudge and Baeckea imbricata (Gaertn.) Druce was unitive, with germination increase only occurring following combined heat and smoke application. Epacris coriacea A. Cunn. ex DC. and Epacris obtusifolia Sm. had low levels of dormancy and hence it was not possible to find a fire response. Gahnia sieberiana and K. capitata responded differently to the combination of heat shock and smoke than has previously been reported. Germination of species from habitats that are infrequently burnt was not affected by heat shock or smoke. Low‐intensity fire or patches within fire may be important for seedling recruitment as the 50°C heat shock stimulated germination in four of the five species that responded to the heat cue, and germination of Baeckea imbricata declined within the 100°C heat shock treatment. Germination of one species, Baeckea imbricata, was only stimulated by a specific combination of cues, indicating that regeneration niches may be narrow for some species and that the application of a range of heat and smoke doses is required to find such responses. Of the species positively responding to heat shock and smoke, a requirement for both cues was prevalent, therefore the response to these cues in isolation cannot be relied upon to give a true indication of the fire response of a species.     

Influence of an abscisic acid (ABA) seed coating on seed germination rate and timing of Bluebunch Wheatgrass

Semi‐arid rangeland degradation is a reoccurring issue throughout the world. In the Great Basin of North America, seeds sown in the fall to restore degraded sagebrush (Artemisia spp.) steppe plant communities may experience high mortality in winter due to exposure of seedlings to freezing temperatures and other stressors. Delaying germination until early spring when conditions are more suitable for growth may increase survival. We evaluated the use of BioNik? (Valent BioSciences LLC) abscisic acid (ABA) to delay germination of bluebunch wheatgrass (Pseudoroegneria spicata). Seed was either left untreated or coated at five separate rates of ABA ranging from 0.25 to 6.0 g 100 g^?1 of seed. Seeds were incubated at five separate constant temperatures from 5 to 25°C. From the resultant germination data, we developed quadratic thermal accumulation models for each treatment and applied them to 4 years of historic soil moisture and temperature data across six sagebrush steppe sites to predict germination timing. Total germination percentage remained similar across all temperatures except at 25°C, where high ABA rates had slightly lower values. All ABA doses delayed germination, with the greatest delays at 5–10°C. For example, the time required for 50% of the seeds to germinate at 5°C was increased by 16–46 d, depending on the amount of ABA applied. Seed germination models predicted that the majority of untreated seed would germinate 5–11 weeks after a 15 October simulated planting date. In contrast, seeds treated with ABA were predicted to delay germination to late winter or early spring. These results indicate that ABA coatings may delay germination of fall planted seed until conditions are more suitable for plant survival and growth.