Seed production and subsequent seed germination of Senecio vulgaris (groundsel) grown alone or in autumn-sown crops

Senecio vulgaris is a common weed of agriculture in the UK, but is also of food value to invertebrates and birds. Thus, it may be beneficial to retain it within agricultural ecosystems to enhance overall biodiversity. A less intensive approach to weed management requires a sound understanding of weed population dynamics so as to avoid unacceptable population growth. Experiments were carried out in 2003 and 2004 to assess seed production, and subsequent germination, by S. vulgaris growing alone, in winter wheat, or in winter field beans. Plant and seed samples were collected during May and June. There was a strong allometric relationship between capsule number and plant weight, irrespective of the year or the presence of crop competition. Numbers of seeds/capsule varied slightly from 51 to 66 seeds per capsule. Plants growing alone were estimated to produce 8471 to 12 887 seeds per plant, whilst those in wheat only 923 to 2156. Germination tests in Petri dishes in incubators showed that virtually all seeds were viable and germinated under daily alternating light:dark conditions within 10 days. Seeds in continuous dark germinated less readily, reaching only 30% after 21 days. On the basis of this and other published work, it would appear that the retention of S. vulgaris in arable fields will not pose a major threat to the long-term viability of crop production.     

Effect of different weed management systems on the weed populations, and seedbank composition and distribution in tropical coconut plantations

Weeds are a perennial problem in coconut plantations and cause significant losses in the nut yield. The occurrence of a wide range of weeds also causes difficulties in their eradication. The influence of five different weed management practises on the distribution and composition of the soil weed seed bank in coconut plantations in the low-country dry zone of Sri Lanka was evaluated. The treatments imposed included the application of glyphosate (N-[phosphonomethyl]-glycine), cover cropping with Pueraria phaseoloides , tractor harrowing, tractor slashing, and tractor plowing. All the treatments were applied twice per year, except for the cover cropping treatment. In terms of a reduction in the weed biomass, the application of glyphosate and cover cropping ( Pueraria ) were more efficient in reducing the ground weed population. These methods were very effective in reducing the weed seed density in the top soil layers. Plowing and harrowing significantly reduced the seed bank in the top soil layers and shifted significant numbers of weed seeds to deeper soil profiles. However, the total germinated weed seed count increased by 123.5, 691.4, 1133.1, and 1216.5% in the 10–15, 15–20, 20–25, and 25–30 cm soil depths, respectively, compared with the initial germinated weed seed count in the plowing treatment. Considering all the soil layers, the decline in the germinating weed seed count was very high in the treatment plots with cover cropping and the application of glyphosate; thus, these are considered to be the best practises to reduce the germinating weed seed count in the soil of coconut plantations.     

Ecological aspects of seed dormancy-break and germination in Heteranthera limosa (Pontederiaceae), a summer annual weed of rice fields

Summary Heteranthera limosa seeds were buried in flooded and in non-flooded soil and exposed to natural seasonal temperature changes in Lexington, Kentucky, USA. Seeds exhumed after various periods of burial ranging from 2 to 36 months were tested for germination under both flooded and non-flooded conditions. Seeds were dormant at maturity in September and became non-dormant during winter. Seeds buried in non-flooded soil during winter germinated to higher percentages and over a wider range of temperatures when tested under flooded conditions (in light) during spring and summer, than did those buried in flooded soil during winter. Thus, the water regime associated with rice culture (non-flooded in winter and flooded in summer) is optimal for dormancy-break and germination of H. limosa seeds. A portion of the buried seeds exhibited an annual dormancy/non-dormancy cycle, whereas others had a conditional dormancy/non-dormancy cycle. Regardless of the type of cycle, seeds buried in non-flooded soil retained the ability to germinate in light at high temperatures under flooded conditions throughout the summer. Thus, seeds potentially can germinate at any time during the growing season, whenever rice fields are flooded. Flooding fields during winter and/or sowing rice relatively early in the growing season may help in establishing rice before seeds of H. limosa germinate.     

Inter-population variabilities in seed mass and germination of Panicum turgidum and Pennisetum divisum in the desert of Kuwait

Understanding variability in seed germination among populations is essential for planning an effective germplasm collection for restoration and conservation purposes.The knowledge of germination and dormancy patterns among populations of desert grasses is crucial for determining the potential of the species and populations to be used for restoration and conservation as well as forage production.Variability in seed germination of Panicum turgidum Forssk and Pennisetum divisum(Gmel.)Henr.in the desert of Kuwait was evaluated in different populations in May 2017.Experiment of seed germination(25 seeds and 4 replicates)was conducted for each population at night/day temperatures of 15℃/20℃and 20℃/30℃under the following light condition:continuous darkness or 12 h/12 h light/dark.Results showed that seed masses of both species strongly varied according to their seed provenances,and both species produced heavier seeds in population with a higher soil electrical conductivity.Seed germination percentage considerably varied between two species,and the variation in P.turgidum was greater(17%–49%)than that of P.divisum(72%–93%).Germination percentage in P.turgidum was greater at high temperature(20℃/30℃)than at low temperature(15℃/20℃).However,temperature regimes had no effect on germination percentage of P.divisum seeds.Mean germination time of both species exhibited significant inter-population variability.This result is especially relevant to assure the selection of the best population of each species and the regeneration success of the species.Besides this,inter-population variability also provides valuable information for enhancing our understanding of the mechanisms that regulate seed germination and how they might be related to seed provenance.     

Environmental maternal effects on seed morphology and germination in Sinapis arvensis (Cruciferae)

Pioneer plants are adapted to grow in unpredictable environments. These plants have evolved several traits related to seed morphology and germination to cope with this unpredictability. The main aim of this study was to investigate the effect of plant identity and maternal environment on seed mass and germination of Sinapis arvensis. This study was undertaken with S. arvensis plants grown in four experimentally manipulated resource availability scenarios: (i) nitrogen addition, (ii) water addition, (iii) nitrogen and water simultaneously added, and (iv) control. Plants grew under field conditions in an emerging plant community. Germination response was mainly affected by maternal plant identity. This reflects not only genotype quality but also phenotypic plasticity, which allows adaptation to habitat conditions. Seed coat colour together with mean seed mass per plant explained significant fractions of the variability in germination rate. Changes in the germination response because of maternal environmental effects were also detected. Germination rate decreased in seeds from nitrogen‐enriched conditions; this may be due to the induction of dormancy caused by high concentration of nitrogen in the seeds. Addition of water to maternal environment caused a decrease in total germination percentage and germination rate of seeds. Thus, our results provide evidence for maternal environmental effects on germination under field conditions. Furthermore, changes in germination timing, as detected in our study, may determine plant development and fitness in unpredictable conditions.     

Impacts of snow on seed germination are independent of seed traits and plant ecological characteristics in a temperate desert of Central Asia

Seed germination profoundly impacts plant community composition within the plant life cycle. Snow is an important source of water for seed germination in the temperate deserts of Central Asia. Understanding how seed germination responds to variations in snow cover in relation to seed traits and plant ecological characteristics can help predict plant community sustainability and stability in Central Asia under a scenario climate change. This study investigated the seed germination of 35 plant species common to the Gurbantunggut Desert in Central Asia under the three snow treatments: (1) snow addition; (2) ambient snow; and (3) snow removal. Two-way analysis of variance (ANOVA) tests were performed to assess interactions among the impacts of snow treatments, seed traits and plant ecological characteristics on seed germination. Phylogenetic generalized least-squares (PGLS) model was used to test the relationships between seed traits and seed germination. The results demonstrated that snow variations had no significant impacts on seed germination overall. Seed germination under the snow addition treatment was similar with that under the ambient snow treatment, irrespective of seed traits and plant ecological characteristics. Snow removal only had negative impacts on seed germination for certain groups of seed traits and plant ecological characteristics. Seed mass positively affected seed germination, showing a linear increase of arcsin square root-transformed seed germination with log-transformed seed mass. Seed shape also profoundly impacted seed germination, with a higher germination percentage for elongated and flat seeds. Seed germination differed under different plant life forms, with semi-shrub species showing a significantly higher germination percentage. Most importantly, although snow treatments, seed traits and plant ecological characteristics had no interactive effects on seed germination overall, some negative impacts from the snow removal treatment were detected when seeds were categorized on the basis of seed mass and shape. This result suggests that variations of snow cover may change plant community composition in this temperate desert due to their impacts on seed germination.     

Changes in seed bank size and dormancy characteristics of the glyphosate-resistant biotype of goosegrass (Eleusine indica[L.] Gaertn.)

A study on changes in the seed bank size of a glyphosate ( N -(phosphonomethyl)glycine)-resistant (R) Eleusine indica biotype was carried out on a naturally occurring infestation of a young oil palm plantation. The total number of shed seeds collected was 53% of the predicted potential total number of seeds produced by the plants. Ametryn ( N -ethyl- N' -(methylethyl)-6-(methylthio)-1,3,5-triazine-2, 4-diamine) was found to be able to control the R seed population in the soil. The periodicity of seedling emergence was influenced by rainfall subsequent to the 1 month period of seed shedding. Seed burial at 2, 10 and 20 cm depths showed that 39, 33 and 79%, respectively, of viable seed persisted in the soil after 2 years. Seeds in the state of enforced dormancy played an important role in maintaining the seed population throughout the 2 year period of burial in the soil.     

Effects of temperature and light on seed germination of ephemeral plants in the Gurbantunggut Desert,China: implications for vegetation restoration

Seed germination is a key transitional stage in plant life cycle and is strongly regulated by temperature and light. Therefore, research on the effects of temperature and light on seed germination is extremely meaningful for vegetation restoration, especially in desert ecosystems. Seeds of 28 ephemeral plants collected from the Gurbantunggut Desert of China were incubated at different temperatures (5°C/1°C, 15°C/5°C, 20°C/5°C, 25°C/10°C and 30°C/15°C) in 12-h light/12-h darkness or continuous darkness regimes, and the responses of seed germination to temperature and light and the germination speed were studied in 2016. Results showed that seed germination percentage of the 28 ephemeral plants significantly differed to temperature and light. We classified the studied plants as the following groups based on their responses to temperature: 1 low temperature responsed plants, 12 moderate temperature responsed plants, 7 high temperature responsed plants, 4 non-responsed plants and 5 plants of no germination. It should be noted that Corispermum lehmannianum Bunge is sensitive to both moderate and high temperatures. There were 4 groups of plant in response to light, i.e., 7 light responsed plants, 10 dark responsed plants, 6 light non-responsed plants and 5 plants of no germination. Based on seed germination speed of the 28 ephemeral plants, we divided them into 4 patterns of germination, i.e., very rapid, moderately rapid, moderate and slow. Combining variations of temperature, precipitation and sand dune types in the study area, we suggested that very rapid and moderately rapid germinated plants could be used to moving sand dunes in early spring during vegetation restoration, moderate germinated plants could be used to semi-fixed sand dunes in late autumn, and slow germinated plants could be used to sand plain in summer. Thus, seedling establishment and vegetation restoration would be improved by considering seed germination characteristics of these ephemeral plants in the Gurbantunggut Desert, China.     

The effect of crop,cultivation and seed addition for birds on surface weed seed densities in arable crops during winter

Weed seeds present an agronomic threat, but are also an important food resource for wildlife in winter. Weed seed densities on the soil surface in winter were examined from 1999 to 2002 in 105 fields on three different farms in UK. The effect of the preceding crop, cultivation, position within the field and the application of seed for birds (bird seed) on surface seed abundance and species composition was tested. Six or fewer species comprised c. 80% of the weed seeds. By January of each study year, the densities of seeds important for farmland birds (key seeds) were 73% or 87% lower compared with early winter on two of the farms, but were stable on the third where seeds were incorporated through cultivation. At the edge and mid‐field, seed densities only exceeded 400 m^?2 in 17%, 10% and 12% of fields for total, key and dicotyledonous seeds respectively. The preceding crop only affected seed densities at one site; stubbles of winter barley had fewer seeds compared with winter wheat or spring barley. Seed densities varied between the edge and mid‐field, but trends were inconsistent between sites. The density of the larger seeds (Atriplex patula, Viola arvensis, Polygonum aviculare and Chenopodium album) were reduced in fields receiving bird seed. The objectives of weed control and conservation may not be mutually exclusive because seed return was most reduced where the ground remained uncultivated through the winter, yet this also provided the best foraging opportunities for surface feeding seed predators.     

Comparative seed germination study across alien grapes (Vitis,Vitaceae) in Europe

Alien grape (Vitis, Vitaceae) species and recently described hybrids are recognised as major environmental weeds in southern Europe, based on their tendency to spread into natural and semi‐natural habitats, often behaving as invasive species. Despite a high number of agronomic, genetic and phytopathological studies on Vitis cultivars, regeneration from seed has been poorly investigated, although it plays a key role in plant distribution and evolution. To this end, in this study we exposed seeds of eight wild grapes in Europe (three species and five nothospecies, including the native Vitis vinifera), to different temperature treatments in the laboratory. Fresh seeds from all studied taxa were dormant and germinated only after cold and/or warm plus cold stratification, but showing significant differences between the species. Seeds of V. vinifera showed an intermediate complex morphophysiological dormancy, while all other tested Vitis taxa exhibited a deep complex morphophysiological dormancy. Dark conditions reduced the germination percentage in Vitis labrusca, Vitis riparia and V. vinifera and their hybrids, and alternating temperatures elicited the highest germination percentages in all populations. Our results demonstrated for the first time that Vitis hybrids are capable of regeneration by seed, even in the absence of dispersal by animals. The germination processes studied here help understand the current expansion of alien Vitis taxa in Europe outside the viticultural areas. Consequently, germination requirements contribute to a better understanding of the mechanisms underlying alien Vitis taxa establishment and invasion.     

低温层积和室温干燥贮藏对4种蒺藜科草本植物种子萌发的影响

研究了低温层积和室温干燥贮藏对河西走廊骆驼蒿(Peganum nigellastrum)、骆驼蓬(P.harmala)、驼蹄瓣(Zygophyllum fabago)和蝎虎驼蹄瓣(Z.mucronatum)蒺藜科4种草本植物种子萌发的影响.结果显示,贮藏条件对4种蒺藜科植物种子萌发率和萌发速率有极显著的影响(P<0.0...     

The influence of the soil management systems on aboveground and seed bank weed communities in olive orchards

The biodiversity of farmed landscapes is, in the context of agricultural intensification, a key aspect with regard to improving the sustainability of agroecosystems. Olive groves are undergoing rapid changes because of the spread of intensive farming systems, which may have negative environmental impacts. This paper reports a survey on the aboveground flora and seed banks in five olive groves located in Andalusia (Southern Spain). In this study, the following three management systems have been compared: no‐tillage, with the mowing of spontaneous weedy vegetation; no‐tillage, with the mowing of planted cover crops (Poaceae); and conventional tillage practices. Results showed that coverage and an abundance of vegetation are favored by spontaneous weedy vegetation with mowing management, while the richness of aboveground species was affected by landscape diversity and the presence of edges, which increases the richness and diversity of aboveground flora species in olive groves. Seed bank composition showed a low relationship with aboveground flora in the three cover crop management systems. The multivariate analysis performed pointed to those seed species that have a major influence on the aboveground flora communities of each of the three agricultural systems. The seed bank was clearly impoverished in terms of both abundance and species richness after the long‐term conventional tillage practices. We conclude that the intensive long‐term conventional tillage dramatically reduces weed communities in olive orchards and the subsequent ecosystem services provided by them.     

野老鹳草Geranium carolinianum种子的萌发条件

为明确野老鹳草Geranium carolinianum种子的休眠特性及萌发适宜的环境条件,采用培养皿法和盆钵法研究野老鹳草种子萌发和出苗适宜的条件,记录种子萌发数,计算种子萌发率、平均萌发时间及萌发指数。结果显示,野老鹳草具有较长的休眠期,新采集的野老鹳草种子在室温干储210 d后可以解除休眠;在10~25℃的恒温条件下种子萌发率均在93.8%以上;有无光照及光周期的长短对种子的萌发无影响;对酸碱度不敏感,在pH 4~10范围内种子萌发率均在91.3%以上;对水势具有一定耐受力,抑制50%种子萌发率所需的水势为-0.42 MPa;盐分对野老鹳草种子萌发具有一定抑制作用,当盐浓度达到160 mmol/L时基本不能萌发;此外,种子在土壤垂直深度5 cm以内时仍然可以出苗,对播种深度适应性较强。表明野老鹳草种子具有较长休眠期,土壤层积可解除种子休眠;而且野老鹳草种子对温度、光照、土壤酸碱度、播种深度适应性较强,水势及盐分对种子萌发有一定影响。     

Influence of environmental factors on seed germination and emergence of Iresine diffusa

Iresine diffusa has become more abundant under no‐till soyabean in Argentina. The influence of temperature, light, cold‐wet storage, osmotic potential, dry storage and depth of seed burial on germination and emergence of I. diffusa was examined in a growth chamber experiment. Iresine diffusa seeds germinated at the highest proportion (>0.80) in all fluctuating day/night temperatures tested. Conversely, under a constant temperature regime, maximum germination rates occurred at 15 (0.78) and 20°C (0.82), and minimum germination rates occurred at 10 (0.19) and 30°C (0.36). Seed germination was not influenced by light exposure. However, germination decreased after 12 (0.76) and 16 (0.65) weeks in cold‐wet storage. To reduce germination significantly, ?0.4 MPa of osmotic potential (induced by PEG‐6000) or 120 mmol L^?1 of salt (NaCl) concentration was required. Seeds of I. diffusa showed high viability (0.85) after 720 days of dry storage. Low emergence was recorded for seeds buried at 2 cm, and seedling emergence was completely inhibited when seeds were buried at 5 and 10 cm. Iresine diffusa seeds had high viability and were capable of emerging in a broad range of environmental conditions. The thermal germination conditions, shallow soil depths and high moisture conditions in germination phase for I. diffusa are congruent with the conditions in Argentina no‐tillage soyabean. Thus, no‐tillage could provide better conditions for germination than conventional tillage systems. However, due to the fact that I. diffusa can reproduce by rhizomes, further research should be conducted to understand the relative importance of the vegetative reproductive strategy in relation to the presence and persistence of this weed in fields.     

Effects of maternal light environment on germination and morphological characteristics of Sicyos deppei seeds

The effect was studied of sunlight and far-red (FR) light during seed development, on seed quality and germination of Sicyos deppei G. Don. Seeds exposed to FR during development were lighter in colour and their weight, size and water content were significantly lower. Less than 10% of non-scarified freshly harvested seeds germinated. Scarified, freshly harvested seeds developed under sunlight had a partially negative photoblastic response; both red (R) and FR light inhibited germination. The highest and fastest germination occurred in darkness, probably due to the effect of the high photon flux densities on the phytochrome during seed development. Scarified seeds ripened under FR light, germinated well in FR light and in darkness, but R light inhibited germination. After 6 months of storage, the permeability of S. deppei seeds increased, the partially negative photoblastic response was lost and germination of scarified seeds increased. Specifically, in seeds developed under FR, germination in darkness was faster than for the other light treatments, but slow in darkness for seeds developed under sunlight. The physiological and morphological heteroblastic responses in S. deppei probably extend its seed germination and seedling recruitment periods.     

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.