The seed is the fundamental unit of the dispersal of dry, dehiscent fruits, in which the fruit splits open at maturity to allow for seed dispersal. However, dry fruits may be indehiscent and therefore represent the dispersal unit (DU). Cereals possess a one-seeded fruit, whereby the seed coat and the fruit coat are fused together to generate the caryopsis. This caryopsis may be covered by floral bracts to generate two types of DUs, namely florets, whereby the caryopsis is enclosed by the lemma and the palea (e.g., Avenasterilis) or spikelet, whereby the floret(s) is further covered by the glumes (Triticum turgidum var. dicoccoides). Here, we highlight the dead coverings enclosing the caryopsis in cereals, namely the husks as an integral component of the dispersal unit that play multifaceted roles in grain biology. Thus, besides protection and dispersal means, the husks function as a rich maternal supply of proteins and metabolites for enhancing growth and development, combat potential pathogens as well as confer tolerance to abiotic stresses. These attributes might have broad implications for crop performance, plant population dynamics and diversity in ecological systems, and for conservation of genetic resources in seed banks.
Soil seed banks may offer great potential for maintaining and restoring desert ecosystems that have been degraded by climate change and anthropogenic disturbance. However, few studies have explored the year-to-year dynamics in the species composition (richness and abundance) of these desert soil seed banks. Thus, we conducted a 4-year study to assess the effects of environmental factors (meteorology and microtopography) and aboveground vegetation on the soil seed bank of the Tengger Desert, China.
We found the seed bank was dominated by annual herb species both in species richness and abundance. More rainfall in the growing season increased the number of seeds in the soil seed bank, and quadrat micro-elevation had a negative effect on soil seed bank size. The species composition in the seed bank had significantly larger between-year similarity than that in the aboveground vegetation due to the dominance of annual herb species. For different life forms, the species composition of annual herbs showed distinctly larger temporal similarity between the aboveground vegetation and the seed bank compared with perennial herbs and shrubs.
Our findings highlight that the combined effects of environmental factors and plant life forms determine the species composition (especially the abundance) of soil seed banks in deserts. However, if degraded desert ecosystems are left to regenerate naturally, the lack of shrub and perennial herb seeds could crucially limit their restoration. Human intervention and management may have to be applied to enhance the seed abundance of perennial lifeforms in degraded deserts.
Indigenous seeds are grown by the farmers over the years with a strong influence from local natural factors. Such seeds have a higher level of intrapopulation variations and the capacity of buffering the adverse factors. Understanding indigenous seeds along with their diversity are useful to diversify their uses, to assess conservation status, to know the factors making farming areas red zone, and to improve their performance. Selection is the simplest and most common method for the improvement of crop varieties. The variation must be created and maintained to impose selection. Different types of selection can be considered depending on the mode of reproduction of crops. Response to selection and correlated response are estimated to make the selection process more effective. Many different selection approaches can target either developing monomorphic or polymorphic varieties. There are five selection units and can be applied in five crop stages. Farmers’ criteria need to be considered during selection process. Based on the genotypic classes, there are three types of selection namely stabilizing selection, directional selection, and disruptive selection. The most simple and common selection methods are pure lines, mass selection, and class-bulking selection. Orthodox seeds in short, medium, and long-term storage facilities are conserved as a seed bank. Major types are household seed banks, community seed banks, national seeds, natural seed banks, and global seed banks. A seed bank is for assuring the availability of crop diversity for research, study, and production. The common works in seed banks are diversity collection, regeneration, characterization, multiplication, and distribution along with online database management.
AbstractSoil seed banks represent a critical but hidden stock for potential future plant diversity on Earth. Here we compiled and analyzed a global dataset consisting of 15,698 records of species diversity and density for soil seed banks in natural plant communities worldwide to quantify their environmental determinants and global patterns. Random forest models showed that absolute latitude was an important predictor for diversity of soil seed banks. Further, climate and soil were the major determinants of seed bank diversity, while net primary productivity and soil characteristics were the main predictors of seed bank density. Moreover, global mapping revealed clear spatial patterns for soil seed banks worldwide; for instance, low densities may render currently species-rich low latitude biomes (such as tropical rain-forests) less resilient to major disturbances. Our assessment provides quantitative evidence of how environmental conditions shape the distribution of soil seed banks, which enables a more accurate prediction of the resilience and vulnerabilities of plant communities and biomes under global changes.
This review explores ways that cover crops alter soil environmental conditions that can be used to decrease seed survival, maintain weed seed dormancy, and reduce germination cues, thus reducing above-ground weed pressures. Cover crops are grown between cash crops in rotation, and their residues persist into subsequent crops, impacting weed seeds both during and after cover crops’ growth. Compared to no cover crop, cover crops may reduce weed seedling recruitment and density via: i) reducing soil temperature and fluctuations thereof; ii) reducing light availability and altering light quality; and iii) trapping nitrogen in the cover crop, thus making it less soil-available to weeds. In addition, cover crops may provide habitat for above- and below-ground fauna, resulting in increased weed seed predation. The allelopathic nature of some cover crops can also suppress weeds. However, not all effects of cover crops discourage weeds, such as potentially increasing soil oxygen. Furthermore, cover crops can reduce soil moisture while actively growing but conserve soil moisture after termination, resulting in time-dependent effects. Similarly, decaying legume cover crops can release nitrogen into the soil, potentially aiding weeds. The multiplicity of cover crop species and mixtures, differing responses between weed species, environmental conditions, and other factors hampers uniform recommendations and complicates management for producers. But, cover crops that are managed to maximize biomass, do not increase soil nitrogen, and are terminated at or after cash crop planting will have the greatest potential to attenuate the weed seed bank. There are still many questions to be answered, such as if targeting management efforts at the weed seed bank level is agronomically worthwhile. Future research on cover crops and weed management should include measurements of soil seed banks, including dormancy status, predation levels, and germination.
Highlights - Cover crops alter the weed seed bank environment, influencing survival, dormancy, and germination. - Weed seed germination may be reduced by decreased temperature and fluctuations thereof, light, and soil nitrogen. - Weed seed germination may be increased by greater soil moisture, soil nitrogen, and oxygen. - Management should maximize cover crop biomass, decrease soil nitrogen, and delay termination for the greatest potential. - Future research should include measurements of weed seed banks, including dormancy status, predation, and germination.
Weeds are one of the problems in rice plants, so the presence of weeds in rice fields must be controlled. Different ways of managing weeds on agricultural land can affect the seed bank of weeds in the soil. This study aims to determine differences in weed seed banks due to differences in weed management, especially the use of herbicides in lowland rice. The study was conducted at the Agricultural Training and Development Research Center, Faculty of Agriculture, Padjadjaran University, Bandung Regency, Indonesia from May–July 2020. The study used a paddy field plot consisting of intensive, less intensive use of herbicides and non-herbicide use. This research was conducted with survey and descriptive methods to see the type and composition of weeds at a certain depth and to see differences in seed banks. Observations were made including analysis of weed vegetation, community coefficients, weed diversity, weed dominance and differences in seed bank from depth. The results showed that there were 7 weed species found, namely Rorippa palustris, Monochoria vaginalis, Leptochloa chinensis, Echinochloa crus-galli, Eclipta prostate, Lindernia procumbens, and Marchantia polymorpha. Weed management with herbicides is proven to reduce weed populations that grow.
There is a pressing need to conserve plant diversity to prevent extinctions and to enable sustainable use of plant material by current and future generations. Here, we review the contribution that living collections and seed banks based in botanic gardens around the world make to wild plant conservation and to tackling global challenges. We focus in particular on the work of Botanic Gardens Conservation International and the Millennium Seed Bank of the Royal Botanic Gardens, Kew, with its associated global Partnership. The advantages and limitations of conservation of plant diversity as both living material and seed collections are reviewed, and the need for additional research and conservation measures, such as cryopreservation, to enable the long-term conservation of ‘exceptional species’ is discussed. We highlight the importance of networks and sharing access to data and plant material. The skill sets found within botanic gardens and seed banks complement each other and enable the development of integrated conservation (linking in situ and ex situ efforts). Using a number of case studies we demonstrate how botanic gardens and seed banks support integrated conservation and research for agriculture and food security, restoration and reforestation, as well as supporting local livelihoods.