Because most processes related to seed germination and seedling emergence occur in the soil and within a very short time (from a few days to a few weeks, depending on the species and sowing date), understanding of what really occurs during this phase and which factors are involved is a challenging task. How can we tackle this complexity and which tools can be developed and mobilized to this objective?
Seed germination , which determines when the plant enters natural or agricultural ecosystems, is a crucial process in the seed plant life cycle and the basis for crop production. The germination of freshly produced seeds is inhibited by primary dormancy, which helps the seeds equip for environments with unfavorable conditions [1–3] . The seeds will enter a germinating state from the dormant state at an appropriate time when the dormancy is lost through moist chilling (stratification) or after-ripening  . Therefore, seed germination is a accurately timed checkpoint to avoid unsuitable weather and unfavorable environments during plant establishment and reproductive growth  . Finally, seed germination in crops will affect seedling survival rates and vegetative growth, which are accordingly associated with ultimate yield and quality. Considering agronomic production, crop cultivars must be prepared for rapid and uniform germination at sowing, which will improve the crop yield and quality; however, this selection during crop breeding usually results in weak dormancy, which is one of the factors leading to PHS in the rainy season, which tends to overlap with the harvest season [6, 7] . Hence, to improve crop agronomic performance, the crop cultivars during breeding must be prepared for uniform and rapid germination at sowing while preventing PHS [7a] .
Seed germination and seedling establishment are highly sensitive to deficit soil moisture conditions. Although management practices can mitigate such stress, it would be appropriate to develop varieties with intrinsic stress tolerance through rapid imbibition rates. Seed germination in finger millet takes 2–3 days both for laboratory germination and field emergence under adequate moisture conditions. During seed germination under rainfed monsoon conditions, the average soil evaporation would be nearly 3–4 mm d − 1 and seed is placed 2 cm deep, within 2 days after sowing, soil moisture in top layer will be depleted; hence rapid imbibition is necessary for seed germination. The rate of imbibition in rainfed soil will be low and seed germination will be inhibited, hence, it is necessity to determine the optimum soil moisture content required for establishment of crop stand for a given soil. Although, dry conditions for sowing can be managed by way of transplanting, under rainfed conditions, transplanting shock will be high and practically difficult when large area need to be planted, hence direct sowing under optimal conditions would be apt for rainfed situations. Therefore, identification of genotypes suitable to rainfed conditions can be identified both under in vitro and field conditions. The simulated drought conditions can be provided using polyethylene glycol (6000 or 8000 MW) which prevents the entry of water into cell wall of the seed coat, thereby creates drought condition. Further, gravimetric approach using pot culture would be more appropriate that simulate field conditions. Identification of specific trait of rapid seed germination through higher imbibition rates, solute concentration of seed, and incorporation of such traits into ruling varieties would be relevant for drought escape.
Research and innovation priorities as defined by the Ecophyto plan to address current crop protection transformation challenges in France
Jay Ram Lamichhane , . Pierre Ricci , in Advances in Agronomy , 2019
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Seed germination and seedling growth are preconditions for conservation of genetic resources and sustainable uses of different products of specific species which depends on perception of genetic inconsistency, evolutionary forces, and breeding system in tree improvement ( Azad et al., 2014 ). Tamarind is commonly grown from seeds. It can also be grown from vegetative propagation (macrovegetative propagation or micropropagation). Vegetative propagation is useful for conservation of different genotypes. Germination from seed is inexpensive and very important for rural tree breeders. It can be used as root stocks to produce large number of grafted ortet. Tamarind seed germination is influenced by different presowing treatments. Different researchers noticed various responses according to the different methods used. Seed germination required 7–20 days in controlled conditions ( Azad et al., 2013 ). It can vary by seed sources, climatic requirements, and cultivars as well. On an average, it starts to germinate from 13 days of seed sowing. Sometimes it may take 30 days to complete the germination process. El-Siddig et al. (2001) recommended 45 days to allow for maximum seed germination. Azad et al. (2013) noticed 58% seed germination in the control situation, and noticed that presowing significantly enhanced seed germination. They found almost 82% seed germination in cold water treatment (immersion in cold water for 24 h at 4°C) and scarification with sand paper. El-Siddig et al. (2001) noticed acid treatment (immersion of seeds in 97% sulfuric acid for 45 min at room temperature) is an effective method for rapid and synchronous germination of tamarind.
The seed grows, and the radicle, or first stage of the root, emerges from the seed. Finally, the first little shoot comes out of the seed with cotyledons, the first two leaves, and photosynthesis can begin.
Specific seed germination requirements vary depending on the plant species. But they generally include water, air, temperature, and ultimately access to light. It helps to know the specific needs for the plants you’re working on to optimize germination. Fall too far outside the requirements and you’ll either get no seeds germinating, or only a portion.
The process of germination is when a seed comes out of dormancy, the time during which its metabolic activity is very slow. Germination begins with imbibition, a big word for taking in water. This is the major trigger to start the period of waking up from dormancy.
What Causes Seed Germination?
As the seed takes in water, it gets bigger and produces enzymes. The enzymes are proteins that ramp up metabolic activity in the seed. They break down the endosperm, which is the seed’s store of food, to provide energy.
Germination is essential for what we do as gardeners. Whether starting plants from seeds or using transplants, germination has to happen for gardens to exist. But many of us take this process for granted and don’t fully understand the factors affecting germination of seeds. By learning more about the process and what seeds need, you can get better results in the garden.
Understanding seed germination requirements is important for growing plants successfully from seed. Know what your seeds need before you get started so you will get a greater percentage germinating and growing into seedlings.
Hoyle, G. L., Steadman, K. J., Daws, M. I., and Adkins, S. W. (2008b). Pre-and post-harvest influences on seed dormancy status of an Australian Goodeniaceae species, Goodenia fascicularis. Ann. Bot. 102, 93–101. doi: 10.1093/aob/mcn062
Of all the ecological correlates that we considered, only those directly associated with seed traits were significantly correlated with germination strategy regardless of whether we assessed the correlation at the level of two major clusters (postponed vs. immediate germination), or at the level of three or four clusters, or whether we accounted for phylogenetic structure or not (Table 2). Species with postponed germination had heavier seeds and were more likely to be endospermic compared to those of species that germinated immediately (Figure 4). Species with staggered germination were intermediate in seed mass and endospermy. However, not all seed characteristics were correlated with germination strategy: there was no correlation between light requirements for seed germination and strategy. Contrary to our expectations, species with higher specific leaf area (potentially indicative of higher growth rates) were not more likely to exhibit immediate germination. Likewise, species with higher average elevation or smaller elevation ranges were not more likely to exhibit postponed germination.
Costin, A., Gray, M., Totterdell, C., and Wimbush, D. (2000). Kosciuszko Alpine Flora. Collingwood, VIC: CSIRO Publishing.
Variation in Germination Strategy
1. Seed germination strategies vary dramatically among species but relatively little is known about how germination traits correlate with other elements of plant strategy systems. Understanding drivers of germination strategy is critical to our understanding of the evolutionary biology of plant reproduction.
Baskin, C. C., and Baskin, J. M. (2004). Germinating seeds of wildflowers, an ecological perspective. Horticult. Technol. 14, 467–473.
Mature seeds of 54 species from 16 families and 37 genera were collected between January and April 2009, 2010, and 2011 (see Table 1 for full names and authorities. Vouchers were lodged at the Australian National Herbarium, Canberra). In total the species represented more than a quarter of the Australian angiosperm flora found in alpine regions (Costin et al., 2000, see Table 1), though many of these species extend to below treeline as well. The viability of all collections was estimated prior to sowing in experimental germination conditions using the tetrazolium chloride (TZ) staining technique (International Seed Testing Association, 2003). For more details on collection and processing see Appendix A in Supplementary Material.
Overall, seed viability and final germination percentage were high. Mean TZ-estimated viability across all collections was 80 ± 1.7%, with more than two thirds of collections exhibiting more than 75% viability (Table 1). There was no difference in the quality of collections across the 3 years (mean viability in 2009, 2010, and 2011 was 79 ± 2.8, 80 ± 2.7, and 81 ± 3.7%, respectively), indicating that the banking of seeds collected in 2009 did not lessen their viability.