Seed Priming: An Interlinking Technology between Seeds, Seed Germination and Seedling Establishment

Biologically seed is a small embryonic plant along with either endosperm or cotyledons, enclosed with in an outer protecting covering called seed coat. During the time of seed development large metabolic conversions take place, including proper partitioning of photo-assimilates and the formation of complex polymeric forms of carbohydrate, protein and fats for storing as seed reserves. In developing phase of seeds, every detail information stored in the embryonic plant are genetically and sometimes epigenetically also predetermined and influenced by various environmental/external factors already faced by the mother plant. In the growth cycle of plants, seed germination and seedling establishment are the two critical phases where survivability of the seedlings in natural habitats is a matter of question until the onset of photosynthesis by the established seedling. The various sequence of complex processes known to occur in both the phases i.e., an array of metabolic activities are initiating which eventually leads to the renewal of embryo growth of the dormant seeds and ultimately seedlings are established. Efficient seed germination is an important factor for agricultural sciences and successful establishment of germinated seedling requires a rapid and uniform emergence and root growth. With these aspects of seed physiology kept in mind the present chapter will be designed in such a way where, a gap filling, inter linking, eco- and farmers\' friendly technology i.e., ‘seed priming’ (a pre-sowing partial hydration of seeds) will be considered to improve the rate and uniformity of germination and seedling establishment. Under optimal and adverse environmental conditions, the primed seeds of diversified species lead to an enhanced germination performance with increased vigor index has been reported by various scientists which indicates a good establishment of seedlings in the field and thereafter enhance the performance of crops as a whole.

Biological and economic values of Dipterocarpaceae, the main timber forest product of Indonesia

Dipterocarpaceae is known as a very important tree family both biologically and economically. Its distribution around the world covers the areas of Peninsular Malaysia, the Philippines, Sumatra, Kalimantan, Java, Sulawesi, Maluku to Papua. Dipterocarpaceae family has a high economic value, such as producing wood, balsam, resin, charcoal, fat, fruit, bark, essential oil, and camphor. Its products have very important roles for domestic use and export needs. As representatives of Dipterocarpaceae, the economic value of Shorea Roxb. ex Gaertner f, Dipterocarpus Gaertner f, and Dryobalanops Gaertner f will be discussed. Considering the very important role of Dipterocarpaceae, both biologically and economically, it is necessary to handle it sustainably, through the following actions such as conservation of genetic resources, seed physiology, seed handling, seedling ecology, root symbiosis and nutrition, pest and disease, management of natural forest, and plantation, and also non-timber forest product from Dipterocarpaceae. Dipterocarpaceae dikenal sebagai famili pohon yang sangat penting baik secara biologis maupun ekonomis. Penyebarannya di seluruh dunia meliputi wilayah Semenanjung Malaysia, Filipina, Sumatera, Kalimantan, Jawa, Sulawesi, Maluku hingga Papua. Famili Dipterocarpaceae memiliki nilai ekonomi yang tinggi, seperti menghasilkan kayu, balsam, damar, arang, lemak, buah, kulit kayu, minyak atsiri, dan kapur barus. Produk-produknya memiliki peran yang sangat penting untuk kebutuhan domestik dan ekspor. Sebagai perwakilan Dipterocarpace, nilai ekonomi Shorea Roxb. ex Gaertner f, Dipterocarpus Gaertner f, dan Dryobalanops Gaertner f akan dibahas. Mengingat peranan Dipterocarpaceae yang sangat penting, baik secara biologis maupun ekonomis, maka perlu dilakukan penanganan secara berkelanjutan, melalui tindakan-tindakan seperti konservasi sumber daya genetik, fisiologi benih, penanganan benih, ekologi semai, simbiosis dan nutrisi akar, hama dan penyakit, pengelolaan hutan alam, dan perkebunan, serta hasil hutan bukan kayu dari Dipterocarpaceae.

Acceleration in Germination Sensu stricto Plays a Central Role on Seedling Vigor in Post-Germination

An obvious relationship between germination sensu stricto and seedling development during post-germination has been considered, but not explained concerning vigor. Taking this into account, we used measurements of water dynamics in germinating seeds and seedling development to clarify that relationship. The biological model was soybean seeds, since it is the most relevant ‘true seed’ produced around world. Our findings suggest that the way energy is used (acceleration) and not its input (velocity) is the main aspect relating seed germination and seedling development, especially when considering vigor. However, velocity and acceleration can be complementary in analyses of seed physiology. Other measurements proposed here also have potential uses for testing vigor in seed lots, such as seedling vigor index and biological activity in the lot. Therefore, water dynamics in germinating seeds can be an interesting way for testing seed lots, because it is an easier, faster and cheaper method in relation to other non-destructive procedures.

A New Role for Plastid Thioredoxins in Seed Physiology in Relation to Hormone Regulation

In Arabidopsis seeds, ROS have been shown to be enabling actors of cellular signaling pathways promoting germination, but their accumulation under stress conditions or during aging leads to a decrease in the ability to germinate. Previous biochemical work revealed that a specific class of plastid thioredoxins (Trxs), the y-type Trxs, can fulfill antioxidant functions. Among the ten plastidial Trx isoforms identified in Arabidopsis, Trx y1 mRNA is the most abundant in dry seeds. We hypothesized that Trx y1 and Trx y2 would play an important role in seed physiology as antioxidants. Using reverse genetics, we found important changes in the corresponding Arabidopsis mutant seeds. They display remarkable traits such as increased longevity and higher and faster germination in conditions of reduced water availability or oxidative stress. These phenotypes suggest that Trxs y do not play an antioxidant role in seeds, as further evidenced by no changes in global ROS contents and protein redox status found in the corresponding mutant seeds. Instead, we provide evidence that marker genes of ABA and GAs pathways are perturbed in mutant seeds, together with their sensitivity to specific hormone inhibitors. Altogether, our results suggest that Trxs y function in Arabidopsis seeds is not linked to their previously identified antioxidant roles and reveal a new role for plastid Trxs linked to hormone regulation.

A comparative study on seed physiology and germination requirements for 15 species of Eucalyptus

Seed physiology of 15 Eucalyptus species of interest for cut foliage plantations was unknown and therefore evaluated. The viability and vigour of seeds and germination potential of 15 Eucalyptus species was determined by using a tetrazolium (TZ) staining test, and the results were compared to a germination test. In a separate experiment, seeds of each lot were subjected to either 0 or 4-week cold stratification at 4 ± 1 °C to investigate their potential stratification requirement. After stratification, seeds were then allowed to germinate at 22 ± 1 °C with 16 h lighting per day for 36 days. Seed viability and vigour were checked by evaluating % root, cotyledon and first true leaves emergence, and the speed of emergence, in the germination test. The germination percentages varied with the species. Seed stratification with the interaction of seed species lots significantly affected both viability and vigour. The seed viability of the different species ranged from 9 to 100% and 2 to 100%, for the TZ test and germination test, respectively, with a high correlation (R2 = 0.89) between the two. Physiology tests revealed that cold stratification of seed was not required for the 15 species to maximise their germination potential and growth in Irish and British climate.

Physiological potential of Dyckia spp. bromeliad seeds under different temperatures

Bromeliads have been gaining ground in the economic scenario due mainly to their use as ornamental plants. Bromeliads of the genus Dyckia exhibit different morphologies, and therefore, have relevance in this market. However, some species are threatened due to the extraction of plants from their natural environments. Many of these species are endemic and native to Brazil and there are few studies on their seed physiology; hence, expansion of research into this topic is essential. An alternative for the preservation of such plants is the production of seedlings using seeds. To this end, the objective of this work was to evaluate the physiological potential of seeds of Dyckia brevifolia, Dyckia beateae, and Dyckia excelsa at different temperatures, and determine the number of days to carry out the tests. A completely randomized design was adopted, with three species of Dyckia, analyzed separately, and four temperatures (20, 25, 30, and 35 °C). The following were evaluated: first germination count, germination, germination speed index, length of seedling, and seedling dry weight. The data were analyzed using the Sisvar software for normality and homogeneity, and when the assumptions were met, they were subjected to analysis of variance using the F test (p < 0.05) and the means were compared using the Tukey test at 5% probability. Seeds of D. excelsa emit the radicle more quickly at 20 and 35 °C; however, temperatures of 25 and 30 °C provide better conditions for seedling growth and development. The greatest vigor of D. brevifolia seeds is observed at temperatures of 30 and 35 °C. Seeds of D. beateae emit the radicle more quickly at 20 °C, and the largest seedlings are observed at 35 °C. The first germination count of D. brevifolia, D. beateae, and D. excelsa should be evaluated on the third day after sowing. The germination evaluations for D. excelsa and D. beateae should be carried out on the ninth day after sowing, and those for D. brevifolia on the sixth day after sowing.

Why Seed Physiology Is Important for Genebanking

Genebank management is a field in its own right; it is multifaceted, requiring a diverse set of skills and knowledge. Seed physiology is one area that is critical to the successful operation of seed genebanks, requiring understanding of seed quality during development and maturation, seed dormancy and germination, and seed longevity in storage of the target species. Careful management of the workflow between these activities, as seeds move from harvest to storage, and the recording and management of all relevant associated data, is key to ensuring the effective conservation of plant genetic resources. This review will discuss various aspects of seed physiology that genebank managers should be aware of, to ensure appropriate decisions are made about the handling and management of their seed collections.