Rapid seed germination and stand establishment are critical factors to crop production under salt‐stress conditions. In many crop species, seed germination and early seedling growth are the most sensitive stages to salinity stress. Salinity may delay the onset, reduce the rate, and increase the dispersion of germination events, leading to reductions in plant growth and final crop yield. The adverse effects of salt‐stress can be alleviated by various measures, including seed priming (a.k.a. pre‐sowing seed treatment). The general purpose of seed priming is to partially hydrate the seed to a point where germination processes are begun but not completed. Most priming treatments involve imbibing seed with restricted amounts of water to allow sufficient hydration and advancement of metabolic processes but preventing germination or loss of desiccation tolerance. Treated seeds are usually redried before use, but they would exhibit rapid germination when re‐imbibed under normal or stress conditions. Various seed priming techniques have been developed, including hydropriming (soaking in water), halopriming (soaking in inorganic salt solutions), osmopriming (soaking in solutions of different organic osmotica), thermopriming (treatment of seed with low or high temperatures), solid matrix priming (treatment of seed with solid matrices), and biopriming (hydration using biological compounds). Each treatment has advantages and disadvantages and may have varying effects depending upon plant species, stage of plant development, concentration/dose of priming agent, and incubation period. In this article, we review, evaluate, and compare effects of various methods of seed priming in improving germination of different plant species under saline and non‐saline conditions. We also discuss the known metabolic and ultra‐structural changes that occur during seed priming and subsequent germination. To maximize the utility of various seed priming techniques, factors affecting their efficiency must be examined and potential benefits and drawbacks determined. For example, quality of the seed before treatment, concentration/dose of priming agent, time period for priming, and storage quality of the seed following priming treatment must be carefully determined. Furthermore, such assessments must be based on large‐scale experiments if seed priming is to be used for large‐scale field planting. A better understanding of the metabolic events that take place in the seed during priming and subsequent germination will improve the effective application of this technology. The incorporation of advanced molecular biology techniques in seed research is vital to the understanding and integration of multiple metabolic processes that can lead to enhanced seed germination, and consequently to improved stand establishment and crop yield under saline and non‐saline conditions.

Pre‐Sowing Seed Treatment—A Shotgun Approach to Improve Germination, Plant Growth, and Crop Yield Under Saline and Non‐Saline Conditions

The study was conducted to determine whether salt tolerance could be induced in maize at germination stage by soaking of seeds for 8 h in distilled water or in 200 meq·L−1 of NaCl, KCl, CaCl2·2H2O. Both primed and un-primed seeds were subjected for 14 days to 0, 100 or 200 mol·m−3 NaCl under controlled conditions. Although all priming agents were effective in alleviating adverse effects of salt stress on maize at germination stage, CaCl2·2H2O proved to be more effective since the seeds primed with this salt had significantly higher final germination, rate of germination and fresh and dry weights of plumules and radicles than those treated with other salts or distilled water. Concentration of Na+, K+ and Ca2+ increased significantly in all parts of germinating seeds of maize seeds primed with NaCl, KCl, or CaCl2·2H2O, respectively. In addition, seeds primed with CaCl2·2H2O were the highest in Cl− accumulation in all parts of the germinating seeds, followed by seeds treated with NaCl and KCl. Most of the Ca2+ was retained in seeds and mesocotyl, because of which, transport of this ion to plumules and radicles was low.

Inducing salt tolerance in maize (Zea mays L.) through seed priming with chloride salts: Growth and ion transport at early growth stages

Time-course changes in the inorganic and organic components of germinating sunflower achenes under salt (NaCl) stress

Germination of Seeds and Propagules Under Salt Stress

Drought and salt stress, together with low temperature, are major problems for agriculture because these adverse environmental factors prevent plants from realizing their full genetic potential. Salt stress afflicts agriculture in many parts of the world, particularly irrigated lands [4]. Compared to salt stress, the problem of drought is even more pervasive and economically damaging [1; 3]. Temperature and precipitation are key determinants of climate. The Koppen Climate Classification System recognizes five major climatic types: A, Tropical Moist Climates; B, Dry Climates; C, Moist Mid-latitude Climates with Mild Winters; D, Moist Mid-latitude Climates with Cold Winters; and E, Polar Climates. The Dry Climates are easily recognized (a desert is after all a desert) but water-limited environments can be difficult to classify precisely [30]. Meigs [30] developed a widely used system for classifying water-limited environments based upon mean precipitation. Extremely arid lands have at least 12 consecutive months without rainfall, arid lands have less than 250 mm of annual rainfall, and semiarid lands have a mean annual precipitation of between 250 and 500 mm.

/pdf/abiotic-stress-tolerance-in-plants-with-emphasizing-on-17twpp8sqy.pdf

Abiotic Stress Tolerance in Plants with Emphasizing on Drought and Salinity Stresses in Walnut

Osmotic and ionic effects of NaCl were investigated in germinating wheat. Approximately isotonic solutions of NaCl and sorbitol inhibited germination and seedling growth to similar degrees. When dry kernels were pre-imbibed in salt for 24 h and then transferred to water, germination was equivalent to that of kernels imbibed continuously in water and the development of embryos was delayed to about the same extent as kernels pre-imbibed in sorbitol for 24 h. Measurements of water uptake, respiration, biosynthetic activities and rubidium uptake in embryos dissected from grains imbibed in NaCI or sorbitol for the first 24 h demonstrated that salt supplied to dry kernels closely mimicked sorbitol in counteracting the reactivation of embryo metabolism. No toxic effects of salt were observed when dry kernels were pre-imbibed in very high NaCI concentrations for 24 h and then transferred to water, even though embryo sodium contents increased considerably. Ultrastructural observations of embryo tissue further showed that salt influx into dry grains did not produce ion-specific damage in cell organization. On the other hand, salt specific effects became evident when the 24 h salt exposure was applied to kernels pre-hydrated for 24 h and, even more, for 30 h. We conclude that in wheat the inhibition of germination by salt corresponds to that induced by an osmoticum, provided that the caryopsis has not reached the stage of germination associated with active embryo expansion.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0960258500000738

T. Bleve-Zacheo

Papers

The sensitivity of germinating Triticum durum L. kernels to saline environment