Seed treatments to overcome salt and drought stress during germination in sunflower (Helianthus annuus L.)

Maize is grown under a wide spectrum of soil and climatic conditions. Maize is moderately sensitive to salt stress; therefore, soil salinity is a serious threat to its production worldwide. Understanding maize response to salt stress and resistance mechanisms and overviewing management options may help to devise strategies for improved maize performance in saline environments. Here, we reviewed the effects, resistance mechanisms, and management of salt stress in maize. Our main conclusions are as follows: (1) germination and stand establishment are more sensitive to salt stress than later developmental stages. (2) High rhizosphere sodium and chloride decrease plant uptake of nitrogen, potassium, calcium, magnesium, and iron. (3) Reduced grain weight and number are responsible for low grain yield in maize under salt stress. Sink limitations and reduced acid invertase activity in developing grains is responsible for poor kernel setting under salt stress. (4) Exclusion of excessive sodium or its compartmentation into vacuoles is an important adaptive strategy for maize under salt stress. (5) Apoplastic acidification, required for cell wall extensibility, is an important indicator of salt resistance, but not essential for better maize growth under salt stress. (6) Upregulation of antioxidant defense genes and β-expansin proteins is important for salt resistance in maize. (7) Arbuscular mycorrhizal fungi improve salt resistance in maize due to better plant nutrient availability. (8) Seed priming is an effective approach for improving maize germination under salt stress. (9) Integration of screening, breeding and ion homeostasis mechanisms into a functional paradigm for the whole plant may help to enhance salt resistance in maize.

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Salt stress in maize: effects, resistance mechanisms, and management. A review

Chemical Priming of Plants Against Multiple Abiotic Stresses: Mission Possible?

Plants are exposed to any number of potentially adverse environmental conditions such as water deficit, high salinity, extreme temperature, submergence, etc. These abiotic stresses adversely affect the plant growth and productivity. Nowadays various strategies are employed to generate plants that can withstand these stresses. In recent years, seed priming has been developed as an indispensable method to produce tolerant plants against various stresses. Seed priming is the induction of a particular physiological state in plants by the treatment of natural and synthetic compounds to the seeds before germination. In plant defense, priming is defined as a physiological process by which a plant prepares to respond to imminent abiotic stress more quickly or aggressively. Moreover, plants raised from primed seeds showed sturdy and quick cellular defense response against abiotic stresses. Priming for enhanced resistance to abiotic stress obviously is operating via various pathways involved in different metabolic processes. The seedlings emerging from primed seeds showed early and uniform germination. Moreover, the overall growth of plants is enhanced due to the seed-priming treatments. The main objective of this review is to provide an overview of various crops in which seed priming is practiced and about various seed-priming methods and its effects.

Seed priming for abiotic stress tolerance: an overview

The effects of salt and drought stresses at the water potentials of -2, -4, -6 and -8 bars induced by NaCl and PEG 6000 (polyethylene glycol 6000) each, on germination and early seedling growth, were investigated for 3 pea cultivars (Bolero, Sprinter and Utrillo). Electrical conductivity (EC) values of the NaCl solutions were 4.5, 8.8, 12.7 and 16.3 dS m-1. Germination percentage, mean germination time, root and shoot length, and seedling fresh and dry weight were measured in the study. The objective was to determine genotypic differences among pea cultivars in terms of salt and drought stress and to determine factors (salt toxicity or osmotic stress due to PEG) inhibiting seed germination. The germination results revealed that the genotypes significantly differed for salt and drought stress. Bolero appeared to be more tolerant to salt stress, but Sprinter cv. gave higher values under drought stress. Both NaCl and PEG inhibited germination and seedling growth in all cultivars, but the effects of NaCl compared to PEG were less on germination and seedling growth. All cultivars were able to germinate at all NaCl levels without a significant decrease in germination, while a drastic decrease in germination was recorded at -6 bars of PEG. It was concluded that inhibition in germination at equivalent water potentials of NaCl and PEG was mainly due to an osmotic effect rather than salt toxicity.

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Effects of Salt and Drought Stresses on Germination and Seedling Growth of Pea (Pisum sativum L.)

Seeds of six soyabean (Glycine max (L.) Merr.) cultivars were germinated between paper towels moistened with a range of solutions of both NaCI (32.2 to 421.1 mmolal NaCI) and polyethylene glycol (PEG, 5-30% w/v). The solutions of NaCI and PEG used had the same water potentials within the range -0.23 to -1.9 MPa. After 8d the ungerminated seeds were transferred to towels moistened with deionised water for 7d. Cultivars differed in their response to salinity and failure of seeds to recover from high salinity when transferred to deionised water, revealed the toxicity of NaCl. In contrast, the increase in germination during the recovery period after exposure to PEG suggested that PEG was not toxic. At the same external water potential, the lower mean germination time (MGT) and higher final germination in NaCl than in PEG could be explained by the more rapid imbibition in NaCl solutions and achievement of a moisture content that allowed germination. The influence of seed vigour on the response of soyabean to stress was examined using seeds having high percentage germination but a range of seed vigour, produced by rapid ageing at 15% moisture content (MC) and 45°C for up to 9h. The germination of aged seeds having reduced vigour fell with increased salinity (330, 421 mmolal NaCI) but there was no significant interaction between salinity and seed ageing. Transfer of unaged and aged seeds to 0 MPa after exposure to NaCI resulted in a greater increase in the germination of unaged seeds. The negative correlation of seed leachate conductivity and MGT with the increase percentage germination after transfer to 0 MPa suggested that seed vigour influences the ability of seeds to recover from saline conditions.

The interaction between salinity stress and seed vigour during germination of soyabean seeds

Early counts of radicle emergence during germination as a repeatable and reproducible vigour test for maize.

Summary In this brief review, the use of wild flower seeds is described as a contribution to the enhancement of biodiversity and as a way of improving grassland and other plant communities. Ecological concerns about sowing seeds in locations that are climatically contrasted to the countries from which the seed is sourced are discussed. Characteristics that aid the spread and survival of normally uncultivated species create difficulties in seed production and use. Establishment of a crop for seed production and subsequent weed control can be troublesome and procedures to achieve these have been developed based on experience. Harvesting methods are selected and modified to suit the maturity and dispersal characteristics of different species. Drying and processing, to ensure the removal of a large proportion of the unwanted material, such as appendages that aid wind dispersal, insect parts and weed seeds, can consist of as many as 10stages for some species. As the final stage in production, seed quality cont...

Scottish wildflower seeds: Production and use

Experimental approach influences soybean (Glycine max L.)seed and seedling response to salinity

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A.A. Powell

Papers

The interaction between salinity stress and seed vigour during germination of soyabean seeds

Early counts of radicle emergence during germination as a repeatable and reproducible vigour test for maize.

Scottish wildflower seeds: Production and use

Experimental approach influences soybean (Glycine max L.)seed and seedling response to salinity

The effects of reduced water availability and salinity on the early seedling growth of Soybean