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Drought and temperature stresses are known as primary factors limiting germination and seedling growth. Seed priming with plant growth regulators is one of the popular approaches to minimize adverse environmental stresses. This study was carried out to examine the role of seed priming with 5-aminolevulinic acid (5-ALA) at different levels (0, 25, 50, and 100 mg L-1) in germination and seedling growth of three wheat (Triticum aestivum L.) 'Emam', 'Gomria', and 'Zakia' under high temperature and drought stresses using a range of temperatures (25, 30, and 35 °C) and water potentials (0.0 and -0.5 MPa). Water uptake, germination and early seedling growth attributes were measured. Drought stress and high temperature decreased germination%, germination index, and shoot fresh weight by 39.2%, 35.4%, and 48.6%, respectively, as compared with 0.0 MPa and 25 °C. Seeds of 'Zakia' primed with 50 mg L-1 5-ALA at -0.5 MPa, and 35 °C increased fresh and dry weights of the root by 19.8% and 68.4% relative to 0 mg L-1. For interaction between variety and 5-ALA, the highest germination% (90.3%) was recorded in 'Emam' with 50 mg L-1 5-ALA. Treatment 100 mg L-1 5-ALA decreased mean germination time by 24.5% and 28.9% at 25 and 35 °C, respectively; 50 mg L-1 5-ALA increased seedling vigor index by 16.3% as compared with 0.0 mg L-1 at -0.5 MPa and 35 °C. The 5-ALA enhanced water imbibition of the three varieties under drought and temperature stresses. This study suggested that seed priming with 5-ALA is a possible way to mitigate the negative effects produced by drought and temperature stresses on germination and early seedling growth of wheat. [ABSTRACT FROM AUTHOR]

Salinity limits germination and plant growth and development in 45 million ha worldwide. Techniques to overcome this problem are needed. This project investigated the effects of jasmonic acid (JA) (0, 5, and 10 mM JA) and humic acid (HA) (0, 3, and 6 g HA kg−1 soil) on growth and physiological parameters of forage sorghum (Sorghum bicolor L. Moench) under different NaCl salinity levels (0, 100, and 200 mM NaCl, with an equivalent electrical conductivity (EC) of 0.12 dSm−1 as control treatment, 3.22, and 5.78 dSm−1, respectively). NaCl salinity reduced emergence percentage, emergence rate, salt tolerance index and seedling vigor index, all seedling growth parameters, ascorbate peroxidase (APX) activity, chlorophyll a, b and total chlorophyll content. Proline content and soluble protein content were increased with salinity. At the 200 mM salinity level, seeds treated with 10 mM JA had a positive effect on emergence percentage, emergence rate, shoot length, total fresh weight, salt tolerance index, seedling vigor index, chlorophyll a and total chlorophyll content. At 200 mM NaCl salinity level, seeds treated with 6 g HA kg−1 soil had increased root length, total dry weight, salt tolerance index, seedling vigor index, shoot length, protein content, APX, chlorophyll b, and total chlorophyll in seedlings. The application of 5 mM JA combined with 6 g HA kg−1 soil was most effective in minimizing salinity stress. Our study suggested that the appropriate combined application of HA and JA could efficiently protect early seedlings from salt stress damage and alleviate abiotic stress. [ABSTRACT FROM AUTHOR]

Salinity is a growing problem worldwide, and techniques are needed to mitigate this problem. This study was conducted to determine if biochar (BC) can alleviate the adverse impacts of salinity stress on sorghum (Sorghum bicolor L.) seedling growth. Sorghum variety Kambal was sown in salinized soils at levels of 1.2, 3.1, and 7.3 dS m−1. The saline soils were treated with four BC rates of 0, 2, 4, and 8% (w/w). The test was a factorial design arranged as a completely randomized design with three replications. Seedling emergence percentage; root and shoot length; root and shoot dry weight; relative water content (RWC); and the activity of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) were affected by the interaction between salinity and BC. At the 7.3 dS m−1 salinity level, 2% BC increased seedling emergence percentage by 25.0% (P =.012). At the 7.3 dS m−1 salinity level, 4% BC level increased root and shoot length (P =.009) and RWC by 46.0, 28.0, and 19.8% respectively. At the 7.3 dS m−1 salinity level, 8% biochar decreased CAT by 50.6%. At the high salinity level, 4% BC decreased POD and SOD by 24.9 and 23.4%, respectively. Biochar amendment proved to be more useful to alleviate the effects of salinity on the seedling growth stage. These findings suggest that using BC in suitable amounts could mitigate the adverse effects of salinity, but excess BC application may have negative influences on seedling growth. [ABSTRACT FROM AUTHOR]

• Salt stress adversely affected the photosynthesis and biochemical traits of forage sorghum. • Jasmonic acid and humic acid in regulating stress responses, plant growth and development. • Jasmonic acid and humic acid may be used as a tool to mitigate salinity-induced photosynthesis and biochemical parameters injury in forage sorghum Soil salinity, whether natural or induced, is one of the most serious environmental stresses limiting crop production in the world. In this study, the impacts of foliar application of jasmonic acid and soil amendment with humic acid on growth parameters, forage yield, chlorophyll content, and physiological characteristics of forage sorghum were studied to mitigate salinity in combination with different concentrations under greenhouse conditions. The plants were subjected to salinity at 0.26 (S0), 2.3 (S1), and 4.7 dS m−1 (S2), different rates of humic acid at 0, 373.21, and 746.42 kg HA ha−1, were designed as HA0, HA1, and HA3 respectively, and jasmonic acid at 0 (JA0), 5 (JA1) and 10 mM (JA2) as a foliar application. Salinity stress had detrimental effects on all the parameters and they were gradually reduced with increased salinity. Applications of humic acid and jasmonic acid mitigated the inhibitory effects of salt stress on these variables at all salinity levels. The rate of HA1 increased fresh weight, chlorophyll a and b , transpiration rate, relative humidity, stomatal conductance to CO 2 and stomatal conductance by 14.2%, 45.6%, 41.8%, 50.2%, 11.2%, 32.1% and 18.5% respectively, under S2. In addition, jasmonic acid at JA1 treatment increased plant height, elongation percentage, fresh and dry weight, chlorophyll a and b , relative humidity, and stomatal conductance to CO 2 under S2. Interaction between JA2 and HA1 improved all the traits except plant height, elongation percentage, and leaf area, suggesting that JA and HA can reduce the negative effects of salinity on the sorghum. In conclusion, jasmonic acid and humic acid treatments improved the forage sorghum performance under salinity conditions through anthesis stages, better photosynthetic and growth parameters, which reduced the impacts of salinity, and resulted in better plant growth and biomass production, and help the plant to improved salt tolerance. [ABSTRACT FROM AUTHOR]