Effect of calcium and light on the germination of Urochondra setulosa under different salts

Valorization of Posidonia oceanica biomass: Role on germination of cucumber and tomato seeds

Biostimulants are organic compounds from plant sources such as botanical extracts and bioactive substances that promote plant growth, enhance photosynthesis and increase crop quality. The accumulation of detached Posidonia oceanica leaves on coasts of the Mediterranean Sea results in economic problems, due to the rejection of the tourists who frequent the beaches in the summer months. However, it is a plant with high content of secondary metabolites that can be used in sustainable agriculture. In this study we investigated the physicochemical characterization of Posidonia oceanica extracts with three different solutions and their application in tomato and cucumber seeds germination. The results showed that the aqueous extract of Posidonia oceanica had a high concentration of macro and micronutrients, as well as secondary metabolites with bioactive activity. The aqueous extract had a beneficial effect on both leaf and root growth on tomato seeds, specifically, an increase of 76% for the relative root growth and 73% for the germination index was obtained with respect to the control using the sample with the intermediate dilution (POe0.5). In addition, the extracts did not show toxicity to either germination or growth of the tomato plant. As for cucumber seed germination, the improvement was less significant and did result in a phytotoxic effect on both germination and plant growth. The most diluted extract had better results on seed germination. Therefore, the application of aqueous extracts of Posidonia oceanica were suitable to be appropriate for tomato germination and in turn contribute to eliminate the lots of Posidonia oceanica remains recovered in summer months in Mediterranean beaches.

Plant Nutrition: An Effective Way to Alleviate Abiotic Stress in Agricultural Crops

By the year 2050, the world's population is predicted to have grown to around 9-10 billion people. The food demand in many countries continues to increase with population growth. Various abiotic stresses such as temperature, soil salinity and moisture all have an impact on plant growth and development at all levels of plant growth, including the overall plant, tissue cell, and even sub-cellular level. These abiotic stresses directly harm plants by causing protein denaturation and aggregation as well as increased fluidity of membrane lipids. In addition to direct effects, indirect damage also includes protein synthesis inhibition, protein breakdown, and membranous loss in chloroplasts and mitochondria. Abiotic stress during the reproductive stage results in flower drop, pollen sterility, pollen tube deformation, ovule abortion, and reduced yield. Plant nutrition is one of the most effective ways of reducing abiotic stress in agricultural crops. In this paper, we have discussed the effectiveness of different nutrients for alleviating abiotic stress. The roles of primary nutrients (nitrogen, phosphorous and potassium), secondary nutrients (calcium, magnesium and sulphur), micronutrients (zinc, boron, iron and copper), and beneficial nutrients (cobalt, selenium and silicon) in alleviating abiotic stress in crop plants are discussed.

Effects of Sodium Chloride and Sodium Sulfate on Haloxylon ammodendron Seed Germination

Haloxylon ammodendron is a perennial xerophyte that can survive in extremely harsh desert conditions of Central Asia. This study evaluated the effect of salinity, and their ability to recover on seed germination of H. ammodendron, which were collected at three different desert areas, Bakanas takyr plain (H1), Gurbantüngüt Desert (H2), and Gobi Desert (H3), respectively. Seeds were treated with different concentrations of NaCl and Na2SO4 (0.00 (control), 0.05, 0.10, 0.20, 0.40, 0.60, 0.80, 1.00, 1.20, and 1.40 mol/L) to detemine the germination and recover ability to salt stress. The results of the study were that H. ammodendron were more resistant to Na2SO4 than to NaCl. Regarding inhibition of seed germination H. ammodendron was in the following order: H3 > H2 > H1. Based on the tolerance and recovery, seeds can be demonstrated as follows: NaCl: H3 > H1 > H2; Na2SO4: H1 = H2 = H3. Non-germinated seeds in all salt treatments with low osmotic potential showed high recovery when transferred to distilled water, indicating that these treatments were not too toxic to affect seed viability. These results suggest that H. ammodendron can withstand high levels of salinity at three desert environments. Thus, H. ammodendron could be used to reconstruct vegetation and sustanbility development in the desert areas with high salinity.

Calcium Improves Germination and Growth of Sorghum bicolor Seedlings under Salt Stress

Salinity is a major constraint limiting plant growth and productivity worldwide. Thus, understanding the mechanism underlying plant stress response is of importance to developing new approaches that will increase salt tolerance in crops. This study reports the effects of salt stress on Sorghum bicolor during germination and the role of calcium (Ca²⁺) to ameliorate some of the effects of salt. To this end, sorghum seeds were germinated in the presence and absence of different NaCl (200 and 300 mM) and Ca²⁺ (5, 15, or 35 mM) concentrations. Salt stress delayed germination, reduced growth, increased proline, and hydrogen peroxide (H₂O₂) contents. Salt also induced the expression of key antioxidant (ascorbate peroxidase and catalase) and the Salt Overlay Sensitive1 genes, whereas in the presence of Ca²⁺ their expression was reduced except for the vacuolar Na⁺/H⁺ exchanger antiporter2 gene, which increased by 65-fold compared to the control. Ca²⁺ reversed the salt-induced delayed germination and promoted seedling growth, which was concomitant with reduced H₂O₂ and Na⁺/K⁺ ratio, indicating a protective effect. Ca²⁺ also effectively protected the sorghum epidermis and xylem layers from severe damage caused by salt stress. Taken together, our findings suggest that sorghum on its own responds to high salt stress through modulation of osmoprotectants and regulation of stress-responsive genes. Finally, 5 mM exogenously applied Ca²⁺ was most effective in enhancing salt stress tolerance by counteracting oxidative stress and improving Na⁺/K⁺ ratio, which in turn improved germination efficiency and root growth in seedlings stressed by high NaCl.