Diethyl Aminoethyl Hexanoate Priming Ameliorates Seed Germination via Involvement in Hormonal Changes, Osmotic Adjustment, and Dehydrins Accumulation in White Clover Under Drought Stress

Drought is a serious outcome of climate change reducing the productivity of forage species under arid and semi-arid conditions worldwide. Diethyl aminoethyl hexanoate (DA-6), a novel plant growth regulator, has proven to be involved in the amelioration of critical physiological functions in many agricultural crops under various abiotic stresses, but the role of the DA-6 in improving seed germination has never been investigated under drought stress. The present study was carried out to elucidate the impact of the DA-6 priming on seeds germination of white clover under drought stress. Results showed that seed priming with the DA-6 significantly mitigated the drought-induced reduction in germination percentage, germination vigor, germination index, seed vigor index, root length, shoot length, and fresh weight after 7 days of seed germination. The DA-6 significantly increased the endogenous indole-3-acetic acid, gibberellin, and cytokinin content with marked reduction in abscisic acid content in seedlings under drought stress. In addition, the DA-6 significantly accelerated starch catabolism by enhancing the activities of hydrolases contributing toward enhanced soluble sugars, proline content and ameliorated the antioxidant defense system to enhance the ability of reactive oxygen species scavenging under drought stress. Furthermore, exogenous DA-6 application significantly increased dehydrins accumulation and upregulated transcript levels of genes encoding dehydrins (SK2, Y2SK, or DHNb) during seeds germination under water deficient condition. These findings suggested that the DA-6 mediated seeds germination and drought tolerance associated with changes in endogenous phytohormones resulting in increased starch degradation, osmotic adjustment, antioxidants activity, and dehydrins accumulation during seed germination under water deficient condition.

Research on the Mechanisms of Plant Enrichment and Detoxification of Cadmium

The heavy metal cadmium (Cd), as one of the major environmentally toxic pollutants, has serious impacts on the growth, development, and physiological functions of plants and animals, leading to deterioration of environmental quality and threats to human health. Research on how plants absorb and transport Cd, as well as its enrichment and detoxification mechanisms, is of great significance to the development of phytoremediation technologies for ecological and environmental management. This article summarises the research progress on the enrichment of heavy metal cadmium in plants in recent years, including the uptake, transport, and accumulation of Cd in plants. The role of plant roots, compartmentalisation, chelation, antioxidation, stress, and osmotic adjustment in the process of plant Cd enrichment are discussed. Finally, problems are proposed to provide a more comprehensive theoretical basis for the further application of phytoremediation technology in the field of heavy metal pollution.

Exogenous Methyl Jasmonate Improves Heat Tolerance of Perennial Ryegrass Through Alteration of Osmotic Adjustment, Antioxidant Defense, and Expression of Jasmonic Acid-Responsive Genes

Perennial ryegrass (Lolium perenne L.) is an important cool-season grass species that is widely cultivated in temperate regions worldwide but usually sensitive to heat stress. Jasmonates (JAs) may have a positive effect on plant tolerance under heat stress. In this study, results showed that exogenous methyl jasmonic acid (MeJA) could significantly improve heat tolerance of perennial ryegrass through alteration of osmotic adjustment, antioxidant defense, and the expression of JA-responsive genes. MeJA-induced heat tolerance was involved in the maintenance of better relative water content (RWC), the decline of chlorophyll (Chl) loss for photosynthetic maintenance, as well as maintained lower electrolyte leakage (EL) and malondialdehyde (MDA) content under heat condition, so as to avoid further damage to plants. Besides, results also indicated that exogenous MeJA treatment could increase the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), thus enhancing the scavenging ability of reactive oxygen species, alleviating the oxidative damage caused by heat stress. Heat stress and exogenous MeJA upregulated transcript levels of related genes (LpLOX2, LpAOC, LpOPR3, and LpJMT) in JA biosynthetic pathway, which also could enhance the accumulation of JA and MeJA content. Furthermore, some NAC transcription factors and heat shock proteins may play a positive role in enhancing resistance of perennial ryegrass with heat stress.

Response of Lawn Grasses to Salinity Stress and Protective Potassium Effect

The salinity effects on lawn grasses caused by mine salts (halite and carnallitite) due to road de-icing processes was the aim of this study. Biometric and physiological parameters were evaluated after salt dosage of 50 and 100 g m−2 applied to a lawn surface twice and four times, in weekly intervals. The alleviating effect to the salinity on the grasses from potassium enriched soil was also evaluated. Protective effect of potassium included mostly plasma membrane integrity and an increase in the level of photosynthetic pigments. This probably resulted in more efficient photosynthesis and thus increased lawn growth. Simultaneously, only a slight reduction in relative water content (RWC) was noted, so the recorded increase in proline level may indicate its participation in osmotic adjustment. Our results confirm the importance of proper, and even over-optimal, potassium fertilization of lawn grasses exposed to salinity. Moreover, it is advisable to use other fossil salts instead of halite for the de-icing of near-green areas. The mined salt carnallitite which, besides NaCl, contains about 30% of carnalite (KCl·MgCl2·6H2O) could be such a substance.

Insight into phytohormonal modulation of defense mechanisms to salt excess in a halophyte and a glycophyte from Asteraceae family

Aims The aim of this study was to compare the efficiency of three defense mechanisms (ionic balance, osmotic adjustment and counteracting oxidative stress) under low, moderate and high soil salinity in two related species of contrasting tolerance to salinity: the halophyte Aster tripolium and the glycophyte Aster alpinus, and to elucidate their phytohormone-mediated regulation. Methods The phytohormonal profiling was performed to asses correlations between the pool of plant growth regulators and parameters depicting ionic homeostasis, osmotic adjustment and antioxidant system. Results Defense mechanisms in both species were based on accumulation/activity of distinct compounds (Na+ and K+ ions, antioxidants), but differences among species concerned particularly soluble carbohydrates and betaines. The halophyte accumulated mannitol, uronic acids and sucrose, while the glycophyte mostly glucose and proline-betaine. The halophyte responses also correlated with changes in the content of plant growth promoting PGRs, as well as jasmonates and benzoic acid. The glycophyte responses corresponded with changes in content of abscisic acid and ethylene precursor, as well as salicylic acid. Conclusions We provided evidence that benzoic acid rather than salicylic acid is involved in salt tolerance in the halophyte and elevated SA content may enhance vulnerability to salt excess. An important element of tolerance trait is also JA-GA network that influences the intensity of defense responses. This study uncovers new aspects of internal phytohormonal regulation of plant reaction to soil salinity and enables further insight into extremophyte biology.