Abscisic Acid, Paclobutrazol, and Salicylic Acid Alleviate Salt Stress in Populus talassica × Populus euphratica by Modulating Plant Root Architecture, Photosynthesis, and the Antioxidant Defense System

Abstract

The exogenous plant growth regulators (PGRs) represent a useful strategy for reducing the adverse effects of salt stress in plants. In order to investigate the regulatory effect of exogenous PGRs on the salt tolerance of Populus talassica × Populus euphratica seedlings, in this study, the effects of different foliar spray concentrations of ABA (5 mg·L−1, 15 mg·L−1, 25 mg·L−1), PP333 (300 mg·L−1, 900 mg·L−1, 1500 mg·L−1), and SA (40 mg·L−1, 120 mg·L−1, 200 mg·L−1) on P. talassica × P. euphratica seedlings under salt stress (soil salt concentration of 2%) were determined. The results showed that the dry weight, total root length, root surface area, root volume, total Chl content, and photosynthetic parameters of P. talassica × P. euphratica seedlings significantly decreased under salt stress and increased their contents of malondialdehyde (MDA), hydrogen peroxide (H2O2), superoxide anion (O2−), free proline (Pro), superoxide dismutase (SOD), and peroxidase (POD). However, ABA, PP333, and SA can mitigate the adverse effects of salt stress on these indicators. Especially, the 15 mg·L−1 ABA, 900 mg·L−1 PP333, and 120 mg·L−1 SA treatments had the best effect on alleviating salt stress, with significant increases in dry weight, root parameters, total Chl content, and the photosynthetic parameters of the P. talassica × P. euphratica seedlings, improving their photosynthetic characteristics; meanwhile, increased Pro content and enzyme activity and decreased MDA, H2O2, and O2− content protected the integrity of membrane system and enhanced the salt tolerance of the seedlings. SA resulted in a better ameliorative effect on salt stress compared to ABA and PP333.

The Euphrates Poplar Responses to Abiotic Stress and Its Unique Traits in Dry Regions of China (Xinjiang and Inner Mongolia): What Should We Know?

“…Additionally, most physiological mechanisms depend heavily on the photosynthetic activities of P. euphratica. For example, exogenous plant growth factors are essential for P. euphratica's ability to withstand drought by controlling photosynthesis and lowering salt stress [82]. Additionally, P. euphratica demonstrates heat tolerance and leaf protein accumulation [83].…”

Deciphering the Genetic Mechanisms of Salt Tolerance in Sorghum bicolor L.: Key Genes and SNP Associations from Comparative Transcriptomic Analyses

“…At the molecular level, salt stress triggers the activation of various signaling pathways, including the mitogen-activated protein kinase cascade, the calcium-dependent protein kinase pathway, and the abscisic acid signaling pathway. These pathways mediate the expression of stress-responsive genes, such as those encoding transporters, enzymes, and transcription factors, which regulate various physiological and biochemical processes involved in salt stress tolerance [ 5 , 6 , 7 ].…”