The combination of salt and drought benefits selective ion absorption and nutrient use efficiency of halophyte Panicum antidotale

Abstract

Soil salinity and water deficit often occur concurrently, but understanding their combined effects on plants’ ion regulation is limited. With aim to identify if introducing drought with salinity alleviates salt stress’s ionic effects, Panicum antidotale – a halophytic grass- was grown in the presence of single and combined stressors, i.e., drought and salt (low and high). Regulation of cations and anions along with the antioxidant capacity and modifications in leaf anatomy were investigated. Results showed a combination of low salt and drought minimally affected plant (dry) mass by improving the selective ions absorption and nutrient use efficiencies. The lowest ratio for efficiency of photosystem II and carbon assimilation (ΦPSII/ΦCO2) suggested less generation of reactive oxygen species, which were probably detoxified with constitutively performing antioxidant enzymes. In contrast, the combination of high salinity and drought escalated the adverse effects caused due to individual stressors. The selective ion absorption increased, but the non-selective ions transport caused an ionic imbalance indicating the highest ratio of Na+/K+. Although the area of mesophyll increased, a reduction in epidermis (cell number and area) predicted a mechanical injury prone to water loss in these plants. The compromised activity of antioxidant enzymes also suggested treatment-induced oxidative damage. Yet, the synergistic interaction between high salinity and drought was not detrimental to the survival of P. antidotale. Therefore, we suggest planting this grass in habitats with harsh environmental conditions to meet the increasing fodder demands without compromising agricultural lands’ productivity.

Salinity and exogenous H2O2 improve gas exchange, osmoregulation, and antioxidant metabolism in quinoa under drought stress

“…This improvement is consistent with the results ofHussain et al (2020Hussain et al ( , 2023 andStavridou et al (2020) He et al (2019). showed that moderate levels of soil salinity could improve growth and abate the drought-induced injuries in salt-tolerant plants Hussain et al (2023). and Sun et al (2020) revealed that plants subjected to the coexistence of salt and drought stress showed the ability to use inorganic ions for F I G U R E 5 Effects of exogenous H 2 O 2 and different growth conditions (well-watered, drought, salt, and drought + salt stress) on SOD, POD, and CAT activities (U mg À1 protein) in quinoa.…”

“…1). This improvement is consistent with the results ofHussain et al (2020Hussain et al ( , 2023 andStavridou et al (2020) He et al (2019). showed that moderate levels of soil salinity could improve growth and abate the drought-induced injuries in salt-tolerant plants Hussain et al (2023).…”

“…Similarly, the quinoa plant exhibited markedly increased proline, TSS, and GB contents under drought stress (Figure 4). However, in saline conditions, plants uptake inorganic ions, especially Na + , in large amounts to achieve osmotic adjustment (Hussain et al, 2023;Sun et al, 2020).…”

“…However, plants grown under combined stress showed higher antioxidant enzymes' activity than plants grown under single drought and salinity (Figure 5). Recently, some studies reported that accumulation of osmolytes, (ROS)-scavenging enzymes, antioxidant system and phytohormones (ABA) production was more pronounced in combined stress conditions (i.e., drought and salinity) than in individual stress in different plants including quinoa (Abbas et al, 2023;dos Santos et al, 2022;Hussain et al, 2020Hussain et al, , 2023Zhang et al, 2017). In this study, a more strenuous antioxidant system might be plausible due to the efficient uptake of inorganic ions as osmotic adjustment (Table 4), which saves energy and eventually results in increased antioxidant (SOD, POD, and CA) activity under combined drought and salt stress (Figure 5).…”