This study was undertaken to elucidate the role of trehalose (Tre) in mitigating oxidative stress under salinity and low P in maize. Eight-day-old maize seedlings of two maize varieties, BARI Hybrid Maize-7 and BARI Hybrid Maize-9 were subjected to salinity (150 mM NaCl), low P (5 µM KH2PO4) and their combined stress with or without 10 mM Tre for 15-d.Salinity and combined stress significantly inhibited the shoot length, root length, and root volume, whereas, low P increased the root length and volume in both genotypes. Exogenous Tre in the stress treatments increased all of the growth parameters as well as decreased the salinity, low P and combined stress-mediated Na+/K+, ROS, MDA, LOX activity and MG in both genotypes. Under salinity and low P stress, the SOD activity increased in both genotypes, but the activity decreased in combined stress. POD activity increased in all stress treatments. Interestingly, Tre application enhanced the SOD activity in all the stress treatments but inhibited the POD activity. Both CAT and GPX activity were increased by saline and low P stress while the activities inhibited in combined stress. Similar results were found for APX, GR, and DHAR activities in both genotypes. However, MDHAR activity was inhibited in all the stresses. Interestingly, Tre enhanced CAT APX, GPX, GR, MDHAR and DHAR activities suggesting the amelioration of ROS scavenging in maize under all the stresses. Increased GST activity in presence or absence of Tre might involve in detoxification of hydroperoxides as well as leaf senescence. On the other hand, increased glyoxalase activities in saline and low P stress in BHM-9 suggested better MG detoxification system because of down-regulation of Gly-I activity in BHM-7 in those stresses. Tre also increased the glyoxalase activities in both genotypes under all the stresses. Tre improved the growth in maize seedlings by decreasing Na+/K+, ROS, MDA, and MG through regulating antioxidant and glyoxalase systems.

Elevated salinity is one of the major environmental limitation factors of plant growth and development and salinity stress compromises the production and survival of plantation and urban forests and agricultural crops in the arid, semi-arid, and intertidal zones. Ulmus pumila, a salt- indigenous tree species in Asia and is widely deployed in salt-affected areas in China, and U.pumila is promising for multi-varietal forestry in plantation and urban forests. The comprehensive mechanism of the intraspecific salt tolerance is still not clear yet. Here, we investigated the physiological responses of the salinity stress based on the antioxidant enzyme activities, osmotic adjustments, and gas exchange among salt-tolerant U. pumila genotypes for 100 days under five different NaCl levels (0%, 0.3%, 0.5%, 0.7%, and 0.9% w/v) with natural surroundings and rain shade at age-2. Salt stress decreased height (HR), ground diameter (DR), and dry weight (biomass) were significantly different among genotypes. HR and performance indices were positively correlated with photosynthesis rate (Pn), apparent mesophyll conductance (AMC), and chlorophyll (CHLL) with (r= 0.7 - 0.8 ***), but were negatively related to the free proline, sugar, and protein accumulation (r=-0.5 ~ -0.7***). We found that high accumulation of sugars and more activities of SOD enzyme in leaf tissue contribute to the osmotic adjustment and ROS scavenging system under salinity treatment; the sugar content and SOD activity play key roles in U. pumila’s tolerance to salt stress, and are promising indicators for U. pumila species ex vitro selections. The ex vitro selection results align with the previous in vitro studies [37] and is promising for the MVF development.