Do plants respond and recover from a combination of drought and heatwave in the same manner under adequate and deprived soil nutrient conditions?

Impact of singular versus combinatorial environmental stress on RONS generation in Drosophila melanogaster larvae

We investigated environmentally correlated abiotic stressor desiccation (D), heat (H), and starvation (S) in the generation of reactive oxygen and nitrogen species (RONS) using Drosophila melanogaster larvae as an experimental model, subjected to either individual stressors or exposed to a combinatorial form of stressors (D + H, H + S, and D + S). The study was also extended to find synergistic endpoints where the impacts of all three stressors (D + H + S) were exerted simultaneously. We estimated the lethal time (LT20) at specific doses using regression and probit analyses based on the larval survival. LT20 values were used as the base-level parameter for further oxidative stress experimental analysis work. First, all stressors led to the activation of a typical common oxidative stress-mediated response irrespective of the mode of exposure. As envisaged, D. melanogaster larvae exhibited a homeostatic stress tolerance mechanism, triggering an antioxidant defense mechanism, indicated by an elevated level of total antioxidant capacity and enhanced activities of superoxide dismutase, catalase, glutathione reductase, and glutathione peroxidase. In all types of stress-exposed regimes, we found a negative impact of stressors on the activity of mitochondrial enzyme aconitase. Elevated levels of other oxidative stress markers, viz., lipid peroxidation, protein carbonyl content, and advanced oxidative protein products, were obvious although the increment was treatment-specific. Desiccation stress proved to be the most dominant stressor compared to heat and starvation. Among the combination of stressors, rather than a single stressor, D + H impacted more than other binary stress exposures. Focusing on the impact of singular versus combinatorial stress exposure on RONS generation, we observed an increase in the RONS level in both singular and combinatorial forms of stress exposure although the magnitude of the increment varied with the nature of stressors and their combinations. The present study indicated an "additive" effect when all three stressors (D + H + S) operate simultaneously, rather than a "synergistic" effect.

Enhanced Cd phytoextraction by rapeseed under future climate as a consequence of higher sensitivity of HMA genes and better photosynthetic performance

This study aimed to investigate the underlying physiological, biochemical, and molecular mechanisms responsible for Brassica napu's potential to remediate Cd-contaminated soil under current (CC) vs. future (FC) climate (400 vs. 800 ppm of CO2, 21/14 °C vs. 25/18 °C). B. napus exhibited good tolerance to low Cd treatments (Cd-1, Cd-10, i.e., 1, 10 mg kg-1) under both climates without visible phytotoxicity symptoms. TI sharply decreased by 47 % and 68 % (p < 0.05), respectively, in Cd-50 and Cd-100 treated shoots under CC, but to a lesser extent (-26 % and -53 %, p < 0.05) under FC. This agreed with increased photosynthetic apparatus performance under FC, primarily due to a significant decrease in the closure of active PSII RCs ((dV/dt)o, TRo/RC) and less dissipated excitation energy (DIo/RC, φDo). Calvin Benson cycle-related enzyme activity also improved under FC with 2.2-fold and 2.4-fold (p < 0.05) increases in Rubisco and TPI under Cd-50 and Cd-100, respectively. Consequentially, a 2.2-fold and 2.3-fold (p < 0.05) boosted Pr resulted in a 2.3-fold and 2.4-fold (p < 0.05) increase in the DW of Cd-50 and Cd-100 treated shoots, respectively. This also led to a decrease (26 %, p < 0.05) in shoot Cd concentration under both high Cd treatments with a slight reduction in BCF. Translocation factor (TF) decreased (on average 42 %, p < 0.05) by high Cd treatments under both climates. However, under Cd-100, FC increased TF by 1.7-fold (p < 0.05) compared to CC, which could be explained by significant increases in the expression of HMA genes, especially BnaHMA4a and BnaHMA4c. Finally, Cd TU increased under FC by 65 % and 76 % (p < 0.05) under Cd-50 and Cd-100. This led to a shorter hypothetical remediation time for reaching the Cd pollution limit by 35 (p > 0.05) and 61 (p < 0.05) years, respectively, compared to CC.

Drought-free future climate conditions enhance cadmium phytoremediation capacity by Brassica napus through improved physiological status

This study aimed to assess Cd phytoextraction efficiency in well-watered and drought-stressed B. napus plants under current climate (CC, 21/14 °C, 400 ppm CO₂) and future climate (FC, 25/18 °C, 800 ppm CO₂) conditions. The underlying physiological mechanisms underpinning the obtained results were investigated by studying Cd (1, 10, 50, and 100 mg kg^-1) effect on B. napus photosynthetic performance and nutritional status. Only the Cd-50 and Cd-100 treatments caused visible leaf lesions, growth retardation, reductions in both gas exchange and chlorophyll fluorescence-related parameters, and disturbed mineral nutrient balance. Under CC conditions, well-watered plants were affected more than under FC conditions. The most important pathway by which Cd affected B. napus photosynthetic efficiency in well-watered plants was the damage to both photosystems, lowering photosynthetic electron transport. Meanwhile, non-stomatal and stomatal limitations were responsible for the higher reduction in the photosynthetic rate (P_r) of drought-stressed compared to well-watered plants. The significantly higher shoot dry weight, which had a strong positive relationship with P_r, was the main factor determining significantly higher shoot Cd accumulation in high Cd treatments in well-watered plants under FC conditions, resulting in a 65% (p < 0.05) higher soil Cd removal rate in the Cd-50 treatment.

Oilseed rape (Brassica napus L.) potential to remediate Cd contaminated soil under different soil water content

Changes in soil moisture content accompanying ongoing climate change are expected to affect plant growth and contaminants behaviour in the soil. The study was aimed at investigating soil water content impact on the energy crop oilseed rape (Brassica napus L.) efficiency to remediate Cd contaminated soil (1-250 mg kg^-1). B. napus growth, Cd accumulation and removal efficiency were evaluated under optimal, reduced and elevated soil water content (SWC). B. napus showed good tolerance to Cd contamination and ability to phytoextract Cd from the soil. Cd accumulation in oilseed rape increased with Cd soil concentration, whereas removal efficiency was regulated by rape growth and Cd soil concentrations. B. napus has demonstrated good efficiency to cope with low and moderate Cd pollution (with tolerance index TI > 0.69), while high Cd soil pollution had a highly significant adverse impact on plant growth (growth was reduced up to 90%) resulting in low Cd removal efficiency. SWC governed plant growth, Cd accumulation and removal from the soil. Oilseed rapes grown under elevated SWC were of higher biomass (18%) compared to those grown under reduced SWC though the detrimental effect of Cd was more severe at elevated SWC. Reduced SWC led to decreased Cd uptake, conversely elevated SWC promoted Cd uptake. The optimal SWC ensures the highest Cd removal efficiency, whereas soil water deficit or excess restricts B. napus potential to remove Cd from the soil and prolongs remediation.

Plant Diversity, Functional Group Composition and Legumes Effects versus Fertilisation on the Yield and Forage Quality

Elevating plant diversity and functional group composition amount in the swards may contribute to lower N fertiliser use. The excessive use of fertilisers in agriculture is one of the causes of environmental pollution issues. We investigated the effects of plant diversity, functional community composition, and fertilisation on the dry matter yield and its quality at the Lithuanian Research Centre for Agriculture and Forestry, Central Lithuania. The study aimed to determine the productivity potential of single-species and multi-species swards with three, four, six, and eight plant species in the mixtures including four grasses and four legumes. Two experimental backgrounds were used with N0 and N150 kg ha−1 yr−1 for all treatments. In the two-year experiment manipulating species richness and functional group diversity had a positive effect on the dry matter yield and produced better quality of the forage when compared with single-species swards. Crude protein in the forage of grass–legume mixtures was significantly greater than for grass monocultures. Investigating fertilisation background was a concern; it had a positive effect on the single-species sward yield but decreased the yield of multi-species swards.