The climate changes expected for the next decades will expose plants to increasing occurrences of combined abiotic stresses, including drought, higher temperatures, and elevated CO₂ atmospheric concentrations. These abiotic stresses have significant consequences on photosynthesis and other plants’ physiological processes and can lead to tolerance mechanisms that impact metabolism dynamics and limit plant productivity. Furthermore, due to the high carbohydrate content on the cell wall, plants represent a an essential source of lignocellulosic biomass for biofuels production. Thus, it is necessary to estimate their potential as feedstock for renewable energy production in future climate conditions since the synthesis of cell wall components seems to be affected by abiotic stresses. This review provides a brief overview of plant responses and the tolerance mechanisms applied in climate change scenarios that could impact its use as lignocellulosic biomass for bioenergy purposes. Important steps of biofuel production, which might influence the effects of climate change, besides biomass pretreatments and enzymatic biochemical conversions, are also discussed. We believe that this study may improve our understanding of the plant biological adaptations to combined abiotic stress and assist in the decision-making for selecting key agronomic crops that can be efficiently adapted to climate changes and applied in bioenergy production.

The cultivated area of soybean has increased worldwide in past decades, including regions with saline soils, strongly decreasing growth and productivity. The use of amino acids (AAs) as buffering compounds against stressful conditions can be a useful strategy to mitigate salt stress in these regions. This study aimed to evaluate the effects of foliar application of AA mixtures on the growth, physiology, and biochemistry traits of salt-stressed soybean plants. A pot experiment was designed as a factorial scheme (4 × 3) in a randomized complete design (RCD). Treatments consisted of four concentrations of AA mixtures of a non-VA application, 0.4 mL L⁻¹, 0.8 mL L⁻¹, and 1.2 mL L⁻¹ (VIUSID Agro^® (VA) source), which were combined with non-salt stressed and salt-stressed groups (50 and 100 mmol L⁻¹ NaCl), to analyze improvement in growth and potassium (K⁺) accumulation, maintenance of relative water content (RWC), net photosynthesis rate (A), transpiration (E), stomatal conductance (gs), and chlorophyll content, and increase of proline accumulation and water use efficiency (iWUE). Moderate and high salinity induced a notable increase in oxidative and ionic biomarkers, coupled with higher Malondialdehyde (MDA) concentration and Na⁺ accumulation. Alternatively, soybean growth, K⁺ accumulation, and physiological and biochemical parameters were decreased under salinity. Foliar spraying of AAs drastically increased osmolyte accumulation associated with sustained iWUE and RWC, increased proline accumulation, and improved A, E, gs, and chlorophyll content. Greater outcomes were achieved with the foliar spraying of amino acids at 1.2 mL L⁻¹. Collectively, foliar application of AA mixtures plays an important role in salt stress remediation by modifying important physiological and biochemical processes, thereby resulting in a higher growth of soybean plants.

Changes in leaf anatomy and ultrastructure are associated with physiological performance in the context of plant adaptations to climate change. In this study, we investigated the isolated and combined effects of elevated atmospheric CO₂ concentration ([CO₂]) up to 600 μmol mol^-1 (eC) and elevated temperature (eT) to 2°C more than the ambient canopy temperature on the ultrastructure, leaf anatomy, and physiology of Panicum maximum Jacq. grown under field conditions using combined free-air carbon dioxide enrichment (FACE) and temperature free-air controlled enhancement (T-FACE) systems. Plants grown under eC showed reduced stomatal density, stomatal index, stomatal conductance (g_s), and leaf transpiration rate (E), increased soil-water content (SWC) conservation and adaxial epidermis thickness were also observed. The net photosynthesis rate (A) and intrinsic water-use efficiency (iWUE) were enhanced by 25% and 71%, respectively, with a concomitant increase in the size of starch grains in bundle sheath cells. Under air warming, we observed an increase in the thickness of the adaxial cuticle and a decrease in the leaf thickness, size of vascular bundles and bulliform cells, and starch content. Under eCeT, air warming offset the eC effects on SWC and E, and no interactions between [CO₂] and temperature for leaf anatomy were observed. Elevated [CO₂] exerted more effects on external characteristics, such as the epidermis anatomy and leaf gas exchange, while air warming affected mainly the leaf structure. We conclude that differential anatomical and physiological adjustments contributed to the acclimation of P. maximum growing under elevated [CO₂] and air warming, improving the leaf biomass production under these conditions.