Drought and high temperature are major abiotic stresses that increasingly threaten crop productivity under climate change. Although responses to individual stresses are widely documented, the combined effects of drought and heat often induce distinct physiological and metabolic adjustments that remain insufficiently understood. This study investigated short-term responses of garlic plants (cv. Istarski crveni) grown under water-available and ambient temperature (W+/T−), water-available and high temperature (W+/T+), drought-induced and ambient temperature (W−/T−), and drought-induced and high temperature (W−/T+) conditions in controlled climate chambers. Morphological and physiological traits (leaf color parameters, chlorophyll fluorescence, and dry matter), together with metabolite profile (abscisic acid, gamma-aminobutyric acid, proline, glycine, serine, glucose, fructose, mannitol), were assessed over an 8-day period using ANOVA and PLS-DA analyses. Exposure to drought reduced substrate water content and induced abscisic acid (ABA) accumulation, followed by increased proline levels and changes in leaf dry matter. When occurring with high temperature, accumulation of osmolytes, including glucose, fructose, and serine was observed, while photosystem II efficiency remained stable. Multivariate analysis revealed that temperature dominated treatment differentiation during first three days, whereas water availability became an important factor from day 4 onwards. Serine and fructose emerged as potential early biomarkers of combined drought and temperature stress, while leaf color and fluorescence parameters emerge as candidate non-destructive indicators of plant stress responses, warranting validation under field conditions.
T. Kovačević, N. Major, Marina Krpan et al.· Frontiers in Plant Science· 1 citation
Biochar has traditionally been investigated as a soil amendment for improving fertility, carbon sequestration, and nutrient retention. However, recent advances in fine milling, colloidal stabilization, and nanotechnology have enabled the development of biochar-derived materials for foliar application. Unlike conventional soil application, foliar delivery enables direct interaction with leaf tissues, potentially providing faster physiological responses, improved resource-use efficiency, and complementary functions to existing plant biostimulants. This review critically evaluates the scientific basis, agronomic performance, and regulatory implications of foliar biochar applications across diverse crop systems. We synthesize and compare major formulation types, including finely milled suspensions, aqueous extracts, nano-biochar dispersions, and biochar-based composite carriers, based on their formulation characteristics, application methods, and reported biological effects. Across multiple crops, foliar biochar has been associated with enhanced chlorophyll content, improved gas exchange, strengthened antioxidant systems, better osmotic adjustment, and increased nutrient uptake, particularly under abiotic stresses such as salinity, drought, and heat. Mechanistically, these responses are linked to surface deposition effects, redox-active functional groups, modulation of leaf microclimate, and delivery of soluble bioactive compounds. Nevertheless, outcomes remain highly context-dependent, influenced by feedstock origin, pyrolysis conditions, particle size, formulation chemistry, dose, and crop species. Potential risks including phytotoxicity, nanoparticle exposure, environmental fate, and regulatory ambiguity especially for nano-scale formulations pose additional challenges for large-scale adoption. By integrating physiological, agronomic, environmental, and legislative perspectives, this review also highlights key barriers to commercialization, including formulation stability, limited field-scale validation, environmental safety, and regulatory uncertainty, while identifying research priorities needed to determine whether foliar biochar can become a scalable and scientifically validated biostimulant for sustainable agriculture.
I. Palčić, Qaiser Javed, Dominik Anđelini et al.· Horticulturae· 0 citations
