Said Bouhraoua ･Mohamed Ferioun ･Srhiouar Nassira ･Abdelali Boussakouran ･Mohamed Akhazzane ･ Douae Belahcen ･Khalil Hammani ･Said Louahlia. J Plant Biotechnol 2023;50:115-26. https://doi.org/10.5010/JPB.2023.50.015.115

Among heavy metals, cadmium (Cd) is shown to have adverse consequences for plants. Due to its harmful nature and ability to move through the soil–plant system, it is a very worrying element for soil experts and plant physiologists. In this work, we designed a pot experiment to study the influence of three soil concentrations of cadmium (0, 15, and 30 mg/kg) to explore its physiological impacts, and its portioning in the whole plant of three hulless barley varieties. Our findings demonstrated marked Cd accumulation in roots, leaves, and stems under severe Cd stress (30 mg/kg). Cd stress was also shown to reduce photosynthetic activity, chlorophyll fluorescence (Fv/Fm), and transpiration rates (E). The application of Cd in the soil increased the activities of catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase (POD) enzymes, as well as the levels of oxidative stress markers such as malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and proline. These results reflect the negative effects of cadmium on morpho-physiological traits in barley genotypes. However, the principal component analysis indicated a significant correlation between oxidative stress indicators and enzymatic activities, along with different levels of Cd tolerance between Tombari, Assiya, and Giza 130 genotypes. When exposed to Cd, these varieties shifted a significant amount of energy from growth to produce antioxidant compounds and osmolytes. Despite this, these defenses did not effectively shield the plant from the detrimental effects of oxidative stress induced by Cd accumulation at vegetative stages. Consequently, we highly recommend testing these varieties under Cd-contaminated soil to investigate the rate of cadmium accumulation in the seeds, the harvested part used in human nutrition.

In Morocco, the use of phosphate fertilizer in farming system represents a source of cadmium that accumulates in soil and would affect negatively the growth and yield. Cadmium toxicity decreases nutrients and water translocation and absorption, it leads to an increase in oxidative harm, affects the metabolism of plants, and inhibits plant morpho-physiology as well. This experiment was conducted to examine the impacts of various concentrations of Cd (0, 15, 30 mg leg-1) in the flag leaf of three hulless barley varieties: Assiya (Morocco), Tombari (Tunisia), and Gizal30 (Egypt). Several morpho-physiological parameters were measured at vegetative stage encompassing measurements like Flag leaf length (FLL), Flag leaf area (FLA), Flag leaf width (FLW), and Flag leaf dry weight (FLDW), water relative content (RWC), total chlorophyll content (SPAD), and Fluorescence (Fv/Fm). ANOVA analysis showed that all morphological traits (except for FLDW) were primarily affected by the variety effect (>62% of total variance). In contrast, the treatment of Cd largely influenced physiological traits (>90% of total variance). Moreover, the interaction between the two factors was in general of lower importance. Comparison among varieties showed significant differences for all traits. In fact, the Moroccan variety (Assiya) displayed the highest values for physiological and morphological parameters.