The effect of biochar and methyl Jasmonate on biochemical alterations, yield and yield components of barley (Hordeum vulgare L.) under drought stress

Barley (Hordeum vulgare L.) is among the most influential cereals, and a wide range of populations in several regions of the world (Sallam et al., 2019). However, there are some restrictions for accomplishment to the potential production, which the most consequential one among them, water shortage, a drastic obstacle in many regions of the world, in particular in arid and semi-arid areas. Water scarcity, results in plenty of disturbances in plant functions like cell division and elongation, water and nutrients relations, photosynthesis, enzymes activity, stomata movement, assimilate partitioning, respiration, oxidative damage, growth, and productivity, as several types of researches show that water shortage in the soil cause many disorders in plant tissues, which in turn leads to a punctual diminish in the photosynthesis rate (Todorova et al., 2022). Under circumstances of water shortage, the electron transport through PSII is prohibited, and the oxygen-evolving complex of PSII is damaged (Georgieva et al., 2005). In repercussion, depends on the times, duration of facing, and stress intensity, developmental stage, and kind of tissue, plant defenses against it differently.

An experiment as a factorial in a completely randomized block design in five replications at the experimental greenhouse of the University of Zanjan was carried out in two years 2021 and 2022. In this study two regimes of irrigation (D0, regular irrigation as the control, D1, Water Deficit for two weeks immediately after flowering), four levels of biochar (zero% as the control treatment, 0.25, 0.5 and 1 percent of soil weight) and three levels of spraying Methyl Jasmonate (zero μmol as the control treatment, 50 and 100 μmol) at the same time with flowering stage and starting withholding water, were executed.

Results demonstrated that utilized treatments had significant effects on studied parameters. Results illustrated that, despite the fact that proline content, carbohydrate and quantity of electrolyte leakage were elevated as a result of drought stress, and accumulation of photosynthetic pigments were dwindled, however, application of biochar in the soil and foliar spraying of methyl Jasmonate caused modulating the effects of drought stress. Lack of water can reduce the concentration of photosynthetic pigments, mainly chlorophylls and carotenoids, as it causes oxidation which leads to diminishing the biosynthesis of pigments (Pandey et al., 2012). It is claimed that using biochar ameliorates the reduction of pigments in stressed plants as a result of better surface area, higher water holding capacity, more cation exchange capacity, and useful absorptive features of biochar (Ibrahim et al., 2020). Moreover, the drought stress resulted in a substantial elevation in the concentration of proline (PC) which might be as a result of devastating impacts of drought on the performance of plasma membrane as well as the process which leads to dehydration of cytoplasm, which in turn results in boosting proline concentration in Barley plants under drought situation (Hafez et al., 2020). It is said that biochar reduces proline content, because of its impact on maintenance of plasma membrane in a stable situation, modulating the pressure of water in cell, and enhancing the ability of plants in conserving relative water content (Ahmed et al., 2016). Furthermore, methyl Jasmonate (MJ) may facilitate the strengthening of cell walls and effectively neutralize excessive increase in the level of ROS during further exposure to the stress factor, thereby preventing the damage of cellular membrane structures and changes in their permeability under stress conditions (Hayat and Ahmad., 2007).

The current study represents that Barley can tolerate drought stress through several mechanisms such as modulating some biochemical compounds. In this study drought was shown to have negative impacts on some of the studied physiological and biochemical parameters. Results demonstrated that the use of biochar and Methyl Jasmonate can improve the adaptation ability of Barley plants to water shortage, associated with enhancement in morpho-physiological and biochemical traits. Soil content of biochar at 0.25% w/w and Methyl Jasmonate leaf applies at 50 micro moles protected plants against drought stress. Importantly higher doses of biochar and Methyl Jasmonate had negative impacts, highlighting the need to better understand optimal doses, and mechanisms of action of these amendments.