Investigation the impacts of mineral biochar and methyl jasmonate application on biochemical characteristics and yield of barley under drought stress

Barley (Hordeum  vulgare L.) is among the most important cereal crops and  large portions of human  populations in many  parts of the world depend on them  as a source of food and animal feed. Drought is one of the most important environmental stresses which affects yield and yield components of plants significantly which plants respond and adapt to drought stress by means of various morphological, biochemical and physiological changes. Nowadays Biochar has been employed for scientific and commercial usage as a soil amendment for improving the productivity of crops. Results of researchs showes that Biochar makes a great contribution in crop plant's growth. For instance investigations showed that drought stressed chickpea plants exhibited considerable reduction in uptake of nitrogen and phosphorous which was ameliorated by Biochar treatments. Jasmonic acid (JA) and its methyl ester, methyl jasmonate (MeJA) are important cellular regulators involved in many growth, developmental and physiological processes. It was found that exogenous application of MeJA improved tolerance to drought, salinity, chilling (Rehman et al., 2018) and heavy metal  stresses in different plant species.

In order to investigation of the impacts of different levels of mineral biochar and methyl Jasmonate on growth, yield and yield components of spring barley under different levels of drought stress a factorial experiment in  randomized complete block design in pots in 5 replications was done in 2019-2020 at the experimental field of university of Zanjan. Reviewed factors included in three levels of drought stress (100% FC as the none stressed, 60% FC as the mild stress and 30% FC as the severe stress), biochar application before cultivation in three levels (without biochar, 1.5% and 3% of the soil weight) and foliar spraying of methyl Jasmonate in three levels (0, 75 and 150 μmol per liter Studied factors included  electrolyte leakage, proline and photosynthetic pigments concentration, water use efficiency, relative water content and economical yield.

Results showed a significant impact of used treats on most of the characteristics. All studied factors in this experiment including WUE, RWC, proline, EL, photosynthetic pigments and yield were affected by drought stress but 1.5% biochar  and 75 μmole per liter methyl Jasmonate resulted in enhancement of studied factors of stressed plants both in 60% of FC and in 30% of FC in comparison to untreated plants. But increasing in usage of these materials  didn’t have any positive impact on studied plants. The highest economical yield was obtained in normal irrigation circumstance with foliage application of 75 μmole per liter of methyl jasmonate and using 1.5% of biochar per soil weight and the lowest yield was obtained when we used 30% of field capacity in irrigation without using methyl jasmonate.

We can find out from these results that as a whole drought in middle and severe levels can be disastrous for both morphological and physiological characteristics of every plant which results in reduction in economical yield. But it's necessary to mention this point that using stress moderator  materials whether materials which are used in soil like Biochar or plant growth regulators like methyl Jasmonate which are known as the anti stress substances cause moderation in the catastrophic effects of drought stress which through enhancing some indexes like the relative water content and ameliorating of water use efficiency in comparison to untreated plants with these materials can diminish the severe impacts of stress and eventually through boosting economical yield can dwindle damages of drought. Nevertheless it's absolutely comprehensible from the results of the experiment that using too much of these materials not only do not have any positive effect on growth, physiological or biochemical indicators under drought stress but also can reduce these characteristics even to lower than their quantity in untreated plants.