Effects of biochar and salicylic acid on some characteristics of (Borago officinalis L.) in water deficit condition

Borage officinalis L. is an annual herbaceous plant that is distributed in temperate and subtropical regions, especially in the Mediterranean. Nowadays, foliar application of salicylic acid (SA) as one of the growth regulator for improving plant stresses tolerance such as drought stresses. Biochar is a carbon-rich product in the stable form that benefits from organic fertilizers and is used soil fertility. Considering the importance of medical plant cultivation especially in the drought region, investigation the effects of water deficit on Borage officinalis L has particular importance and according to previous studies on the positive effect of salicylic acid and biochar on mitigation of adverse effects of drought as well as improving water relations in soil, therefore this study aimed to investigate the effects of biochar and salicylic acid (SA) on some characteristics of Borage officinalis L under different irrigation intervals

These experiments were performed in a four replicated-split plot factorial arranged in CRBD with three factors irrigation intervals (5, 10, and 15 day) in the main plots and biochar application (0, 5 and 10 tons per hector) and foliar application of salicylic acid (0,0.5Mm) in sub plots. This study was carried out in research field of Shahrood university of technology, Shahrood, Iran during 2017-2018.

the results indicate that with increasing irrigation intervals in all biochar levels, leaf relative water content (RWC) significantly decreased and biochar application had no significant effect on drought stress. Salicylic acid increased leaf relative water content (RWC) in both irrigation intervals of 10 and 15 days compared to non-treated treatments but it had no positive effect on stress reduction due to increases irrigation intervals. As the irrigation intervals increased, flavonoid levels also declined significantly, salicylic acid partially moderating its use, but biochar application had different effects on flavonoid depending on irrigation intervals. Increasing irrigation intervals up to 10 days increased the level of anthocyanin, but with increasing irrigation intervals to 15 days, it decreased significantly. Biochare application had no significant effect on anthocyanin content (both under and without salicylic acid application) but with increasing irrigation intervals to 10 days, biochar application alone without salicylic acid caused anthocyanin content increased. Nitrogen percentage of borago officinalis.L leaf increased significantly with 5 tons/ha biochar for 5 days irrigation intervals and 10 tons/ha biochar for 15 days irrigation intervals, compared to control (non-biochar). The results also show that the application of biochar 10 tons/ha at 10 and 15 days' irrigation interval moderated the stress caused by increased irrigation interval for leaf nitrogen. Increasing irrigation intervals also reduced the number of flowering shoots, which improved by biochar and salicylic acid application.

biochar had a positive effect on the improvement of some physiological and qualitative indices of borago officinalis. L under drought stress condition, but there were no significant differences between different levels of biochar in terms of positive effects in reducing the effects of irrigation intervals on some traits, Besides, the simultaneous application of biochar and salicylic acid in most traits increased their efficiency in reducing drought stress effects.