Effects of salicylic acid on yield and nutrient uptake of borage (Borago officinalis L.) under interrupting irrigation conditions

Borage (Borago officinalis L.) is an annual plant and belongs to the Boraginasea family, that afford curative properties. This plant has deep roots and can absorb soil, water and nutrients from the depths of the soil, and is therefore somewhat resistant to drought. Increasing people's tendency toward medicinal plants to treat diseases has conduct to and essential the cultivation of medicinal plants globally and in Iran. Water deficit stress is one of the most important non- biological stresses that reduces water absorption by root system. Water deficit is considered as the most important limiting factor for non-living plant growth and yield that, in addition to a negative effect on yield, causes exacerbates other stresses, in particular the stress of the deficiency of nutrients in the plant. Drought stress is one of the most important limiting factors yield in the world. Today, phenolic compounds and plant growth regulator has been proposed, to reduce the negative effects of stress. Thus, this experiment carried out in order to Effects of salicylic acid on yield and nutrient uptake borage (Borago officinalis L.) under interrupting irrigation conditions.

A field study was conducted as a split plot arrengement based on randomized complete blocks design (RCB) with four replications at farm at experimental field of Khouzestan Agriculture Science and Natural Resources University, Iran during 2017-2018 cropping season. Three interrupting irrigation (stress at stemming stage, stress at flowering stage, stress at seed fill stage and control) as main plat and four application of salicylic acid including of 0, 69, 138 and 207 mg.L-1 as sub plots comprised experimental treatment. With reach each of these stages, from stem emergence to flowering initiation, from flowering initiation to seed fill interrupting irrigation and from seed fill initiation to beginning seed harvesting interrupting irrigation was carried out. This continued until the end of the physiological stages. Salicylic acid application was carried out during two stages during vegetative period (stem emergence and flowering initiation) simultaneously with applying moisture stress treatment. After applying the respective treatments, traits were measured at full flowering stage. Grain yield, oil percentages, ash contents of flower and leaf, nutrients of nitrogen, phosphorus, potassium, and sodium in two parts of the flower and leaf of Borage were measured. Analysis of variance and comparison of means was performed by SAS software and test LSD, 5% level probability .Respectively.

The result of analysis of variance showed that interrupting irrigation and salicylic acid had significant effect on grain yield, oil percentages, ash contents of flower and leaf ash and nutrients of nitrogen, phosphorus, potassium, and sodium in two parts of the flower and leaf. Also interaction effect of interrupting irrigation and salicylic acid on flower ash, potassium flowers, and leaf, phosphorus and sodium flowers was significant. Mean comparison test showed that with interrupting irrigation in stemming and flowering stages, only the concentration of sodium and potassium elements and oil percentages increased significantly. Maximum grain yield in the control treatment was 633.43 kg. ha-1. Foliar application with 207 mg.L-1 salicylic acid increased 50% grain yield. Salicylic acid increased all the traits studied, other than sodium. Consumption of 138 mg.L-1 salicylic acid in interrupting irrigation condition increased 36% of flower ash and 38% of leaf phosphorus, due to non-consumption of salicylic acid and drought stress. The highest amount of potassium of flower and leaf were obtained by application 138 and 207 mg.L-1 salicylic acid in interrupting irrigation stress at flowering stage and maximum flowering sodium without application salicylic acid with interrupting irrigation in this stage.

The results suggested salicylic acid application in borage can increase uptake of macro nutrients required for plant growth and reduce the negative effects of drought stress damage.