The effect of foliar application of some micronutrients and salicylic acid on root morphological characteristics and seed yield of rapeseed (Brassica napus L.) under water deficit stress

canola (Brassica napus L.) is one of the most important oilseed plants that has been ranked third in the oil production after soybeans and oil palm. Drought is seriously the most important factor limiting the growth and production of canola in Iran. By foliar application of micronutrients, plant growth condition can be improved under stress. Salicylic(SA) acid plays an important role in abiotic stress tolerance, and more interests have been focused on SA due to its ability to induce a protective effect on plants under adverse environmental conditions. It is necessary to know the traits related to drought tolerance and their relationship with seed yield. due to the important role of roots in the absorption and conduction of water and nutrients, recognition the root system and how it is distributed in the soil is special importance. therefore, the purpose of the present study was to investigate the Effect of foliar application of some micronutrients and salicylic acid on root characteristics and seed yield of canola (Brassica napus L.) under water deficit stress.

the experiment was conducted as split factorial in a randomized complete block design with three replications in Lorestan University, Iran, in two cropping seasons (2016-2018). water deficit was considered as the main factor in levels irrigation at 80 (control) and 30% of field capacity, and the combination of foliar application of micronutrient fertilizer (non-consumption and spraying at a concentration of 0.2%) and salicylic acid concentration of 0, 0.5, 1 and 1.5 mM were considered in sub-plots. the time of water deficit stress coincided with the stage of the beginning of regrowth (BBCH32). foliar application of micronutrient fertilizer in rosette stage (BBCH29) and foliar application of salicylic acid in two stage of flowering beginning (BBCH60) and pod filling (BBCH72). the measured traits included root dry weight, root volume, root area, seed yield, oil percentage, and water use efficiency. the data was analyzed by statistical analysis system (SAS version: 9.1). the means were analyzed using the Duncan test at P=0.05.

the results of analysis of variance showed the effect of year on seed yield, effect of salicylic acid on seed yield and oil percentage, double interaction of micronutrient fertilizer in salicylic acid on root volume and triple interaction of stress in micronutrient fertilizer and salicylic acid on root weight, root volume and water use efficiency were significant. the results of comparative analysis of the mean data showed that the highest percentage of oil was obtained from concentration of 1 to 1.5 mM of salicylic acid.the highest root volume (49.90 cm3) was obtained from the treatment composition (foliar application of 1.5 mM salicylic acid and concentration of 2 per thousand micronutrient fertilizers). the highest root dry weight (28.95 gr), root area (4360 cm2) and water use efficiency (1.26 kg m-3) from the treatment composition (no stress + 1.5 mM salicylic acid spraying and concentration of 2 per thousand fertilizers Micronutrients) was obtained. the highest seed yield (4955.7 kg ha-1) was obtained from foliar application 1.5 mM of salicylic acid, In the first year, the highest seed yield (4427.7 kg ha-1) from the combination (no stress + foliar spraying of 1.5 mM salicylic acid and a concentration of 2 per thousand micronutrient fertilizers) and in the second year of the combination (no stress + foliar spraying of 1 mM salicylic acid) and a concentration of 2 per thousand micronutrient fertilizers with an average (4955.7 kg ha-1) was obtained.

therefore, a triple micronutrient fertilizer (iron+zinc+ manganese) with a concentration of 0.2% is recommended along with a concentration of 1.5 mM of salicylic acid to reduce the negative effects of water deficit stress and achieving acceptable seed yield.