Effect of auxin, cytokinin and planting pattern on grain yield and salt tolerance indicators of maize

Salinity of soil and irrigation water is the most important factors limiting crop production in arid and semi-arid areas. Corn because of diversity, adaptation and high nutritional value is among the best crops in the world and in terms of production in the first place. Planting pattern can be effective on access to light, water and nutrients. Cytokinins by accumulation of chlorophyll and conversion of etioplast to chloroplasts and Collection of free radicals delay leaf senescence. Auxins also have a very important role in salinity tolerance. Auxin is involved in the transport of carbohydrates in their production time. Therefore, the objective of this study was to evaluate the effect of cytokinin and auxin foliar application on salt tolerance indices of maize under different planting patterns in salinity conditions.
The experimental design was split plot based on randomized complete design with three replications in Bushehr Agricultural and Natural Resources Research Center in 2014. Planting patterns (ridge planting, double rows of planting on ridge in zigzag form and furrow planting) as the main factor and use or non-use growth regulators (not consumption, application of cytokinin hormone in the time of V8-V10 and application of auxin hormone at the silking stage) were investigated in sub plots. The electrical conductivity of soil and water is equal to 5.2 and 4 dS/m. Plant spacing in the ridge planting and furrow planting patterns was 17.5 cm and in the double rows planting was 35 cm and thus for all treatment plant density was 75,000 plants/ha. Benzyladenine (BA) and indole-3-butyric acid (IBA) were used as cytokinin and auxin hormone at a concentration of 50 and 10 mg/lit, respectively.
The results showed that pattern of double rows and pattern of furrow planting compared with conventional planting (ridge planting) increased grain yield to 30.6% and 43.4%, respectively. The highest chlorophyll a, b and carotenoid content of starch and Potassium ions (K) were obtained with pattern of furrow planting, while the highest relative permeability of the membrane, proline, total soluble sugars, sodium ions (Na), Chlorine ions (Cl-) and Naﲯ were devoted to the pattern of conventional planting (ridge planting). Foliar application of cytokinin and auxin increased grain yield to 34.3 % and 43.5 %, respectively. Foliar application of benzyladenine (BA) and indole-3-butyric acid (IBA) decreased relative permeability of the membrane, total soluble sugars, sodium ions (Na) and Naﲯ. However, chlorophyll a, chlorophyll b and carotenoid pigmens, proline and starch content increased with foliar application of growth regulators and the highest amount was obtained with the application of auxin hormone. The highest proline in furrow planting pattern was obtained by auxin while in double rows planting highest proline was obtained by foliar application of cytokinin. In each pattern the highest total soluble sugars was without application of growth regulator. In different planting patterns the highest of sodium ions was without regulator while the lowest amount of sodium ions was obtained with application of auxin.
Generally, results showed that change planting pattern to furrow planting and foliar application of cytokinine and auxin at the concentration 50 and 10 mg/l, respectively, increase salt tolerance of maize.