Evaluation of some the physiological and growth responses of three walnut genotypes to different bicarbonate concentrations in irrigation water

In order to evaluate the effects of sodium bicarbonate of irrigation water on the physiology and growth characteristics ofwalnut genotypes, a factorial experiment was performed with two factors including bicarbonate at 3 levels (0, 20 and 40 mM) and walnut genotypes (including local genotype A and wild genotypes B and C), based on completely random design. In this study, the effect of bicarbonate on various traits such as growth, photosynthetic parameters, osmotic adjustment compounds and nutrient elements of each genotype were examined. Results showed that bicarbonate affected all traits, and the differences among the three genotypes were clearly obvious. Irrespective of genotype, iron concentration decreased in shoots of all plants. The lowest reduction (15.17%) of iron concentration of shoots at 40 mM bicarbonate was related to the genotype A. The lowest chlorophyll percentage was observed in genotype A when exposed to bicarbonate, as compared with control. Results showed that walnut belongs to the group of horticultural crops that are highly sensitive to bicarbonate existance in irrigation water. So that, the growth of plants began to reduce from 20 mM treatment. According to the results of this study, genotype A had the highest tolerance to bicarbonate and had better growth in these conditions. Although, there was no significant difference between genotype B and C. Therefore, genotype A can be introduced as a tolerant genotype to bicarbonate existence in irrigation water and can be used in walnut breeding programs.