M.A. Thesis:

Effect of putrescine on morphological characteristics of shoots and roots of maize under salt stress

In order to investigate the effect of foliar application of putrescine on morphological characteristics of root and shoot of corn under salinity stress, a factorial experiment in a randomized complete block design with three replications was carried out in greenhouse of agricultural faculty, Islamic Azad University, Sabzevar branch. Experimental factors included three levels of salinity stress: 0 (control), 4 and 8 dS/m and concentration of putrescine at four levels of: 0, 0.5, 1 and 2 mM. Foliar application of putrescine was performed in two stages of complete plant establishment and one month after that. The results showed that salinity stress significantly reduced leaf chlorophyll index, plant height, total root area, total root length, root dry weight, shoot dry weight and leaf relative water content of corn. The root volume was not affected by 4 dS/m salinity level, but significantly decreased by 8 dS/m salinity level. Different levels of salt stress caused a significant increase in root diameter compared to control. Putrescine foliar application at 0.5 mM concentration, increased leaf chlorophyll index, plant height, root volume and shoot dry weight compared to non-foliar application treatment. Foliar applications of higher concentrations of putrescine had no significant effect on plant height and shoot dry weight, but decreased leaf chlorophyll index and root volume. Different levels of putrescine foliar application caused a decrease in total root area, root average diameter and root dry weight compared to non-foliar application conditions. In 8 dS/m salinity level, foliar application of putrescine at concentration of 0.5 mM significantly increased root volume; total root area and root dry weight by decreasing the negative effects of salinity stress. The foliar application of putrescine at concentration of 0.5 mM also significantly increased the root dry weight in 4 dS/m salinity level. The foliar application of putrescine at concentration of 2 mM significantly increased root/shoot ratio in 4 and 8 dS/m salinity levels. According to the results, two foliar applications of putrescine at concentration of 0.5 mM is recommended for improving the shoot and root growth of corn under salinity stress.

Keywords: Salinity, polyamine, relative water content, foliar application, corn