The effects of short-term chilling stress on proline changes and carbon hydrates of sorghum (Sorghum bicolor L.)

In current study, the effects of short-term refrigeration on 15 sorghum cultivars was studied based ongrowth indices and germination percentage. Cultivars Var1 and Sofra were selected from fifteencultivars as the most resistant and sensitive cultivars for further studies about chilling stress. In nextstage, after germination of tolerant and sensitive seeds, seedlings were kept under light-dark cycles of16:8 and a temperature of 25 ± 2 ° C for 14 days. After that, seedlings were exposed to 4± 1, 8 ± 1 and12 ± 1℃ temperatures in growth chamber for 12 hours of darkness. Dry weight, leaf water content andelectrolyte leakage of membrane, chlorophyll changes, lipid peroxidation, and proline amount weremeasured at two stages: a) the end of chilling stress b) seven days after retrieval opportunity. Resultsshowed that chilling affected both cultivars growth. At the end of stress, relative water content of theleaves was decreased due to reduction in turgor potential. This reduction was significant in higherlevels of chilling. It also showed a positive correlation with reduction in shoot fresh weight. Thisreduction was more sever in Sofra cultivar. Electrolyte leakage and lipid peroxidation are increasedafter the stress period. This increase was more and significant for Sofra cultivar in comparison withVar1. Chilling caused significant increase in osmolytes amount (including proline) in leaves of bothcultivars and this increase was in consistent with the trend of chilling increment. Tolerant cultivarshowed considerable increment. Increase in proline amount was more in retrieval period. According tothe results of this research we can conclude that sorghum is a chilling sensitive plant and chillingreduces its dry weight. This plant tries to provide some toleration mechanism such as synthesis andaggregation of osmolytes. It can be concluded that reducing the damage caused by the cooling inretrieval time depends on the genotype of the plant.

Keywords:

chilling stress , proline , dry weight , sorghum , rehydrate and soluble carbohydrate , electrolyte leakage , lipid peroxidation