Effects of Exogenous Auxin on Mesocotyl Elongation of Sorghum

The length of sorghum mesocotyl plays a vital role in seed emergence from the soil, which is the foundation of healthy growth. In this study, we aimed to understand how exogenous auxin (IAA) promoted mesocotyl elongation of sorghum and its physiology mechanism. The results presented that exogenous IAA significantly promoted mesocotyl elongation in MS24B (short mesocotyl inbred line) by increasing the cell length, while with extra exogenous NPA (IAA inhibitor) application, the mesocotyl length presented a significant short phenotype. In Z210 (long mesocotyl inbred line), exogenous IAA had a slight effect on mesocotyl length elongation, while the NPA treatment decreased the mesocotyl length considerably. In MS24B, IAA treatment increased the activity of amylase to degrade starch to soluble sugar, and the activity of hexokinase was improved to consume the increased soluble sugar to offer more energy. The energy will help to increase the activity of PM H+-ATPase and the expression of expansin-related genes, which ultimately will promote the acidification of the plasma membrane in MS24B for cell elongation. Overall, the exogenous IAA functioned on the activation of energy metabolism, which in turn, inducted the acidification of the plasma membrane for mesocotyl elongation.

Automated summary

This study aimed to investigate the physiological mechanism of exogenous auxin (IAA) promoting mesocotyl elongation in sorghum. The results showed that exogenous IAA significantly increased cell length and promoted mesocotyl elongation in the short mesocotyl inbred line MS24B, while the application of the IAA inhibitor NPA resulted in a significant decrease in mesocotyl length. In the long mesocotyl inbred line Z210, exogenous IAA had a slight effect on mesocotyl elongation, while NPA treatment considerably reduced mesocotyl length. Overall, exogenous IAA activated energy metabolism, leading to plasma membrane acidification and mesocotyl elongation.