Effects of ATP production on silicon uptake by roots of rice seedlings

Abstract

The activities of several respiratory metabolism enzymes and ATP concentrations in the roots of four genotypes of rice raised in hydroponic culture and treated with three levels of silicon (Si) (0, 1.25, and 2.00 mM) were studied. ATP concentrations in roots of the four rice cultivars were significantly higher with Si application than in the control. Phosphoglucose isomerase (PGI) activity and the combined activity of glucose-6-phosphate dehydrogenase (G-6-PDH) and 6-phosphogluconate dehydrogenase (6-PGDH) in roots were also significantly enhanced by Si addition, as was malate dehydrogenase (MDH) activity. PGI and MDH activity increased more than 50% and 25%, respectively, in TN1 roots supplied with Si compared to the control. Among the four genotypes, higher MDH activity and combined activity of G-6-PDH and 6-PGDH were detected in roots of TN1 and Bai Xiang Jing, which had higher Si uptake. ATPase activity and ATP concentrations were inhibited by four metabolic inhibitors: HgCl₂, 2,4-dinitrophenol (2,4-DNP), malonic acid (C₃H₄O₄), and sodium phosphate (Na₃PO₄). Succinate dehydrogenase (SDH) activity in roots also decreased significantly upon treatment with C₃H₄O₄. In summary, Si application can stimulate activity of key respiratory metabolism enzymes to provide more ATP for energy-dependent processes, including Si uptake, during plant growth.

Keywords:

• ATPase
• ATP
• respiratory metabolism
• rice
• silicon

Acknowledgments

This work is jointly supported by the grants from Science and Technology Department of Henan (no. 091100910100) and Provincial Natural Science Foundation of Henan (no. 0211030400) and a grant from Henan Agricultural University to Dr. J Zhang.