Low temperature induced metabolic changes in the shoot meristematic region of Marquillo × Kenya Farmer wheat dwarf 1 plants

Abstract

Marquillo × Kenya Farmer 1 (Mql × KF 1) wheat plants respond to very short 16° treatment by decreased meristematic activity of the apical meristem and extensive cellular destruction in young leaf and stem tissues. By radiotracer techniques the metabolism of 3H-thymidine, 32P, and 14C-leucine fed to intact shoot tissues of Mql × KF 1 and normal Marquillo (Mql) plants were studied.Immediately after the onset of 16° treatment, the incorporation of both 3H-thymidine and 32P into the DNA of Mql × KF 1 meristematic regions began to decline rapidly although the total uptake of label into the meristematic tissue remained constant. The incorporation of 32P into the RNA, the acid-soluble organic phosphate compounds, and phospholipids of the Mql × KF 1 meristems also declined during the first 24 h and the inorganic phosphate radioactivity increased. After the initial decrease, the proportion of radioactivity in the RNA and acid-soluble organic compounds increased to near control levels. The distribution patterns of both 3H-thymidine and 32P were unchanged in the meristematic region of Mql × KF 1 plants at 26° or Mql plants at 16° or 26°. Protein synthesis in meristematic regions, measured by the incorporation of 14C-leucine, responds to temperature similarly in Mql × KF 1 and Mql plants.The inhibitions of mitosis, phospholipid synthesis, and DNA synthesis were extremely rapid and reversible after short 16° exposures, and are thought to be close to the primary process of temperature lethality of Mql × KF 1 plants. Although it is not known if any of these processes are responsible for the others, it is proposed that the cellular destruction is caused by the inability of cells in the elongating regions to synthesize the phospholipid components of membranes.