GROWTH AND DHURRIN METABOLISM IN SORGHUM SEEDLING 2: THE EFFECT OF TEMPERATURE, GIBBERELLIC ACID, 2, 4 DINITROPHENOL AND GLYPHOSATE

Abstract

A small increase in temperature stimulated growth and dhurrin biosynthesis in green Sorghum bicolor (Linu) Moench Sudan 70 var- Redland x Greenleafseedlings. Growth and dhurrin synthesis in the shoot are highly correlated with a coefficient r of 0.95. Gibberellic acid had no significant effect on either growth or dhurrin synthesis. 0.1 mM 2,4dinitrophenol reduced growth rate by 50% but stimulated dhurrin biosynthesis by 60% while 0.2 mM reduced growth rate by 85% and dhurrin synthesis by 30%.

Low concentrations of glyphosate inhibited growth and dhurrin formation but this inhibition can be partially reversed by supplementation with aromatic amino acids. 2.0 and 4.0 rnM glyphosate inhibited growth and dhurrin biosynthesis by 90% with a 24-hour lag period.

Glyhposate inhibited the conversion of ^t4C-shikimic acid to dhurrin by 90% in whole seedlings with shikimic acid accumulating predominantly in the roots. Glyphosate also inhibited by 50-60% the reaction leading to the formation of p-hydroxyphenylacetonitrile by sorghum microsomal fraction while reducing the products by 20%.

GA₃ Gibberellic acid

DNP 2,4-dinitrophenoI