Changes in cell wall composition of rice mesocotyls in relation to growth and treatment with 4-ethoxy-1-(p-tolyl)-s-triazine-2,6(1H, 3H)-dione

A synthetic substance, 4-ethoxy-l-(p-tolyl)-s-triazine-2,6(1H,3H)-dione [TA] dramatically promoted mesocotyl growth in dark-grownrice (Oryza sativa L. cv. Nato) seedlings, the optimal concentrationbeing 0.1–0.2 mM. Changes in the cell wall compositionof the rice mesocotyls were examined in relation to growth andtreatment with 0.1 mM TA. The amount of the cell wall increasedduring the elongation in control and treated mesocotyls. Particularly,TA caused a large increase in the amount of the cell wall permesocotyl but a decrease per unit length of mesocotyl. Hydrolysisof the cell wall with trifluoroacetic acid liberated xylose,glucose, arabinose, galactose, and trace amounts of rhamnose,fucose and mannose. An increase in the relative amount of xyloseand a decrease in that of glucose in the noncellulosic fractionduring growth were found in control and treated mesocotyl walls.On the 2nd day after planting when the mesocotyl emerged, TAsignificantly affected the cell wall composition; TA decreasedthe relative amount of -cellulose in the wall, and caused anincrease in the relative amount of glucose and decreases inthose of xylose and arabinose in the noncellulosic fraction. ¹This paper is Part 7 in the series "Plant Growth-regulatingActivities of Isourea Derivatives and Related Compounds." (Received March 18, 1980; )