Effect of Ophiobolus graminis infection on the assimilation and distribution of ¹⁴C in wheat

SUMMARY The uptake of 14 C and movement of 14 C‐labelled assimilates in wheat plants inoculated with Ophiobolus graminis was examined following exposure of the second youngest leaf to 14 CO 2 . Autoradiographs of plants with infected seminal roots showed that assimilates were not translocated past the sites of root infection but accumulated in the undamaged portions of infected root systems, in particular the developing crown roots. There was no evidence that assimilates accumulated in the vicinity of O. graminis lesions. The net assimilation of 14 CO 2 by wheat plants over a 5 h feeding period was not significantly affected by O. graminis infection. However, infection reduced the amount of 14 C lost through respiration. Infection delayed the transfer of labelled assimilates from the fed leaf to the remainder of the plant but increased the proportion translocated to the roots. The latter effect was not apparent when infected plants were continuously irrigated during, and for 20 h following, the feeding period.