Temperature Response of Endogone Mycorrhiza on Soybean Roots

SUMMARYGrowth of an Endogone sp. on soybean roots was evaluated in autoclaved soil maintained at temperatures ranging from 17 to 41 C. Maximum arbuscular development of Endogone in the root (mean of four experiments) occurred near 30 C. Mycelial development of Endogone on the root surface was greatest between 28 and 34 C. Spores/50 ml of soil and echinulate vesicle clusters/55 cm of root were most numerous at 35 C. Root growth after 60 da without Endogone mycorrhiza was less than that with Endogone, but shoot development was similar for both. No plant growth occurred at 41 C. The affinity of this species of Endogone for high temperatures correlated well with its abundance in the rhizosphere of summer crops rather than crops grown at other seasons of the year.