Sensitivity of Grain Sorghum to High Temperature Stress during Reproductive Development

Sorghum (Sorghum bicolor L. Moench) grown in semiarid regions is often exposed to short periods of high-temperature (HT) stress during reproductive development. Objectives of this research were (i) to quantify the effects of short episodes of HT stress during reproductive development on physiological, growth, and yield processes of grain sorghum and (ii) to identify the stage(s) most sensitive during the reproductive development phase to HT stress. Plants of hybrid DK-28 E were grown in growth chambers at daytime maximum/nighttime minimum optimum temperature (OT) of 32/22°C until 29 d after sowing. Thereafter, plants were exposed to OT or HT (40/30°C) or were reciprocally transferred at 10-d intervals (10 d before fl owering, 0, 10, 20, and 30 d after fl owering [DAF]) from OT to HT and vice versa. Transferred plants remained in the new temperature regime for 10 d before being returned to their original temperature regime. Continuous HT stress delayed panicle emergence and decreased plant height, seed set, seed numbers, seed yield, seed size, and harvest indices but did not infl uence leaf photosynthesis. Exposure to short (10-d) periods of HT stress at fl owering and 10 d before fl owering caused maximum decreases in seed set and seed yield, and HT stress during postfl owering stages (10, 20, and 30 DAF) decreased seed yield, with a larger reduction at early stages of seed development. Dep. of Agronomy, 2004 Throckmorton Hall, Kansas State University, Manhattan, KS 66506; M.R. Tuinstra, current address: Dep. of Agronomy, 1150 Lilly Hall, Purdue Univ., West Lafayette, IN 47907. Contribution no. 08-213-J from the Kansas Agricultural Experiment Station. Received 18 January 2008. *Corresponding author ([email protected]). Abbreviations: DAF, days after fl owering; DAS, days after sowing; HT, high temperature; OT, optimum temperature. Published in Crop Sci. 48:1911–1917 (2008). doi: 10.2135/cropsci2008.01.0036 © Crop Science Society of America 677 S. Segoe Rd., Madison, WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.