Heat waves imposed during early pod development in soybean (Glycine max) cause significant yield loss despite a rapid recovery from oxidative stress

Abstract

Heat waves already have a large impact on crops and are predicted to become more intense and more frequent in the future. In this study, heat waves were imposed on soybean using infrared heating technology in a fully open-air field experiment. Five separate heat waves were applied to field-grown soybean (Glycine max) in central Illinois, three in 2010 and two in 2011. Thirty years of historical weather data from Illinois were analyzed to determine the length and intensity of a regionally realistic heat wave resulting in experimental heat wave treatments during which day and night canopy temperatures were elevated 6 °C above ambient for 3 days. Heat waves were applied during early or late reproductive stages to determine whether and when heat waves had an impact on carbon metabolism and seed yield. By the third day of each heat wave, net photosynthesis (A), specific leaf weight (SLW), and leaf total nonstructural carbohydrate concentration (TNC) were decreased, while leaf oxidative stress was increased. However, A, SLW, TNC, and measures of oxidative stress were no different than the control ca. 12 h after the heat waves ended, indicating rapid physiological recovery from the high-temperature stress. That end of season seed yield was reduced (~10%) only when heat waves were applied during early pod developmental stages indicates the yield loss had more to do with direct impacts of the heat waves on reproductive process than on photosynthesis. Soybean was unable to mitigate yield loss after heat waves given during late reproductive stages. This study shows that short high-temperature stress events that reduce photosynthesis and increase oxidative stress resulted in significant losses to soybean production in the Midwest, U.S. The study also suggests that to mitigate heat wave-induced yield loss, soybean needs improved reproductive and photosynthetic tolerance to high but increasingly common temperatures.

Selection and Breeding of Suitable Crop Genotypes for Drought and Heat Periods in a Changing Climate: Which Morphological and Physiological Properties Should Be Considered?

“…Since genotypes must be selected before the growing season (with or without severe stress phases), experiences from preceding years may serve as a basis. Since more frequent and more severe extreme events including droughts and heat waves must be expected in the course of global change, breeding of crop plants with an improved performance during and after stress periods becomes a key determinant [9][10][11]141,157,175].…”

“…Upregulation only for catalase is reported in heat stressed roots [123] while concerted increase in the activities of several antioxidative enzymes is found in stressed leaves [124,125]. Control of ROS accumulation and detoxification are key processes during abiotic stress phases, which play critical role for yield stability [10]. As ROS protection is common mechanism mobilized in many abiotic stresses including drought [126][127][128][129], heat [10,115,125,130,131] and their combination [122,132], ROS scavenging enzymes and compounds are good candidates for enhanced protection to multiple stress situations.…”

“…Control of ROS accumulation and detoxification are key processes during abiotic stress phases, which play critical role for yield stability [10]. As ROS protection is common mechanism mobilized in many abiotic stresses including drought [126][127][128][129], heat [10,115,125,130,131] and their combination [122,132], ROS scavenging enzymes and compounds are good candidates for enhanced protection to multiple stress situations. Higher tolerance to drought and/or heat is associated with concerted up-regulation of key detoxifying enzymes in several crop species/varieties leading to better ROS protection along with stability of key metabolic processes like photosynthesis [132] and maintenance of the alternative mitochondrial respiration [123].…”

“…Key aspects for the comparison of drought sensitivity in crop varieties are summarized in Figure 1. Performance during non-stress phases is often lower for drought-tolerant than for well yielding standard varieties ( Figure 1A) [10]. The performance during moderate drought may decline more rapidly and then remain stable on a lower level in drought-tolerant genotypes, while standard varieties may decline more steadily ( Figure 1B).…”

“…Another aspect to be considered is that good overall performance of crop plants under stress does not necessarily coincide with yield stability [10]. Breeding for stress-tolerant crops should focus on acceptable yields under limited environmental conditions and not only on survival after stress [8].…”