Timing effect of high temperature exposure on the plasticity of internode and plant architecture in maize

Abstract

The occurrence of high temperature (HT) in crop production is becoming more frequent and unpredictable with global warming, severely threatening food security. The state of an organ's growth and development is largely determined by the temperature conditions it is exposed to over time. Maize is the main cereal crop, and its stem growth and plant architecture are closely related to lodging resistance, and especially sensitive to temperature. However, systematic research on the timing effect of HT on the sequentially developing internode and stem is currently lacking. To identify the timing effect of HT on the morphology and plasticity of the stem in maize, two hybrids (Zhengdan 958 (ZD958), Xianyu 335 (XY335)) characterized by distinct morphological traits in the stem were exposed to a 7-day HT treatment from the V6 to V17 stages (Vn presents the vegetative stage with n leaves fully expanded) in 2019–2020. The results demonstrated that exposure to HT during V6–V12 accelerated the rapid elongation of stems. For instance, HT occurring at V7 and V12 specifically promoted the lengths and weights of the 3rd–5th and 9th–11th internodes, respectively. Meanwhile, HT slowed the growth of internodes adjacent to the promoted internodes. Interestingly, compared with control, the plant height was significantly increased soon after HT treatment, but the promotion effect became narrower at the subsequent flowering stage, demonstrating a self-adjusting mechanism in the maize plant in response to HT. Importantly, HT altered the plant architectures, including a rising of the ear position and increase in the ear position coefficient. XY335 exhibited greater sensitivity in stem development than ZD958 under HT treatment. These findings improve our systematic understanding of the plasticity of internode and plant architecture in response to the timing of HT exposure.