Diurnal temperature amplitude alters physiological and growth response of maize (Zea mays L.) during the vegetative stage

• Lower diurnal temperature amplitude negatively impacts maize growth.
• Decrease in diurnal temperature amplitude increases leaf night respiration.
• Increased night respiration reduces carbohydrate and biomass accumulation.
• Studies dealing with temperature stress would need to consider amplitude changes.

Global climate models predict increase in mean daily temperature to be mainly driven by rapid increase in nighttime temperature compared to daytime temperature, leading to narrowing diurnal temperature amplitude. Higher day and night temperatures induce significant negative impact on growth and development of different crops. However, limited studies have focused on quantifying impacts associated with different diurnal temperature amplitudes maintaining the same daily mean temperature. The main objectives were to (i) quantify the impact of diurnal temperature amplitudes on the carbon balance of the plant (photosynthesis versus night respiration rate) and (ii) evaluate the significance of variable day and night temperature with a common mean on the carbohydrate composition and overall plant growth. A maize hybrid (DKC47-27RIB) was grown in controlled environments at two mean daily temperatures (30 °C and 35 °C) with three different combinations of day and night temperatures resulting in diurnal temperature amplitudes of 2 °C, 10 °C and 18 °C. After 42 days of temperature treatments, lower diurnal temperature amplitude led to a linear increase in night respiration and a linear decrease in total sugars, non-reducing sugars, starch concentrations, plant height, total leaf area and total biomass accumulation. However, there was no significant change in photosynthetic rate among the treatment combinations, while photochemical efficiency (Fv/Fm) and chlorophyll index decreased only with diurnal temperature amplitude of 18 °C and 2 °C, respectively. A significant negative relationship was found between night respiration and total biomass accumulation (R2 = 0.73; P < 0.01), total leaf area (R2 = 0.82; P < 0.01), specific leaf area (R2 = 0.21; P < 0.01), non-reducing sugars (R2 = 0.50; P < 0.01) and starch concentrations (R2 = 0.50; P < 0.01). The results imply that narrowing diurnal temperature amplitude as a result of higher night temperature is the major driver of the negative impact on vegetative growth in maize.