Maize Physiological Responses to Heat Stress and Hormonal Plant Growth Regulators Related to Ethylene Metabolism

Abstract

Hormonal plant growth regulators (HPGRs) have been evaluated in field grown maize (Zea mays L.), but never as a tool for prevention or mitigation of heat stress. We analyzed grain yield determination of maize crops exposed to contrasting temperature regimes (nonheated control plots [TC]; heated plots [TH]) and the application of HPGRs associated with ethylene metabolism (ethephon [ETH]; MCP [1‐MCP]). Heating extended over daytime hours between V11 and tasseling (VT), and products were sprayed immediately before (V11) and/or during (V16) heating. Plants treated with ETH always had reduced height (10–21%) and leaf area (3–10%), but these trends usually had no effect on light interception during treatment period. Biomass production was markedly affected by heating, but a significant interaction effect (P < 0.01) indicated that HPGRs caused (i) no effect among TH plots, and (ii) a decrease (13–19% for ETH and 3.8–9.4% for MCP) among TC plots. The interaction effect computed for grain yield highlighted that ETH had mild negative effects (≤ 18%) among TC plots and large positive effects among TH plots (up to 73%), whereas MCP had no effect among the former and mild positive (V16) or negative (V11) effects among the latter. Variations in grain yield were due to variations in kernel numbers (r2 ≥ 0.92), which were explained by ear growth rate around flowering (r2 ≥ 0.97). Timely application of HPGRs was critical for improving biomass allocation to the ear (ETH) and having adequate blockage of ethylene receptors (MCP).

Delayed pollination and low availability of assimilates are major factors causing maize kernel abortion

“…Therefore, the mechanism by which inferior kernels switch from weight reduction to abortion may involve sugar signaling ( Kakumanu et al , 2012 ). To this end, ethylene has been suggested to be involved in ovary abortion in maize and wheat ( Young et al , 1997 ; Young and Gallie, 1999 ; Hays et al , 2007 ; Cicchino et al , 2013 ). Glucose could play a vital role in suppressing ethylene biosynthesis ( Hong et al , 2004 ; Wang et al , 2014 ) and its signaling pathway ( Yanagisawa et al , 2003 ; Iqbal et al , 2013 ).…”

Ethylene involvement in the regulation of heat stress tolerance in plants

“…The effect of heat stress and subsequent ET production has been investigated in multiple reproductive tissues including pollen grains (Firon et al 2012), anthers (Jegadeesan et al 2018a, stigma/style, ovaries (Savada et al 2017), flowers (Jegadeesan et al 2018b, kernels (Cicchino et al 2013), developing grains (Dias et al 2010), and fruits (Alba et al 2005;Ketsa et al 1999). While the majority of the studies showed a positive role of ET in heat stress tolerance, a few highlighted a negative interaction between ET and heat stress tolerance.…”

“…While the majority of the studies showed a positive role of ET in heat stress tolerance, a few highlighted a negative interaction between ET and heat stress tolerance. For example, exogenous application of ET biosynthesis inhibitor improved grain weight under heat stress conditions in wheat (Hays et al 2007), while exogenous treatment of ET releasing compound ethephon showed beneficial results in terms of kernel set and grain yield during heat stress conditions in maize (Cicchino et al 2013).…”

Yield response to heat stress as affected by nitrogen availability in maize

“…The likelihood of mitigations through using plant growth regulators (Cicchino et al, 2013), or adequate management of magnesium (Mengutay et al, 2013) are being discussed. Around the world, food production increased linearly with the increment of N use in the agricultural systems (Tilman, 1999), and N fertilisation is likely one of the most common management practices implemented in maize production worldwide.…”