Photosynthetic performance of maize subjected to low temperatures

Abstract

The introduction of early maturing cultivars has enabled forage maize to be grown in climatically marginal areas of Europe. The major constraint in growing maize in North-west European countries is the impact of sub-optimal temperatures during early growth and establishment. The use of plastic coverings to improve the establishment of seedlings in the field has considerable practical, economic and environmental costs, so breeders are now directing their attention at improving establishment and yield under cool-temperate conditions in the absence of plastic mulches. The objectives of the present study were to screen seedlings of nine commercial hybrids recommended for Ireland for photosynthetic performance under spring and early summer conditions. Maize seedlings subjected to sub-optimal temperatures show major variety-dependent reversible reductions in photosynthetic performance, although isotope data indicate that all have a functional C4 pathway. Non photochemical quenching (NPQ) may be a significant factor in protecting the photosynthetic apparatus of maize seedlings subjected to sub-optimal temperatures. The patterns of variation between varieties observed during cold exposure at 15 °C and after recovery at 20 °C were not directly correlated. This indicates that both the traits associated with an enhanced performance under low-temperature exposure as well as those associated with recovery may need to be considered when breeding improved maize varieties for cool-temperate regions.