Field pea cardinal temperatures, growth and vigor traits of winter- and spring-adapted germplasm at germination and seedling stages.

There are few estimates of cardinal temperatures [T (base), T (optimal), T (maximum)] for pea (Pisum sativum L.) seed germination and seedling growth traits, with variable results, and there is almost no understanding of how these traits vary among pea varieties or classes. The objective of this controlled-environment study was to compare these among multiple varieties of food-grade winter and spring field peas and Austrian winter pea (AWP). Contrary to hypothesized outcomes, there were no collective differences in any of the three cardinal temperatures between winter- and spring-adapted food-grade field peas. Overall estimates were - 0.98 °C for T, 27.5 °C for T, and 37.5 °C for T. AWP, known for exceptional cold hardiness, contrasted from the food peas in having lower T (25.7 °C) and T (36.1 °C). Metrics of seedling vigor and growth (germination rate and percentage, shoot elongation) were markedly higher for AWP than the food peas. The food-grade winter pea seeds were collectively somewhat more vigorous than the spring peas. Considering both cardinal temperatures and germination rate, the average thermal time requirements for 50% germination were 31.0, 46.6, and 55.9 °Cd for AWP, winter food, and spring food peas, respectively. These results provide improved metrics and understanding of field pea seedling responses to temperature.