Growing degree days (GDD) is a tool to predict plant growth and can be adapted for use in any plant species, including cover crops. A limitation of the GDD calculation is accurate temperature parameters used to predict plant development. For most cover crop species, the cardinal temperatures are not well defined in the literature, leading to a less accurate calculation of GDD. The objective of this study was to determine the cardinal temperatures of eight cover crop species, including Austrian winter pea (Pisum sativum), balansa clover (Trifolium michelianum), barley (Hordeum vulgare), black‐seeded oats (Avena sativa), common vetch (Vicia sativa), cereal rye (Secale cereale), crimson clover (Trifolium incarnatum), and hairy vetch (Vicia villosa), using a growth chamber experiment. Seven different temperature regimes from 4 to 34°C were implemented, and the number of leaves was counted from day 0 to 21. As a result, the data were regressed to estimate the cardinal temperatures for each species. The results of this research identified base (2), optimum (3), and maximum (8) temperatures for cover crops that were not previously reported. Five cardinal temperatures determined in this study were different from what was previously recorded; base and optimum temperatures were −4.5 and 24.8°C for cereal rye, 3.9 and 26.6°C for crimson clover, and the base temperature was 3.4°C for balansa clover. The successful identification of these cardinal temperatures for cover crops will allow the development of plant growth and biomass prediction models to aid in cover crop termination decision support tools.

Common bean is a plant species cultivated around the globe. The objective of this study was to demonstrate how the physiological parameters associated with transpiration, photosynthesis and ethylene production vary in common bean plants under different periods without irrigation. Three experiments were carried out to assess leaf water potential, stomatal conductance, transpiration, carbon assimilation, and ethylene production as a function of different irrigation intervals. A fourth experiment with exogenous application of abscisic acid (ABA) in plants with daily irrigation was also carried out. In all experiments there was a reduction in stomatal conductance at the very early period without irrigation, which consequently influenced transpiration and carbon assimilation. It was also verified that the exogenous application of ABA caused a reduction on ethylene production in common bean plants. The relationship between increased ABA production and the reduction of ethylene production is discussed.