3.1. Coordinated growth responses
The rates of seed germination, leaf appearance, tillering or branching
and leaf expansion show coordinated responses to warm temperature in
crops (Parent & Tardieu, 2012), but with large variation among
different cultivars from the same species (Bahuguna et al., 2014;
Friend, 1965; Li, Kennedy, Huybrechts, Dochy, & Geuten, 2019). High
temperature delays the start of stem elongation and results in faster
stem growth rates, but without modifying total time to heading in wheat
and barley (BorrĂ s-Gelonch, Denti, B Thomas, & Romagosa, 2011; Karsai
et al., 2013; Kiss et al., 2017). However, a temperature above the
optimum decreases the number of leaves and tillers, as well as final
stem height (Dixon et al., 2019; Hemming et al., 2012; Karsai et al.,
2013). Some species, however, react differently to elevated ambient
temperatures during vegetative growth. For example, soybean does not
exhibit big changes during vegetative development at higher temperatures
(Choi, Ban, Seo, Lee, & Lee, 2016; Lippmann et al., 2019).