Table 1.
Temperature threshold values for various wheat growth stages.
| # | Growth phases | Min. and Max. (Tolerable Temp. Limit) | Optimum Temp. (Ideal Growth Cond.) | Optimum duration for growth phases | References |
|---|---|---|---|---|---|
| 1 | Germination and emergence (E) | >4 and <40°C | 12–30°C | 3.5–10 d (depending on soil moisture) | Spilde, 1989; Mian and Nafziger, 1994; Jame and Cutforth, 2004 |
| 2 | Floral Initiation (GS1- Prior Vernalization) | −20°C*, >20 | 21–16°C | 20 d (Spring) 35 d (Winter) | Evans, 1975 |
| 3 | Floral Initiation (GS1-Vernalization) | 7 and 18°C (Spring) 0 and 7°C (Winter) | 4–10°C | 5–15 d (Spring) 30–60 d (Winter) | Ahrens and Loomis, 1963; Trione and Metzger, 1970; Evans, 1975 |
| 4 | Heading to Anthesis (GS2) | >4.5 and <31°C | 12°C | 100 d (Spring) 130 d (Winter) | Fischer, 1985; Stapper and Fischer, 1990; Acevedo et al., 2009 |
| 5 | Anthesis to Physiological Maturity (GS3) | >6 and <35.4°C | 21°C | 140 d (Spring) 170 d (Winter) | Lyons, 1973; Porter and Gawith, 1999 |
*
Only for winter wheat, while spring wheat shows mild to no response to frost.