Interaction of high temperature and moisture content on seed viability

In nature, seeds are often exposed to high, temperatures. This may occur while seeds are still attached to the parent plant or after they have fallen to the ground and are exposed to intensive thermal radiation. Levitt (1956) indicates that soils exposed to direct sunlight may reach temperatures as high as 65 to 85°C, depending on soil type. In regions in which fire is an important factor in the environment, many seeds must sometimes tolerate extremely high temperatures if they are to survive. Sampson (1944) measured soil temperatures during a fire. Maximum soil temperatures in dense annual grass and manzanita was 515°0 at a depth of one-half inch, and 100°C at one and one-half inches. Stone (1951) demonstrated that a soil temperature of 12000 lasting for more than five minutes resulted in total seed destruction.