Can Germination Requirements Predict Tolerance to Extreme Weather? — An Assessment for Heirloom Maize from the P'urhépecha Plateau

摘要

The temperature and water potential requirements for seed germination were determined for five heirloom maizes from three different agroclimatological regions from the P'urhépecha community of San Francisco Pichátaro, Michoacán, Mexico. Germination experiments were conducted in environmental controlled chambers exposing seeds to dayight air temperatures (12 h photoperiod) of 15/5, 20/10, or 35/25oC, and to water potentials of 0, –0.01, –0.05, –0.1, or –0.5 MPa, which were created with aqueous solutions of polyethylene glycol (molecular weight 20,000). Germination was maximal and occurred at a faster rate for seeds incubated at 35/25oC. In turn, a high water potential of 0.0 or –0.01 MPa was necessary to achieve maximum germination, which decreased under more negative water potentials until germination was completely inhibited for seeds incubated under –0.5 MPa failed. Although an environmental specialization for germination was not observed among the heirloom maize evaluated, their ability to germinate maximally under high temperatures is indicative of their cultivation potential under the increasing air temperatures expected to occur during the present century. In contrast, germination sensitivity to relatively mild water potentials may be a conservative ecophysiological trait of drought-escape for this tropical annual plant.