Parental environmental effects on seed quality and germination response to temperature of andropogon gerardii

Parental environments (PEs) affect seed quality and might alter the re-establishment of big bluestem grass due to impacts on seed germination. An in vitro study was conducted to quantify the temperature response of seed germination and its interaction with the PE in big bluestem. Seeds developed under eight PEs consisting of a combination of four day/night growth temperatures (GTs) (20/12, 25/17, 30/22, and 35/27 °C) and two CO₂ levels (360 and 720 μL L..1) were germinated at eight temperatures (germination temperatures (GRTs)) ranging from 10 to 42.5 °C. Quadratic and modified bilinear regressions best described the cardinal temperatures for the estimated maximum seed germination (MSG) and seed germination rate (SGR), respectively. The average MSG and SGR showed differential responses to the PEs and significantly declined above a 35 °C GRT across the PEs. For the SGR, the minimum and optimum temperatures showed significant differences from other treatments but the opposite response to elevated CO₂, while maximum temperatures significantly declined at high (35/27 °C) and low GTs (20/12 °C). Seed quality parameters, individual seed weight, and C and N contents showed a high correlation (R2 > 60) with the average percentage of seed germination and the SGR. Thus, high temperatures for both the PEs (>30/22 °C) and GRTs (>30 °C) could significantly reduce germination, affecting the re-establishment of big bluestem.