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The phase of pollen development observed in P. edulis at June 1 2013 across an elevational gradient near Sunset Crater Arizona. There is a negative relationship between pollen development and elevation. Temperature difference between low and high elevation in the elevational gradient for P. edulis was 4°C, with 28, 30, and 32°C for high, middle, and low elevation, respectively, when considering only daylight temperatures.
