The base temperature for growth is an important element in plant growth models that utilize heat accumulation methods. The effect of location (environment) on the base temperature for growth of sorghum [ Sorghum bicolor (L.) Moench] genotypes was studied. Seeds of six sorghum genotypes were obtained from three locations: Manhattan, KS, College Station and Lubbock, TX. The seeds were placed on moist germination blotter paper on a one‐way thermal gradient plate. Observations were made at least daily for 3 wk to determine the number of days required for (i) germination (i.e., protrusion of the radicle from the seed), (ii) root elongation to 10 mm or longer, and (iii) shoot elongation to 10 mm or longer. The base temperature for germination of each genotype was then determined as the x‐intercept from regressing the rate of germination (i.e., the reciprocal of the number of days required to germinate) vs. the mean temperature. A similar regression was used to determine the base temperatures for shoot elongation and for root elongation of each genotype. The values of base temperature for shoot and root elongation were similar for the genotypes studied, and were consistent with the values of base temperature for emergence of sorghum reported in the literature; whereas the base temperature for germination values were up to 4.6 °C lower than reported values. Results indicated that: the base temperature for shoot elongation is not affected, the base temperature for root elongation is somewhat affected, and the base temperature for germination is more affected by the location (environment) of seed production.
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Lawlor et al. (1990) studied this question.