Resumen

BARRIOS-GOMEZ, Edwin J.  y  LOPEZ-CASTANEDA, Cándido. Base temperature and leaf extension rate in bean. Agrociencia [online]. 2009, vol.43, n.1, pp.29-35. ISSN 2521-9766.

Temperature is one of the most important abiotic factors that influence physiological and biochemical processes in the growth and development of plants. For bean (Phaseolus vulgaris L.), it is postulated that the minimal temperature for growth is 10 °C. With this purpose, a foliar extension rate was calculated (FER, µm d^-1) by measuring the central leaflet (mm) from the first trifoliated leaf at 18:00 and 06:00 h; in addition, the base temperature (T_b , temperature at which growing stops) was calculated with the FER, in seedlings of commercial and Creole bean varieties. Therefore, two experiments were carried out in the open at the Colegio de Postgraduados, Montecillo, México. Experiment I (E-I) was from January 19th to February 8th and experiment II (E-II) from February 8th to the 27th in 2005. The seedlings were exposed to nocturnal environmental temperature (E-I, average maximum of 15.8 °C and average minimum of 3.9 °C; E-II, average maximum of 16.0 °C and average minimum of 3.9 °C) from 18:00 to 06:00 h, with artificial light (800 µE m^-2 s^-1). The FER in E-I was 58.7 µm d^-1 and 61.5 µm d^-1 in E-II, and the T_b in E-I was 8.2 and 8.4 °C in E-II, with an average value of 8.3 °C in both experiments. This value of the T_b is useful for calculating the degree-day or development units of heat in Mexican genotypes of bean.

Palabras llave : Phaseolus vulgaris L.; growth; phenology; degree-day.

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