Abstract

Full plant growth and development require, among others, air temperatures and water availability at levels appropriate to each crop. The effect of temperature on plant development can be represented by the thermal sum, which requires the lower basal temperature for each plant species. However, plant responses may be different when associated with different soil water contents. This work determined the lower and upper basal temperature of Jatropha curcas L. and verified the relationship between thermal sum and crop development under different water regimes, in the climatic conditions of Goiânia, GO, Brazil. We evaluated twenty-four plants cultivated at the planting density of 2,222.2 plants ha^-1. Of these, twelve plants were irrigated from October 2010 to October 2012, whereas the other twelve remained unirrigated. Basal temperatures were estimated by four different methods described in the literature, in two phases of observation, maturity and total cycle. From the results, regression analysis was performed. The lower basal temperature was 4.9 and 7.2 °C, and upper basal temperature was 38.8 and 36.8 °C, respectively, for the maturity and total cycle stages. The accumulated thermal sum for the complete plant development of jatropha was 10,314.55 DD (±1574.73) for the non-irrigated treatment, and 9,260.67 DD (±735.06) for the irrigated treatment. The results of plant development showed good coefficient of determination in relation to the accumulated thermal sum.

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