Influence of temperature on seed germination and on the vigour of seedlings of cupuaçu (Theobroma grandiflorum (Willd. ex-Spreng) Schum.)

Abstract

The effects of different temperatures on seed germination and on the vigour of seedlings of Cupuaçu (Theobroma grandiflorum (Willd. ex-Spreng) Schum.) were studied. The experimental design consisted of 5 x 3 test variants, carried out in 12 replications each with 17 seeds. The effects of five different temperatures (15, 20, 25, 30 and 35°C) and three different substrates (sand, sawdust and vermiculite) were tested in darkness. After the fifth day from sowing, the percentage of the viable seeds were estimated daily. Additionally, the total germination rate and the percentage of normally developed seedlings were recorded. From the numbers of seeds which germinated daily, an "index of germination velocity" was calculated. Measurement of seedlings height, radicle length and dry weight of the cotyledones were done. At the 15°C temperature level seed germination was inhibited while accelerated at the 35°C level although damaged the cotyledones and the radicles. The best germination temperature was between 20 and 30°C independently of the substrate used.