Efeito do estresse hídrico e térmico na germinação e no vigor de sementes de cenoura Effect of heat and water stress on germination and vigour of carrot seeds

ABSTRACT The objective of this study was to evaluate the effect of water and thermal stress on the germination and vigor of carrot seeds. Two experiments were performed in the Universidade Federal de Vicosa; three lots of carrot seeds were used, lot 1 of cv. “Carandai “ and the lots 2 and 3 of cv. “Brasilia “. In experiment 1 – Water stress - Four osmotic potentials, 0.0; –0.3; –0.6 and –0.9 MPa were used to humidify the paper substratum, with a solution of PEG 6000 in concentrations of 0; 17.16; 25.68 and 32.16 g L –1 . Germination and vigor were estimated. For experiment 2 – Thermal stress - Three temperatures were used, 15o, 20o and 35o C, to evaluate the quality of the seeds. It A paper towel humidified with water was used as substratum, in the proportion of 2.5 times the weight of the paper. It is concluded that the germination of the carrot seeds was not affected by potentials of –0.3 MPa. The length of the roots and the first germination count were efficient to evaluate the vigor of the carrot seeds, under water and thermal stress, allowing the classification of the tested lots. Temperatures of 15o and 35o C influenced the germination and the vigor of the carrot seeds negatively.