Resumo

VALADEZ-GUTIERREZ, Juan et al. Seed sizes, invigorization substances, and vigor tests in cold tolerant sorghums. Agrociencia [online]. 2007, vol.41, n.2, pp.169-179. ISSN 2521-9766.

Slow growth during the field establishment of cold tolerant sorghum (Sorghum bicolor L. Moench) in the Central High Valleys of México, has been attributed to the effect of low temperatures and to small seed size. From April to May of 2005, under laboratory conditions, 36 treatments were evaluated in a complete randomized block design with four replicates, product of the factorial combination of three genotypes (VA-110 and two maintainer lines, B1 and B9), three seed sizes (large, medium and small) and four types of seed invigorization (osmoconditioning, Maxi Grow T.S.®, potassium nitrate, and control), in three vigor tests: 1) standard germination; 2) cold; 3) modified cold, in which the germination phase was maintained without light. The experimental unit consisted of 25 seeds. The variables analyzed were: percentage of germination, abnormal seedlings, and dead seeds; average length (cm) of plumule and radicle per seedling; and total dry weight (mg) of plumules, radicles and remains of seeds of each experimental unit. The length of the plumule was greater (p≤0.05) in the cold test, but the radicle was longer (p≤0.05) in the modified cold test. Total dry weight of plumules was 3 to 4 times greater than the total dry weight of radicles, according to the germination conditions. The variety VA-110 surpassed (p≤0.05) lines B1 and B9 in germination and vigor. The largest seed sizes did not always exhibit the highest expressions of germination and vigor, due to their interaction with genotypes and with the invigorization substances. The invigorization treatments were not a viable alternative for overcoming the problem of slow growth of the seedling of the sorghum genotypes.

Palavras-chave : Sorghum bicolour L. Moench; osmotic conditioning; germination; cold test.