RETENÃÃO DE CLOROFILA E SEUS EFEITOS SOBRE A QUALIDADE FISIOLÃGICA DE SEMENTE DE SOJA / Chlorophyll retention and its effects on physiological quality of soybean seed

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

This study was composed by three experiments related to the effects of chlorophyll retention in soybean seeds. The first one determined the effects of water deficit and high temperature stresses during maturation on the expression level of green seeds. The second evaluated the susceptibility of different genotypes to the expression of this problem. The third determined the maximum level of green seed that can be tolerated in a seed lot after storage. With the objective of determining the stage of development of soybean plants in which environmental stresses can be imposed, resulting in the production of high levels of green seed, plants of âCD 206â were cultivated in green house. At the end of R6 e R7.2 plants were transferred to growth chambers (phytotrons) for imposition of water deficit and high temperature stresses. Seeds harvested at R9 had their quality evaluated by germination, tetrazolium and electrical conductivity tests. Percentage of green seed and weight of 100 seed at the upper, medium and lower thirds of each plant were also evaluated. In the second experiment, plants of BRS 133, CD 206, MG/BR 46 (Conquista) and BRS 251 (Robusta) cultivars were transferred to phytotrons at R6 for inducing water and temperature stresses. The effects of the treatments were evaluated by the percentage of green seed production and by the weight of 100 seeds in the three thirds of the plants. Contents of a, b and total chlorophylls and chlorophyllase activity were determined. The third experiment determined the maximum tolerated level of green seed in lots of CD 206 and FMT Tucunare cultivars after storage, by mixing green and yellow seed in the proportions of 0%, 3%, 6%, 9%, 12%, 15%, 20%, 30%, 40%, 50%, 75% and 100%. Seed quality was evaluated by germination, accelerated aging, tetrazolium and electrical conductivity tests. Additionally, seed contents of a, b and total chlorophylls were determined. Imposing high temperature stress (28oC to 32oC) associated with no water supply at R6 resulted in high level of expression of green seed. Intensive water stress after R6 associated with normal temperatures (19oC to 26oC) does not result in the occurrence of significant levels of green seed. The expression of green seed production under these unfavorable environmental conditions varies among cultivars: Conquista and Robusta were considered more susceptible to the production of green seeds under these stressful conditions as compared to âBRS 133â and âCD 206â. These cultivars produced lower levels of green seeds, lower retention of chlorophylls and higher activity of chlorophyllase when compared with Robusta and Conquista. Soybean plants submitted to water and temperature stresses produce high levels of green seed which are small and light and have high contents of chlorophylls and low chlorophyllase activity. The contents of a, b and total chlorophylls in green seeds was inversely proportional to the activity of the enzyme chlorophyllase. The study related to the level of tolerance of green seed indicated that seed quality was negatively affected after storage. Content of chlorophyll increased with the increment of the percentage of green seed. Levels above 6% of green seed significantly reduce the quality of the seed. Seed lots with 9% or more green seed have their physiological quality significantly reduced to the point their commercialization is not advised.

ASSUNTO(S)

temperatura temperature agronomia germination germinaÃÃo deficiÃncia hÃdrica vigor semente verde green seed stress vigor water stress estresse chlorophyllase clorofilase

ACESSO AO ARTIGO

Documentos Relacionados