Germinação e vigor de sementes de Phaseolus vulgaris L. em diferentes potenciais osmóticos induzidos por polietileno glicol - 6000.

Abstract

Seeds of ten bean cultivars {Phaseolus vulgaris L.) were submitted to six levels of osmotic tension (0; -0,2; -0,4; -0,6; -0,8 e -1 MPa) of PEG-6000, with the purpose of studying the induced effects of water stress on the germination of the seeds and seedlings' growth. The experiment was conducted in laboratory conditions, in a germinator with controled temperature and relative humidity, making use of a neutral pH paper towel as a substract. The experimental design was completely randomized in a 10 x 6 factorial scheme with four replications each consisting of 50 seeds for germination and 10 seeds for vigor test. The results obtained have shown that there was influence of PEG-6000 on the seeds' germination and on the seedlings' vigour. The cultivars Jalo Precoce and Onix were found to be more tolerant on water stress, both in terms of germination and vigour (first counting of germination). On the other hand, the cultivars Diamante Negro, Goytacazes and São José were the most sensitive ones. In the seedlings vigour test the vDimante Negro' was found to be the most vigourous cultivar under reduced osmotic potential (-0,4MPa and -0,6MPa), in terms of measurement of hypocotyl, radicle and of seedling (hypocotyl + radicle), while ^Safira' was the most sensitive one. The abnormality seedlings index was expressive beyond the potential -0,4MPa (N3) of PEG-6000, resulting in absence and atrophy of the radicle and producing a short radicle system, without principal root and with few secondary roots. The percentage of infected seeds increased in the same proportion to PEG-6000 concentration levels. The seedlings vigour test became unworkable when a ten seeds sample was used for each replication on potentials of -0,8MPa and -1,0MPa induced with PEG-6000. In water stress conditions radicles tended to be longer than the hypocotyl, in the initial phase, after the germination of the seeds.