Condicionamento fisiológico em sementes de eucalipto urograndis

Abstract

Phisiologial conditioning is a technique based on the partial hydratation of seeds in order to activate the germination methabolism, but without the occurence of root protusion which will promote, in the subsequent imbibition, increases on both the germination and the vigor of the conditioned seeds lots??. In order to icrease the germination performance in Eucalyptus grandis x Eucalyptus urophylla (urograndis eucalyptus) pyisiological conditioning protocols were evaluated. The work was carried out at the UFLA Seeds Central Laboratory. Seeds were conditioned at 20°C temperature in three different types of soluto (PEG; KNO3 and PEG+KNO3), in four hydric potentials (-0,0; -0,6;-0,8 and -1,0 Mpa), for four imbibition periods (1; 3; 5 and 7 days) and non conditioned seeds (witness). The water content was determined before and after the physiological conditioning and also after the seeds had been conditioned. The treatments effect were evaluated by germination, by vigor tests (the first germination counting, germination speed index, emergence, emergence speed index, and electric conductivity), and isoenzimes eletroforetical analysis: alchool dehydrogenizis (ADH) and malatum dehydrogenizis (MDH). The physiological conditioning in PEG solutions in a -1,0MPa concentration for 1 or 3 days and in -0,8 Mpa and -0,6 MPa concentrations for 5 or 7 days were found to effectively increase the urograndis euchalyptus seeds physiological performance. However the best results in KNO3 solution were found when the seeds were stored in a -0,8Mpa concentration for 5 days, and in -0,6 Mpa concentration for 1 or 3 days. Although high activity level has been found for ADR enzyme, which is a charecteristic of breathing araerobic routes, and low MDH enzyme, the physiological conditioning technique, even without aeration, promotes increases in the urograndis euchalyptus seeds lot physiological quality.