Aperfeiçoamento do uso de hipoclorito de sódio para acelerar a germinação de sementes e a emergência de plântulas de cafeeiro (Coffea arabica L.) / Improved use of the sodium hypochlorite to accelerate the seed germination and emergence of the coffee seedling (Coffea arabica L.)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

This study aimed at the evaluation of the effect of sodium hypochlorite concentrations in the aqueous presoaking solution of the coffee seeds with moisture content from 10 to 33% upon the performance of those seeds under laboratory conditions, the emergence of the seedlings under nursery conditions, as well as to evaluate the development of the seedlings. Three experiments were carried out with coffee seeds, variety Catuaí Vermelho IAC 44, that were dried under shadow until reaching the appropriate moisture contents. In experiment I, five assays were accomplished by evaluating the seeds for germination and vigor under laboratory conditions. Five moisture contents of the seeds were used (13, 18, 23, 28 and 33%). Each moisture content constituted an assay with 12 treatments, that were composed by combinations of five sodium hypochlorite concentrations in the presoaking solution (3, 4, 5, 6 and 7% active chlorine) and two presoaking times (3 and 6 hours), besides the seeds with and without endocarp, being this last one manually removed (control). The results showed that, the presoaking of the coffee seeds into sodium hypochlorite at concentration of 6% active chlorine for three hours, besides efficiently degrading the endocarp, also provided both germination and germination speed index similar to the control, when the seeds presented initial moisture level from 23 to 33%. In the seeds showing 18 and 13% moisture level, the presoaking into sodium hypochlorite provided inferior germinative performance, relative to those seeds from which the endocarp was manually removed, independently from combination between the soaking concentration and time used. The experiment II was accomplished with the best treatments obtained in experiment I. The same moisture contents of the experiment I were used, by evaluating the seeds for emergence percent and speed as well as the seedling for development under nursery conditions. Each moisture content of the seeds gave rise to a assay constituted by five treatments, that were composed by seeds presoaked into three sodium hypochlorite concentrations (4, 5 and 6% active chlorine) for a three-hour period, besides the seeds with and without endocarp, being the last one manually removed (control). The results from experiment II showed that presoaking the seeds into aqueous solution containing sodium hypochlorite at concentration of 4% active chlorine rather increased the percentage and emergence speed of the coffee seedlings, besides improving the development of the seedlings, relative to the seeds with endocarp. This treatment with sodium hypochlorite showed to be as efficient as the manual removal of the endocarp, when the seed moisture contents were equal or higher than 23%. In experiment III, the seeds owing initial moisture level of 10, 15 and 20% were used. Each moisture level of the seeds gave rise to one assay. The seeds were rehydrated until reaching the moisture contents 231 and 331%, by using four rehydration methods: 1-rehydration by soaking into water; 2-rehydration by soaking into aerated water; 3-rehydration by soaking into running water; and 4-rehydration in towel paper rolls moistened. The non-hydrated seeds at each initial moisture content and also after hydration treatments were subjected to the treatments for degradation of the endocarp by presoaking into aqueous solution containing sodium hypochlorite at concentrations of 5 and 6% active chlorine for three-hour period. In addition, for each initial moisture content of the seeds and each rehydration method, some treatments were accomplished with seeds from which the endocarp was manually removed after rehydration, as well as one treatment constituted by rehydrationless seeds, from which the endocarp was also manually removed (control). The results showed that rehydration of the seeds in running water or towel paper rolls moistened until reaching 33% moisture level, associated to presoaking into sodium hypochlorite at concentration of 6% active chlorine, was efficient for either degradation of the endocarp and acceleration of germination, when seeds showed 15 and 20% for initial moisture content.

ASSUNTO(S)

fitotecnia coffee seedling hipoclorito de sódio coffea arabica sementes seeds café mudas coffea arabica sodium hypochlorite

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