Sistema antioxidante em mudas de cafeeiro sob condiÃÃes de dÃficit hÃdrico / Antioxidant system in coffee seedlings in conditions of water dÃficit

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The present research aimed to evaluate the antioxidant capacity in coffee seedlings on different water deficit levels and the effect of exogenous application of ascorbic acid (Asc) and H2O2 in antioxidant enzymes activity and in the stomata aperture and closing. Seedlings of Coffea arabica cv. Catuai IAC 99, with 8 months, of age were submitted to field capacity (CC), gradative suspension (SG) and total suspension (ST) of irrigation for a 21 days period. Considering the CC, each three days, the pots were weighed and the lost water was added again. For the SG, the water lost was replaced in 80%, 60%, 40%, 20% and 0%, each three days. For the ST system, the water was suspended from the first day. There were realized the leaf water potential evaluations at 6 h. The enzymatic analysis, lipÃdica peroxidation and ascorbic acid and dehydroascorbate levels were made in leaves collected at 17 hours, each three days. In greenhouse conditions cited below after 12 days from the beginning of the experiment were pulverized with Asc (20 mM) and H2O2 (1 mM). The same pulverization was made in plants kept in growth chamber in conditions of field capacity. After pulverizations, there were evaluated stomatic resistance, transpiration and enzymatic activity. In plants CC, the water potential was constant during the evaluation period. For the SG, occurred a expressive drop since 12 days reaching close to -2,5 MPa in the end of the experiment. For the ST, it was observed a drop in water potential from the sixth day of the evaluation reaching -2,5 MPa nine days later, period that was observed an increase in lipÃdica peroxidation in relation to plants in CC. This decrease in water potential for the plants in SG and ST reflected the increase in stomatic resistance and decrease in transpiration. The activity in antioxidant enzymes as wells as the levels of Asc and DHA, also showed a pattern according to water potential, being observed increases in these antioxidants in the periods of lower water potential. The plant pulverization with H2O2 promoted increases in the stomatic resistance and decrease in transpiration in relation to control plants. Although, the exogenous Asc caused the contrary effect. The H2O2 effect was reverted by Asc application. The plant pulverization with H2O2 and Asc also altered the antioxidant enzymes activities in relation to control plants.

ASSUNTO(S)

fisiopatologia da reproducao animal

ACESSO AO ARTIGO

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