RESPIRATORY ACTIVITY OF APICAL MERISTEMS OF PLAGIOTROPIC BRANCHES OF Araucaria angustifolia (Bertol.) Kuntze

Abstract

Araucaria angustifolia apresenta redu\ue7\ue3o da taxa de crescimento durante o ano, podendo ser resposta \ue0s condi\ue7\uf5es ambientais desfavor\ue1veis, como ocorre nas fruteiras de clima temperado, que apresentam dorm\ueancia de gemas como forma de sobreviv\ueancia. O objetivo deste trabalho foi avaliar a din\ue2mica da atividade respirat\uf3ria de meristemas apicais de ramos plagiotr\uf3picos de Araucaria angustifolia. Foram coletadas amostras de 0,4 g de brota\ue7\uf5es terminais de ramos plagiotr\uf3picos de plantas jovens e adultas, as quais foram mantidas em 5 mL de solu\ue7\ue3o de cloreto de 2,3,5 trifeniltetraz\uf3lio (1,2%) em sala de crescimento a 25\ub0C. Em seguida, foram mantidas em 4 mL de \ue1lcool et\uedlico absoluto para leitura por espectrofotometria da absorb\ue2ncia a 560 nm. A atividade respirat\uf3ria de meristemas apicais de ramos plagiotr\uf3picos de Araucaria angustifolia \ue9 vari\ue1vel durante o ano. A maior atividade respirat\uf3ria ocorre na metade da primavera e a menor atividade respirat\uf3ria ocorre no inverno, em plantas jovens e adultas. Plantas adultas permanecem em alta atividade respirat\uf3ria por um per\uedodo maior, at\ue9 o in\uedcio do ver\ue3o.Araucaria angustifolia decreases its growth ratio during the fall and winter in response to adverse environmental conditions such as in temperate fruits where bud dormancy as a survival startegy. The aim of this study was to evaluate the dynamics of the respiratory activity of apical meristems of plagiotropic branches of Araucaria angustifolia. To determine the respiratory activity, samples with 0.4 g of apical buds of plagiotropic branches of young and adult plants were collected. These buds were maintained during two hours in 5 mL of 2,3,5-triphenyl tetrazolium chloride (1.2%) in a growth room at 25 \ub0C. Then, it was maintained during one hour in 4 mL of absolute ethyl alcohol and then the absorbance was determined by reading in spectrophotometer at 560 nm. The respiratory activity of apical meristems of plagiotropic branches of Araucaria angustifolia changed during the year, reducing in mid-spring and become lower in the winter in both young and adult plants. Adult plants remained with lower respiratory activity for a longer period, until the beginning of summer