Abstract

OLIVEIRA, Lenaldo Muniz de et al. Effect of cytokinins on senescence and foliar abscision during in vitro Annona glabra L. cultivation. Rev. Bras. Frutic. [online]. 2007, vol.29, n.1, pp. 25-30. ISSN 0100-2945.  http://dx.doi.org/10.1590/S0100-29452007000100008.

The micropropagation of Annonaceae has been limited by early foliar abscission in shoots, which makes the maintenance and development of plants in vitro environment difficult. This is mainly due to ethylene accumulation in closed tubes and the ethylene/cytokinin ratio in leaves. Based in these circumstances it was evaluated the effect of cytokinins sources on foliar senescence delaying in shoots of Annona glabra L. and its implications on its development. Node segments were cultivated in test tubes containing 15mL of WPM medium, supplemented with 30g L^-1 of sucrose, 500mg L^-1 of benomyl and 1g L^-1 of activated charcoal. It was added to this medium 6-benzilaminopurine, thidiazuron, kinetin and zeatin, all of them in the concentration of 1mg L^-1. After 45 days of inoculation, plants were submitted to senescence in a dark environment during 9 days, and the leaves were collected in each three days for quantification of chlorophylls "a" and "b", carotenoids, proteins and total soluble sugar. In the final steps of multiplication and rooting, it was obtained a dry matter accumulation, a foliar area index and the number of abscised leaves in plants without senescence treatments. The experimental design used was random blocks, and each senescence period was composed by a block, with four replicates per treatment. The results showed that kinetin and zeatin, followed by thidiazuron and 6-benzilaminopurine, preserved the higher chlorophylls "a" and "b" and carotenoids levels during the period of induced senescence. The 6-benzilaminopurine and kinetin promoted higher foliar area retention during the multiplication and rooting phases of Annona glabra L.

Keywords : Chlorophyll; Annonaceae; Carotenoids.