Abstract

WILSON-GARCIA, Claudia Y.; ZAVALETA-MANCERA, Hilda A.; LOPEZ-DELGADO, Humberto  and  HERNANDEZ-GARAY, Alfonso. The cytokinin BAP delays senescence and increases antioxidants, protein and growth in orchard grass (Dactylis glomerata L.). Agrociencia [online]. 2008, vol.42, n.7, pp.799-806. ISSN 2521-9766.

Senescence is one of the main causes in the reduction of forage nutritive quality and green area. Cytokinins promote delay of leaf senescence, but little is known of their effect on regulation of oxidative stress in forages. This study assessed the effect of the cytokinin 6-benzylaminopurine (BAP) on growth, senescence, soluble protein (PS) ascorbic acid (AA), hydrogen peroxide (H₂O₂), and activity of ascorbate peroxidase (APX) in orchard grass (Dactylis glomerata L.). Ten-month-old plants were used to measure growth and 4-month-old plants were used to assess APX, AA, H₂O₂, and soluble protein (PS). After cutting the plants 5 cm above ground level, they were sprayed weekly for seven weeks with a BAP (0.1 mM) solution. The experimental design was completely random. Results were analyzed with ANOVA (SAS, 1995), and means compared with the Tukey test (p£0.05). Spraying with BAP increased (p<0.05) leaf elongation and growth (cm stem^-1) by 36% 17 weeks after cutting. Accumulated leaf senescence per stem (cm stem ^-1) decreased (p<0.05) in plants treated with BAP, and senescence was delayed from week 13 after cutting. Leaves sprayed with BAP increased (p<0.05) PS by 18% between 14 and 47 d after cutting and surpassed (p<0.05) the control by 64%. In plants with delayed senescence (BAP) the AA content, APX activity, and H₂O₂ increased. It is concluded that the cytokinin BAP promoted growth, accumulation of soluble protein, and delayed leaf senescence, by regulating signaling through H₂O₂, in AA accumulation and APX activity, with a protective function against the oxidative stress of senescence.

Keywords : Dactylis glomerata; ascorbic acid; ascorbate peroxidase; growth; senescence; 6-benzylaminopurine.