Resumen

MARTINEZ-GUTIERREZ, Ricardo et al. Gas exchange and water relations during delay of leaf senescence in wheat (triticum aestivum l.) by cytokinin BAP. INCI [online]. 2008, vol.33, n.2, pp.140-145. ISSN 0378-1844.

The effect of cytokinin 6-benzylaminopurine (BAP) on gas exchange and water relationships of Triticum aestivum L. during delay of leaf senescence in greenhouse. Plants of 21 days after sowing (DAS) were sprayed with BAP (0.1mM) or water (control) every 3 days for 20 days. Delay of leaf senescence in BAP treated plants was monitored by quantification of chlorophyll and totally soluble protein. Gas exchange was estimated by stomatal conductance (g_s) and CO₂ fixation rate. The water relationships were evaluated by the water potential (Ψ_A) and its components, osmotic (Ψ_s) and turgor potential (Ψ_t) every 5 days for 20 days. BAP treated leaves showed higher total concentration of chlorophyll and protein from day 26, in comparison with the control. The difference increased with time and 41 DAS they were 7 times higher than the control. The g_s values were not significantly different from the pre-senescent green state. These responses were associated with higher CO₂ fixation rates with concentrations near those in the pre-senescent green leaves (6.2μmol·CO₂·m^-2·s^-1). The Ψ_A remained constant under BAP and Ψ_s was significantly lower than in the controls, favoring the retention of solutes in cytoplasm of leaves with delay of senescence. The Ψ_t of BAP leaves was significantly higher than the respective controls from 31 to 41 DAS. Therefore, cytokinin BAP promoted the maintenance of the CO₂ fixation rate and water relationships during the delay of leaf senescence

Palabras clave : Citonicinina ; CO₂; Potencial Hídrico; Potencial Osmótico; Senescencia.