Metabolism and efficiency of phosphorus utilization during senescence in pepper plants:: Response to nitrogenous and potassium fertilization

Application rates of nitrogen and potassium were studied in relation to parameters of phosphorus metabolism in pepper plants (Capsicum annuum L. cv. Lamuyo) during senescence. All plants, grown under controlled conditions in a greenhouse, were 2 administered 4 rates of nitrogen (N) as NH4NO3 (N1: 6 g N m(-2), 12g Nm(-2), N3: 18 g N m(-2), N4: 24gN m(-2)) and three rates of potassium (K) as K2SO4 (K1: 4 g K m(-2), K2: 8 g K m(-2), K3:12 g K m(-2)) at the onset of flowering. The plants treated with the N2 treatment had the highest leaf concentrations of phosphorus (P) forms (inorganic P, lipid P, DNA-P, RNA-P, proteic P and total P), whereas the concentrations of organic and soluble P were the lowest. In these plants potassium fertilization exerted a negative effect on the concentrations of the different P forms, although yield significantly rose with K applied, reaching the highest values at K3. Finally, acid phosphatase activity and carbohydrate proved to be good indicators of the nutritional status of P.