Relationship between biochemical indicators and physiological parameters of nitrogen and physiological plant age

Abstract

A study was carried out to compare the biochemical and physiological indicators of phenological stages in 2 horticultural crops which differ in the length of their vegetative cycle (long (tomatoes) vs. short (cucumbers)) and in their sink characteristics. Leaves were sampled from greenhouse-grown tomato cv. Dombo and cucumber cv. Pepinex plants at 2-week intervals during flowering and fruiting, through to leaf senescence. Leaf N concentration decreased over time, as did DW and the concentrations of nitrates, amino acids and total and soluble proteins. NH4+ concentration, nitrate reductase activity and fruit productivity (kg plant-1 0.5 m-2) peaked during the period of greatest metabolic activity, coinciding with flowering and the initial and final phases of fruit ripening, and were lowest during foliar senescence. Total and soluble vegetative indices (relationship between mobile N, P, K and immobile Ca, Mg) declined, and transient alterations coincided with certain morphological and metabolic changes. All physiological alterations during the different physiological stages were seen in both species regardless of the size of the sink; however, the magnitude of the alterations was conditioned by the sink and by exogenous and endogenous N levels.