Physiological plant age dependent biochemical indicators and physiological parameters of iron nutrition

Abstract

Iron indicators were studied in two crop species, tomato and cucumber, of different sink (fruit) characteristics but similar in terms of phenological stages: flowering, fruit development, early ripening, foliar senescence and fruit senescence. Leaves were sampled every two weeks throughout the period of maximum fruit production in order to determine biochemical indicators and physiological parameters known to fluctuate as the plant develops. Total phenols and σ-diphenols increased as the leaf aged, whereas peroxidase levels did not change with plant age. Catalases and chlorophylls became scarcer as the leaf approached senescence in both tomato and cucumber. The inorganic and soluble fractions of P declined in tomato but remained unchanged in cucumber, while P bound to DNA structures increased with physiological leaf age in both crops. The phosphorylated lipid-bound P fraction also increased as the plant aged. Both the soluble and the organic Ca fraction became higher in the leaf of both species as this organ approached senescence. Total Fe levels increased with plant age, while soluble Fe levels decreased.