Senescence Retarding Effect of Metal Ions: Pigment and Protein Contents and Photochemical Activities of Detached Primary Leaves of Wheat

Al³⁺ significantly delayed the loss of chlorophyll (Chl), protein, and carotenoids when compared to K⁺ and Mg²⁺ during dark-induced senescence of detached primary leaves of Triticum aestivum. Thylakoid membranes isolated from Al³⁺ - treated leaves showed a better retention of photosystem (PS) 2, PS1, and whole chain electron transport activities than thylakoids of K⁺- or Mg²⁺-treated leaves. These ions protected the electron transport activities and restored the DCMU-dependent fluorescence increase of thylakoid membranes in a valency-dependent manner. Al³⁺ also delayed the change of excitation energy distribution during senescence.