Physiological mechanisms for delaying the leaf yellowing of potted geranium plants

The ornamental quality of flowering pot plants mainly depends from flower health and the colour of the leaves. During the post-production stages, potted plants undergo severe stress and the quality is often compromised. Therefore, the present study was aimed to evaluate the effect of 10 μM thidiazuron (TDZ), 200 μM gibberellic acid 3 (GA), 300 μM 5-aminolevulinic acid (AA) or 300 μM glutamic acid (GLU) in the reduction of leaf yellowing of potted geranium plants during transport and permanence to retail shelves. In control plants F0 values increased after 6 d of permanence in the simulated retail environment (SRE), while the Fv/Fm ratio declined. The net photosynthesis showed the highest values in the plants treated with TDZ and GA. The relative water content (RWC) values were lower in the control plants. The leaf TBARS content was higher in control and GLU treated plants. TDZ and GA treatments delayed the reduction of chlorophyll a and b contents in leaves, by improving the precursors of chlorophyll biosynthesis and reducing the catabolites. Plants sprayed with GA and TDZ significantly inhibited leaf yellowing and showed lower ABA contents in SRE conditions. Exogenously application of TDZ and GA are able to prevent leaf senescence by preserving the leaf pigments, membrane integrity and antioxidant activity keeping ABA at the basal level.