Physiological effects of pruning in rose plants cv. Grand Gala

The effect of pruning in rose plants (cv. Grand Gala) was studied in different types of leaves, focusing on chlorophyll (Chl) a fluorescence, carbohydrates, ammonium content, nitrate reductase (NR) activity and biomass parameters. Results on pruned plants showed a higher maximum efficiency of photosystem II (PSII) of dark-adapted leaves, a higher actual quantum yield and a higher proportion of PSII reaction centres that are open, but a lower non-photochemical quenching, indicating a lower energy dissipation as heat, compared to non-pruned plants. These results related to Chl a fluorescence, indicate that pruned plants have a higher capacity for better promoting the photosynthetic light reaction than non-pruned plants. The increased nitrate reductase activity in pruned compared with non-pruned plants, can result from a higher photosynthetic activity resulting in a lower NH₄⁺ accumulation in leaves. Pruning promoted a large number of metabolic sinks (flower removal) that may cause depletion of stored carbohydrates flowing from lower plant parts (arched shoots) to the new developing flower shoots. However, although in a lower concentration, carbohydrate contents were sufficient to promote the development of new flower shoots since the yield was similar for pruned and non-pruned plants. However, pruned plants showed higher turgor than non-pruned plants.