Physiological effects of pruning in rose plants cv. Grand Gala
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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. (c) 2007 Elsevier B.V. All rights reserved.