Abstract

Time set of inflorescence emergence stage independent from delayed ontogenesis by drought periods in winter rape

Author(s): Peter Lentzsch, Dietmar L�������¼ttschwager, Thomas M�������¼ller

Drought stress affects plant physiology and phenology and therefore influences crop productivity. The impact of different periods of water stress on various physiological parameters in winter rape (Brassica napus) was studied under climate chamber conditions. Drought periods applied to various ontogenetic stages of winter rape plants resulted in water loss, photosynthesis decrease, delayed ontogenesis as well as loss of biomass and yield. Furthermore, vacuolar, cytosolic and extracellular invertases were strongly downregulated on the 29th day after vernalization (d.a.v.), which was also the case in control plants, concurrently in the phase of inflorescence development. This time effect was also found by means of corrected osmolality. Unaffected by stress application, the corrected osmolality decreased significantly on the 29th d.a.v.. Between the 35th and the 45th d.a.v., corrected osmolality increased markedly in all variants, as control plants matured frommain inflorescence to flowering stage. In the following stage of fruit development, stressed plants differed significantly from control regarding corrected osmolality and invertase activities indicating stress compensation reactions. However, the duration of the stress compensation reaction was found to be limited by fixed time signals. Stress tolerance thus seems to be related to a more flexible reaction to fixed time signals in order to fully use the existing compensatory potential.