Transient abiotic stresses lead to latent defense and reproductive responses over the Brassica rapa life cycle

• DOI: 10.1007/s00049-012-0113-y
• Publication Date: 2012-09-21T07:19:05Z
• Authors: Adam D. Steinbrenner; Niels Agerbirk; Colin M. Orians; Frances S. Chew
• Keywords: Brassica rapa

Plants can alter physiological and developmental trajectories in response to environmental cues by means of phenotypic plasticity. While cases of immediate plastic responses to different environments are well studied, phenotypic changes can also be delayed and occur in later life cycle stages. In this study, we investigated latent phenotypic plasticity in the development and chemical profile of Brassica rapa plants exposed to transient stress as seedlings. Four different stresses were applied to germinating seedlings: salinity, drought, nutrient deficiency, or acidity. Growth, reproduction, and glucosinolate chemical defenses (in leaves and seeds) were measured over the plants’ life cycles after normal conditions were restored. Despite initial stunting, B. rapa individuals recovered in total stem length and seed count compared with unstressed controls. There were, however, latent responses in flowering time, which was delayed in salinity-, drought-, or acid-stressed plants. Reductions in total flower count and total seed pod count were also observed in nutrient-deficiency stressed plants. Strikingly, previously stressed plants also showed latent differences in glucosinolate chemical defenses. Acid-stressed plants had higher concentrations of the plants’ major glucosinolate, gluconapin (3-butenylglucosinolate), in leaves and seeds, while nutrient deficiency-stressed plants had lower seed levels of gluconapin. Our experiments show that, despite outward recovery of growth, previously stressed B. rapa plants alter later defense and reproduction, leading to a plastic response delayed across life cycle stages. Thus, even transient, recoverable stress can have latent consequences for ecologically important chemical traits.