Differences in morphological and physiological responses to water-logging between two sympatric oak species (Quercus petraea[Matt.] Liebl.,Quercus roburL.)

Abstract

-Pedunculate (Quercus robur L.) and sessile (Q. petraea [Matt.] Liebl.) oaks are known to display different ecological requirements, particularly relative to root hypoxia induced by water-logging. Q. robur is more tolerant to hypoxia than Q. petraea. We designed an experiment aiming at identifying morphological and physiological responses to root hypoxia that might differ between the two species. Potted seedlings were submitted during seven weeks to a water-logging treatment with O 2 concentrations below 3 mg L −1 in the vicinity of roots. The treatment induced growth cessation in both species. Q. petraea displayed a lower tolerance to hypoxia as demonstrated by the higher number of seedlings suffering shoot dieback and leaf chlorosis as compared to Q. robur. This difference should be related to the high number of adventitious roots and hypertrophied lenticels that were formed in Q. robur, compared to Q. petraea. In the fine roots of the two species, the activity of pyruvate decarboxylase (PDC), the key enzyme of the fermentative pathway, was stimulated after 24 h of water-logging. Transcripts of PDC increased after 48 h of water-logging in Q. robur and not in Q. petraea. Interestingly, transcripts of haemoglobin (Hb) (possibly involved in the putative nitric oxide cycle) followed the same pattern of response than those of PDC. Enzymes of the sucrose degradation pathway displayed decreased activities after 3 weeks of water-logging, probably due to decreased carbohydrate availability. Alcohol dehydrogenase (ADH), sucrose synthase (Susy), and pyruvate kinase (PK) activities were higher in Q. robur after 3 weeks of water-logging. This study provided a set of markers characterizing the differences of tolerance to hypoxia between the two species for further studies on intra and inter-specific diversity.water-logging / hypoxia / adventitious root / hypertrophied lenticel / carbon metabolism Résumé -Différences de réponses morphologiques et physiologiques à l'ennoyage entre deux espèces sympatriques de chêne (Quercus petraea [Matt.] Liebl., Quercus robur L.). Les chênes pédonculé (Quercus robur L.) et sessile (Quercus petraea [Matt.] Liebl.) présentent des différences de tolérance à l'hypoxie racinaire induite par ennoyage, Q. robur étant plus tolérant que Q. petraea. Nous avons mené une expérience visant à identifier des différences inter-spécifiques dans les réponses morphologiques et physiologiques à l'hypoxie racinaire. Des semis en pots ont été soumis à un ennoyage de 7 semaines avec une concentration en O 2 maintenue en dessous de 3 mg L −1 au voisinage des racines. Le traitement a provoqué un arrêt de croissance chez les deux espèces. Q. petraea a montré une plus faible tolérance que Q robur, avec un nombre plus élevé de plants présentant un dessèchement de l'appareil aérien ainsi qu'une plus forte chlorose des feuilles. Cette différence pourrait être due au plus grand nombre de racines adventives et de lenticelles hypertrophiées formées au collet de Q. robur. Dans les racines fines des deux espèces, l'...

Seasonal variations in stem CO2 efflux in the Neotropical rainforest of French Guiana

“…To our knowledge, no study has yet directly tested the effect of hypoxic conditions on E s . The main effect of flooded conditions on plant carbon metabolism is through the deprivation of oxygen to the root system, which usually leads to a decrease in carbon and energy metabolism at the whole plant level and can induce morphological or phenological adaptations (Parelle et al 2006;Parolin 2001). Our results suggest that these same processes influence stem CO 2 efflux.…”

Flooding effects on starch partitioning during early growth of two oak species

“…Taking into account of these new conditions, photoassimilates and cotyledon carbohydrates could be redirected to parts of the Q. robur root system growing at shallow depths that are more likely to stay in or return to normoxia. In older flooded seedlings, the higher capacity of adventitious roots formation in Q. robur than in Q. petraea was also reported Schmull and Thomas 2000;Parelle et al 2006). Thus, this feature favours the establishment of Q. robur seedlings on water-logging stands and begins as early as the first flush of growth.…”

“…Further studies have identified physiological and anatomical features that account for the ecological advantage enjoyed by Q. petraea at the expense of Q. robur, especially under drought stress (Epron and Dreyer 1993;Ponton et al 2001;Thomas et al 2002). However, Q. robur seedlings appear to be more tolerant to hypoxic soil conditions than Q. petraea seedlings Wagner and Dreyer 1997;Schmull and Thomas 2000;Parelle et al 2006).…”

Flooding: Abiotic Constraint Limiting Vegetable Productivity

“…Although, the actual physiological role of lenticels is still unclear, their presence is often linked to waterlogging tolerance in plants. 56 Moreover, the number of hypertrophied lenticels is more under the water surface that supports the argument stating their involvement in maintenance of plant water homeostasis and deviating from the argument that dictates their role as important facilitators of oxygen entry toward the root system. Their potential role in the plant water homeostasis is evident from their active involvement in partially replacing the decaying roots and facilitating water intake for the shoot.…”