No abstract

Polyploidy, defined as the coexistence of three or more complete sets of chromosomes in an organism’s cells, is considered as a pivotal moving force in the evolutionary history of vascular plants and has played a major role in the domestication of several crops. In the last decades, improved cultivars of economically important species have been developed artificially by inducing autopolyploidy with chemical agents. Studies on diverse species have shown that the anatomical and physiological changes generated by either natural or artificial polyploidization can increase tolerance to abiotic and biotic stresses as well as disease resistance, which may positively impact on plant growth and net production. The aim of this work is to review the current literature regarding the link between plant ploidy level and tolerance to abiotic and biotic stressors, with an emphasis on the physiological and molecular mechanisms responsible for these effects, as well as their impact on the growth and development of both natural and artificially generated polyploids, during exposure to adverse environmental conditions. We focused on the analysis of those types of stressors in which more progress has been made in the knowledge of the putative morpho-physiological and/or molecular mechanisms involved, revealing both the factors in common, as well as those that need to be addressed in future research.

Morphological shade-avoidance responses have been hypothesized to be a form of adaptive plasticity to improve competition for light; however, little is known about their intraspecific variability and their effect on reproductive fitness. To compare plant responses either at a common age or at a common phenological stage, two experiments were conducted with early-and late-flowering Chenopodium album plants exposed to different red (660 nm) to far red (730 nm) ratios. In the first experiment, plant height and number of leaves were recorded at several times during the vegetative stage, and at the onset of flowering, each plant was harvested and other growth traits were measured. In the second experiment, three destructive harvests were performed across the whole plant cycle. Plant growth and development markedly differed between early-and late-flowering plants in all of the conditions tested. Light treatments significantly affected stem length, total leaf number, total leaf area, and relative allocation to leaf biomass. In all families, the response of stem elongation to light treatments decreased later in the development, while changes in the other plastic responses were mostly due to variations in plant growth. No significant treatment effect was found on relative biomass allocation to reproductive structures. However, individual seed mass significantly differed between certain groups, indicating that light quality can affect reproductive fitness through changes in traits other than fruit or seed set. Résumé :On formule l'hypothèse que les réactions pour éviter l'ombrage constituent une forme de plasticité adaptative visant l'amélioration de la compétitivité pour la lumière, cependant on connaît peu de choses à propos de leur variabilité intra-spécifique et leur effet sur l'ajustement reproductif à l'environnement. Afin de comparer les réactions des plantes, soit à un âge donné ou soit à un stade phénologique donné, les auteurs ont conduit deux expériences en exposant des plants de Chenopodium album, à floraison hâtive et à floraison tardive, à différents ratios de lumière rouge (660 nm) sur rouge sombre (730 nm). Dans la première expérience, ils ont enregistré la hauteur des plants et le nombre de feuilles à plusieurs reprises au cours du stade végétatif et ils ont cueilli, au début de la floraison, chaque plante pour en mesurer d'autres paramètres de croissance. Dans la deuxième expérience, ils ont effectué trois récoltes destructives au cours de l'ensemble du cycle vital. La croissance des plantes et leur développement diffèrent nettement entre les plants à floraison précoce et les plants à floraison tardive, sous toutes les conditions expérimentées. Les traitements lumineux affectent significativement la longueur de la tige, le nombre total de feuilles, la surface foliaire totale, et l'allocation relative à la biomasse foliaire. Dans toutes les familles, la réaction de l'élongation de la tige aux traitements lumineux diminue vers la fin du développement, alors que les modifications des autres réactions plastiq...