Phenotypic plasticity and morphanatomic responses of Sonchus oleraceus L. according to environmental conditions

Abstract

Underexplored species such as Sonchus oleraceus L. have the capacity as viable alternative crops, supporting the impacts of climate change and meeting the needs of specific markets seeking regional and ecologically correct foods. To increase our understanding of how this species adjusts to varied ecological conditions, more research is relevant. In view of the above, the objective was: (i) to investigate the effect of the cultivation system, storage time and temperature on the physiological potential of S. oleraceus seeds, (ii) to evaluate the phenotypic plasticity of S. oleraceus as a function of the season, the cultivation system and the phenological stage and (iii) to investigate the morphoanatomical responses of S. oleraceus as a function of the season and the cultivation system. For the germination test, S. oleraceus seeds from two cultivation systems (organic and conventional) were used in three storage times (0, 90 and 180 days) and submitted at two temperatures (20 and 30 ºC). The germination parameters evaluated were the first count, germination percentage and germination speed index, while seedling growth was evaluated by root length and hypocotyl growth. The results showed that the cultivation system and temperature influenced the quality of the seeds during storage, and seeds of conventional cultivation presented higher percentage of germination and germination speed index at 30ºC. However, there was a reduction in root and hypocotyl growth at 180 days, especially at 20°C. In the phenotypic plasticity experiment, for S. oleraceus plants grown at different times and cultivation systems, and in three phenological stages, several parameters were evaluated, including height, number of leaves, dry mass, leaf area, growth rate, photosynthetic pigments and antioxidant system. The results showed that the plant cycle was reduced in the summer and there was significant interaction between the treatments for most of the variables evaluated. The production of photosynthetic pigments was higher in winter, and the enzymatic responses of the antioxidant system were influenced by cultivation and season. In the anatomy experiment, plants of S. oleraceus were grown at two different times and two cultivation systems to determine the impact of these factors on the morphoanatomical characteristics of their leaves. Stomatal density, beam diameter, xylem area and thickness of the different leaf layers were analyzed. The planting season had the most significant influence on the characteristics analyzed. The high temperatures negatively impacted the stomatal density, especially in organic cultivation. These results suggest that environmental conditions play a vital role in plant growth and development, affecting the production of S. oleraceus.