Conference “Monocots VI”
6th International Conference on Comparative Biology of Monocotyledons – Monocots VI
2nd World Congress of Bromeliaceae Evolution – Bromevo II
Natal, Rio Grande do Norte, Brazil
This international meeting put together a diverse group of scientists working with systematics, ecology, and evolution of Monocotyledons and Bromeliaceae.
I had the opportunity to present the following two oral presentations:
Ecophysiological strategies in Bromeliaceae: how distinct traits favored their irradiance in a wide range of environments
Bromeliaceae is a monophyletic family that occupies many resource-poor environments; however, they possess traits that allow their efficient water and nutrient use and uptake, including the presence of foliar trichomes, phytotelmata (tank with water), the diversification of the carbon metabolism and contrasting growth forms. Besides distinct subfamilies, bromeliads are divided into five ecophysiological types according to their sources of nutrients (soil, tank) and their way to access them (trichomes, roots). In this context, new researches are showing distinct physiological, anatomical and molecular traits among Bromeliaceae subfamilies and ecophysiological types. For example, bromeliads have a trade-off between the use of nitrogen for soluble protein production and immediate growth or to store it in amino acids for transamination reactions during nutritional stress. In another example, Guzmania monostachia performed a weak CAM but keep the integrity of the PSII, suggesting a metabolic strategy to maintain plant fitness even in water deficit conditions. Additionally, the expression of genes associated with the nitrogen metabolism and the resistance to oxidative stress appears to be different in bromeliad leaf portions, suggesting high foliar adaptation to nutritional and water variations. These results highlight the ecophysiological plasticity of bromeliads to deal with a wide range of environments.
Key words: Nitrogen use efficiency, Water use efficiency, Foliar adaptation, Resource-poor environment, Ecophysiological types .
Funded by: FAPESP (Proc n° 2016/09699-5)
RuBisCO activity and the efficiency of photosynthesis in the C3-CAM bromeliad Guzmania monostachia
Plants that perform the Crassulacean acid metabolism deal successfully with environments with intermittence of water and nutrients, which has been at least in part associated with higher water- and nitrogen-use efficiencies. Limitations of water and nutrients can impair photosynthesis, through the reduction of RuBisCO and plant carbon balance. In this context, we conducted a controlled experiment with the epiphytic C3-CAM bromeliad Guzmania monostachia to investigate how the combined water and nutritional deficits affect the RuBisCO activity and its activation state (RAS), and the efficiency of photosynthesis during the transition from C3 to CAM. We observed that, besides the increment in CAM activity, bromeliads submitted to both water and nutritional deficits showed higher RAS compared to C3 bromeliads and, surprisingly, the quantum efficiency of photosynthesis increased. Additionally, glucose, fructose, and starch contents were kept while sucrose concentration increased even with both deficit impositions. These results combined with high RAS strongly suggest an increment in the efficiency of RuBisCO functioning. Our results reinforce the ability of epiphytic plants to deal with stressful habitats, in which higher efficiency of RuBisCO during the transition to CAM maintain photosynthesis and their carbon balance, which ultimately favored their evolution in the epiphytic environment.
Key words: CAM pathway, Guzmania, photosynthesis, photosynthetic quantum yield, RuBisCO activation state.
Funded by: FAPESP (2016/09699-5; 2011/50637-0), CAPES (Finance Code 001), CNPq (309504/2014-7).