Impactos da seca e das mudanças climáticas no metabolismo das plantas: Uma revisão

Drought and predicted changes in climate, such as increased atmospheric CO2 concentration and high temperature, may affect the growth and productivity of crop plants and generate varying responses, including morphological, physiological, biochemical and molecular changes. Water deficit negatively affects photosynthesis, while increasing CO2 can benefit plants and attenuate photo-oxidative damage, especially in C3 metabolism species. However, the excess heat associated with this increase can affect photosynthetic efficiency differently, depending on the species and/or variety studied. In addition, the responses to the combination of these factors are poorly understood and cannot be extracted directly from the effects of each of these agents applied in isolation. This review sought to address the isolated and combined effects of water deficit and climate change on agricultural production, reporting how plant metabolism is affected by rising temperatures and high CO2 concentration. This understanding is important to monitor the behavior of plants in the face of future climatic scenarios in order to develop strategies that can confer resistance to plants and ensure food security for agricultural production.

Intramolecular 13C/12C signals inform about carbon allocation in plant leaves

- Stable isotopes at natural abundance are key tools to study physiological processes occurring outside the temporal scope of manipulation and monitoring experiments. Whole-molecule carbon isotope ratios (13C/12C) enable assessments of plant carbon uptake yet conceal information about carbon allocation. Here, we identify an intramolecular 13C/12C signal at tree-ring glucose C-5 and C-6, develop experimentally testable theories on its origin, and test these theories. - First, we assess the potential of processes within C3 metabolism for signal introduction based (inter alia) on constraints on signal propagation posed by metabolic networks. Second, we support our theoretical framework by re-analysing published 13C/12C data and modelling signal-environment relationships. - We propose the intramolecular signal reports carbon allocation into major metabolic pathways in actively photosynthesising leaf cells including the anaplerotic, shikimate, and non-mevalonate pathway. This is supported by previously reported whole-molecule 13C/12C increases in cellulose of ozone-treated Betula pendula and a highly significant relationship between the intramolecular signal and tropospheric ozone concentration. Additionally, we postulate a pronounced preference of leaf-cytosolic triose-phosphate isomerase to catalyse the forward reaction in vivo (dihydroxyacetone phosphate to glyceraldehyde 3-phosphate). - In conclusion, intramolecular 13C/12C analysis resolves information about carbon uptake and allocation enabling more comprehensive assessments of carbon metabolism than whole-molecule 13C/12C analysis.

Acquisition and metabolism of carbon in the Ochrophyta other than diatoms

The acquisition and assimilation of inorganic C have been investigated in several of the 15 clades of the Ochrophyta other than diatoms, with biochemical, physiological and genomic data indicating significant mechanistic variation. Form ID Rubiscos in the Ochrophyta are characterized by a broad range of kinetics values. In spite of relatively high K 0.5 CO 2 and low CO 2 : O 2 selectivity, diffusive entry of CO 2 occurs in the Chrysophyceae and Synurophyceae. Eustigmatophyceae and Phaeophyceae, on the contrary, have CO 2 concentrating mechanisms, usually involving the direct or indirect use of . This variability is possibly due to the ecological contexts of the organism. In brown algae, C fixation generally takes place through a classical C3 metabolism, but there are some hints of the occurrence of C4 metabolism and low amplitude CAM in a few members of the Fucales. Genomic data show the presence of a number of potential C4 and CAM genes in Ochrophyta other than diatoms, but the other core functions of many of these genes give a very limited diagnostic value to their presence and are insufficient to conclude that C4 photosynthesis is present in these algae. This article is part of the themed issue ‘The peculiar carbon metabolism in diatoms'.