Elevated CO₂ increases photosynthesis, biomass and productivity, and modifies gene expression in sugarcane

Abstract

Because of the economical relevance of sugarcane and its high potential as a source of biofuel, it is important to understand how this crop will respond to the foreseen increase in atmospheric [CO2]. The effects of increased [CO2] on photosynthesis, development and carbohydrate metabolism were studied in sugarcane (Saccharum ssp.). Plants were grown at ambient (~370 ppm) and elevated (~720 ppm) [CO2] during 50 weeks in open-top chambers.The plants grown under elevated CO2 showed, at the end of such period, an increase of about 30% in photosynthesis and 17% in height, and accumulated 40% more biomass in comparison with the plants grown at ambient [CO2]. These plants also had lower stomatal conductance and transpiration rates (-37 and -32%, respectively), and higher wateruse efficiency (c.a. 62%). cDNA microarray analyses revealed a differential expression of 35 genes on the leaves (14 repressed and 22 induced) by elevated CO2. The latter are mainly related to photosynthesis and development. Industrial productivity analysis showed an increase of about 29% in sucrose content. These data suggest that sugarcane crops increase productivity in higher [CO2], and that this might be related, as previously observed for maize and sorghum, to transient drought stress.

The effects of carbon dioxide and temperature on microRNA expression in Arabidopsis development

“…In C. reinhardtii, elevated [CO 2 ] downregulated the expressions of five SPLs, although in the opposite direction of that observed in this study 15 . In sugarcane, ARF2 was found to be downregulated, suggesting that auxin-signalling is also involved 14 .…”

“…It was demonstrated that a high level of [CO 2 ] altered the expression of the genes involved in regulating flowering time 12 , carbon accumulation, defence, redox control, transport, signalling, transcription and chromatin remodelling in Arabidopsis 13 . It can also modify gene expression in Populus 14 , sugarcane 15 , Chlamydomonas reinhardtii 16 and soybean 17 . Similarly, a mild increase of 2-4°C above the optimum 23°C affected the expression of a significant number of genes, including splicing regulatory genes, and several robust early markers for flower development 4 .…”

Spatio-temporal variability of sugarcane yield efficiency in the state of São Paulo, Brazil

“…Sugarcane is one of the world's major food-producing C4 crops, providing about 75% of the sugar harvested for human consumption (Souza et al, 2008), and is one of the most important crops for the Brazilian economy. It was introduced into Brazil in the 17 th century to break a world monopoly, and became socially important around the country (Canabrava, 2005).…”

Mecanismos de aclimatação das plantas à elevada concentração de CO₂

“…A maior concentração de CO 2 na atmosfera faz com que a concentração deste gás no interior da folha também aumente (SOUZA et al, 2008), elevando a eficiência fotossintética por diminuir a fotorrespiração. A fotorrespiração, segundo TAIZ & ZEIGER (2013), é o processo bioquímico em que a enzima Rubisco, responsável pela carboxilação na fotossíntese, catalisa a reação de oxigenação ao invés da carboxilação, por ter afinidade tanto pelo CO 2 quanto pelo O 2 em seu sítio ativo, o que caracteriza perda de eficiência no processo fotossintético.…”