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.

Increasing water scarcity and depleted water productivity in irrigated soils are inducing farmers to adopt improved varieties, such as those with high-capacity tolerance. The use of tolerant varieties of sugarcane might substantially avoid the decline of productivity under water deficit. This research aimed to evaluate the harmful effects of drought on the physiology of two sugarcane varieties (RB867515 and RB962962) during the initial development. Young plants were subjected to irrigation suspension until total stomata closure, and then rewatered. Significant reduction on stomatal conductance, transpiration, and net photosynthesis were observed. RB867515 showed a faster stomatal closure while RB962962 slowed the effects of drought on the gas exchanges parameters with a faster recovering after rewatering. Accumulation of carbohydrates, amino acids, proline, and protein in the leaves and roots of the stressed plants occurred in both varieties, substantially linked to reduction of the leaf water potential. Due to the severity of stress, this accumulation was not enough to maintain the cell turgor pressure, so relative water content was diminished. Water stress affected the contents of chlorophyll (a, b, and total) in both varieties, but not the levels of carotenoids. There was a significant reduction in dry matter

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The control of gene expression in precise time and space is a desirable attribute of chemically inducible systems. Ethanol is a chemical inducer with favourable features, such as being inexpensive and easy to apply. The aim of this study was to identify ethanol-responsive genes in sugarcane. The cDNA macroarray technique was adopted to identify transcript changes in sugarcane leaves (Saccharum spp. cv SP80-3280) exposed to ethanol. The expression profiles of sugarcane genes were analysed using nylon filters containing 3,575 cDNA clones from the leaf roll library of the SUCEST project. Seventy expressed sequence tags (ESTs) presented altered expression patterns, including ESTs corresponding to genes related to transcriptional and translational processes, abiotic stress and others. Several genes of unknown function were also identified. Among the 48 ESTs up-regulated by ethanol, an abiotic stress-responsive protein and an unknown function gene presented rapid induction by ethanol. The macroarray data of selected ethanol-responsive EST were confirmed by RNA-blot hybridisation. The expression profile of the 48 up-regulated genes was compared in two other cultivars: SP89-1115 and SP90-3414. Surprisingly, no gene showed a similar expression profile in the three cultivars. This result suggests that sugarcane plants have a high diversity in their responses to ethanol.

Sugarcane (Saccharum spp.) is an important crop and is affected by many abiotic stresses, such as drought, the single most important cause of losses in agriculture. Co-chaperones have been found to protect plants from water defict. We identified a sugarcane gene encoding a D' co-chaperone and have produced transgenic sugarcane plants overexpressing this protein. These plants will be used to assess the role of D' co-chaperones in sugarcane under water deficit stress.