Geoscience Reference
In-Depth Information
depletion in the soil, which increases resistance to drought (Vu
and Allen 2009). Higher CO
2
levels change both the metabolites
and transcript level of a number of sugarcane genes (Vu et al.
2006; de Souza et al. 2008), but how each change impacts sug-
arcane physiology remains unknown. Yield increases of 60%
were observed on sugarcane grown in open top chamber under
720 ppm CO
2
, which indicates that yields potential may increase
under those conditions (de Souza et al. 2008).
Many other physiological traits need to be detailed before a
strategy can be designed to improve them. For example, numer-
ous details of sugarcane C4 photosynthesis and other metabolic
pathways are needed to detect which steps constrain sugarcane
yield. Understanding the mechanisms regulating the transi-
tion from vegetative to reproductive growth would allow the
control of flowering for breeding and reduce the loss of fixed
carbon for reproduction. In addition, little is known about what
limits the capacity of sugarcane to store high concentrations
of sucrose in the parenchyma tissue of the stalk (McCormick
et al. 2008a). Sucrose content variation depends on the mor-
phology of the plant, such as size of the canopy and responses
to ripening stimuli, such as mild water stress, and how these
traits influence the supply and demand for photo assimilation
(Inman-Bamber et al. 2009). The photomorphogenic control of
sugarcane development can be modified by treatment with gib-
berellic acid (GA
3
). This phytohormone induces a significant
increase in stem cell elongation, which increases the capacity
for sucrose storage in sugarcane seedlings.
In the next few years, many physiological puzzles have to
be solved. Initially, the results obtained in more controlled
greenhouse conditions under varying field conditions will need
to be confirmed. Sugarcane transgenics, either overexpressing
or silencing specific candidate genes will allow the testing of
many hypotheses, while physiological experiments will help in
identifying new candidate genes. System biology coupled with
yet-to-be developed models will integrate physiology data with
massive amounts of proteomic, metabolomic and transcrip-
tomic data, to allow a more targeted approach toward under-
standing the limits of sugarcane productivity.
7. 2
present scenario
Indian sugar industry, the second largest after the textile industry,
plays a vital role in the socio-economic transformation of rural
India. India is the second largest producer of sugar after Brazil.
