Sugarcane Responses at Water Deficit Conditions

Sugarcane (Saccharum spp.), a plant of the Poaceae family, is an important source of sucrose and ethanol in many tropical and sub-tropical countries. It was introduced in Brazil during the colonization period, and today represents one of the main cultures of the economy. Brazil is currently the world’s largest sugarcane producer. The 08/09 crop yielded approximately 569 millions of tons, totaling 27.5 million liters of ethanol and 31.0 million tons of sugar (ÚNICA, 2011). This makes Brazil responsible for providing 25% of the sugar consumed all over the globe (ÚNICA, 2011), sharing with the United States the leadership in ethanol production. The search for alternative, renewable sources of energy, placed the spotlight on Brazilian ethanol, causing an increase in the production of bi-fuel automobiles, which estimates foresee will represent 85% of the market in a few years. Today, in Brazil, more than 9 million ha are currently used to cultivate sugarcane, but the demand for sugar and ethanol will have it increased to 64 million ha by the years 2018/2019. The growing demand for ethanol leads to an increase in production, which subsequently demands expansion of cultivated areas as well as the search for new technologies which will enable higher agricultural and industrial productivity. The current occupied agricultural area is reportedly, only 2.4%, and expansion has occurred in regions of the country where this culture will need adjustments due to soil and weather characteristics. Plants are exposed to adverse environmental conditions, and drought is the major abiotic factor that can damage its growth and development. Drought also limits the areas suitable to agriculture. It is known that, as for any crop, during vegetative growth water is essentially required to obtain maximum yield and drought events in this stage can significantly decrease productivity. Sugarcane is among the crops which produce a higher amount of biomass per unit of cultivated area and water requirement varies throughout the developing stages, thus for higher tillering and development of culms, there is a higher water requirement than during the maturation stage, when this need is diminished. In some countries as Australia, Sudan and South Africa about 60% of sugar produced is grown in irrigated areas (Inman-Bamber & Smith, 2005), a practice which always results in production cost increase.