Physiological Interventions for Enhancing Sugarcane and Sugar Productivity

Sugarcane is one of the most efficient quantum converters, endowed with vast tillering, ratooning and biomass potential. Vast tillering potential, innumerable root primordia, two types of roots and emergence of leaves constitute a Compensatory Physiologic Continuum which imparts this plant a unique ability to tide over abiotic stress conditions, gaps in the field and agro-physiological disorders arising in its 12–18 months long cycle. Despite this, the recorded yields of sugarcane are about 168 mt ha⁻¹ year⁻¹ that is just 36 % of the theoretical maximum of 470 mt ha⁻¹ year⁻¹ (in Hawaii) and in India it is only 28.6 % of the theoretical maximum. The knowledge of the physiological constraints for improving the productivity by increasing the crop efficiency by use of light, CO₂, water and nutrients, has not been of much help as the details of how to manage them and bring them to some practical optimums, is yet unknown. The major difficulty in relating any physiological parameter directly to the crop yield is the complexity of the interactions among the processes and pools of the plant. As the inputs of CO₂, water and light can be limiting to the yields, more economical yields can be obtained by increasing the photosynthesis, nutrient use and transpiration efficiency. So despite the fact that each of these processes possess the potential for improvement of yield, the interrelationships between them show great difficulty in identifying an ideal ideotype that can result in yield increases under all the circumstances. The article attempts to elucidate upon the ways of improving the productivity of sugarcane under the Indian subtropics by utilizing knowledge on interactions of various plant processes involving indirect increased utilization of light through increased proportion of light absorbed and increase of efficiency in CO₂ reduction by absorbed quanta that turn the plant more efficient with assimilate transport from leaf, phloem translocation and parenchymatous import of sucrose for removal of feedback inhibition to allow maintenance of high photosynthetic efficiency, increasing light absorption by increasing the leaf size, number of leaves per stalk and number of stalks per unit area, increasing the CO₂ uptake through increase in stomatal conductance and decrease in boundary layer resistance to CO₂ by decreasing leaf width, increasing the efficiency of partitioning of photosynthates and reducing the yields losses.