Photosynthesis in Sugarcane

Abstract

Sugarcane and related species utilize the NADP malic enzyme type of C 4 photosynthesis, which confers superior radiation-, nitrogen-, and wateruse efficiencies relative to C 3 plants in the warm environments where sugarcane thrives. By being able to concentrate CO 2 around Rubisco, sugarcane avoids limitations due to photorespiration and exhibits superior photosynthesis over C 3 plants at low CO 2 levels and warm temperatures (> 30 • C). At current atmospheric CO 2 levels, reported photosynthetic capacities of sugarcane are often low relative to other cultivated C 4 species and frequently are equivalent to photosynthesis rates in C 3 crops such as wheat and rice. These reduced photosynthetic capacities are present in older sugarcane plants because leaf nitrogen values become depleted as cumulatively more tissues are produced, and high carbohydrate levels may downregulate photosynthesis. This is particularly apparent when growers limit late nitrogen applications to boost sugar production. When photosynthesis is measured in young plants with cumulatively low leaf area, or in plants where leaf nitrogen is maintained by regular or heavy nitrogen applications, then sugarcane photosynthetic capacities are typical of C 4 plants and higher than observed in most C 3 species at current CO 2 levels. In leaves with reduced N, photosynthesis in sugarcane could become less efficient, because an imbalance between the C 3 and C 4 metabolic cycles may promote leakage of bundle sheath CO 2 out of the leaf. These observations indicate that photosynthesis in sugarcane could be improved by creating new varieties that either maintain high leaf nitrogen or enhance photosynthetic nitrogen-use efficiency to match that of productive C 4 crops such as maize.

Photosynthetic response and nitrogen use efficiency of sugarcane under drought stress conditions with different nitrogen application levels

“…In fact, at fertilized treatment, A rose rapidly, then slowly when PFD reached to approximately 1000 μmol m −2 s −1 . The same trends were found in previous studies in another C 4 plant Amaranthus retroflexus (Sage & Pearcy, 1987), and sugarcane (Allison et al, 1997;Sage, 2014) under normal and mild stress conditions (Zhao et al, 2013). .…”

Conditional up-regulation of cytokinin status increases growth and survival of sugarcane in water-limited conditions

“…In sugarcane, light and dark reactions are less sensitive to stress than stomates as photosynthesis continues for a considerable time when stomates are closed (Sage et al, 2013). However, severe or prolonged water deficit affects the integrity of photosynthetic machinery and contributes to the inhibition of photosynthesis.…”

“…Despite photosynthesis being the key process underpinning sugar production, our knowledge of the impact of water stress on the biochemical network of photosynthesis is very limited (Saliendra et al, 1996, Du et al, 1998, Sage et al, 2013). …”

“…In addition to stomatal limitation, inhibition of photosynthesis occurs through reductions in leaf area and chlorophyll content (Sage et al, 2013). In sugarcane, water restriction affects crop canopy development negatively by inhibiting leaf expansion and accelerating leaf senescence (InmanBamber, 2004) which adversely affects sugarcane yield and productivity by reducing interception of radiation and photosynthesis, and consequently biomass production (Lawlor and Tezara, 2009, Gan, 2010, Ribeiro et al, 2013.…”

Analysis of genes controlling biomass traits in the genome of sugarcane (Saccharum spp. hybrids)

“…None of the data in the literature implies that significant photosynthesis occurs in this type of tissue. Photysynthesis requires a functional photosystem (PS) II and PSI system, carbon fixation and a reductive pentose phosphate (RPP) pathway (Sage, 2004, Sage et al, 2013. It is noteworthy that the RPP pathway is present in all plastids, which are found in sugarcane culms, as it is crucial for many vital reactions.…”