The temporal and species dynamics of photosynthetic acclimation in flag leaves of rice (Oryza sativa) and wheat (Triticum aestivum) under elevated carbon dioxide

Abstract

In this study, we tested for the temporal occurrence of photosynthetic acclimation to elevated [CO₂] in the flag leaf of two important cereal crops, rice and wheat. In order to characterize the temporal onset of acclimation and the basis for any observed decline in photosynthetic rate, we characterized net photosynthesis, g(s) , g(m) , C(i) /C(a) , C(i) /C(c) , V(cmax) , J(max) , cell wall thickness, content of Rubisco, cytochrome (Cyt) f, N, chlorophyll and carbohydrate, mRNA expression for rbcL and petA, activity for Rubisco, sucrose phosphate synthase (SPS) and sucrose synthase (SS) at full flag expansion, mid-anthesis and the late grain-filling stage. No acclimation was observed for either crop at full flag leaf expansion. However, at the mid-anthesis stage, photosynthetic acclimation in rice was associated with RuBP carboxylation and regeneration limitations, while wheat only had the carboxylation limitation. By grain maturation, the decline of Rubisco content and activity had contributed to RuBP carboxylation limitation of photosynthesis in both crops at elevated [CO₂]; however, the sharp decrease of Rubisco enzyme activity played a more important role in wheat. Although an increase in non-structural carbohydrates did occur during these later stages, it was not consistently associated with changes in SPS and SS or photosynthetic acclimation. Rather, over time elevated [CO₂] appeared to enhance the rate of N degradation and senescence so that by late-grain fill, photosynthetic acclimation to elevated [CO₂] in the flag leaf of either species was complete. These data suggest that the basis for photosynthetic acclimation with elevated [CO₂] may be more closely associated with enhanced rates of senescence, and, as a consequence, may be temporally dynamic, with significant species variation.

Expression patterns of C- and N-metabolism related genes in wheat are changed during senescence under elevated CO2 in dry-land agriculture

“…This may be associated with greater availability of carbohydrates and more specifically, increases in sucrose and starch 'cycling' under e[CO 2 ] [64] as a consequence of greater net CO 2 assimilation rates [65]. Previous studies have also shown increased post-anthesis wheat leaf starch content under e[CO 2 ] [22,24], although starch is considered a minor soluble carbohydrate pool compared to fructans in wheat. Higher fructan synthesis with a drastic reduction post-anthesis was reported for wheat under e[CO 2 ] [66].…”

“…As carbon assimilation increases and N concentration decreases under elevated [CO 2 ], tissues can have greater C/N ratios, and altered metabolite concentrations [22][23][24]. Elevated [CO 2 ] may also change leaf senescence: In cereals such as wheat and barley, changes in leaf functioning under elevated [CO 2 ] were ascribed to accelerated senescence processes, marked as faster chlorophyll decline [25].…”

Historical and experimental evidence for enhanced concentration of artemesinin, a global anti-malarial treatment, with recent and projected increases in atmospheric carbon dioxide

“…The study was conducted at the FACE facility located at Zhongcun village (119°42'0^E, 32°35'5^N), Yangzhou city, Jiangsu province (Zhu et al 2012). The operation and control systems for the FACE facilities were the same as those used at the Japan FACE site (Zhu et al 2012).…”

“…The operation and control systems for the FACE facilities were the same as those used at the Japan FACE site (Zhu et al 2012). In brief, three rectangular adjoining fields were used.…”

Grapevine nutritional status and K concentration of must under future expected climatic conditions texturally different soils

“…Martins et al (2014) reported that the influence of enhanced atmospheric CO 2 concentrations on plant productivity and growth has often been explored in combination with alterations in photosynthesis, respiration and carbon use and allocation (Zhu et al, 2012), whereas corresponding modifications in mineral composition (with the exception of nitrogen) have received much less attention (Thiec et al, 1995). Heavier and more frequent rainfall events could increase the incidence of water logging, leaching and erosion, thereby causing unfavourable conditions for nutrient uptake, as well as a loss of nutrients from the soil (Proffitt and CampbellClause, 2012).…”