Can improvement in photosynthesis increase crop yields?

Abstract

The yield potential ( Y p ) of a grain crop is the seed mass per unit ground area obtained under optimum growing conditions without weeds, pests and diseases. It is determined by the product of the available light energy and by the genetically determined properties: efficiency of light capture ( e i ), the efficiency of conversion of the intercepted light into biomass ( e c ) and the proportion of biomass partitioned into grain ( h ). Plant breeding brings h and e i close to their theoretical maxima, leaving e c , primarily determined by photosynthesis, as the only remaining major prospect for improving Y p . Leaf photosynthetic rate, however, is poorly correlated with yield when different genotypes of a crop species are compared. This led to the viewpoint that improvement of leaf photosynthesis has little value for improving Y p . By contrast, the many recent experiments that compare the growth of a genotype in current and future projected elevated [CO 2 ] environments show that increase in leaf photosynthesis is closely associated with similar increases in yield. Are there opportunities to achieve similar increases by genetic manipulation? Six potential routes of increasing e c by improving photosynthetic efficiency were explored, ranging from altered canopy architecture to improved regeneration of the acceptor molecule for CO 2 . Collectively, these changes could improve e c and, therefore, Y p by c . 50%. Because some changes could be achieved by transgenic technology, the time of the development of commercial cultivars could be considerably less than by conventional breeding and potentially, within 10-15 years.

The relationship between the soil water storage and water-use efficiency of seven energy crops

“…They can also result from changes in their metabolism of subtype C 4 photosynthesis (Ripley et al 2010). The findings of our study confirmed those of Hall (2003) and Long et al (2006), who warned that the cultivation of energy crops can adversely affect both the level of soil moisture and soil water storage, especially in the deeper layers. A clear reduction in moisture and soil water storage under cultures of HPP, together with its lowest E among all studied energy crop groups, is associated with a high area of leaves (usually equal to a critical or above LAI, providing 95% absorption PAR by the canopy), the total transpiration of which causes increases in both the water uptake and the evaporation of soil water.…”

“…Nearly the same phenomenon occurred in our studies. The use of instantaneous WUE in the performance assessment of various crops is complicated due to the leaf PN, which is poorly correlated with the yield when the different genotypes of a crop species are compared (Long et al 2006). This is a result of the increased g s and E in C 4 G.…”

Glyphosate influence on the physiological parameters of Conyza bonariensis biotypes

“…The increase of the CO 2 concentration inside the leaf induces increases in photosynthetic efficiency, primarily by inhibiting the rubisco enzyme oxygenase activity (ribulose-1, 5-bisphosphate carboxylase/oxygenase) (Long et al 2006). Both biotypes showed a reduction in CE, especially from the third DAH ( Figure 1); until 7 DAH, the susceptible biotype presented significantly lower CE compared to the resistant biotype.…”

Assessment of the energy and exergy efficiencies of farm to fork grain cultivation and bread making processes in Turkey and Germany

“…Receiving non-optimal levels of radiation reduces the efficiency of photosynthesis further; therefore, only 3 to 6 % of total solar radiation may be used in photosynthesis [11,12]. Ways to increase the photosynthetic efficiency of the plants is being actively researched to improve their yields, including those of the grain crops [13]. The pollutants such as sulfur dioxide and herbicides (weed killers) inhibit the photosynthesis [14,15].…”