Effects of polyploidy on photosynthesis

Abstract

In polyploid plants the photosynthetic rate per cell is correlated with the amount of DNA per cell. The photosynthetic rate per unit leaf area is the product of the rate per cell times the number of photosynthetic cells per unit area. Therefore, the photosynthetic rate per unit leaf area will increase if there is a less than proportional increase in cell volume at higher ploidal levels, or if cell packing is altered to allow more cells per unit leaf area. In autopolyploids (Medicago sativa, C3 species, and Pennisetum americanum, C4 species) there is a doubling of photosynthesis per cell and of cell volume in the tetraploid compared to the diploid. However, there is a proportional decrease in number of cells per unit leaf area with this increase in ploidy such that the rate of photosynthesis per leaf area does not change. There is more diversity in the relationship between ploidal level (gene dosage) and photosynthetic rates per unit leaf area in allopolyploids. This is likely to reflect the effects of natural selection on leaf anatomy, and novel genetic interactions from contributed genomes which can occur with allopolyploidy. In allopolyploid wheat (C3 species) a higher cell volume per unit DNA at the higher ploidal level is negatively correlated with photosynthesis rate per unit leaf area. Although photosynthesis per cell increases with ploidy, photosynthesis per leaf area decreases, being lowest in the allohexaploid, cultivated bread wheat (Triticum aestivum). Alternatively, doubling of photosynthetic rate per cell with doubling of DNA, with apparent natural selection for decreased cell volume per unit DNA, results in higher rates of photosynthesis per leaf area in octaploid compared to tetraploid Panicum virgatum (C4) which may be a case of allopolyploidy. Similar responses probably occur in Festuca arundinacea. Therefore, in some systems anatomical factors affecting photosynthesis are also affected by ploidal level. It is important to evaluate that component as well as determining the effect on biochemical processes. Current information on polyploidy and photosynthesis in several species is discussed with respect to anatomy, biochemistry and bases for expressing photosynthetic rates.

Transgressive physiological and transcriptomic responses to light stress in allopolyploid Glycine dolichocarpa (Leguminosae)

“…Polyploidy has been shown to increase photosynthetic capacity per cell in many taxa (citations in Warner and Edwards, 1993), and we have shown that this is true in the recently formed natural allotetraploid, G. dolichocarpa (T2) Ilut et al, 2012). Here we showed that under conditions of chronic EL, NPQ capacity (NPQ max ) is also significantly enhanced in T2 relative to its diploid progenitors.…”

“…Photosynthesis as a whole is known to be affected by polyploidy (Warner and Edwards, 1993;Coate et al, 2012). Studies involving a wide range of polyploid species, including auto-and allopolyploids in both C3 and C4 species, have shown that polyploids often have larger mesophyll cells with more chloroplasts, higher chlorophyll and rubisco contents and greater photosynthetic capacities per cell than their diploid counterparts (for example, Dunstone and Evans, 1974;Molin et al, 1982;citations in Warner and Edwards, 1993;Coate et al, 2012).…”

Comparative Evolution of Photosynthetic Genes in Response to Polyploid and Nonpolyploid Duplication

“…Chloroplast number per cell increases with nuclear genome doubling (Warner and Edwards, 1993), which might serve initially to maintain dosage balance between nucleus-encoded gene products and chloroplast-encoded gene products. Coordination of nucleus-and plastid-encoded subunit stoichiometry, therefore, might represent a more significant challenge in PSII than in PSI, thereby driving longer term retention of balanced duplicates in PSII than in PSI.…”

“…Photosynthesis is a prime example of how polyploids can differ phenotypically from their diploid progenitors. Polyploids consistently exhibit larger mesophyll cells with more chloroplasts and greater photosynthetic capacities per cell than their diploid progenitors (for review, see Warner and Edwards, 1993). The causes of these differences at the level of underlying genes are unknown.…”

Environmental Regulation of Heterosis in the Allopolyploid Arabidopsis suecica

“…The effect of polyploidy on photosynthesis has long been of interest to researchers using a wide variety of species and experimental approaches (Warner and Edwards, 1993;Vyas et al, 2007;Coate et al, 2012;Pärnik et al, 2014). One complicating factor in comparing published research reports of diploid versus tetraploid photosynthetic activity in various species has been the use of different anatomical or biochemical units, on which to base the expression of measurements.…”